Tell me about limp mode at the track

[Dave B]

So I know the car has issues with cooling at the track and it is possible that a vented hood and a PWR radiator may help but what I want to know is, what happens when the car goes in to limp mode.

1) does it suddenly lose power? If so, how much? i.e. does it make you unsafe until you can cool down?
2) do you get a dash light and if so what does it look like? Any warning before it triggers?
3) how long to get out of limp mode? Do you have to stop and let the engine cool or will it revert to normal within a lap or so?
4) what are the triggers? ( I know this is a tough one because there are likely a number of triggers and a true measure of oil temps is not one of them)

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[MisterC]

Don't run under half a tank! I started getting buck and fuel cut going into the back straight at mid ohio and had to pit due to fuel sloshing. Had to fill up and take a few laps around the paddock to settle it down.

 

[ayau]

1. Yes. How much power loss? Don't know. The ECU will pull timing and decrease boost to help protect the engine. There shouldn't be any permanent damage as long as you slow down and let it cool back down, e.g., cruise at 60mph in 6th gear to let allow plenty airflow through the engine bay.

2. Without any aftermarket gauges, watch the water temp gauge. As soon as you start seeing it go up, slow down and do cool down laps.

3. Don't know. Just continue to drive slow until you see the water gauge go back to normal.

4. A lot of variables that the ECU looks at. Probably a combination of coolant, exhaust gas temps, etc etc.

Crank up the heat to the max and run the fan on high. Watch for water temp gauge. Slow down when you start to see the needle climb.

 

[Dave B]

1) is there any warning light on the dash when in limp mode? Also how do you know when the ECU has returned to normal?

2) by pulling power, is it so drastic that it is unsafe to be on the race track with other cars? Can I go up a gear and tool around enough but still be fast enough in a corner to not surprise the folks behind me?

I have a new 2020 and have not experienced limp mode. Would be interesting to know if using a vented hood or bigger radiator alone is the best approach to prevent it (other than running a lower fuel level) or do you need both. The factory race cars obviously don't have AC but I am not prepared to remove that.

 

[ayau]

If there's a light, I would guess it would be some kind of check engine light. Maybe a boost reduction CEL? Haven't read too much into it, but your water temp gauge should be a clear indicator that you're overheating.

I don't think so much timing would be pulled that you become dangerous to be on track, but I'd pit as soon as you can and not go wide open throttle and stay off boost.

Nobody knows if you'll overheat or not. Too many variables. If you consistently overheat, then I don't think a vented hood and bigger radiator will be sufficient. It'll probably be a bunch of small changes to help control the heat, e.g., custom ducting, bigger grille, etc etc. There's no magic bullet solution.

 

[oceancamp]

So I know the car has issues with cooling at the track and it is possible that a vented hood and a PWR radiator may help but what I want to know is, what happens when the car goes in to limp mode.

1) does it suddenly lose power? If so, how much? i.e. does it make you unsafe until you can cool down?
2) do you get a dash light and if so what does it look like? Any warning before it triggers?
3) how long to get out of limp mode? Do you have to stop and let the engine cool or will it revert to normal within a lap or so?
4) what are the triggers? ( I know this is a tough one because there are likely a number of triggers and a true measure of oil temps is not one of them)

I’ve had the car go in limp mode on track due to fuel starvation a couple of times.
The dashboard lights up with check engine and just about every other check light there is. Speed is limited also (can’t remember if it’s 40 or 60 mph). In my experience it can be a bit dangerous if you’re caught off-guard. Just keep your tank more than a half full.
Regarding the cooling issue: I’ve reached very high ECTs on track. I’ve never had the car go into actual limp mode. Just very slow responding and fatigued. As some have said watch your coolant gauge. It’s not a big problem if it just started rising. It usually takes just a cooldown lap to make it go down again. You don’t want to pin it to the top of course.
Also do not start adding power (hondata, intercooler, etc) if you’re not prepared to spend a good amount of money on cooling mods.

 

[Dave B]

No, I will likely just keep stock power for now. Obviously more power means more heat which means less track time.

 

[goodvibes]

This is what I got the first time I tracked the car stock. The power loss varies, the first time it happened I lost power on were I could only go about 45-60mph at a very low rpm, but second time it just wouldn’t go pass 45mph. So is hard to know how much power the car will lose when on limb mode.

 

[Dave B]

How long did it take to clear?

 

[goodvibes]

How long did it take to clear?

First time about 20-30 minutes since it wasn’t as hot outside. But second time it took about 1 hour since the temperature was about 98 outside and water temps were very high. You can still do a cool down lap to lower the temps but that is as long as the car doesn’t lower the power as much.

 

[the8rotor]

No, I will likely just keep stock power for now. Obviously more power means more heat which means less track time.

I hope to have some good track info come September. I am keeping power completely stock EXCEPT a c&r intercooler.
Track mods:
-c&r race radiator
-c&r fmic
-'20 front grille
-HKS oil cooler
-mishimoto expansion tank
-first molding vented hood

I have zero intentions of ever turning the power wick up. I want a super reliable track car that is cheaper per weekend than my heavy muscle cars were. I will have more suspension mods, aero mods, etc., as I get comfortable with the stock suspension setup.

Thanks to a few members on here having early success with the c&r race radiator, I think a stock motor/tune should be fine for staying cool even in the Texas heat I track in.

 

[oceancamp]

How long did it take to clear?

The few times it happened to me I just connected an OBD2 dongle and cleared the codes. This is useful especially if you have to fill up the tank and don’t want to limp around.

 

[spyder57]

I hope to have some good track info come September. I am keeping power completely stock EXCEPT a c&r intercooler.
Track mods:
-c&r race radiator
-c&r fmic
-'20 front grille
-HKS oil cooler
-mishimoto expansion tank
-first molding vented hood

I have zero intentions of ever turning the power wick up. I want a super reliable track car that is cheaper per weekend than my heavy muscle cars were. I will have more suspension mods, aero mods, etc., as I get comfortable with the stock suspension setup.

Thanks to a few members on here having early success with the c&r race radiator, I think a stock motor/tune should be fine for staying cool even in the Texas heat I track in.

Sounds like you have a very reasonable strategy for being to run consistently at the track. Keep us posted on your results!

 

[Dave B]

The few times it happened to me I just connected an OBD2 dongle and cleared the codes. This is useful especially if you have to fill up the tank and don’t want to limp around.

That is good news. I would assume finishing the lap at low RPM and lots of airflow would help get back to better temps pretty quickly but if it can take an hour, I would sure like to erase the codes.

 

[the8rotor]

Sounds like you have a very reasonable strategy for being to run consistently at the track. Keep us posted on your results!

Will do. I should add, I think engine mods can be very reliable... I'm just too old to fart around with go-fast stuff ?. I got that out of my system a few cars ago.

I hope to hand my car over to an experienced factory Audi driver to really get some good data. My 100% is probably his 60% ?

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