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clord

Observation: EGas Shuts Throttle When...

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Interesting observation on the GT3. EGas shuts the engine throttle to idle (I think) when the brake is simultaneously applied beyond a minimum amount. I noticed this when trying to dry my brakes after a car wash. I was holding the throttle open a medium amount while applying the brake with my left foot to create a little heat in the brakes. Braking beyond a very light pedal would cause the engine to go to idle. I don't remember this effect in my '99 C4.

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This is a standard e-gas "feature". You can't left foot brake an e-gas car, including the TT, GT2, and GT3. I'm not sure of the logic, perhaps it is done for emissions purposes or for fuel mileage but they all work this way. That's why the Cup cars don't use e-gas.

Karl

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Correct me if i'm wrong but I think my 03 C2 has the same 'feature'. When I apply the brake and press on the accelerator for a quicker launch (TipTronic) the car loses all power. Didn't try too hard didn't want to brake anything.

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Correct me if i'm wrong but I think my 03 C2 has the same 'feature'. When I apply the brake and press on the accelerator for a quicker launch (TipTronic) the car loses all power. Didn't try too hard didn't want to brake anything.

Yup, all MY99 C4's (not C2's) had egas as well as all cars through current. So only MY99 C2's (and European GT3 mk1's) did not have egas.

Hehe... no egas for me :D

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I don't understand this. Surely you can blip to rev match a downshift while under braking. Can you not? Surely. Egas must disengage its throttle kill in certain situations.

Edited by mds

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Yes....you guys are right. I, too, can/have blipped the throttle for downshifts under braking, on the old '99C4 and on the new GT3. The eGas programming must be able to distinguish the two situations and allow blips. Interesting......

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There is no load on the engine when heel toeing and the Motronic must recognize this. Try the same excercise without the tranny in neutral and see what happens.

Karl

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I think the clutch is the difference. You can heel & toe cause the clutch is in, you can't dry your brakes cause the clutch is out.

I agree, when the clutch is depressed, you can brake hard and gas it at the same time with no problem.

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I think it was Karl who posted this somewhere, but, I tried yesterday and it works. If you are on the gas, and press the brakes with your left foot, after a short delay, the throttle will drop to idle no matter the accel pedal position... BUT, if you release the accel pedal and get right back on it while still left foot braking, the throttle will now stay open and you can drag the brakes. It may not be what you want to be thinking about and doing on the track, but, you can, at least, dry your brakes after a car wash. Again, all this does NOT interfere with throttle blipping to match revs/double clutch while braking.

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There are two switches connected to the clutch pedal, one opens when the pedal is first pressed, the other closes when the pedal is fully pressed. I tried defeating each of these switches individually, and then both together, hoping to defeat the throttle cutoff on left foot braking, but was unsuccessful. I am surprised since clutch position appears to be a factor. Maybe there is another switch hidden somewhere. Or maybe Karl is right and the ECU is looking at engine loading and not pedal positions. I hope to find a wiring diagram and look into this more. It may also be possible to tweak the brake pedal wiring somehow. Any suggestions?

Edited by mds

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It is possible to enable left foot braking by playing with the brake pedal switch!!!

There are three wires connected to three of the terminals of the brake pedal switch connector. I will call these terminals bottom, side and top. Releasing the brake pedal shorts the bottom and side terminals. Pressing the brake pedal shorts the bottom and top terminals.

The first experiment I tried was to disconnect the connector and short the bottom and side terminals of the connector with a piece of wire. This simulates a permanent brake pedal released condition. Left foot braking is possible now! But of course the rear brake light stays out.

The second experiment was to remove the wire shorting the bottom and side terminals. In other words, the situation here is that the connector is simply unplugged. No other change. Left foot braking is still possible! I was surprised by this result. Of course, still no rear brake light.

My third experiment was to short the bottom and top terminals, to simulate a permanent brake pedal pressed condition. The rear brake light is now on always. And left foot braking is still possible! I was again surprised.

Between all of these experiments the car was turned off with the key removed.

So, for track driving in situations where you think you don't need a rear brake light, simply remove the connector.

In cases where you really do want the rear brake light, I do not have a solution. However, I have a suspicion that if you leave the connector connected and cut the side wire, you may get everything you want. I am trying to figure out how to remove the terminal from the connector without cutting the wire, but so far no luck.

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I'm still stumped. I still have not been able to get both LFB and the brake lights working simultaneously. Also, I discovered that playing with the pedal wiring may interfer with proper ABS operation. The workshop manual wiring diagrams so far are not too helpful but I need to study them more.

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I discovered today while playing with LFB that when you go to the brakes while holding the gas you have about 1.5 seconds before the throttle is cut. This doesn't sound like much time, but it does seem to be enough to complete a smooth transition from gas to brake. So maybe this gas cutoff thing is not a big issue after all???

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Another comment. Once you've completed the LFB gas to brake transition within 1.5 seconds, the brake is still pressed and the gas is completely released. Now you can continue to LFB and transition back to the gas with the brake still pressed with no restriction. There is no further gas cutoff even though you are still braking.

So I've concluded that you actually can left foot brake without an issue in any reasonably typical driving situation. You can transition smoothly from the gas to the brake and then back to the gas, the only restriction being the first transition must be completed within 1.5 seconds.

Edited by mds

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hey all,

just bring up an old theme and here is my question:

if the E-Gas shuts down the throttel and goes back to idle and if your idle gas is to low, could the engine die?

and what should idle rpm be around?

mine runs around 600 rpm (warm condition), is it to low?

cause, it happend 3 times that the engine died on me when I made a brake, with the clutch down of course when braking.

at first I thought I had same low/bad fuel (1/4 tank) but then it happend again at 3/4 and reasonable fuel quality so my idea was maybe this could be that the idle gas was to low.

any idea what this could be?

cheers,

Tony

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hey Mike,

that has cross my mind, could a test with a fuel cleaner fluid help?

I mean instead going to the dealer, cause it happend only 3 time until now and it is really hard to re-produce it.

But could they check that with the PST2 device?

cheers,

Tony

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I don't understand this. Surely you can blip to rev match a downshift while under braking. Can you not? Surely. Egas must disengage its throttle kill in certain situations.

You can blip under braking when the clutch is in preparing for the down shift...

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