Merc 300E Turbo rebuild

[BGSP]

Originally Posted by NaughtyGT

Anyway. I just want it right

I agree if you want it done right do it the first time

[NaughtyGT]

Been researching my proverbial off to decide on right turbo to choose. One Turbo keeps popping up that challenges a twin set up. No debate worth going into whether twins are better as it's well established the right set up twin system is awesome but considering $$$$, labour & pita set up. A single able to get similar performance is worth a look into. A proper look into.

The GT35R! Has both High & Low advantages. Best of both worlds? Been around only for a few years or so as I can gather? The trim is a tricky decision to make although here's what I've managed to decipher so far: Be it 3563; 3582 or a hybrid of a 35 compressor, bolted to a T4 turbine housing. Some go for the 3540 size that would give great low-mid range performance! Seems very nice on a 3.0L. These rate @ 600 or so hp so would easily give you 400, reliably that is

If you consider the mad Russian (living in Sweden haha) runs high boost on stock compression with even bigger units. This begs consideration. Certainly makes me think twice.

For me personally. It would have to spool @ 3500rpm @ least & if @ 3000rpm with right dimensions/specs then, done deal There is also the Billet compressors & surge valves etc to consider but it is all depending on $$$ & practicality in the end. The info is awesome though for those who want to stretch the boundaries.

Will be looking closely @ this beast that's for sure.

After heaps of neck-acing research I still have to decide on right dimensions etc but with little time now to make my mind up . These turbos are working real nice on 3.0L platforms so may just be what I'm looking for

[NaughtyGT]

um......been researching (what's new) all this talk about going for a smallish turbo to ensure quicker spool. Not necessarily so! Yes, obviously it would make sense & many will support this reasoning. But unless engine is strengthened (bottom end wise.....piston composition more precisely), to withstand the heat/stresses placed on it by a hard-working little turbo maxing out......stock pistons will be @ the mercy of dangerously high heat & thus efficiency extremely compromised. Not ideal conditions for reliability what?

A large turbo, especially the newer high-end ones such as GT; GTR; Billet etc have anti-surge compressor snouts which brings me to another equally important bit of information. A turbo that is too small for an application can cause surging & resulting lack of power/response through the power band. I guess akin to fuel-cut?

Just something very important when listening to advice form just anyone cause they have a car & it's quick. Again. This is mainly only a problem when you have a bigger engine such as a 3.0L or >

P.S. Then there's twin scroll verse single or, twin scroll exhaust flange to suit twin scroll exhoust manifold (to be more precise ) = quicker spool time. Below is a link explaining the ins & outs of choosing the right turbo for road application (not track/drag)

http://www.supraforums.com/forum/sho...=530737&page=4

Surely some folk will find this helpful

I'm leaking what I am 99.9% sure I am going with....check this little sweetheart out

Based on my calculations:

With the GT3582R and 0.63 A/R housing you could expect 17psi by 3000RPM and 360ft-lb @ 4500 and 400hp @ 7000. The backpressure will be high at this level with ~24psi of backpressure at 7000 RPM vs the 17psi boost pressure. If you turned this setup up you could get 450 ft-lb@ 4500 and 460hp@ 6500 at 25psi. Backpressure here would be REALLY high, ~36psi at redline.

P.P.S.S......with it in mind that he is referring to a 3.0L Supra.....I like his calculations

[BGSP]

99.9 I want the whole 100

[NaughtyGT]

Originally Posted by BGSP

99.9 I want the whole 100

hehe.....just gotta research a bit more & speak with workshop Monday then I'll know

[NaughtyGT]

Here's a little (very informative) passage on the ins & outs of choosing the right turbo & how it all works for those that are keen on the workings of a turbo:

This is how to choose the Garrett GT turbo that will rock you!

The clever turbine engineers at Garrett have shared with us their turbo and performance specifications in the form of measurements, and compressor and turbine maps, and with a little knowledge we can use them to find the right turbo for every application. As we collect more actual results we will be able to even more accurately predict performance on the 3S-GTE. But we already have the tools we need, and you can learn a lot of the nitty-gritty stuff from the section "Turbine Efficiency - Part 2...the missing piece to the turbo selection puzzle".
http://www.turbobygarrett.com/turbob...o_tech101.html
http://www.turbobygarrett.com/turbob...o_tech102.html
http://www.turbobygarrett.com/turbob...o_tech103.html

I'll just cover the highlights from that thread, and highlight the highlights in bold, to present this information in an easy to understand form, and use it to establish some general guidelines to finding the turbo of your dreams...the one that will provide the realistic best possible spool for the strongest bottom end, fullest mid-range, and extended top end.

A quick and dirty review of how a turbo works is essential as it is fundamental to understanding the tools we have to help us choose. A turbo is an air pump that’s powered by the energy contained in the engine's exhaust gas flow by spinning a turbine impeller wheel. That wheel rotates on a shaft that has a compressor wheel mounted to the other end that then also spins and forces more air into the engine's intake. It's the exhaust energy and turbine wheel that powers the compressor wheel to increase intake air pressure, and your boost controller that determines the amount of pressure (with the wastegate redirecting exhaust flow as required to prevent over-boosting). It's important to recognize that it's the compressor wheel that's in charge of reaching the desired boost pressure, and the turbine wheel’s job to spin it accordingly. When the turbine is struggling to do its job effectively the compressors ability to provide boost in a timely manner is compromised and we recognize this effect as turbo lag. When it's completely up to the challenge to power the compressor we recognize it as providing excellent throttle response.

In fact, our success in choosing the best turbo for our use rests solely on our ability to understand this relationship between turbine and compressor. And for our purposes of choosing among the GT line that relationship is primarily determined by (a) the relative diameters of those two wheels and (b) the aerodynamics of the turbine housing. The resulting performance is called Turbine Efficiency, and its measure is expressed as a percentage. A turbo whose turbine can efficiently power the compressor to produce quick spool and less restricted top end flow has a higher %, often close to or slightly exceeding 70%, while others are as low as 60%.

Here's what we're looking for in the Garrett specs:

(a) Garrett recommends a wheel diameter ratio range between 1.1:1 and 1.25:1 (compressor:turbine) to provide the best overall performance. As an example the GT28RS has a ratio of 1.1:1 (60mm/53.8mm) at the quickest spooling end of the range, and the GT3076R has 1.27:1 (76.2mm/60mm)…barely outside the other end of the range. The reason a large compressor wheel mated to a smallish wheel would not be able to spool as quickly is because a largish compressor wheel will need to turn slower to provide any given intake airflow than a smaller wheel would, and this in-turn forces the turbine wheel on the other end of the shaft to turn slower, and at speeds that it can’t operate as efficiently at. This is contrary to those that believe a comparatively small turbine wheel and housing will cause the largish compressor to spool more quickly. Dyno results confirm Garrett’s recommendations every time, while I have never seen evidence of a small turbine/large compressor spooling nearly as quickly.

Good examples to see this effect would be the GT28RS, GT2871R (or HKS GTRS), and GT2876R (or HKS GT2540R). All three share the identical turbine housing and wheel, but are mated with 60mm, 71mm, and 76 mm compressor wheels. The latter two compressor wheel diameters push the wheel ratio well outside of the recommended range to 1.32:1 and 1.45:1. Each larger compressor wheel causes a delay in spool of perhaps 750 rpm to ~17 psi and makes less top end power as well. The only way to make these wider spaced wheel combinations make more power is to significantly raise boost pressure. This however will not reduce lag, the restrictively small turbine wheel and housing will limit high rpm power as it reduces the entire engine’s VE, less ignition timing can be run at high rpm causing reduced power from the airflow, exhaust temps will be higher, and you’ll have to deal with all of the risks associated with higher boost levels. The solution is to follow Garrett’s recommendations whenever possible.

(b) The turbine housings are designed to maximize turbine efficiency. In some cases though a turbine housing will be made or modified to fit specific user applications like space constraints or the lack of suitable sized exhaust manifold turbine mounting flanges for some popular applications. This has led to small turbines modified to stuff in large wheels, large turbos with small turbines made to fit onto small exhaust manifold flanges, smallish turbos modified to fit onto large flanged manifolds, etc…and all of them have reduced the turbine’s efficiency to spool quickly and produce the strongest powerband. The impact of some twin scroll housings can’t be predicted because of their lack of turbine efficiency ratings by Garrett, but their impact will be seen in dyno results. In some of these cases the wheel ratio will appear to be ideal, but the modification to the turbine housing itself can negatively affect turbine efficiency. This is why it’s important to know the Garrett tested Turbine Efficiency % rating.

The various iterations of GT3071R is a good example of these variables. All models use the 71 mm compressor wheel, but some have a 56.5mm turbine wheel stuffed into a machined T28 turbine housing, some have the better matched 60mm turbine wheel fitted to a twin scroll housing of unknown efficiency, and the one that mates it with the 60 mm turbine wheel and T3 single scroll housing. The latter is surely the best of the bunch using Garrett’s specs and recommendations, and it’s very high efficiency rating of 72% and ideal wheel ratio of 1.18:1means that for this size of turbo you are unlikely to find anything that will out-spool or out-flow it. It also means that the similarly flow rated GT2871R models with less than ideal wheel ratio and as little as 60% turbine efficiency will not perform as well as the GT3071R at 72%. Some feel that the GT3071R versions that have been used on the 3S-GTE have been less than stellar performers, but these results I'd suggest are consistent with Garrett’s specs, ratings, and the recommendations presented here. Let’s choose the best model and set some powerband records!

I’d recommend that you first use the Garrett compressor maps to identify the compressor that can flow your requirements (see Garrett’s Turbo Tech section for these calculations), and then to consider the wheel ratios and the turbine efficiency ratings found on their turbine maps as a guide to matching that compressor with a suitable turbine wheel and housing. While efficiency actually varies with flow rate, pressure ratio (think boost level), and turbine wheel rotation speed, the stated maximum efficiency rating is going to be quite comparable among all models within the GT line.

Now you need to choose the turbine housing AR. You’ll notice on the turbine maps that the efficiency curves are different for the various available turbine housing AR. These shows that the lower AR housings are more efficient at lower flow rates generated at lower engine rpm, while higher AR housings are more efficient at higher rpm flow rates. These housing options will allow you to choose between maximum low rpm spool and power at the cost of a little high rpm peak power, or maximum peak power at the cost of a little lower rpm performance, or something in-between if there’s a 3rd option. Valendia and RickyB provided a good dyno comparison of this AR housing trade-off using a .64 and .82 AR on the GT28RS. The lower AR made for a significantly stronger powerband overall on this setup, and I believe we will see this trend with each turbo model and engine setup…if peak power is your goal the higher AR will likely provide that every time.

I hope this will help you better choose from the GT turbo options that are available.

Bruce Hadfield

Garrett specs, compressor and turbine maps can be found at http://www.turbobygarrett.com/turbob...ochargers.html , and

Compressor selection guidelines at http://www.turbobygarrett.com/turbob...ch_center.html

Turbine Efficiency - Part 2...the missing piece to the turbo selection puzzle

Let’s quickly review the resources we’ve been using to choose a turbo so we can better appreciate our current needs:

1. Testimonials. While it may be entertaining to hear about how somebody smoked another car at a stop light, or how they got pushed back into the seat when the turbo kicked in, the general lack of useful information and the subjective nature of the comments leads us directly to #2.

2. Dyno Graphs. Dynos measure power at the wheels (or hubs) and that power is affected by many non-turbo factors. While dyno results have been widely regarded as the best tool we have to measure the difference certain modifications make, they are not a perfect tool. General engine condition, supporting mods, boost levels that can change during a run, aggressiveness of the air/fuel ratio and ignition timing, octane, 3rd vs. 4th gear, and a wide range of dyno equipment and testing factors and conditions can make it difficult to clearly see the impact of only the turbo, or compare one turbo to another. Throw in some mods that can greatly differ from car to car, such as the state of tune of an EMS, or mods that affect volumetric efficiency like a set of cams and cam gears, custom intake, and maybe a little head-work, and it becomes almost impossible to determine how much of the dyno results are the result of the turbo alone. At best you can see what is possible on a given set-up. If you want to research a turbo not yet dyno’d, or learn more about the ones you see in the dynos, you proceed to the dreaded step #4.

3. Turbo “Power Ratings/Estimates” Often around as useless as Testimonials and with all the limitations of Dyno plots (so many other things that effect power other than turbo by itself)

4. Compressor Maps. These are the turbo manufacturer’s graphic representations of the compressor’s ability to flow air across a range of pressure ratios. Compressor efficiency and shaft speeds are shown. We then need to “estimate” our engine’s airflow requirements throughout our desired powerband using a complicated formula designed by the devil him self, and then learn all about a compressor map so we can check to see which compressor “might” be able to provide the required amount of airflow. You really should struggle through the formula of estimating your engine’s airflow requirements to truly appreciate all the factors that affect it. While you may have been led to believe that finding a suitable compressor map will identify a suitable turbo, this isn’t necessarily true, and many members have discovered this the hard way. That’s because the ability of the compressor to deliver its indicated airflow is dependant on the turbos turbine section, and something called turbine efficiency…the subject of this article.

Turbine Efficiency

So what is turbine efficiency and why should we care? The compressor relies on the turbine to use the exhaust gas energy to power the shaft that spins the compressor wheel that pushes the air through the engine to create ungodly amounts of torque when mixed with fuel and a well-timed spark. And if the turbine goes about it’s job in a sloppy and inefficient way then the compressor won’t be able to do its job well, and performance will suffer. A turbine operating at high efficiency will be able to more quickly spool a compressor when called upon to make good low-end power, and/or will provide less back-pressure at high rpm to enable the turbo to make more top-end power by actually improving the engine’s volumetric efficiency. Turbine efficiency is the ratio of useful exhaust energy to total energy supplied, the flow at which it’s efficiency is the highest at all pressure ratios is plotted on it's “turbine map”. and it's maximum efficiency is stated as a percentage.

Turbine efficiency and maps are closely related to the compressor, and further discussion would be easier if related to an actual turbo. Only Garrett publishes turbine maps to my knowledge, and since I was able to use them to select my turbo and then acquire actual 3S-GTE results, let’s use my GT28RS for our example. It will then be interesting to see how we can carefully navigate through a staggering choice of 17 GT turbos models and predict their performance. I’ll make this clear by keeping it fairly simple…I promise!

Example - Crunching the numbers for a stock Gen 2 3S-GTE

Calculating Engine Airflow Requirements

The turbo analysis starts with finding a compressor that might meet our engine’s air flow needs. As mentioned in step #3 above, we calculate those estimated requirements with a formula, and then try to plot them on the compressor map. The stock 3S-GTE will flow ~15 lbs/min of air @ 3000 rpm up to ~30 lbs/min @ ~6000 rpm at a pressure ratio (Pr) of 2.25, which is approximately a boost level of 17 psi at sea level when accounting for normal intake system pressure losses, and making various educated guesses including a volumetric efficiency of ~95% at 6000 rpm. This estimate is telling us how much air the engine is capable of ingesting at 17 psi, and we calculate it over the range of rpm that we are hoping it will have full boost. I focused on 3000-7000 rpm as being the most important area for the widest range of driving needs, and you might choose something else for your needs. Power at any given rpm is dependant on the amount of air (and fuel) that the engine is consuming, and this is why we study airflow. Garrett very generally uses 9.5-10.5 flywheel hp per lb/min of flow for power estimates…so let’s think massive flow!

Compressor Map

See the compressor map below where I have plotted these airflow requirements at 3k, 4k, 5k, 6k and 7000 rpm on the map at the 2.25 Pr. Note that airflow is shown on the x axis and Pr on the y axis, and that all of these points fit nicely on the map suggesting that the compressor should be able to provide the required amount of air to maintain 17 psi from around 3000-7000 rpm. Plotting all of these points was not possible on other compressor maps that I had found back in the summer of 2003. The various concentric lines and numbers are noting the changing compressor efficiencies as airflow increases. Lower compressor efficiency at each side indicates that more heat will be added to the intake air than when it’s providing the airflow shown in the middle of the map where it’s more efficient. Temperature has an impact on air density, which is one determinant of airflow. Lower intake air temperature generated by a more efficient compressor, or improved inter-cooling does make more power…and so does higher turbine efficiency!

Please note that a stock VE motor will reach it's maximum airflow around 6000 rpm, and after that the VE drops off and less air is consumed. The 7000 rpm plot would therefore only apply to a motor that had improved VE, and it could be more or less than what I've shown, and I'd suggest that both 264 and 274 cams could cause the motor to use considerably more air at 7000rpm.

Source of both maps: http://www.turbobygarrett.com/turbo...RS_739548_1.htm

Compressor maps show only the flow of air that may be possible under ideal conditions, but to predict how it will perform when attached to any given turbine we must get into the turbine maps.

Turbine Map

This map indicates the turbine’s ability to convert the exhaust gases kinetic and thermodynamic energy into mechanical power to turn the shaft (and the compressor wheel) through the use of a turbine wheel. This “ability” is expressed as an efficiency rating. The manufacturer’s detailed map contains a lot of information related to exhaust flow, pressure ratio, shaft speeds, and efficiency. Garrett publishes a simplified version which can be found on their website, and I have shown the GT2860RS map below. Using this info can be a very good way to choose between two turbos with seemingly suitable compressor maps, and between two turbines with different area radius (AR) housings for the same turbo. It’s the missing piece to the turbo selection puzzle that turbo-machinery engineers have used for years.

This map shows a range of Pressure Ratios (Pr) on the x-axis and Turbine Flow on the y-axis. It also states that the turbo has a maximum turbine efficiency of 72%. There is a blue line showing the flows and pressures using the .64 AR housing that I have, and a red line for the .86 housing. Without knowing the exact method of calculating the turbine flow or pressure ratio, I think it suffices for the purpose of this discussion to assume that the turbine flow and pressure ratio is about the same as the compressor flow and pressure ratio that we would be looking at when using a compressor map, and we can jump between both maps and use the same measures inter-changeably.

Carrying on with our example at 17 psi (2.25 Pr), we can see that when this turbo with .64 AR housing is operated at a pressure ratio of 2.25, that its best efficiency will be achieved when flowing about 17.5 lbs/min as read from the y axis. I have highlighted that point in red. It also means that at any flow other than 17.5 lbs/min that the efficiency will be lower. If we now plot 17.5 lbs/min @ 2.25 Pr on the compressor map we find that it is half way between our 3000 and 4000 rpm points, or at about 3500 rpm. You will see later that 72% is an extremely high efficiency rating, which should indicate that the turbine will be able to meet the demands of the compressor to spool, and in fact my dyno plot and boost gage both indicate that the turbo actually spools slightly sooner to 17 psi @ 3250 rpm (where airflow would be close to 16.5lbs/min), but not by 3000 rpm that was plotted on the compressor map! This indicates that the turbine was not quite efficient enough at the 3000 rpm flow rate of 15 lbs/min to extract enough energy from the exhaust to power the shaft to spin the compressor to provide the airflow to reach 17 psi by 3000 rpm, but by 3250 rpm and 16.5 lbs/min it was! This is important because it shows how high turbine efficiency has to be to reach our spool goals, and at 15 lb/min flow, the rating of 72% @ 17.5 lb/min was not quite enough.

Go back and make sure you grasp that last paragraph and the rest will just fall into place…I promise!

Now what happens when airflows goes much higher than 17.5 lbs/min, and all the way up to 30 lbs/min at 6000 rpm? That’s a long ways from our best efficiency flow. The engine already finished spooling to 17 psi at 3250 rpm so why do we even care? Because turbine efficiency also affects turbine backpressure at high flow rates, and that reduces the engines volumetric efficiency and limits power. Although we do not know what the efficiency is at a flow of 30lb/min, we can assume that the turbine isn’t too small and restrictive, and still has a high enough efficiency, because the 200 ft-lb @ 7000 rpm result on the dyno is typical of those using even larger and less restrictive turbos. This turbos compressor and turbine is therefore not limited in airflow capacity or efficiency within the requirements of the stock 3S-GTE and 17 psi.

My dyno using the GT2860RS .64AR turbine

If you go back to the turbine map on page 3, you can see that the .86 AR also has a 72% efficiency but the whole curve is raised up 3-4 lbs/min to 21 lbs/min at the same Pr of 2.25. This means that at the lower rpm and flow rates that the engine consumes during spool up, that the turbine isn’t capable of working as hard, and it will not spool as quickly as the .64 AR. While we don’t know what the exact efficiency would be at 6000 rpm, we can assume that the .86 should be more efficient than the .64 AR, and that it may provide slightly more power...at those higher rpms. The 21 lbs/min peak efficiency would be a flow of about 4200 rpm, and it might also reach 17 psi a couple of hundred rpm sooner if our experience with the .64 AR is any indication.

Conclusions

We can see from our example that the GT28RS compressor map is a great match for the airflow requirements of the stock 3S-GTE VE engine because we were able to plot all of our calculated flow requirements from 3000 to its flow peak at 6000 rpm, and then out to redline where it actually consumes less airflow. The .64 AR, 72% @ 17.5 lb/min efficiency turbine is a great match for the compressor because it was able to power the compressor to reach each of those requirements, only barely missing the 3000 rpm point by 2 psi, and because it also provided the required flow to reach 200 ft-lbs @ 7000 rpm that is the standard set by the larger turbos. We can tell that the .86AR turbine will not be able to spool quickly enough to reach the flow requirements until closer to 4000 rpm, but its higher efficiency above 4000 may help it to make a little more power at 6000 rpm.

Garrett’s estimates 10-11 flywheel horsepower per lb/min of flow, and Ray Hall figures 10.86 per lbs/min of flow. So at a flow of 30 lbs/min @ 6000 rpm I should be making about 326 flywh.hp (10.86 X 30). Factoring in 15% driveline losses would mean ~277 whp @6000 rpm, and this is about what you'll see on the dyno. This perfect match is quite a coincidence given the number of variables involved, but it should at least show that making good educated guesses can get you awfully close.

You can analyze other models in the same way. While it’s an imperfect science, it can help you find the best match for your needs, and it can definitely identify a poor match. Even if a turbine map is not available for the turbo you are analyzing, there are things to consider.

Factors that will improve spool

There are a variety of ways that you can improve your spool, and while buying a different turbo, or perhaps a different turbine housing, is the big one because it directly addresses turbine efficiency, there are others also:

-Turbine Efficiency

1. Compressor wheel to turbine wheel ratio. That’s the compressor wheel exducer diameter divided by the turbine wheel inducer diameter. A large compressor wheel will not be as efficiently powered by a small turbine wheel. Garrett claims this is because the larger compressor wheel will need to turn at a slower speed to provide any given airflow, and that will force the smaller turbine wheel to work at shaft speeds that it is not as happy with. And a small turbine wheel will eventually cause a restriction with increasing exhaust flow, thereby limiting high rpm power. Garrett recommends a ratio in the range of 1.1:1 to 1.25:1 to provide the best compromise between spool and high rpm power. Considering wheel ratio alone can be misleading if the turbine wheel isn’t well matched to the turbine housing.

2. Turbine wheel to housing match. A larger turbine wheel adapted to fit into a smaller turbine housing will restrict exhaust flow and decrease turbine efficiency. Note the GT3071R with 56.5mm turbine wheel below, where turbine efficiency drops due to the housing matching.

3. Wheel and housing design. The most modern turbines outperform the older ones with increased turbine efficiency. They spool quicker and make more power. Choice of housing AR will shift the efficiency from faster spool to higher flow capability with each higher AR selection.

-Exhaust Flow Energy:

Increase flow at lower rpms by improving volumetric efficiency with headwork, increased displacement, etc.

-Exhaust Temperature Energy

Increase the exhaust temperatures at lower rpm with ignition tuning, exhaust cam timing, heat coatings, etc.

-Expansion Ratio

Reducing turbine housing and exhaust system flow backpressure improves expansion ratio. And since reducing backpressure also improves the engines volumetric efficiency, this improvement will also increase your power as more air is consumed.

TURBO ANALYSIS

Let’s look at several Garrett models, and compare their compressor map flow ratings, compressor/turbine wheel diameters, wheel ratio, and the maximum turbine efficiency and flow rate that it occurs. For ease of comparison I will record this information in a chart instead of trying to post all the maps, and I’ll use a Pressure Ratio (Pr) of 2.25, which is roughly the equivalent of 17 psi with a normal intake. I’ll list them from the smallest to largest turbo. I will then try to interpret the data using our knowledge of turbine efficiency, information from Garrett, and observations from a very limited number of dynos that I’ve seen on our member’s cars. Note that airflow range listed is for 2.25 Pr (~17 psi) where our engine airflow requirements are estimated to range from approx. 15 lbs/min @ 3000 to 30 @ 6k, and then less to redline on a stock VE Gen 2 3S-GTE. Stock VE refers to the motors internals, and flow requirements include bolt on VE mods like high flowing downpipes and exhausts. Readers should calculate their own airflow requirements, as there are various factors that can affect it. Many of these turbos will be used on modified engines that will actually consume more air at each rpm level and have extended rev limits.

GT2860RS 12-35 lbs/min, 60/53.8mm, 1.1:1 wheel ratio, 72% eff. @ 17.5 lbs/min.

This turbos is a great match, it can efficiently provide the required 30lb/min flow I needed for 17 psi, and has achieved terrific results on the stock VE 3S-GTE. See the “Conclusions” in the example above for details.

GT2871R 13-38 lbs/min, 71/53.8mm, 1.32:1 whl. ratio, 66% eff. @ 17.5 lbs/min.

This turbos compressor would have provided the airflow required from below 3000 rpm if the turbine efficiency was higher. The lower turbine efficiency of 66% however suggests that it will not spool as quickly as the GT28RS, nor make as much top end power regardless of housing AR choice. The 1.32:1 wheel ratio is less than ideal and would be the factor in the lower max. efficiency. The one dyno I’ve seen with unknown turbine AR appeared to spool approx. 750 rpm later and made no more power than the GT28RS despite 4 psi more boost. This is the comparison that best illustrates to me the significance of a lower efficiency rating since the turbos are identical except for the GT2871R having a larger compressor wheel which throws off the wheel ratio and efficiency. While variations in engines and dynos can be misleading, I think this does confirm Garrett’s own claim that on this size of turbine, a difference of 8-15% efficiency can cause a spool change of roughly 1500 rpm.

GT2876R 16-48 lbs/min, 76/53.8mm, 1.41:1 whl. ratio, 62% eff. @17.5 lbs/min.

The compressor has a much higher flow, and the 3000 rpm requirement of 15 lbs/min can not be plotted. It has a very low turbine efficiency caused entirely by the mismatched wheels according to Garrett, and the 1.41:1 wheel ratio results in efficiency of only 62%. Even Garrett does not recommend this turbo for general use, and a number of our members with the identical GT25R would readily agree…enough said.

GT3071R 15-47 lbs/min, 71/56.5mm, 1.26:1 whl. ratio, 64% eff. @18.5 lbs/min.

This compressor has a very appealing flow rating, and the 3000 rpm requirement can just barely be plotted. But the turbine has a poor efficiency rating, despite the acceptable wheel ratio. They used a larger GT30 turbine wheel that has been modified to fit into the smaller T25 housing according to Garrett, and this would explain the poor efficiency. The one dyno I’ve seen unfortunately seems to confirm that it will spool slowly in keeping with its turbine efficiency rating.

GT3071R, T3 turbine, single scroll 14.5-45 lbs/min, 71/60mm, 1.18:1 whl ratio, 72% eff. @19 lbs/min. Great new turbo for those with a mild build that can consume more airflow that the stock VE motor...see post #46 below for details.

GT3076R 18-52 lbs/min, 76.2/60mm, 1.27:1 whl. ratio, 72% eff. @ 21 lbs/min.

This compressor can flow even more air, but again misses the 3000 rpm point. The lowest flow requirement would plot ~3600 rpm. Those with a build that will flow this kind of air at the top will likely not mind the lag in exchange for the huge power. The turbine efficiency rating is excellent, reaching its peak at 21 lbs/min of flow. That means this turbo will spool like crazy reaching 17 psi around 4000 rpm with the .64 AR turbine, and will flow to beyond redline with any of the three turbine ARs. This could be the next GT champ for those with a power goal up to 500hp if they have the build to flow this kind of air. That could mean whp exceeding 400 whp with modest boost. This turbo is the best reason I’ve seen to buy an EMS, large cams, cam gears, intake manifold, a full head job, possible stroker, and professional tuning. Somebody try this one quick and post your results!

GT3271 15-38 lbs/min, 71/64 mm, 1.11:1 whl. ratio, 64% eff. @ 19.5 lbs/min.

This journal bearing GT has an appealing compressor map, but a low efficiency turbine. Looks like it could flow a bit more top end than the GT28RS until you realize the turbine just won’t support it with only 64% efficiency. The only dyno I’ve seen did produce slightly more power at 7000 rpm with an extra 4 psi of boost, and spooled what appeared to be ~750 rpm later.

GT3571 14-38 lbs/min, 71/68 mm, 1.04:1 whl. ratio, 70% eff. @ 29 lbs/min.

This journal bearing GT has a compressor map that fits our requirements, gives a little extra flow at the top, and it also has a high efficiency rating. I’m a bit puzzled by the max. efficiency being reached at a high 29 lb/min flow. That means it will spool hard around 6000 rpm to reach 17 psi. It has the compressor flow to support another 400 rpm, and the turbine should go along with the plan. Let me know if anyone has tried it.

GT3082R ? lbs/min, 82/60 mm, 1.37:1 whl. ratio, ? eff.

Also known as the GT3040, I’ve included this model as it’s a turbo that a few members have used and it is available in a kit. There are no maps shown for it on the Garrett site, but I’ve listed the only details pertaining to turbine efficiency that I can find.

What we’ve discussed about the wheel ratio affecting turbine efficiency perhaps doesn’t even apply in the same way at this power level. The 60mm turbine looks undersized for the top end power that a 82mm compressor might flow. See the dyno results in the Racing Records section to see the impressive results.

GT3582R 22-59 lbs/min, 82/68 mm, 1.21:1 whl. ratio, 70% eff. @ 22 lbs/min.

Also known as the GT35R, this compressor has huge flow capabilities and high turbine efficiency intended for the seriously modified engine (and perfect for the 3.0L Supra!). I'd refer you to the Racing Records section to see various impressive results.

I hope you’ve found this information of interest and will be able to apply it to your search or understanding of turbo performance.

Bruce Hadfield

Sources

“Turbo Matching” by Mike Kojima, SCC June 2003. Formula for calculating engine airflow, and plotting a compressor map.

“Performance Dictionary” by Jason Kavanagh, SCC July 2002. The Garrett engineer uses a detailed turbine map to discuss turbine efficiency.

Garrett website http://www.turbobygarrett.com/turbobygarrett/index.html. Compressor and turbine specifications and maps.

[NaughtyGT]

concerning engine/turbo matching some may find this quote from a pretty knowledgeable Supra owner very interesting? (the 35R mentioned is purely for example only as this is what I am interested in. It could relate to any particular size)........In my experience it doesnt matter what the displacement of the engine is nor its cyl count. a 35R likes .63 or .82 singlescroll and 1.06 twinscroll. a 42R likes 1.15 or 1.28 twinscroll (it does ok as a singlescroll, but definitely not great). a 408R likes .95 or 1.06 twinscroll (and SUCKS as a singlescroll). It doesnt matter if its a 1.6L b series honda or a 3.4L stroker 2JZ every turbo has a sweet spot turbine housing. the turbo doesnt care what "pump" (engine) its attached to, it just sees mass flow rates and behaves accordingly

[NaughtyGT]

Spent good hr speaking stuff over with workshop techi & have settled on the turbo I'll be putting on the car. Also fuel management & a TIMELINE ahhu

The turbo I chose is a BB GT3582R (aka GT3540R or GT35R) with .84 exhaust housing, billet compressor wheel & ceramic bearing case. Modified @ the shop. Purely custom for balance between spool time & reliability. I was almost going to run with the .63 turbine housing but 2 things stopped me.

1) it would light up the wheels too quickly & this car in the wet.....er.....no!
2) the smaller exhaust housing will place more heat on the inlet parts so.....no!

Probably looking @ 300rwkw reliably on 15psi with hopefully not too greater lag than if I used the smaller housing? After so much trouble to get a good low km engine & all the money I'm spending to get this car together I'm not willing to sacrifice reliability & safety just to get more punch

Another important point to using a bigger turbo is economy. Instead of the smaller turbo arching to spool when you just want to drive easy. The bigger one will tend to not punch rather, sit mostly idle allowing better economy on slow drives remaining @ low boost. Workshop guy runs the same turbo on his XR6 & he drives @ 1/4 throttle with turbo pulling 6psi around town all day. Sounds OK to me

In the end longevity outweighed performance risks.

Important new mods we've settled on:

a) Modified MT8 Stand Alone with timing chip only (all LPG needs)
b) Larger IC

.....@ the best part.......we've decided to go hammer & tongs & car should be ready in month! From engine apart & still on stand to running down the road.

[NaughtyGT]

After talking over with workshop again today & another Merc owner have decided to let go of the HP bar & concentrate more on the sprint The heat scare will be sorted by larger IC.

Amazingly. The performance difference between the 30 series & the 35 series DOWN LOW & MID sincerely negligible! I actually found an EVO owner who fitted both GT's to same car & powerband on dyno readings were almost identical :shock: only real difference, as you'd expect (& I'm positive you'd know) is right @ the top-end say, 5500-6000rpm. This range is limit for my application anyway. Thois is why I chose the larger compressor housing/wheel to get that power down.

I am going for the smaller .63 a/r which really isn't that small lol. The T03 highflow I have now for sale is .63 exhaust! If I don't like the responsiveness than I will simply swap it out to the .84 housing & be done with it. The only trade-off will be top-end power seen only in dyno chart & good only for track/drag use.

P.S. I can always pull more boost though 8) hehe....to close the gap a little.....

P.P.S.S. btw......has it occurred to anyone to get relief from lag......just change down a gear haha.... :lol:

[NaughtyGT]

HP/KW ratings aside, I'm tempted to try 16-17psi to allow the GT35 to work closer within it's efficiency range. Have noted people saying 14-15psi or, 1 bar, is a reliable boost to run with this engine in stock, unopened trim. The only member I have noted however going past this is Roman (Pumpish) going to 20-21psi. Not sure (he hasn't replied) whether he used the custom steel head gasket or if original one is in place? The stock 12V running gear, especially the diff size, is concerning me a tad @ these higher boosts. This I need to decide in the next few weeks.

Since I'll be using the MT8 for timing control. Most will be aware of the benefits of software -programmable ECU's over the basic timing computer like the MSD range sell that V8's employ (as in the original set up on my car by previous owner) Basically you set the timing to retard say, 2 degrees @ a given psi/bar boost level. Ie: for each 5 psi of boost, the timing is retarded 2 degrees. Works OK but not alot of control over AFM's. No ability to accurately map parameters like you can if you use the stand alone ECU's. What really sold me was with the sand alone, you can pretty much 'guarantee' the engine is going to be provided with correct desired 'AFR's right through the rev/boost range. Not just better performance but the safety/piece of mind of knowing car is told exactl what to do @ any given time & NEVER lean out

I'm hoping to get sound advice from Roman (Pumpish). A member from a US Forum who has featured his mad projects all over the place getting absolutely sic results. Regardless. He proves/shows what performance these engines are capable of producing along with it's limits. Important to keep in mind, he thrashes the bags off his cars so the testing is quite impressive!

P.S. my head hurts atm Just reading on how various exhaust housing A/R's play @ different boosts & the danger of heat/detonation when exhaust flow is restricted! Again. With my build. There is not much tech stuff to sort through. The main engines that closely match the M103 are Supra 2.5L 1jz engines. The 3.0L 2jz heads flow better so aren't are real hot comparison to the lazy-ass M103 head lol. Also. LPG inherently poses less detonation risk anyway so alot of stuff I read concerns pump fuel & therefore furthers to my 'guessing game crusade' I've embarked upon haha.....NOT

What is for sure (yet, once again, little tested on the Merc) is the custom exhaust will greatly assist exhaust flow & therefore ease the horrid problem of exhaust heat/restriction greatly so.......again, except for Pumpish's projects, uncharted waters I paddle

P.P.S.S. Also. A bigger compressor housing with smaller wheel, as seen with the GT30 (afaik, uses same comp housing size as GT35?) turbo would be better suited for those wnating to run higher boost. Me on the other hand, want to keep boost down (due to stock compression) so this is why I am opting for the GT35 over simply settling for the GT30. Keeping in mind down low & mid, powerband seems pretty much similar. A rare case, as mentioned by another where going bigger turbo than you might think to is OK

[chicaboo]

Don't tempt fate...

[NaughtyGT]

Originally Posted by chicaboo

Don't tempt fate...

ohhhhh......your know fun .....always sound advice though from you Gav I guess I am bit bamboozled with the best boost to run for the turbo. It's easy for folk to talk about "full boost" @ some certain revs but they make too little light on when boost begins to really kick in. They quickly point out when engine goes bazurk but not when it starts to liven things up. I think this is an important point @ least part of the time left not considered? The XR6T that my workshop guy uses as his daily runs the GT3540 with the large 1.06 A/R exh housing. He gets 6psi happening with 1/4 throttle! That's a 4.0L so a larger straight six. He can afford the larger housing A/R than me & the lag is less a drama with his engine obviously than mine.

On this note......looking back now, with Naughty, I would have been better running with stock VJ14 exh housing & not the 15R BPT one Oh well. The MT8 may cover this a bit?

Back to boost for the GT35.....think I will try the 15psi & see how it goes under different driving conditions then go from there.......

[NaughtyGT]

hmmmmm.....interesting how you forget the basics......higher compression equates to quicker spool. LPG, higher boost ability (as long as you can guarantee gas keeps up with the airflow )

I'm kinda agreeing with some of the Merc guys contributing to my performance thread on Merc forum.......this thing is really gonna hammer I'm just not allowing myself to get too ahead of myself until I believe the gas delivery is adequate. I know this is the main reason I am paying experts to build the car but I'm trusting their judgement with alot of my own personal hope. If I pull this off. This thing will be a 1 & only build. If I fug it? I know what I'm faced with doing but won't go down that path unless necessary. I've spent most of the money so far so except for twin convertors/vapourisers, reco'd mixer, custom inlet & ext manifold, wastegate, BOV?, now it's mainly labour, pipe work & hoses, clamps & other misc bits to join it all together. Still some $$$$ though Rear screen. Also. turbo back mandrel exhaust.

The dyno however will be a scary thing for me. I figure on doing a couple of passes say, 10psi first then 12, then 14-15? Maybe to 17 but canot decide just yet until I research more info. If I had the forgies & multi-layer gasket.....bost would be never a prob!

Just a recap:

These are the areas I've focused on with Jamie (workshop guy responsible):

Turbo extra specs:
Billet compressor wheel (lighter alloy as opposed to cast metal) = quicker spool
Ceramic bearings (as opposed to Garrett plastic bearing case that can melt) = can handle more/prolonged heat
Smaller exhaust housing (A/R) again for quicker spool time (more low-end response/power)

Turbo Exhaust Manifold:
Steampipe 16guage tig-welded with external wastegate = quicker spool & more flow volume

Inlet Manifold:
More precise gas flow & altered volume

so I keep going........

[NaughtyGT]

The inlet Manifold build with custom Boxy Plenum has been concerning me a bit until I spoke again with Jamie from JD Custom here in Mornington. Once the manifold is made they do a bench flow test to make sure it's all flowing even. Apparently he has made heaps of Supra manifolds the same way. He gets the Plenums made up with JD Custom in raised machined writing in top. Too bad if you wanted to remain stealth

Mr Turbo in Sydney have begun makng custom turbo Finally I'm starting to believe in this thing

[NaughtyGT]

Decided to raise the boost in increments when we, eventually do get to tune car Initially do a run @ 10psi using a 45mm external wastegate then @ 15psi @ see how she fairs & what hp we can achieve @ this boost. As I've said before, hp will be down due to small turbine housing but the trade off is quicker low down response so I can live with that I won't be running a BOV as the auto's stalled @ 2300-2500rpm so unlike manual gear changes where you would definitely run a BOV, gear change will be pretty much instantaneous & BOV in this case would be for the wank effect only. Back pressure will be negligible & the large wastegate will do that job well. Also the larger comp wheel ensure large volume of airflow & counter the back pressure anyway. All in the set up @ this stage.

Also @ this stage I think I'll call it a day @ 15psi for reliability purposes more than anything. The LPG will work in my advantage in this area with it's higher octane ability however, this hp will be a big enough shock I think for the stock car including running gear, brakes, suspension per se.

The MT8 has to be made up especially & will be a few weeks wait bugger it. Hopefully there is enough to be done in the meantime with fabrication anyway?

P.S. I may still run a BOV. Plumbed back though but awaiting workshops call

[NaughtyGT]

Just an important note I'd like to make when plumbing IC piping. Ensure you butt pipes together as close as you possibly can, avoiding too much gap between piping taken up by joiners ie: clamp joins close to each other to eliminate vacuum on joins caused by the sucking action of compressor wheel on the IC, especially with silicone joiners.

If silicone joins suck in too far, effectively narrowing the diameter & thus create a bottle-neck in the flow, this can cause 'boost creep' & resulting increased heat/damage to turbo &/or engine!

Even better! Don't use silicone joiners but heavy duty cotton-threaded rubber hosing

[Mad Mat]

nice write up......

nut there is still one thing missing..

where is the update pictures lol

[NaughtyGT]

Originally Posted by Mad Mat

nice write up......

nut there is still one thing missing..

where is the update pictures lol

Hey Mat

none unfortunately. Cause' car is @ workshop & not much of anything is complete. Manifolds are still being made so this holds everything up damit

Another important point I found was when building a car to run a certain output such as you build an engine to a certain hp rating say 250. Your worried though now as to whether or not the drive chain will cope? Will something brake with the extra hp output?

I've been going down the wrong path & maybe others have/are? I was thinking about traction. I don't want wheels to light up too easy, drawing attention from the leaches etc. BUT. While your figiting around making sure the wheels will GRIP.....you are in actual fact forcing the car to stress the drive chain, instead of allowing slippage, you are in risk of breaking something. If you allow tyres to spin a bit. You are taking the strain off the driveline. This especially goes for manual transmission!

This is why you use a stall converter in an aoto so it acts kinda like a 'cushion'.

To put it into perspective. With a drag car. You don't want slippage. Instead you want traction. Some even screw tyres to the rims so they won't slip on rim. BUT when you do this you ENSURE your drive chain is built strong to handle the power. To HOLD it back. If you don't something will break. Tailshaft, box?

What's this remind you of concerning the 4WD G series boxes in the BF & BG 323 turbo cars? Broken boxes due to 'launching' & 'traction biting' the bitumen!

Below is a really straight forward introduction to turbocharging that is well laid out in paragraphs for ease of reading Although it's long, you can right click on link, save it & read it in bits & pieces when you feel like reading more. I reckon it's invaluable to understanding how it all works & you can refer back to it. Want more technical reading than look @ the above writing posted few posts up or google technical questions

http://www.nicoclub.com/archives/tur...rcharging.html

[NaughtyGT]

why couldn't the workshop have saved me hrs of searching & 100 grey hairs today wondered why I can't get the lowdown on the GT3540 turbo, thinking the 40 meant the turbine size & that it was smaller than the say, 71 so it would spool quicker yaddi yadda......the friggin 40 concerns the compressor side of things & uses the GT40 front......basically the GT3582 is the genuine Garrett Ford Australia used for their XR6T's & uses the 1.06 A/R turbine housing.

Put simple the GT35 turbo = the GT3571 (10.2mm smaller compressor than the R series) R denotes BB, the GT35R = the GT3582R, whilst the GT3540R is essentially a hybrid GT35R using the GT40 front. Sheesh!!!!

This means the turbo I'm getting is actually a GT35R with GT40 front (comp wheel) but small rear (GT30 54mm turbine wheel) as opposed to 68mm in the GT3582R, the GT40 rear wheel is 77mm.....oh dear hands to the forehead again

Here is a bit of info comparing the different top brand turbos: Mine is the last one (Billet)

HKS GT3040:
Compressor Wheel:
50 trim GT40, Inducer 58mm, Exducer 82mm.
Turbine:
84 trim GT30, Inducer 60mm, Exducer 55mm, Material GMR.
Core & bearing system:
Cast iron core, Twin Steel ball bearings, Phenolic (Plastic) bearing cage’s.

Garrett GT3040R:
Compressor Wheel:
56 trim GT40, Inducer 61.2mm, Exducer 82mm.
Turbine:
84 trim GT30, Inducer 60mm, Exducer 55mm, Material GMR.
Core & bearing system:
Cast iron core, Twin Steel ball bearings, Phenolic (Plastic) bearing cage’s.

Billet R-GT3:
Compressor Wheel:
The Billet R compressor wheel is a tweaked version of the above compressor wheels.
Billet-R 54 trim Inducer 60.2mm Exducer 82mm.
Billet-R 52 trim Inducer 59mm Exducer 82mm.
Billet-R 50 trim Inducer 58mm Exducer 82mm.
Turbine:
Billet-GT3. Inducer 65mm, Exducer 56.6mm, Material Inconel.
Core & bearing system:
Anodized billet aluminium core & back plate, Twin full complement silicon nitride (Ceramic) ball bearings (No bearing cage)

[NaughtyGT]

I've only just realised something about these blasted GT turbos. Prior to later models in the GT series. They offered hybrid, mismatched models such as 3040 & 3540 with the intent of having a larger compressor wheel & smaller turbine wheel. As I've alluded to in bove post right?

So, I probably would've been better getting the flamin' GT3040R having known all this earlier. Then I would've ended up with a GT35 comp wheel & a GT30 turbine wheel, which was in fact what I was after & thought I was getting in the first place bugger it Wouldn't that **** ya? Unless the engine & more specifically the head can flow the extra air that the larger comp wheel produces?