New Exhaust - sounds like a MX-5!!!

[project.r.racing]

after killing the previous exhaust, refer to thread: -

http://www.astinagt.com/forums/showthread.php?t=7978

i had to get a new axle back section made up.

once i had the car up on the hoist. i measured the intake of my old muffler, and to my surprise. it was only 51mm (2") in diameter. wow! all this time i've been thinking it was 58mm (2.25") damn shafty buggers who originally put in the exhaust and charged me for the bigger. and to think that i was getting all that power from a 51mm (2") system.

anywayz - from the rear axle back i had new mandrel bend piping, super cat muffler and old 4" tip fitted and now it sounds like a race car quad throttle mx5 engine!!! it's quiet as all hell compared to the old exhaust. but releases noise and extra power/torque between 3500-5000 rpm.

i'm very happy with it...

next on the list to do is new flex joint, 63mm (2.5") commonwhore catalytic convertor and the piping between them. can't wait to have that small 45mm (1.75") piping removed to unlock more powah!!!

next after that is the piping between the cat and rear axle. it's still 51mm (2") press bent piping with a big resinator. just gonna get 58mm (2.25")mandrel bend piping and no resinator fitted.

then finally - replace my 4-2-1, 42mm (1.5/8") id piping extractors for port matched, 4-1 42mm (1.5/8") with way longer primaries.

check readers rides for more details if you wanna know more about it. it's a full race exhaust that has been tried and tested. but i'll probably have to test and replace it many time again. lol

going from 2" to 2.25" now, thinking that i already had a 2.25" system has now thrown my end power calculations into a spin. after thinking/calculating that 115-125kW was achievable with the 2" exhaust at the wheels. it'll be interesting to see what the 2.25" could do now.

ryan

[pr1mo]

haha sweet! shifty buggers to begin with tho grr! goos to see you playing with the car!

cheers mike

[W.A.I.]

good stuff

off topic a little, has anyone here tried removing the catalytic convertor? would that make any difference? also, which one is better? 4-2-1 extractor or 4-1 extractor? any difference between the two of them???

Andrew

[project.r.racing]

remove the cat and face massive fines!!! department of transport would hang you for it. the car will smoke and you'll stink the roads out. also your insurance will be void.

4-2-1 - better for street cars
small decrease in low range torque,
small increase in mid range torque,
small increase in high rev kW

4-1 - better for high revving race cars
big decrease in low range torqure
big increase in high rev kW,

and each of these factors can be different again due to other engine modifications done.

ryan

[W.A.I.]

ya, i had a quick look last night and found an article from the US. it experimented an 99 Civic Si for a number of difference choice of cats including cat removal. cat removal only gives like 5hps gained at wheels while the best cat gives 4hps.

so, for an auto car like mine, which one is a better header choice? i have a feeling that 4-1 is better for auto from what you've just said.

Andrew

[project.r.racing]

well whatever you do - the auto is gonna hold you back...

autos ARE NOT high revving cars, so i'd personally think a 4-2-1 headers would be better. cos in a auto you cannot hold the engine in high revs. hence you'd be wasting the reason that the 4-1 headers were made for.

go 4-2-1 headers if you thinking about extractors.

ryan

p.s. how are the hong kong coilovers going?

[W.A.I.]

they are doing good. well, i m not sure what's good good, but i think mine is good enough except i think the springs ain't stiff enough. will have my front strut brace installed in the coming few weeks i think.

Andrew

ps: sorry for hijacking the thread

[twilightprotege]

Originally Posted by deejayryry

4-2-1 - better for street cars
small decrease in low range torque,
small increase in mid range torque,
small increase in high rev kW

4-1 - better for high revving race cars
big decrease in low range torqure
big increase in high rev kW

total and utter BS

i can make a 4-1 with FAR FAR FAR better low range than any 4-2-1 will ever make.

the 4-2-1 vs 4-1 debate has a lot of misconceptions.

first of all. 4-1 headers have 1 large power band. 4-2-1 headers have 2 small powerbands. usually 4-2-1 headers are designed to have one of those small powerbands down low and 1 up high, thus giving the misconception that 4-2-1's are better for the street. it would be just as easy to make a 4-2-1 that has 2 powerbands right beside each other (like 7000 and 8000rpm) giving a broader peak power band.

4-1 headers can have the power band where ever and will always give a stronger power band than anything a 4-2-1 can do. this is the reason they have the misconception they are for racing only. i could easily make a 4-1 header that has a powerband at 2000rpm if i really wanted to. again, would kill any 4-2-1 power band for that area.


as for this comment

Originally Posted by deejayryry

autos ARE NOT high revving cars, so i'd personally think a 4-2-1 headers would be better. cos in a auto you cannot hold the engine in high revs. hence you'd be wasting the reason that the 4-1 headers were made for.

again, see my above comments. personally i'd think auto's would be best with a lower powerband 4-1, something in the 3000rpm range

then again if you're talking about off the shelf headers - they are all wrong. the mathematics behind them is all wrong, 4-2-1s have way too short primaries (usually). 4-1's usually have too short primaries as well. obviously these are all general statements, but the point i'm trying to raise is the misconception that 4-2-1's are best for street and 4-1's are best for racing is BS

[project.r.racing]

ok, forget i said anything - don't go and buy the $400 set that have been tuned with 2 powerbands, 1 at 3500 rpm to work with your VRS and the other at 5000 rpm to close out at redline.

just go buy $800 custom made ones like andy just said. tuned for 1 3000 rpm and wasted by the time you get to 5000 where all your top power is. it'll have a better power band, NOT!!! lol these engines rev up to 7000 rpm easily remember.

when referring to my comments on previous posts - i was also making general statements. every header and manufacturer is different so you can only generalise. it's on your own back to do some testing and research after recieving some information.

ryan

[twilightprotege]

a 4-1 power band can be as wide as 4000rpm if the pipe ID and collector are designed correctly.

and there is no friggen way in hell a $400 4-2-1 is tuned for those rpm points....unless you can prove me wrong by answering the following (and then i'll work out if they are right) :

- how long are the primaries. all of them. they'll almost certainly be all different lengths
- how long are the secondaries. both of them.
- how do the collection points merge together?


anyway, my point was you CANNOT generalise with headers. no friggen way. i spose the same people that made you think that 4-2-1's are street and 4-1 is race also think you need backpressure in an exhaust system to make power too? there is just so much BS out there in the exhaust world. all by places like rob bliss, dodgy bob, right price (gav you cheapo) etc...all they are trying to do is sell you a product, and they'll do whatever and use whatever terminology they can to sell it to you.

i am however glad to see you have got a 4-1 as (obviously) i am a very strong believer in 4-1 headers. tell us more about them

[project.r.racing]

Originally Posted by twilightprotege

a 4-1 power band can be as wide as 4000rpm if the pipe ID and collector are designed correctly.

you'll need to move the radiator cos there ain't enough room in a astina engine bay for id piping and primaries shooting out 200mm before 1st bend to get that broad range, haha. but would like to see it done 1 day. you got something up your sleeve andy we don't know about?

Originally Posted by twilightprotege

obviously these are all general statements,

that's generalising andy.

i said 4-2-1 better for street. i didn't say prefect/right/best. maybe i shouldv'e said "normally better."

i do not believe in back pressure - a car that is breathing right doesn't need it at all.

no one made me believe anything about exhausts - but driving at an age of 11 and racing from 15 - 1st car was a 1100cc morris mini with 4-1 headers. since then there has been about 19 different na tuned race and rally cars that i've tested and driven in.

i learnt a few things along the way and found 4-1 tuned for high revs were slugs in the low revs - not bad for street, just uncomfortable to drive with.

personally i prefer 4-1 but i think for some street drivers it isn't the way to go.

for more info about exhaust andy - read 1st post mate, it'll give you some idea of what i'm trying to achieve.
to be honest - i'd luv to just shoot the 4 primaries out the side of the front bumper, but legally i can't. Sux to be environmentally friendly. lol

ryan

[project.r.racing]

Originally Posted by twilightprotege

- how long are the primaries. all of them. they'll almost certainly be all different lengths
- how long are the secondaries. both of them.
- how do the collection points merge together?

that would be interesting to know andy - i'll get back to ya when it's light and i can look under the bonnet.
i do know the merges are 15deg i think
id is 1 5/8 inches i think also.

ryan

[twilightprotege]

^ are you referring to your old 4-2-1 or new 4-1? i can work out either

merge - 15 degrees is the average. most use this and it only really changes when you want to amplify or widen the powerband. F1 cars use something crazy like a 45 degree merge collector to give an insane powerband increase, but only over a very short range (never seen figures, but rumoured to be less than 1000rpm "peak" powerband)