Rev Limiter kill switch/ working around the ecu, Adding variables to a factory ecu Options

[Agent21]

Ok so I know there is a happy little pulse width modulation signal that goes to the ECU to tell it how fast you are going. I have heard this is a purple wire with white tracers. I have heard you can cut this wire or add a chip to reduce the pulses and lie to the ecu. I know it triggers the cel but I have suspicions it throws the ECU into safety mode as well. Anyone got better info?

This post has been edited by Agent21: Nov 8, 2005 - 11:22 AM

[Supersprynt]

Tricking the ECU is a bad thing, why exactly do you wanna get rid of the limiter? Its there for the engines protection.

[Agent21]

Well #1 the race car is pegging at 7400 RPM and we need it to go higher. It bounces off the rev limiter on some of the longer tracks and we can't get another gear unless it is custom cut. #2 I want the ability to cut mine at will and really uncork the car.

[Kwanza26]

Well #1 the race car is pegging at 7400 RPM and we need it to go higher. It bounces off the rev limiter on some of the longer tracks and we can't get another gear unless it is custom cut.  #2 I want the ability to cut mine at will and really uncork the car.
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Why are you running a stock ECU on a race car? On a side note... get on a dyno. That'll let you know whether or not you need a higher rev limit.

This post has been edited by Kwanza26: Nov 6, 2005 - 5:06 PM

[Agent21]

We have to run it. We are in the factory fours division. Alot of our parts have to remain factory (the intake for instance). And we know we need to cut the rev limiter because we bounce off it half way down the back stretch at one of the 1/2 mile speedways and get very close to this on the 3/8 mile track. I just need to cut the sucker or modify it I don't need to get into why just how folks.

[Defgeph]

could you share your mods with us. Maybe some pics of your car.

[Agent21]

Well I don't have any pictures of it at the moment. It pretty much looks like a stock 86 coupe in retro TRD paint sceme. Minus the 4" nascar style spoiler on the back (no we really needed that other wise the car has wicked unpredictable over steer). The engine 3SGE 2nd gen has and has to remained fairly stock (for this season ideas in the works for next year) The intake and piping for it is still factory and has to remain that way, we even have to run a paper air filter. The exhaust is full straight pipe. Engine runs leaner then you can imagine. All accessories are off the motor minus the alternator. The Ecu needs to be worked with. Not just for this engine to get the air fuel and the timing more adjustable but also for the motor in the works. I have a 3sge ecu on the way to me so I can fiddle with it. But I need people who know the ecu a little better then me. This is the only front wheel drive circle track racing celica in the South Eastern US and possible the counry so it is very difficult to get data and we have had to do a lot of work blind. Please help. We got 5th in the Championship this year (the teams first full season) and the car is very good but needs to be faster.

[Defgeph]

Sound cool. I have a 3sge tranny in my swap. What ecu are you currently running ?

[Agent21]

Factory 87 3SGE

[Defgeph]

you might be able to find your answer at celicatech.com, they have a 4th gen section.


Good luck, and get some picsa up will ya !

DEF

[macavely]

for anyone that wants to disable the rev limiter and most other enigne safty fitures.. just hit your hazord lights ..

[Batman722]

check here

http://turbotrdcelica.proboards29.com/index.cgi

good luck

[soulshadow]

Its probbaly pretty good to do it for high revving engines, but for engines that run on VVT its a terrible idea cause thats wat tells the ECU to activate the VVT system.
So, bad for 4age ST and Beams engine.

[Kwanza26]

Just FYI... fuel cut defense or rev limiter removal is considered ECU modification... and isn't legal for stock classes... last I check at least. Anyway... there aren't a lot of easy ways to simply bypass the ecu rev limiter by jumping wires. Depends a lot on the ecu... but the rev limiters are sometimes hard coded and aren't determined by ignition outputs/inputs alone. FYI... for the swap guys that have run into wiring problems... it'll be the situation where you get a bad ignition signals and the ecu cuts out the engine at 4000 rpms... In other words... the ECU NEVER allows higher rpm cut out. If proper inputs for fuel cut function are missing or incorrect... the ecu cuts the fuel at low rpms.

This post has been edited by Kwanza26: Nov 7, 2005 - 11:14 PM

[Agent21]

Well legal is sorta a question we are raising. The guys with Carbs can rev their motors till they blow so why can't we? Last I heard from the MR2 guys the 4AGE can be altered be altering the clock crystals and the 5sfe can be altered by simply cutting said purple wire with white tracers. You pretty much brought up the same concern as I did earlier about the ECU going into safetly mode. Now in our case the only time we would be below I'd say 5000 rpm would be during pace laps and entering and exiting the pits which our heat races don't usually include unless something went BAD wrong. Really if I could change the clock rate of the ECU it would be near ideal. It would run the engine a little richer I believe because it will think the car is at a lower RPM then it really is. Taking that into consideration since we already need to run the car much richer we can then adjust with the right injectors. Now comes a really tricky part I know I can alter the timing slightly with the temp sensor by making it a variable resistor. Essentially raising or lowering the temp it thinks it is outside to advance or retard the timing HOWEVER we do need an correct reading for the actual gauge in the car to make sure we don't cook the engine. Really I know I am trying to do all this the hard way and an aftermarket management system is the way to go but really I got no choice and if I can get this to work there will be more Celicas on the circle tracks.

This post has been edited by Agent21: Nov 8, 2005 - 9:56 AM