Hitting the rev limiter?
03-01-2003, 10:22 PM
#16
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Car Info: 2000 2.5RS Silverthorn
Originally posted by msg101
Not trying to steal your thread, but I have a related question.
Redline in the WRX is 7,000, but my rev limiter doesn't cut in until 7,500. This usually only occurs when at the track, and I am unable to keep an eye on the tach. But it has happened a few times......
Should I be worried? I expect to install some type of shift light in my peripheral vision before track season starts. It's only 500 RPM, but it can't be good... Your thoughts/opinions?
FYI, no engine/ECU mods.
MSG
Not trying to steal your thread, but I have a related question.
Redline in the WRX is 7,000, but my rev limiter doesn't cut in until 7,500. This usually only occurs when at the track, and I am unable to keep an eye on the tach. But it has happened a few times......
Should I be worried? I expect to install some type of shift light in my peripheral vision before track season starts. It's only 500 RPM, but it can't be good... Your thoughts/opinions?
FYI, no engine/ECU mods.
MSG
Also, hitting the limiter is bad because it leans out the engine for a little. If it completley cut the fuel to the engine it would shut off there for it just limits how much fuel is being entered and there will be more air than fuel making it lean.
03-02-2003, 10:16 AM
#17
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Originally posted by scoobiesnacks
Redline and rev limiter are 2 different things. The redline is there to let you know you are at or near the rev limiter.
Also, hitting the limiter is bad because it leans out the engine for a little. If it completley cut the fuel to the engine it would shut off there for it just limits how much fuel is being entered and there will be more air than fuel making it lean.
Redline and rev limiter are 2 different things. The redline is there to let you know you are at or near the rev limiter.
Also, hitting the limiter is bad because it leans out the engine for a little. If it completley cut the fuel to the engine it would shut off there for it just limits how much fuel is being entered and there will be more air than fuel making it lean.
But don't you have it backwards? Isn't the rev limiter there to let you know you have hit the engine's redline/maximum recommended rev's?
What is the maximum RPM for a stock WRX? I assumed it was 7,000, and that Subaru would program the limiter to cut in at that engine speed. Is 7,500 O.K.?
03-06-2003, 05:51 AM
#18
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Here's a little tid bit for you, i found this @ www.rev-lite.com/flat.html bcs i'm setting up flat shifting on my car and launch control and wanted to learn more about it before doing it. So check out the site alot of good info such as this:
Why fuel and spark must BOTH be cut.
Old style spark only rev limiters where designed to operate on old fashioned carby and dizzy type engines. They operated by intermittently grounding the negative side of the single ignition coil to cut spark.
A rev limiter designed for a modern EFI motor needs to cover a few more bases.
1/ A spark only system on an EFI car will allow raw fuel straight through the engine and will rapidly contaminate the catalytic converter and destroy it. Excess fuel will also wash the bores and contaminate the engine oil system risking long term bottom end damage.
2/ Most modern EFI cars have multi coil ignition systems which bare no resemblance to old dizzy and points systems so you can't simply ground a coil to the same effect.
3/ A fuel cut only system runs the risk of leaving small amounts of fuel flowing through the engine which may ignite risking lean burn and engine damage.
The most effective and safest method of reducing power output independent of throttle position (i.e. WOT) is to stop fuel supply and simultaneously cut spark activity to eliminate any possible lean burns situations. On an EFI car, it's the only safe way of rev limiting.
Cheers,
Dave........................
Why fuel and spark must BOTH be cut.
Old style spark only rev limiters where designed to operate on old fashioned carby and dizzy type engines. They operated by intermittently grounding the negative side of the single ignition coil to cut spark.
A rev limiter designed for a modern EFI motor needs to cover a few more bases.
1/ A spark only system on an EFI car will allow raw fuel straight through the engine and will rapidly contaminate the catalytic converter and destroy it. Excess fuel will also wash the bores and contaminate the engine oil system risking long term bottom end damage.
2/ Most modern EFI cars have multi coil ignition systems which bare no resemblance to old dizzy and points systems so you can't simply ground a coil to the same effect.
3/ A fuel cut only system runs the risk of leaving small amounts of fuel flowing through the engine which may ignite risking lean burn and engine damage.
The most effective and safest method of reducing power output independent of throttle position (i.e. WOT) is to stop fuel supply and simultaneously cut spark activity to eliminate any possible lean burns situations. On an EFI car, it's the only safe way of rev limiting.
Cheers,
Dave........................
03-07-2003, 11:37 AM
#19
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Location: Bass Harbor, Maine
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Car Info: Impreza OBSTI Ver. V
thats exactly what i thought of dave! (of OakosAutomotive) its was scc that paul tracy did that. it was when scc and other car companies were given a civi si to mod within the boundries of the law(they all cheated BTW) and tracy decided instead of upshifting and downshifting he'd just peg it off the rev limiter a few times while making a turn. the funny thing is i did the same thing and when i read the article i sadi to myself i gotta stop doing that! next autocross...did the same thing ! its like being a crack addict, you know its wrong but you can't help yourself.
the thing that makes it justifyable(at least to me) is that it always seems hard to downshift to first when not going very slow or at least stopped. i dont know if its just my car but it always seems that downshifting to first ,even when its ok to do it rpm-wise, the car fights you too much, and you lose valuable seconds either fighting it or staying in second.
its like being a crack addict, you know its wrong but you can't help yourself.the thing that makes it justifyable(at least to me) is that it always seems hard to downshift to first when not going very slow or at least stopped. i dont know if its just my car but it always seems that downshifting to first ,even when its ok to do it rpm-wise, the car fights you too much, and you lose valuable seconds either fighting it or staying in second.
03-09-2003, 05:43 PM
#20
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I know what you meen i auto cross as well and i have the same problem some times getting into first gear but i find that doudle shifting works well to get it in fast. I have yet to get my Unichip set up for launch control and flat shift but it should be done mid April and i'm hoping that'll make a difference.....not with getting into first but with keeping the boost up between shifts, and i don't think i want to try to many lauches at 4000rpm on tarmac!!!
Dave...............
Dave...............
03-09-2003, 06:04 PM
#21
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Join Date: Nov 2002
Location: Bass Harbor, Maine
Posts: 41
Car Info: Impreza OBSTI Ver. V
double clutching..... i cant believe i never thought of that! of course next autocross i'll do just that. i(and more importantly..my car) thank you dave. i am already used to double clutching from 4th to 5th(seems to be a common prob) to avoid an annoying grinding sound so it should be no prob to do it autocrossing...thanx!
-Lou
-Lou
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