engineermike
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I had been interested in upgrading the HPFP on my Whipple 2018 GT for some time, but I could find very little information on it or anyone outside of a shop who’s installed one. I recently purchased one from 5 Star Tuning and installed it, so I thought I would put this out there in case anyone else was interested.
First off, the point of gdi is to reduce knock as a result of charge cooling from vaporization of fuel. Port injection mainly cools the metal surfaces but gdi cools the air more. This is what allows the gen3’s 1 number compression increase over gen2. The stock gen3 calibration runs 90% gdi and 10% port at wot and the stock High Pressure Fuel Pump is not far from max capacity. So, when boost is added, while you need MORE knock suppression, the capacity isn’t there and you wind up running only 60-65% gdi. The xdi HPFP45 has 45% more capacity than the stock pump so at 10-11 psi you can get back to the 90% gdi range like stock. Keep in mind that at 60% gdi you are still getting decent benefit from the gdi, just not all of it. Note that the benefits of running gdi over port are even more pronounced on e85 than gasoline, but there also isn’t as much need.
Installation: My kit didn’t come with instructions. I thought there just wasn’t any because the install seemed straight forward enough. I was wrong on both counts. It’s more complicated than it seemed at first. I contacted xdi and they emailed me instructions which are critical. You have to swap the #2 coil-on-plug with #3 coil-near-plug to make room for the pump. This also involves re-pinning the coil connectors and reversing polarity, which isn’t as hard as it sounds. I found it interesting that the #3 coil uses a different plug and polarity than the rest. If I could do it over I believe I would buy an additional coil-near-plug coil/wire and run that on both 2 and 3, which would take a little trimming with an xacto. As it’s installed, I don’t think you can remove the #3 coil without first removing the high pressure fuel line from the pump. ***Edit: see post #9 below***
Tuning: Understand that there are two aspects to the tuning. One is making the pump work, and the other is how you take advantage of it. If you use a tuner, my bet is that someone like Lund will handle both aspects. For mine, prior to the pump install, I had disabled knock advance for reasons that would take much longer to explain. I set it up such that the spark timing ramped up and it had knock retard in the middle of the power range. I could repeatably get 1.2-1.4 deg of knock retard right around 5000 rpm at 65% gdi blend on the stock pump.
Results: I made no other changes to the tune other those required and increasing gdi blend from 65% to 90%. It started and ran perfectly on the first try. I logged several full-throttle pulls and the duty cycle of the new fuel pump never exceeded 80%. I also got zero knock retard on any of the pulls, not even on any individual cylinder, so there is a definite improvement in knock suppression.
The next step will be to start adding spark timing (or boost) to find the new limit.
First off, the point of gdi is to reduce knock as a result of charge cooling from vaporization of fuel. Port injection mainly cools the metal surfaces but gdi cools the air more. This is what allows the gen3’s 1 number compression increase over gen2. The stock gen3 calibration runs 90% gdi and 10% port at wot and the stock High Pressure Fuel Pump is not far from max capacity. So, when boost is added, while you need MORE knock suppression, the capacity isn’t there and you wind up running only 60-65% gdi. The xdi HPFP45 has 45% more capacity than the stock pump so at 10-11 psi you can get back to the 90% gdi range like stock. Keep in mind that at 60% gdi you are still getting decent benefit from the gdi, just not all of it. Note that the benefits of running gdi over port are even more pronounced on e85 than gasoline, but there also isn’t as much need.
Installation: My kit didn’t come with instructions. I thought there just wasn’t any because the install seemed straight forward enough. I was wrong on both counts. It’s more complicated than it seemed at first. I contacted xdi and they emailed me instructions which are critical. You have to swap the #2 coil-on-plug with #3 coil-near-plug to make room for the pump. This also involves re-pinning the coil connectors and reversing polarity, which isn’t as hard as it sounds. I found it interesting that the #3 coil uses a different plug and polarity than the rest. If I could do it over I believe I would buy an additional coil-near-plug coil/wire and run that on both 2 and 3, which would take a little trimming with an xacto. As it’s installed, I don’t think you can remove the #3 coil without first removing the high pressure fuel line from the pump. ***Edit: see post #9 below***
Tuning: Understand that there are two aspects to the tuning. One is making the pump work, and the other is how you take advantage of it. If you use a tuner, my bet is that someone like Lund will handle both aspects. For mine, prior to the pump install, I had disabled knock advance for reasons that would take much longer to explain. I set it up such that the spark timing ramped up and it had knock retard in the middle of the power range. I could repeatably get 1.2-1.4 deg of knock retard right around 5000 rpm at 65% gdi blend on the stock pump.
Results: I made no other changes to the tune other those required and increasing gdi blend from 65% to 90%. It started and ran perfectly on the first try. I logged several full-throttle pulls and the duty cycle of the new fuel pump never exceeded 80%. I also got zero knock retard on any of the pulls, not even on any individual cylinder, so there is a definite improvement in knock suppression.
The next step will be to start adding spark timing (or boost) to find the new limit.
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