thinking out loud... FPR and Tune question...

[sigmafour]

sorry for length here... but a bit of background

 

Sharing a thought here as I have been aware of a problem with my tune on the GT. I have an Aeromotive 13109 A1000-6 Injected Bypass Regulator with Aeromotive 15633 0-100 psi Fuel Pressure Gauge attached - I was dyno tuned back in September 2016 and things were fine - I have noticed more recently that under WOT in 3rd gear (or 4th on the new 6MT) the car misfires and collects a lot of knock value on the AP3 - Engine is fully built but still, not good way to carry on. I had, before I did the 5MT>6MT swap -a wonder if air was leaking in but I didn't get a chance to find out as I pulled everything apart to install the 6MT and once back on the road - misfired badly as 'usual' - stay out of WOT and car pulled well, I have started to pay attention to the problem and look for clues... seems to me the AFR was not great - too lean under boost generally. To add to complications, car has meth and a fuel strategy to remove gasoline under boost to allow the meth - so lots of places for this to have a problem but the meth has a flow sensor and I am not having a meth issue - this is gasoline or more air getting in than I expect. Car can make boost to almost 30psi with a now every custom JMP 20G based off an AMR CXR550

 

Okay... so here's what I have found - an immediate improvement by adding more fuel pressure with the aeromotive. Under the thinking of "WHAT HAS CHANGED?" - really nothing - I haven't added anything or changed anything on the fueling - methanol is fine, the mix hasn't been changed and the pre/post nozzles are good and clean and working and flowing properly (measured and replaced the super fine droplet nozzle in front of the turbo)

 

The gauge on the aeromotive was reading approx 40psi during idle - gauge is under the hood so I can't see it when driving but I have increased to about 45/47psi at idle - and this has dramatically improved the car, better power, almost ALL issues with knock are gone and AFR's seem better - not perfect but I am 'shooting in the dark' a bit.

 

I have never touched the Aeromotive FPR before, never tweaked it - I assume there is a spring in there which adjusting tightens the spring and increases pressure on the regulator - is it possible over time this spring in the FPR could have become 'weak' and over time been slowing lowering the fuel pressure - I don't have an idea or memory of what the gauge said back in 2016 because that would have been a sensible thing and I am not always so bright.

 

So - any thoughts by people that may know or have seen a similar issue as so far, it seems like this has almost completely solved the problem with WOT and almost no misfires at all now, much better power with adding more fuel - AFR shows a richer response under boost - again not sure what it should be - seeing 11.5>11 or so on the wideband but think maybe richer would also be safer...