UMW Stage 2 OVERBOOST
09-28-2007, 05:43 AM
#46
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So we will be finally getting some numbers from a genuine stock 993GT2!! Excellent news. Phelix also has a boost sensor logged into the DL1 I believe, this will provide you with invaluable data and we can then extrapolate it all to HP and torque numbers.Looking forward to have some data from the recent stage 2 UMW setups here as well .
09-28-2007, 07:32 AM
#48
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Does anyone know the Porsche part number of the N75 or frequency valve ?. Sorry for my ignorance but I guess there are obviously two. Would they differ for the GT2 Evo ?. I did speak to Porsche OPC parts department yesterday and he did not have a clue as to what I was talking about.
Having been fairly gentle with the GT2 for a couple of hundred miles, last weekend gave me the opportunity to nail it a few times. She is incredibly fast. The car is totally factory standard even down to the exhaust system. What I did notice was say coming off a roundabout in third, lowish rpm foot in floor, boost comes in and she flies. Can't tell you at what revs to busy looking at the road. But for argument sake lets say at 2750rpm she's on full boost, at 4250 to 5000rpm the power dips like you have backed off the accelerator a little and then comes back on full power all the way to 6400rpm. The car does not misfire or appear to have a rattle (engine detonation). Having talked to Phelix on private message, he kindly will lend me a DL1 box in the future and suggests it is the N75 valve causing the problem. Are they easy to fit. I need to get the boost pressure checked to make sure she's not overboosting. A few years back I raced a narrow bodied 3.2 carrera chassis with a 930 turbo engine, 1100kg and a dynoed 420bhp at 1 bar. I reckon to get the acceleration as the GT2 I would have had to wind it to 1.2 bar. That said it could just be that the GT2Evo camshafts really work very well. Anyway better to be safe than sorry as they say, thanks for your help, regards, Graeme
Having been fairly gentle with the GT2 for a couple of hundred miles, last weekend gave me the opportunity to nail it a few times. She is incredibly fast. The car is totally factory standard even down to the exhaust system. What I did notice was say coming off a roundabout in third, lowish rpm foot in floor, boost comes in and she flies. Can't tell you at what revs to busy looking at the road. But for argument sake lets say at 2750rpm she's on full boost, at 4250 to 5000rpm the power dips like you have backed off the accelerator a little and then comes back on full power all the way to 6400rpm. The car does not misfire or appear to have a rattle (engine detonation). Having talked to Phelix on private message, he kindly will lend me a DL1 box in the future and suggests it is the N75 valve causing the problem. Are they easy to fit. I need to get the boost pressure checked to make sure she's not overboosting. A few years back I raced a narrow bodied 3.2 carrera chassis with a 930 turbo engine, 1100kg and a dynoed 420bhp at 1 bar. I reckon to get the acceleration as the GT2 I would have had to wind it to 1.2 bar. That said it could just be that the GT2Evo camshafts really work very well. Anyway better to be safe than sorry as they say, thanks for your help, regards, Graeme
From the stuff I can glean, the road EVO cars bore little relation to the racers which had a M64/83 engine designation. The original GT2 had engine designation M64/81 and the road GT2s had the turbos M64/60 engine.
Perhaps Graham, you could have a look which of the above codes your engine has ?
The road EVOs had to be road legal (obviously) and that was something Porsche took seriously so I am guessing they would have had just the M64/60 engine with the 450PS K24 kit fitted ie with no special camshafts or induction system or intercooler....
Graham, is there any chance you can take a photo of your intercooler, this (along with the engine designation) will determine what your engine is -there was a slightly bigger side to side I/C which the original GT2 racers (non EVO) used which may have been carried over to the road cars (but I doubt it since the induction system worked with TAG ECU and was in no way allowed for road use)
MY knowledge of the bigger intercooler dates back to this thread:
https://rennlist.com/forums/showthre...&highlight=evo
I was going to go with the new I/C and associated induction etc which by 2000 RS Tuning had working efficiently with a Motronic MAP system but was told by RS that the new I/C was no better than stock and I would not get past the ~530hp which they were getting in those days.
Back to Graham's dip in power between 4200 and 5000rpm -my guess is that this is a classic "Motronic dip" where the ECU lets the boost wind up to approach peak torque and then fumbles a bit when knock is first sensed at 4100rpm abruptly reducing timing and boost creating this type of dip before allowing the timing and boost to climb back up again to give you a smooth (powerful) ride to the limiter.
I have seen many of these types of Motronic power curves, if you look at MOD500s torque engine dyno sheet here, you can see a little dip at 4250 , which is the one described above, he then has one higher up but this is due to aggressive tuning with the ECU going "hunting" for knock
https://rennlist.com/forums/993-turbo-forum/242698-dyno-sheets.html
09-28-2007, 07:42 AM
#49
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Graham
Here is the 450PS Porsche engine dyno chart compared to the stock 408- the dip is hard to make out, but it is there. Does your motor seem to gain from 5750 to 6000rpm like the chart ?
It may well be that your engine has had some "alternative" ECU tuning over the years, and the chart below will not apply, but any ECU tuning may well accentuate the dip at 4200rpm.....
Here is the 450PS Porsche engine dyno chart compared to the stock 408- the dip is hard to make out, but it is there. Does your motor seem to gain from 5750 to 6000rpm like the chart ?
It may well be that your engine has had some "alternative" ECU tuning over the years, and the chart below will not apply, but any ECU tuning may well accentuate the dip at 4200rpm.....
09-28-2007, 01:18 PM
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Does anyone know the Porsche part number of the N75 or frequency valve ?. Sorry for my ignorance but I guess there are obviously two. Would they differ for the GT2 Evo ?. I did speak to Porsche OPC parts department yesterday and he did not have a clue as to what I was talking about.
Having been fairly gentle with the GT2 for a couple of hundred miles, last weekend gave me the opportunity to nail it a few times. She is incredibly fast. The car is totally factory standard even down to the exhaust system. What I did notice was say coming off a roundabout in third, lowish rpm foot in floor, boost comes in and she flies. Can't tell you at what revs to busy looking at the road. But for argument sake lets say at 2750rpm she's on full boost, at 4250 to 5000rpm the power dips like you have backed off the accelerator a little and then comes back on full power all the way to 6400rpm. The car does not misfire or appear to have a rattle (engine detonation). Having talked to Phelix on private message, he kindly will lend me a DL1 box in the future and suggests it is the N75 valve causing the problem. Are they easy to fit. I need to get the boost pressure checked to make sure she's not overboosting. A few years back I raced a narrow bodied 3.2 carrera chassis with a 930 turbo engine, 1100kg and a dynoed 420bhp at 1 bar. I reckon to get the acceleration as the GT2 I would have had to wind it to 1.2 bar. That said it could just be that the GT2Evo camshafts really work very well. Anyway better to be safe than sorry as they say, thanks for your help, regards, Graeme
Having been fairly gentle with the GT2 for a couple of hundred miles, last weekend gave me the opportunity to nail it a few times. She is incredibly fast. The car is totally factory standard even down to the exhaust system. What I did notice was say coming off a roundabout in third, lowish rpm foot in floor, boost comes in and she flies. Can't tell you at what revs to busy looking at the road. But for argument sake lets say at 2750rpm she's on full boost, at 4250 to 5000rpm the power dips like you have backed off the accelerator a little and then comes back on full power all the way to 6400rpm. The car does not misfire or appear to have a rattle (engine detonation). Having talked to Phelix on private message, he kindly will lend me a DL1 box in the future and suggests it is the N75 valve causing the problem. Are they easy to fit. I need to get the boost pressure checked to make sure she's not overboosting. A few years back I raced a narrow bodied 3.2 carrera chassis with a 930 turbo engine, 1100kg and a dynoed 420bhp at 1 bar. I reckon to get the acceleration as the GT2 I would have had to wind it to 1.2 bar. That said it could just be that the GT2Evo camshafts really work very well. Anyway better to be safe than sorry as they say, thanks for your help, regards, Graeme
09-28-2007, 06:12 PM
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Silly question, where do I find the engine code M64/60 ?. Andy at Fearnsport as part of the inspection checked out the ECU and it has never been played with. I can't talk specific revs as in 3rd your to busy looking at the road, by the time you change you are already above the dip and therefore 4th and 5th it's not there. The intercooler looks standard TT to me
09-29-2007, 02:52 AM
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Francis's GT2 from what I understand is perfect. It has done quite a few miles but the price that he is asking reflects this. Andy looks after the car and they are always maintained to the highest standard. I really do not know all the info but if you can afford it I would go for it. You won't loose money.
It is a M64/60 see below.
It is a M64/60 see below.
09-29-2007, 01:46 PM
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Graeme thanks for the pics - Your engine is normal 993tt with the factory 450PS kit as fitted to the Euro Turbo S models so K24 turbos, oil cooler and ECU.... This makes sense since for road going GT2s Porsche were not going to go to the trouble of developing another package and with the race GT2 MAP type induction system Porsche used the TAG ECU which was only really suitable for racing and not for road use, it was only after RS Tuning developed the Motronic 5.2 to work with said induction that the engine could be really civilised.
Does the power delivery feel like the curve above with that big surge at 5750rpm ?
Does the power delivery feel like the curve above with that big surge at 5750rpm ?
09-30-2007, 01:40 PM
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Took her for another spin today the holes got bigger. Now between 4000 and 5500 rpm. The 5750rpm push is now very noticeable. Will order the N75 tomorrow. From what Fearnsport tells me the EVO had different cylinder heads with high lift cams.
09-30-2007, 02:46 PM
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Hi Graeme,
It was the TAG based non street engine with larger intercooler and 465BHP restricted that had the higher lift cams and solid rockers. I need to check my GT2R manual but I believe that was also the same version that had the larger valve heads (certainly the EVO 3.8 twin plug race engine did). This engine is the same as the 993TT with larger KKK24-70 turbos.
It was the TAG based non street engine with larger intercooler and 465BHP restricted that had the higher lift cams and solid rockers. I need to check my GT2R manual but I believe that was also the same version that had the larger valve heads (certainly the EVO 3.8 twin plug race engine did). This engine is the same as the 993TT with larger KKK24-70 turbos.
