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So I just dialed back the fuel pressure a little bit as a test so it was on the high end of 14 at idle and it runs much better. On the highway it was staying in the green almost all the time even when under some throttle. Under boost it was rich, but into the 10-11's which is much better than before which was pegged so probably in the 8-9 range but only showing 10. Feels much better too. I'll check the fuel pressure when I get home, but at least this was a quick fix.
I'll keep sorting this out, but I'm encouraged to even get it to this point for now.
Measure vacuum at the hose going to FPR. Should be 20-24 in.Hg. If you've got cracked hose or intake-leaks, the vacuum will be less and as a result, you'll have too much fuel-pressure.
Yeah, that'll work. And can be used to test FPR's pressure-regulation. With no vacuum, you should have 37psi. With 20-in.Hg, should have 27psi in fuel rail.
Either vacuum leaks and/or bad FPR will result in too high fuel-pressure and too much fuel.
So I measured 15Hg with that tool, which I guess is a bit low. I also noticed that the pressure disappears the moment the engine is off... is that normal? Should it hold pressure?
I also made another alarming discovery. It's actually running really good since I dialed out some fuel pressure. Not perfect, but WAY better. However, when the electric fan came on because the engine temps got hotter off the highway the AFR jumped to 16 which is pegged on my unit and you could feel it starting to run poorly. I have no idea what that could be, but it was alarming. It seemed to run fine once I was moving, but super lean when idling. Any ideas?
I feel like I'm at least making some progress on potential problem areas.
1. Which WB unit do you have? The LM1 uses an analogue (circuit) gauge with digital display. It uses a reference voltage that's not regulated. So when supply voltage changes, the AFR displayed changes regardless of actual AFR.
I prefer only fully digital WB units where the gauges communicate with the controller with binary data rather than voltages.
2. Which FPR do you have? This isn't 1990, tuning with fuel-pressure went away with the dodo. Adjustments are made via laptop. Extremely easy with the Rogue system.
3. Measure voltage at fuel-pump connector. See if there's a drop when the fans turn on. Fuel-pump wiring may need upgrade.
I was thinking to get the Rogue tuner and logger, but wasn't sure how they connect and work. I need to do some reasearch with the old search button I guess. I have the LR FPR (http://www.lindseyracing.com/LR/Porsche/944-4037.html) and dropping fuel pressure was just a quick fix I could do here and now. Compared to before it's WORLDS better. I've spent quite a bit lately and need to let the old wallet recover before I move into the next phase.
I'll try and test the pump voltage. Wish I knew someone with experience with this kind of stuff in Colorado...
Rogue doesn't really reply to much at all, so I've pretty much given up on that route. Also, you know me, I like to work on my own stuff and not really take it to a shop if I can help it. I'm sure I'll figure it all out eventually, I just wish I could get together and have a few beers with someone who already knew what I don't!
Still, the car is light years from where it was. Each step just gets better and I can't wait till I get into the tuning and really get it dialed in!
07-14-2016, 01:27 PM
