heavy boost drop off.
04-02-2005, 07:42 PM
#31
Race Director
"Therefore, what that means is, that the turbo is running out of steam."
TurboTommy's got the right idea. I think Bengt also did some calculations on this as well. Here's some dyno-test results I got using an AVC-R about 3 years ago to squeeze as much power out of the K26/6 as possible. The configuration I used:
- GURU MAP-1.5 (development model)
- stock shimmed wastegate by 7mm (also tried Deltagate and 38mm Tial)
- Apexi AVC-R EBC
I used the baseline MAP-2 chart presented here as a test control. That dyno-run as generated using a stock 7mm shimmed wastegate and a pressure-regulator MBC. Peak of 303 lb*ft was made at roughly the same spot as peak-torque in the mid-range. Boost dropped from 15.69psi peak down to 13.33psi by redline. RESULT: 261rwhp & 303 lb*ft TQ.
1. TEST-CONFIG#1: I installed an AVC-R and set max-boost at 15psi and programmed in a flat-boost curve by varying the duty-cycle vs. RPM.
Results: 265rwhp & 305lb*ft torque, not much different with a flat boost-curve
2. TEST-CONFIG#2: re-adjusted the AVC-R for max-boost of 18psi flat, this is the configuration I used to develop the version-9 18psi chips.
Results: 270rwhp & 330lb*ft torque, big increase in mid-range torque, but HP didn't change much
3. TEST-CONFIG#3: re-adjusted AVC-R for rising boost-curve of 18psi in mid-range up to 21psi by redline. Interesting thing was that I did not have to re-program high-RPM fuel very much to compensate for the rising boost-curve.
Results: 271rwhp & 328lb*ft torque, not much different than 18psi flat boost
4. TEST-CONFIG#4: installed Deltagate, 18psi->21psi boost-curve
RESULT: 269rwhp & 329lb*ft torque, no change
5. TEST-CONFIG#5: installed Tial 38mm with 0.85-bar spring, 18psi->21psi bosot-curve
RESULT: 271rwhp & 327lb*ft torque, no change
I think these experiments showed that total flow from the K26/6 is limited, regardless of max-boost levels. It just heats up the air more and increases its volume and the resulting boost, but actual mass flowed (numbers of oxygen molecules) isn't improved that much. The rubber hose coming out of the turbo was burned to a crisp and I would highly recommend hard-pipes instead if you're going to be using more than 18psi of actual boost at high-RPM on a K26/6. This was on this specific turbo only and a couple of weeks later, it self-destructed with a bent-axle. Timm Baldaulf in NY also recent shattered a k26/8 trying to squeeze as much boost from it as possible.
"and some will say a k26 can hold 25 psi to redline,"
This CAN be done.. but not with the configuration you have. I first tried it with a pressure-regulator **** MBC and I would have one hand on it while doing an acceleration run. As RPMs increased, I would dial in more and more boost to compensate for the drop. At a certain point, even with the controller cranked to full boost (no pressure going to wastegate), it could only muster 17psi at redline.
Then I shimmed the wastegate even more to 10mm and installed a 2x stiffer spring. Changed over to a check-valve MBC and set for 20psi max-boost, but it dropped to 18psi by redline.
Laust's car is the only one I know of that can hold 25psi and water-injection is used to prevent blowing up the motor. There's mechanical mods to the wastegate (a servo-feedback loop) that uses exhaust-pressure to clamp shut the wastegate at high-RPM. This is that cancels the opening at high-RPM to maintain 25psi flat-boost. The heat was intense enough to melt airbox cover where it touches the intercooler. But... we haven't dyno-tested this configuration yet
I wouldn't worry about flat-boost so much on a K26/6, even if you can force it to hold 18psi flat, it won't give you much more HP, but the mid-range torque is thrilling. A k26/8 would be a better option for 18psi flat-boost, numerous people have gotten 300-310rwhp out of it without any problems.
TurboTommy's got the right idea. I think Bengt also did some calculations on this as well. Here's some dyno-test results I got using an AVC-R about 3 years ago to squeeze as much power out of the K26/6 as possible. The configuration I used:
- GURU MAP-1.5 (development model)
- stock shimmed wastegate by 7mm (also tried Deltagate and 38mm Tial)
- Apexi AVC-R EBC
I used the baseline MAP-2 chart presented here as a test control. That dyno-run as generated using a stock 7mm shimmed wastegate and a pressure-regulator MBC. Peak of 303 lb*ft was made at roughly the same spot as peak-torque in the mid-range. Boost dropped from 15.69psi peak down to 13.33psi by redline. RESULT: 261rwhp & 303 lb*ft TQ.
1. TEST-CONFIG#1: I installed an AVC-R and set max-boost at 15psi and programmed in a flat-boost curve by varying the duty-cycle vs. RPM.
Results: 265rwhp & 305lb*ft torque, not much different with a flat boost-curve
2. TEST-CONFIG#2: re-adjusted the AVC-R for max-boost of 18psi flat, this is the configuration I used to develop the version-9 18psi chips.
Results: 270rwhp & 330lb*ft torque, big increase in mid-range torque, but HP didn't change much
3. TEST-CONFIG#3: re-adjusted AVC-R for rising boost-curve of 18psi in mid-range up to 21psi by redline. Interesting thing was that I did not have to re-program high-RPM fuel very much to compensate for the rising boost-curve.
Results: 271rwhp & 328lb*ft torque, not much different than 18psi flat boost
4. TEST-CONFIG#4: installed Deltagate, 18psi->21psi boost-curve
RESULT: 269rwhp & 329lb*ft torque, no change
5. TEST-CONFIG#5: installed Tial 38mm with 0.85-bar spring, 18psi->21psi bosot-curve
RESULT: 271rwhp & 327lb*ft torque, no change
I think these experiments showed that total flow from the K26/6 is limited, regardless of max-boost levels. It just heats up the air more and increases its volume and the resulting boost, but actual mass flowed (numbers of oxygen molecules) isn't improved that much. The rubber hose coming out of the turbo was burned to a crisp and I would highly recommend hard-pipes instead if you're going to be using more than 18psi of actual boost at high-RPM on a K26/6. This was on this specific turbo only and a couple of weeks later, it self-destructed with a bent-axle. Timm Baldaulf in NY also recent shattered a k26/8 trying to squeeze as much boost from it as possible.
"and some will say a k26 can hold 25 psi to redline,"
This CAN be done.. but not with the configuration you have. I first tried it with a pressure-regulator **** MBC and I would have one hand on it while doing an acceleration run. As RPMs increased, I would dial in more and more boost to compensate for the drop. At a certain point, even with the controller cranked to full boost (no pressure going to wastegate), it could only muster 17psi at redline.
Then I shimmed the wastegate even more to 10mm and installed a 2x stiffer spring. Changed over to a check-valve MBC and set for 20psi max-boost, but it dropped to 18psi by redline.
Laust's car is the only one I know of that can hold 25psi and water-injection is used to prevent blowing up the motor. There's mechanical mods to the wastegate (a servo-feedback loop) that uses exhaust-pressure to clamp shut the wastegate at high-RPM. This is that cancels the opening at high-RPM to maintain 25psi flat-boost. The heat was intense enough to melt airbox cover where it touches the intercooler. But... we haven't dyno-tested this configuration yet
I wouldn't worry about flat-boost so much on a K26/6, even if you can force it to hold 18psi flat, it won't give you much more HP, but the mid-range torque is thrilling. A k26/8 would be a better option for 18psi flat-boost, numerous people have gotten 300-310rwhp out of it without any problems.
04-02-2005, 08:00 PM
#32
Nordschleife Master
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Danno, would I benefit from shimming this wastegate? or using a stiffer spring, just to pull a bit more torque out of it. Would I see any benefits from getting MAF right now, or is it pretty much maxed out, and a maf wont do much? The plan is for a larger turbo, but I'd like to concentrate on other things first.
~Eyal
~Eyal
04-02-2005, 09:13 PM
#33
Race Director
"Danno, would I benefit from shimming this wastegate? or using a stiffer spring, just to pull a bit more torque out of it. Would I see any benefits from getting MAF right now, or is it pretty much maxed out, and a maf wont do much."
We would need to put your car on a dyno first to get it fine-tuned in its current configuration. There are so many changes made to your car and we never got it squared away, operating at 100% in stock trim anyway (which is what your chips are mapped for). So.. we should take each step carefully and fully optimize each one. MAF should be done after getting your current configuration fully dialed in. On a K26/6, you can expect a +30-40hp and 20-30lb*ft increase with a MAF upgrade.
We would need to put your car on a dyno first to get it fine-tuned in its current configuration. There are so many changes made to your car and we never got it squared away, operating at 100% in stock trim anyway (which is what your chips are mapped for). So.. we should take each step carefully and fully optimize each one. MAF should be done after getting your current configuration fully dialed in. On a K26/6, you can expect a +30-40hp and 20-30lb*ft increase with a MAF upgrade.
04-02-2005, 09:47 PM
#34
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Danno, I just bought a usb to serial adapter, so I'll get some datalogs of some WOT runs. Would you like me to email them to you and get the fine tuned chips done, or do you want to see how it runs in person?
~Eyal
~Eyal
