E85 Discussion - HPFP lubrication and Flow issues

[phate]

Well, E85 is something we all hear about, but is something a bit unproven in the MS3/MS6 platform. I ran a 50% ethanol mix for a while, and then tried straight E85. The 50% mix ran very well, with almost no degradation of mileage. Once the fueling was optimized and the required load curve updated (due to MAF scaling), the car pulled just a little bit harder than what it has before, but at ~3lbs less boost, and 1* extra timing compared to the 93octane tune.

So, after a little bit of tweaking of my 50/50 tune, I decided to try out some straight E85. I bumped up the MAF curve just a little bit (~10%), and ran a MAF cal. MAF calibration run is here (2nd gear):



As you can see, most of the curve is pretty good at about -3%, and the top end is about +11%. Not bad for a guess. I could see that fueling wasn't too far off, and the ECU was able to adjust with the trims after ~30 miles of driving. I decided to brake boost just a touch to throw it into open loop (at 1.10 load), in 2nd gear. The car seemed to jump into open loop with ~11:1 AFR. Again, not bad for a first attempt.

____________________

So I log a quick 2nd gear run and an attempted 4th gear log, to get more resolution of what the car is actually doing. 2nd gear log seemed fine, AFR's in check. The 4th gear run, about 20 seconds later, is where the problem seems to start. As you can see in the following graph, my fuel pressure starts to dip like crazy in decel after the 4th gear run (which i ended early due to the AFR's climbing into the 13's):



____________________

I could only view the AFR via my AP, so I stopped the 4th gear pulls when I noticed ~13:1 AFR. I figured this was just my MAF curve needing some tweaking. So I turn off the data log, and drive ~1/2 of a mile. The car started to act like it didn't want to accelerate, so I flipped on the data logger on the ~9 minute drive home. At this point, I flipped the AP over to fuel pressure and noticed that it was wwaaaayyy low. Around 60psi cruising, with two points of higher pressure. Unfortunately, I think this was my fuel pump dying As you can see in the next graph of the drive home, my fuel pressure is pretty screwed:



Soooo, my fuel pump is an aftermarket rebuild. I'm going to check tomorrow about this whole issue. Hopefully we can work something out. My plan is to tear down the HPFP tomorrow night. Maybe we'll see some tell-tale signs.

I have read about ethanol being suspect in many HPFP failures in other platforms (primarily BMW's), but nothing is really proven. I have had my car for just over two years and have run ethanol enriched fuels the entire time. I rebuilt the fuel pump about 6 months ago, and it has run very well since. I am running stock turbo and it was completely maxed before running e85, which somehow lowered my boost after adjusting my MAF curve. I think it would be wise to run some kind of extra fuel lubricant if you plan to run high ethanol contents - Marvel Mystery Oil seems to be mentioned in many places.

____________________
____________________

Of importance to the big turbo guys is the injector duty cycle. I am running a stock turbo, and this quick blip in 2nd and 4th gear that I logged shows some pretty high duty cycle. I am running the CPe CAI, and the MAF voltage is showing 4.5+. I'm sure this would be a bit higher in higher gears, which would probably drive the injector duty cycle up even higher (for reference, i was logging 285-290g/s on 93 octane at this voltage). It's already hitting 90%+ in second gear with e85.



____________________
____________________

I'll post the actual logs if anyone is interested in analyzing them.

____________________
____________________

Cliff notes:

-straight e85 might kill HPFP's
-straight e85 requires very high injector duty cycle with a maxed out stock turbo. BT guys should be aware of this.