Engine Management - Very Odd Behaviour
- Thread starter Ian W
- Start date
Andy
Same as you - always Optimax - so in theory the DME should not be backing the timing off very much if at all.
It is my intention to delve into this whole issue much further. Last time my car was running 'badly' (about 300 miles after I'd reset the engine mangement and it had 'adapted' again) I took the car off to my local Porsche specialist who confirmed that there were no fault codes whatsoever. (They have the proper Porsche / Bosch tester). Yet resetting the DME once again brought about the usual perfomance increase. So it's not the electronics working around faults.
Next on my list is to get the car dyno'd before and after the reset and see if we can detect differences in lambda (mixture) values and recorded ignition timing. Once we know what is being altered it may be possible to track down why. As I said at the beginning of the thread, it's not just my car; my last one did exactly the same!
Just to clarify too, we're not talking about a small difference - I'd put money on there being a 20BHP increase after the reset. The difference in top end performace is not in any way subtle!!!
Are there any more owners out there who are willing to try this 2 minute reset? You'll be surprised (if not amazed) and it will confirm that it happens the same way across a number of vehicles. Meantime, I'll try to get a dyno session sorted and report back.
Ian W
Same as you - always Optimax - so in theory the DME should not be backing the timing off very much if at all.
It is my intention to delve into this whole issue much further. Last time my car was running 'badly' (about 300 miles after I'd reset the engine mangement and it had 'adapted' again) I took the car off to my local Porsche specialist who confirmed that there were no fault codes whatsoever. (They have the proper Porsche / Bosch tester). Yet resetting the DME once again brought about the usual perfomance increase. So it's not the electronics working around faults.
Next on my list is to get the car dyno'd before and after the reset and see if we can detect differences in lambda (mixture) values and recorded ignition timing. Once we know what is being altered it may be possible to track down why. As I said at the beginning of the thread, it's not just my car; my last one did exactly the same!
Just to clarify too, we're not talking about a small difference - I'd put money on there being a 20BHP increase after the reset. The difference in top end performace is not in any way subtle!!!
Are there any more owners out there who are willing to try this 2 minute reset? You'll be surprised (if not amazed) and it will confirm that it happens the same way across a number of vehicles. Meantime, I'll try to get a dyno session sorted and report back.
Ian W
Andyg400
Member
I have not tried this yet and it would be intersting to see a dyno of my car now. Especially since it has only really been run on optimax, then reset and dyno again to confirm your results. I have never noticed any change after a service, or after a number of RMS chnages, which I assume the battery would be disconnected.
I also note your car is a 3.6, mine is 3.4, was the other person's car also a 3.6.?
Has anybody tried this on a 3.4 car ?
Oh, my car is a fly by wire version on the throtle.
Thanks
Andy
I also note your car is a 3.6, mine is 3.4, was the other person's car also a 3.6.?
Has anybody tried this on a 3.4 car ?
Oh, my car is a fly by wire version on the throtle.
Thanks
Andy
The DME (engine control unit) adapts itself over a period of time to adjust the fuelling settings, based on the conditions, fuel quality, etc. By disconnecting the battery, it resets these adaption values to the factory default. Therefore, if it hasn't been done for a while, it can make a perceptible difference to the performance.
On cars with electronic throttle (eGas) it is not necessary to disconnect the battery. All you have to do is switch on the ignition, but don't start the car or touch the pedals, for 60 seconds. Then switch it off for at least 10 seconds. This resets the adaption values.
MY1998 and MY1999 C2's (up to August 1999 build date) and Mk1 GT3's have mechanical throttle, so you have to disconnect the battery. Everything else has eGas. To be sure, check the options sticker - M620=eGas.
If you have to disconnect the battery, put the key in the ignition and switch it on, but don't start the car. Switch off all loads, such as aircon, radio, etc. Leave the key in this position and disconnect the negative terminal. If you don't, the alarm siren will sound, as it has a backup battery inside.
Have fun!
On cars with electronic throttle (eGas) it is not necessary to disconnect the battery. All you have to do is switch on the ignition, but don't start the car or touch the pedals, for 60 seconds. Then switch it off for at least 10 seconds. This resets the adaption values.
MY1998 and MY1999 C2's (up to August 1999 build date) and Mk1 GT3's have mechanical throttle, so you have to disconnect the battery. Everything else has eGas. To be sure, check the options sticker - M620=eGas.
If you have to disconnect the battery, put the key in the ignition and switch it on, but don't start the car. Switch off all loads, such as aircon, radio, etc. Leave the key in this position and disconnect the negative terminal. If you don't, the alarm siren will sound, as it has a backup battery inside.
Have fun!
I followed the directions with the fuses last night....so it wasn't my imagination that it felt a bit perkier
glad there's a way to do it not using the battery/fuses, they were a right fiddle!is there anything similar on boxsters or even 993s? i have a couple of friends who might be interested to know!
Cheers,
Marco
Same process can be used for eGas Boxsters. I'm not 100% sure about 993s. IIRC there is a system adaption option on the PST2/PIWIS tester to reset the adaption values, so I don't know if a simple battery disconnect will do the job. UK 993 Carreras used Motronic v3.x DMEs, whereas early 996's used Motronic 5.2.2. It should work on a 993 Turbo, as that used Motronic 5.2.
I did this by accident at the weekend as I went out to programme the satnav then had to wait as she who must be obeyed still wasn't ready. Car felt particularly fine. Glad it wasn't just my imagination!
Posts made and opinions expressed are those of the individual forum members
Use of the Forum is subject to the Terms and Conditions
