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27-07-2010, 10:26 PM | #1 |
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Redline Question
Just wondering if anyone can explain why there is such a sudden loss of power after the revs pass the redline? Is this something to prevent damage/wear in the engine or what?
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27-07-2010, 10:33 PM | #2 |
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Um, how are you suppose to go past a redline?
Remember VICS opens up around 5.5k, and is only open for 500rpm finishing @ 6k rpm, so there is no need to rev past this, its just pointless revving... i cant explain much more then that im afraid as I have been running without VICS for 3yrs come next friday, and it still hurts to read that thread 3yrs on
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28-07-2010, 07:17 AM | #3 |
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I tried it yesterday, not something I usually do, and the car went all the way to 7k before I let off the accelerator. It kept pulling all the way to 6750 which is just after redline at 6.5k. Then there was a complete drop in acceleration but the revs seemed to keep climbing.
Maybe it was the VICS closing??? Also I thought the VICS opened gradually but I can tell exactly when it opens (almost like VTEC yo!) |
28-07-2010, 07:25 AM | #4 |
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it's just the engine reaching it's max potential. after a certain rpm range, not enough fuel and air can be pushed into it fast enough.
if a car has a 6000rpm redline, you'll find it will have the same power output at 6500 and 5000rpm. (roughly speaking). |
28-07-2010, 08:50 AM | #5 |
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Now I'm not sure about the stock ECU's but on the Microtech there are 'soft' and 'hard' rev limits. From my understanding, if you stomp on the accelerator you can rev the car through the 'soft' rev limit and right up to the 'hard' rev limit. This might be something that the stock ECU does as well.
Also remember that the rev needle takes a fraction of a second to react to the signals it is receiving - so it is possible that the needle's momentum showed the engine rev'ing at a speed it actually wasn't. Oh, and the loss of power is probably the engine shutting off the injectors and possibly a few other things in an attempt to protect itself. The FS-DE has been run upwards of 9,000 rpm so there is a lot more left in terms of revs there. The engine won't last very long at those rev's but it is physically possible.
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28-07-2010, 09:42 AM | #6 |
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and to give you an unserstanding of real time rpm, I have seen my car go to 6790rpm, as seen on the scangauge...
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28-07-2010, 09:57 AM | #7 |
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So if you were at the drags, in a stock BA 1.8 astina, you probably going to get a lesser time revving to the redline point, rather than shifting at 6000rpm?
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28-07-2010, 10:08 AM | #8 | |
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28-07-2010, 10:38 AM | #9 |
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That'd be different, you'd be wanting to find the 'sweet spot' in the torque range, there'd be no point going that far.
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28-07-2010, 10:55 AM | #10 | |
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you are potienally going to do big damage head, valves, pistons |
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28-07-2010, 11:28 AM | #11 | |
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Quote:
modified ba astinas could potentially go past 6000rpm as the mod have made the max power rpm to be higher. beather better, more fuel etc. i do not know what rpm my max power is, but when i'm at Lakeside Raceway going down the main straight (500m-ish) i either:- shift @ 6,000rpm = 150kph @ the end. shift @ 6,500rpm = 160kph @ the end. shift @ 7,000rpm = 160kph @ the end. no change between 6,500-7,000rpm, so i got max power somewhere in there... last event, i couldn't get past 155kph, as i was running my street 18 inch heavy big diameter rims. Last edited by project.r.racing; 28-07-2010 at 11:32 AM. |
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28-07-2010, 11:34 AM | #12 |
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As Ryan said the redline is maximum power and then Mazda engineer the engine to work safely within that limit. I've put B spec cams in my BA and it pulls hard to 7,000rpm and possably further (don't know I may have been traveling a little too fast and had to back off).
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28-07-2010, 11:41 AM | #13 |
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Well you could rev the engine a bit past max power so that when you shift, you fall back onto the top part of the powerband again.
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28-07-2010, 11:48 AM | #14 | |
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28-07-2010, 09:37 PM | #15 |
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Almost, but the revs didn't climb any faster, seemed a little unusual, i expected the car to lose power more gradually.
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28-07-2010, 09:42 PM | #16 | |
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projects explanation of getting the fuel/air into the cylinder fast enough makes sense to me, also it pulling past redline might've been because of an inaccuracy/delay in the tacho as orion said |
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28-07-2010, 10:09 PM | #17 |
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Could be fuel cut, if i hit ~6900 rpm (by accident) i get fuel cut which results in dramatic loss of acceleration.
And in regards to acceleration, you still accelerate at higher rpms, to work out whether its worth shifting early depends on you gearbox and the ratios of each of the gears in question.
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30-07-2010, 06:18 AM | #18 |
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There is a rev limiter in place on the SP20 at 7000 rpm a lot of cars use a limiter to try and safe guard the engine. My Corolla SX hatch with the 4age redlined @ 7700 rpm and would go to 8000 rpm when the limiter would cut in.
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30-07-2010, 07:38 AM | #19 |
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yeah thought that would be the case, although my foot was well off the accelerator when it hit 7000rpm lol
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30-07-2010, 01:52 PM | #20 |
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Cars dont accelerate by themselves Remember most gauges are laggy.
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