K24 turbo lag
10-04-2005, 08:25 PM
#61
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TB, yes it is firing before the piston hits top-dead center..
I should explain it better I guess.. The stock ECU will not advance as high as a program that is written for 100 octane.. RS by giving you the octane in a can, enforces waht I said. Your power delivery is based alot on timing.
The actual map table does not allow for more than 8-10 degrees to save the engine if you have a dedicated high octane program.
This is NOT the case for programs written for 91-92-93 octane.. The advance will not go that high. The program can then pull timing to adjust for high knock counts.. I must state that we can't confuse wide open throttle map with 50% throttle or economy cruise maps.. This is a diiferent topic.
I should explain it better I guess.. The stock ECU will not advance as high as a program that is written for 100 octane.. RS by giving you the octane in a can, enforces waht I said. Your power delivery is based alot on timing.
The actual map table does not allow for more than 8-10 degrees to save the engine if you have a dedicated high octane program.
This is NOT the case for programs written for 91-92-93 octane.. The advance will not go that high. The program can then pull timing to adjust for high knock counts.. I must state that we can't confuse wide open throttle map with 50% throttle or economy cruise maps.. This is a diiferent topic.
10-05-2005, 12:11 AM
#63
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Don;
It is constant until you either have better fuel or lower cylinder head temps.. Now again this would be on race gas programs and WOT. Now in area's that have 91 octane, the timing is getting pulled but not to the extent of a race gas program.
It is constant until you either have better fuel or lower cylinder head temps.. Now again this would be on race gas programs and WOT. Now in area's that have 91 octane, the timing is getting pulled but not to the extent of a race gas program.
10-05-2005, 12:43 AM
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Kevin,
My question (and I think Don's) is: I feed your Stage 2 program 91 Octane and timing is pulled. Then I put 100 into the car, pretty much instantly raising the octane to 94-95+. How long does it take the ECU to figure out it has good gas and give back all the timing.
Also, does timing get pulled the same amount across the rev range or different amounts at different RPMs? My butt dyno says on 91 the power is noticably down below say 4200 RPMs, but less so as the revs climb. Or is that wishful thinking?
Greg H.
My question (and I think Don's) is: I feed your Stage 2 program 91 Octane and timing is pulled. Then I put 100 into the car, pretty much instantly raising the octane to 94-95+. How long does it take the ECU to figure out it has good gas and give back all the timing.
Also, does timing get pulled the same amount across the rev range or different amounts at different RPMs? My butt dyno says on 91 the power is noticably down below say 4200 RPMs, but less so as the revs climb. Or is that wishful thinking?
Greg H.
10-05-2005, 01:46 AM
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Greg;
Many people feel that as you increase RPM your need more fuel and engine dynamics as far as the combustion process increases.. Well that is not the case, Maximum and peak combustion pressure is at your max torque, so with good fuel the Stage 2's peak is at 4,620 RPM. Boost is increasing after this point, and max HP does come higher in the RPM range.. You feel the torque, kick in the pants.. To save the engine, the ECU is limiting it's peak torque.. you don't want detonation at max cyl pressures.
When you mix fuel the diffusion process is rather quick, your ECU is adaptive, it will take 20 miles if you have been driving for the last month in 91 octane mode.. This can swing the other way, by disconnecting your battery, and running the 100 octane.. The data that 91 octane has previously placed in the ECU isn't there..
Many people feel that as you increase RPM your need more fuel and engine dynamics as far as the combustion process increases.. Well that is not the case, Maximum and peak combustion pressure is at your max torque, so with good fuel the Stage 2's peak is at 4,620 RPM. Boost is increasing after this point, and max HP does come higher in the RPM range.. You feel the torque, kick in the pants.. To save the engine, the ECU is limiting it's peak torque.. you don't want detonation at max cyl pressures.
When you mix fuel the diffusion process is rather quick, your ECU is adaptive, it will take 20 miles if you have been driving for the last month in 91 octane mode.. This can swing the other way, by disconnecting your battery, and running the 100 octane.. The data that 91 octane has previously placed in the ECU isn't there..
10-05-2005, 02:53 AM
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Thanks Kevin. That makes sense: On 91 Octane, the car seems to have no power at low rpms, and then it comes on fairly late. Maybe like a bad set of K24s. 
So how long do I have to disconnect the battery to reset the ECU? If I go to the track and fill it with 100 then drive 20 miles - that's a full session before the car is up to full power. Hmmm, maybe that's a good thing.
Greg H.
So how long do I have to disconnect the battery to reset the ECU? If I go to the track and fill it with 100 then drive 20 miles - that's a full session before the car is up to full power. Hmmm, maybe that's a good thing.
Greg H.
10-05-2005, 07:17 AM
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Originally Posted by Greg H.
Thanks Kevin. That makes sense: On 91 Octane, the car seems to have no power at low rpms, and then it comes on fairly late. Maybe like a bad set of K24s.
So how long do I have to disconnect the battery to reset the ECU? If I go to the track and fill it with 100 then drive 20 miles - that's a full session before the car is up to full power. Hmmm, maybe that's a good thing.
Greg H.
So how long do I have to disconnect the battery to reset the ECU? If I go to the track and fill it with 100 then drive 20 miles - that's a full session before the car is up to full power. Hmmm, maybe that's a good thing.
Greg H.
10-05-2005, 01:06 PM
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Good info! Remember if you disconnect the battery, you lose your OBD2 readiness codes and it's real tough to get them back to pass your smog check.
10-05-2005, 05:04 PM
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Originally Posted by TB993tt
I would not get hung up on 20 miles - If you can do 4 or 5 runs up through 3rd or even better 4th/5th at WOT to maximum revs. My guess is that the ECU will have learnt and adapted by the 3rd run.
07-15-2023, 05:34 PM
#70
Marty
You have to keep in mind that this article is from 1998, therefore things have progressed quite a bit since then. I have not seen however any rocketship coming from PSI both on the 993TT and the 996TT front, other than the one-offs lightweight etc... Many of these houses (PSI, Roock, etc..) use the same ECU tuner, who is an independent.
I will translate some of the relevant parts:
Apparently “this engine was prepared by a guy called Christian Shumacher in Germany, who worked with PSI Motorsport as well. They commissioned the turbo work to a company called “Turbo Tap” in Germany,” which I have not heard of myself previously, but they seem to mention that “they are THE turbo gurus and leaders in Germany”. “They fitted K24s, that were modified with larger wastegates and they also wanted to reduce the turbo revs to around 120K RPMs vs. 180k RPMs in order to improve reliability and allow for overboost under WOT to 1.2 Bar spikes and 0.95 Bar steady state, same as what the factory did”. For that to happen , “they modified the compressor wings” (They could be mistaken here, I would have thought they modified the turbines instead to larger ones in order to reduce revs and backpressure?) and they “got a reading of 1.6Bar of backpressure as measured behind the racing cats cats, which is 0.1Bar more than the stock readings” (not very clear, as I would think it should be lower). They also “fitted an ECU with EFI origins” (it is not clear whether it is the Motronic or not, as the technical sheet at the end of the article says Motronic M5.2/EFI PSI Motorsport) that was prepared by a racing house in Italy that prepares the mapping for Sauber and Ferrari (TAG, or Thielert?).. They also fitted “GT2 racing cams (EVO?) with 1.6mm lift and mechanical lifters.” Other than that, “a 4 bar variable FPR, K&N filter and the likes”.
TB, I think you raise a good point about the RUF K16 turbos, Bill what have you got under the lid, those ain't the typical RUF K16s
You have to keep in mind that this article is from 1998, therefore things have progressed quite a bit since then. I have not seen however any rocketship coming from PSI both on the 993TT and the 996TT front, other than the one-offs lightweight etc... Many of these houses (PSI, Roock, etc..) use the same ECU tuner, who is an independent.
I will translate some of the relevant parts:
Apparently “this engine was prepared by a guy called Christian Shumacher in Germany, who worked with PSI Motorsport as well. They commissioned the turbo work to a company called “Turbo Tap” in Germany,” which I have not heard of myself previously, but they seem to mention that “they are THE turbo gurus and leaders in Germany”. “They fitted K24s, that were modified with larger wastegates and they also wanted to reduce the turbo revs to around 120K RPMs vs. 180k RPMs in order to improve reliability and allow for overboost under WOT to 1.2 Bar spikes and 0.95 Bar steady state, same as what the factory did”. For that to happen , “they modified the compressor wings” (They could be mistaken here, I would have thought they modified the turbines instead to larger ones in order to reduce revs and backpressure?) and they “got a reading of 1.6Bar of backpressure as measured behind the racing cats cats, which is 0.1Bar more than the stock readings” (not very clear, as I would think it should be lower). They also “fitted an ECU with EFI origins” (it is not clear whether it is the Motronic or not, as the technical sheet at the end of the article says Motronic M5.2/EFI PSI Motorsport) that was prepared by a racing house in Italy that prepares the mapping for Sauber and Ferrari (TAG, or Thielert?).. They also fitted “GT2 racing cams (EVO?) with 1.6mm lift and mechanical lifters.” Other than that, “a 4 bar variable FPR, K&N filter and the likes”.
TB, I think you raise a good point about the RUF K16 turbos, Bill what have you got under the lid, those ain't the typical RUF K16s
