Nick Wong

The one thing you should be wary of is the ignition timing your ECU is pulling as your RPMs and boost increases. The more timing retard, the more heat generated, and I recall you had problems with high EGT levels. Pulling ignition is not the ideal way to control the combustion precisely because of this effect.

TB993tt

Not sure what you mean here ? are you referring to the chart above (showing the misfire ?) showing timing being pulled ? If yes then this has nothing to do with high EGT (no problems with these levels they are well controlled at 920c at full load 208mph modelled according to Durametric) or IAT in fact I have quite advanced timing even at the hottest 65c intake at 208mph I am still showing 17.25deg advance (see previous post for chart) which for a 997tt intake system tune is pretty advanced....
65c is not really a high IAT for these engines I recall TT Turbine sees much higher using his car in the middle eastern climate, they have the capability to work reliably with high IATs, just lose a bit of power..

Nick Wong

Yes, I was referring to the chart. Again, I am not an expert in Porsches so take my statements with a grain of salt. All I am saying is that if there is a misfire you should probably find the root of the cause rather than rely on the ignition retard because that adds to the problem. FYI Champion uses BBI coils on my car and I haven't had a misfire issue, perhaps you can ask RS to source a set of amplified coil packs for you?

TB993tt

Nick, I'll have a look into those coil packs thanks for the advice.

As part of this recent service I had the GT2RS front splitter replaced and was disappointed to see Porsche have put the price up to £250 (about $400 US), On further enquiries they have now put the price of the rear end GT2RS conversion, lights, RS rear PU, carbon inlays from the 1800 Euro I paid to 3800 Euro ( $5300 US) ex tax !!
I was warned this would happen once people started ordering this stuff up .

Nick Wong

How did you fit the front splitter? Did you also change the front bumper cover? I was told the GT2 and GT2RS covers were different and thus could not bolt on the splitter.

TB993tt

I didn't fit it personally but I did watch the first time

It simply bolts into the original splitter's place, no issues or new front bumpers needed....

avader906

It's unfortunate you didnt run additional logging. Note that durametric is not that great (in terms of resolution) if you run multiple traces - but fuelling is always important to trace. What ECU codes where reported when you brought the car in ?

There could of been errors in air mass calculations due to turbo intake and variocam at these RPMs - resulting in too advanced timing / too lean. It's pretty clear that intake runners got blown from backfire (the cause of that could be overboost which in itself could be due to incorrect ignition/boost tables or because of VTG control problems).

Leakdown shows that one cylinder tolerances have degraded - it's unusual given the milage - and confirms a problem exists. Did mechanic who done the leakdown mentione more details specific to that cylinder (where the leak).

If you can publish the pictures of plugs (and particular of that cylinder) - it might help to confirm pre-ignition/detonation.

Running colder plugs could help mask some of the problems in tuning/calculations - this is why you woud usually do it at the last resort and/or to build in some additional safety margin.

Nick Wong

Leakdown tests- Done hot or cold? Cold leak down tests are a waste of time.

What was the leak down result when delivered? Do you know from where it migrated? I'm not swayed one way or another to the reason why the manifolds failed, but I am of the opinion that if boost control is a problem everything else is magnified from there. Fix one thing at a time.

avader906

Nick, what do you specifically mean by "boost control" ? It's ECU > solenoid actuator > Vanes and for vac condition DVs. Actuators have can be re-calibrated (takes <2min) using PIWIS. Are you suggesting mechanical failure somewhere alone the chain due to low ambient temps ? Are you suggesting that electric solenoid actuator design is somehow flawed / not up to the task of controlling the vanes ?

TB993tt

What is interesting is that on the 993 turbo the same thing would happen with ECU controlled boost control, basically the boost will ramp up to peak torque and on a 3.8l RS Tuned 993 turbo with K24/26 the boost ramped up so rapidly if you hit the throttle too abruptly around peak torque and in cold weather the N75 valve could not dump the boost quickly enough and the torque limiter would kick in, it was more similar to a rev limiter than what I can get in the 997 but I wouldn't be surprise if what you describe above is happening and this boost control system of the VTGs is at its limit in terms of controlling rapid boost onset in an increased cubic capacity engine finely tuned for ultra response.

Not so much a "flawed" design but just outside its operating parameters ?

Nick Wong

I am hypothesizing that the displacement increase may be at or slightly above the limit of what the stock VTG diverter valves can control. What I believe I and TB are both hearing, the "shuffling" or surging diverter sounds, are the OEM valves that are popping open and shut more rapidly, but more coarsely, than before. A higher flowing valve with more finetuned control may be the answer, BUT again, this is merely a hypothesis (blanking off the OEM one and installing a more compatible one, whatever that may be). Champion is investigating my issue in conjunction with GIAC and hopefully they will have a solution if this deems to be a problem- at the moment, although it is an aural cacophony, the data logging they have recorded shows no instabilities.

TTurbine

Toby i too experianced the same thing on my 7GT2 last week, at 13deg ambient i felt that the car hit a limiter when the boost ramped up in 2nd gear.

TB993tt

Moe, interesting, is it a bit cooler than your "normal" conditions ? Will you try it in a higher gear, 4th or 5th, try and bring the torque in as abruptly as possible from 2500rpm....
You also have RS Tuning programming I think ?

TTurbine

Yeah It finnaly winter here RS 600ps program , i do recall last winter the same thing happened in 5th gear from 3k rpm
Will give it another try and see what happens

TTurbine

Toby , I just tried out my car , 15C ambient... 5th gear 2500 rpm.... At peak torque the cars ignition shut down... And went into limp mode.. I closed ignition and restarted the car tried it in from 2nd gear and ripped till 4th redline only thing is the 2nd gear limiter at peak torque.. It feels like TC but it isn't,,, I tried it from 4th gear at 2500 rpm and the limiter was present but more obvious than 2nd gear... For half a second or even less then revving till redline with no problems... Checked the car for any faults and it showed an overboost fault... I recall I had the same problem last year in winter annd thought it was due to bad fuel... I talked to a "tuner" and he told me it sounds like the ecu program is missing the overboost maps in conditions that it was not use to I.e cold weather.....

*Edit*

Otherwise the car runs totally fine from gear to gear unless i try to bring the torque abrubtly in 5th from 2xxx rpms.....