I tried searching but only found people switching to aftermarket regulators.

Breakdown of the car. Evo 9, 2.0 LR, ported head, hks 272 cams, hks valve springs, ported intake, stock 9 turbo, PTE 1200cc injectors, buschur fuel rail, walbro 255 high pressure pump.

Car was recently tuned on pump gas after the build. Scalings ended up being around 812. Trims were - 1%. We had very similar scalings when these injectors were brand new tuned on a stock engine one year ago. Thought scalings were low but others on the forum seem to have lower numbers for these 1200 injectors on pump. Everything on the tune was fine. VD was roughly 380 at 25-26 psi. No knock.

Switch the car to e85 a few weeks later. Scalings are as low as 400 and still seeing +15% fuel trims and slowly going higher. I stopped there. Some people say they're around 600-650 on e85. Started doing some investigating. Hooked up a fuel pressure gauge to the rail and my base pressure was around 38. Vacuum line hooked up it was around 32-33. Tried another stock regulator and same thing. Pinch off the return line, the pressure spikes to 85 and drops and holds around 65. Voltage at the pump was like 8.9 v at idle. I believe its supposed to be 9 so that should be fine. Pulled the pump and manually tested flow. It filled up a gallon jug in about 50 seconds which comes out close to the stock rated pressure of the 255 pump. Swapped to a set of stock injectors and put in stock scalings and trims are going up to about 10-15% lean.

Any suggestions I have missed? I'll probably send the injectors out for testing (even though the pump gas scaling is close to the same as when they were fresh out of the box), get the STM kit for supplying full voltage to the pump all the time, and possibly an aftermarket regulator. Maybe even need a low mileage sending unit in case this one has a clogged fuel filter. I don't want to band aid anything but I also don't want to buy new injectors or stock pressure regulator to see if the scalings change.

 

Drill the siphon.

I have a Walbro 255 on an AEM so not low voltage circuit. My fuel pressure at idle is ~40psi. Before I drilled the siphon I would see 42-48psi at idle. So I have to idle the car at 12.0-13.0afr on 2150cc and E85, my IPW was 0.35% on the AEM anything lower than 0.3 it just turns off the injectors.

I tried to wire in the resistor pack, and saw almost no difference, so tonight I am going to replace the return fuel line from the FPR to the hard line and see if that helps.

Sorry I don't have any other awesome advice, but at least you know you are not the only one.

 

I've done extensive fuel rail pressure logging on my stock fpr, and it held exactly the correct differential pressure (43-44 psi) under all conditions except when it was being overrun, in fact it works better than the AEM fpr that I'm using now, so I'm a bit surprised if two OEM regulators are producing the exact same base pressure value. My first suspicion is that the pressure gauge is wrong, but I would imagine that with your tech status that you've verified the accuracy of the gauge.

I'll toss out a few items:

1) A reduction of base pressure from 43.5 to 38 psi only reduces injector flow by ~7%, so that alone is not enough to account for the +15% fuel trims. I assume you are referring to the STFT because the LTFTs max out at +/- 12.5%.

2) Scaling big injectors can be pretty tricky. The injectory latency value can have a pretty big effect on cruise fuel trims, perhaps more so than what many people recognize. Have you tried increasing latency and the raising up the injector scaling?

3) A permanent full voltage rewire of a Walbro 255 will easily overrun the stock FPR at idle and cruise. I don't recommend it unless you plan to run an aftermarket FPR and drill out the siphon in the return line.

4) The filter in the pump carrier can clog. I've not seen it happen on my car, but I have heard of one instance where it happened to a very respectable tuner.

 

The regulator was reading correctly on another car a month or so ago, but it is possible it has failed. It is something I have considered, but like you said its not going to account for the drastic change in trims. I might look into borrowing another gauge to verify.

This is a dual map tune on the v7 rom. Maybe I missed it but latencies can't be changed correct? I used the recommended settings for pump gas and only had to pump it up a hair to fine tune the aftermarket intake. I did not think switching to e85 that it would throw it way off, but perhaps I need to work on a straight e85 tune and mess with the latencies for that to see what happens. Ive tuned 1150's on pump and e85 and had no issues but those were FIC.

I don't want to run the voltage rewire but I do get a slight increase in pressure at idle when I bypass the relay and get straight 12 volts. Still not over 40 psi though.

The last thing I can think of is the filter in the sending unit. Its not my car so I won't be able to check anything else until I get it back to my house probably next week. I put it back on pump so its driveable.

 

Brad, This is what I did with the pump housing I recently bought off of you. I cut off the paper filter housing and plumbed a 3/8" hard line to -6 fuel line. The paper filter was pretty clogged. Probably from sitting for a while or dirty fuel fill ups.

 

There is only one set of latencies for both maps. When the latency values are truly correct, one set works for both E85 and gasoline. However, its quite possible that the latencies that were determined using gasoline are not truly correct. Suggest that you start tweaking both latency and scaling to dial in the trims on E85, and once that's done, go back to gasoline and try iterating the injector scaling, and if needed latency. Eventually you'll get the correct latency values. It can be a major pain to do it well.

The fuel pressure thing still sounds kinda odd. I fully expect that cranking up the voltage to 14 V on a Walbro 255 at idle will cause massive overrun of the stock fpr even if its broken. Seems likely that the fuel filter in the pump carrier is clogged, or perhaps the pump is on its way out.

 

I finally got the car to my place instead of traveling to work on it at my parents 2 hours away. Didn't have much time to tackle the issues but I did have a few new sets of FIC injectors show up Monday. I decided to throw in a set of 1150's, same set I ran in another evo with great results. My scalings on the other evo were 850 on e85, the scaling I had to run on pump gas on the PTE 1200's. This was the first thing that confused me about the PTE's but thats how they were fresh out of the box on a stock 9 car.

The car was basically on empty from pump so I threw in a few gallons of e85, copied the latencies from the other evo and set my scaling to 700 just to have a richer starting point than what I previously ended on. Started the car and let it warm up so enrichment wasn't interfering with my STFT readings and once it got to about 190* the LTFT started going slightly negative. Finally!

Took a look at fuel pressure readings from the same gauge I had used last week and I was seeing over 45 base pressure. Its hard for me to believe that the injectors were bad enough to also cause base fuel pressure to read below 40 but maybe?

I didn't get a chance to actually drive the car, but basically at this point im pretty sure the PTE injectors were junk out of the box. I know others were getting low scalings on pump but seeing a 50%+ drop in scaling for e85 isn't right. Especially when I still hadn't seen the trims go negative yet.

Thats all I have for now. I'll update after the holiday when I actually take it out for a cruise.

 

I had considered that they weren't 100% correct. I used the suggested latencies, and even used the stock intake so I could get the scalings and latencies close without any extras fighting me, then put the aftermarket intake on and dialed it in for that. Im not blaming a bad brand of injector, just thinking this particular set had an issue. I may send them out to have them checked just for the heck of it.

 

The recommend latencies are usually not good enough. In fact, they can be considerably off. At least that's my experience with Evos.