Hi,

I have a very frustrating issue and need some help! I have a 997 2S with the following modifications:

Full Kline exhaust including headers and 200CEL cats
Gruppe M carbon fibre induction system
Remap

Whist on a track day the first lap it performs extremely well, but then it started to loose power at around 6000RPM in every gear.

I had my passenger look at some live data and even though my pedal position stayed at 100% the actual throttle position was reducing to around 45%

I fitted a GT3 throttle body and IPD plenum before the track day and was seeing this issue all the time, I fitted a new MAF in case that was the issue but it was still doing the same and backing off the throttle (45%) at around 5800RPM.

I thought that it must be the GT3 throttle body that was the issue so returned it back to the standard throttle body and plenum for the track day - on the road it felt perfect no power loss. However as explained on the track day it started to do the exact same as when the GT3 throttle body and IPD plenum was fitted - backing off the throttle to 45% at around 6000RPM!

No stored fault codes, no engine lights - nothing to suggest what the issue is.

Could it be the engine map? Or a sensor?

Its infuriating and really frustrating, please help!

 

You have the word 'remap' up there. Is that an ECU flash? If so, that is probably your problem of this is occurring at the same RPM in every gear. You may be running too lean. Not seeing your map, that's my best guess.

 

Hi,

Thank you for your reply, yes an ECU flash is what it has had - I would completely agree but can't understand why the issue wouldn't be felt on the road?

Thanks again

 

Might be a high pressure fuel pump. That would be my second guess. The ECU compensating for less available fuel would close the throttle. It might only be on the track since the fuel pump is pushed hard for that short time. Have you checked for error codes via Durametric?

 

That is a good point - there are no fault codes present. Is there any live data fuel pressure channels I can reliably look at to see what the fuel pressure is doing when it reduces the throttle?

 

Yes there are but you will need a PIWIS for that.

 

I have another cable and software that may have the parameter, can you advise what the channel names are?

 

Yes agreed - is there just one fuel pump that is on the top of the tank? Will it need an uprated one or just a new standard one?

Im still struggling to understand why the fuel pump would perform fine on the road and not on the track but I guess you are demanding full throttle a lot more on the track.

Some suggested reliable parameter names for fuel pressure and also expected values would be greatly appreciated.

Thanks for your help guys!

 

HPFP was a recall item on '09's.

 

Yea they are DFI direct injection though so I think it has different fuel pumps

 

This is the part you're probably going to have to pay for. I wouldn't give this out for free but you never know I guess. Just wanted to help set expectations for you getting this info.

 

When you say it did not do it while you were driving on the street, are able to maintain 6K RPM for as long a period as you are on the track? I ask because I have seen drive by wire systems do this kind of thing before especially when the car has gone past full power.

 

The assessment on the street was a few wide open throttle pulls in 3rd and 4th gear from around 3000RPM.

On the track the revs stayed higher all of the time in order to get the most out of the vehicle.

That;s a very interesting point - is there any way of performing a test on the drive by wire system?

I conducted some stationary tests just with the ignition on (Engine not running) maintaining 100% throttle - the throttle body stayed at 100% the whole time but I understand this test is completely different compared to when the engine is running and in gear.

 

Here is the problem with all the electronics in modern cars, it is very hard to determine what is causing what. One thing you could try is a throttle controller like the Sprint Booster, it might help, and it will make the car feel more responsive as well. I despise drive by wire systems and have some sort of throttle controller in every car I drive. Even my girlfriend has one in her GL550 that thing has terrible throttle delay. I cannot say it will solve the problem, but putting one in will not hurt the car and they do have 30 day return policy. You might want to see if Pedal Commander makes one for your car they have multiple adjustments. Good luck

 

Have you tried a throttle adaptation with the GT3 throttle body on? Requires adaptation anytime it's removed and put back on. It can be done with some aftermarket scanners, but more efficiently with the PIWIS tester. It will not set faults, but essentially the throttle is not calibrated.