This is my second build and so far all is good. As of lately I'm getting 2 completely different answers about running a referenced FPR. I understand why its needed and thats why I have a reference capable regulator. Dyno Tuner is trying to explain to me why on MY setup its causing issues with tuning the fueling. At what point does fuel injectors become to big that they are untunable in higher boosted regions?

My setup consists of:

370, 80mm turbo, 10:1. Aeromotive 5.0GPM variable speed, -10 feed/return, P59 Flex, Fic 1650s, 43.5 base fuel pressure.

Now on gas 91 octane these injectors are to big. I knew that while piecing this combo together. Pure 85% ethanol, according to Fic, I'm inline with my power goals. Fic puts these injectors at 1257whp with 85% Ethanol. At the dyno, (which I had to cut of early because of malfunctioning wastegate and a coil that went belly up) we got up to 863hp on 60% Ethanol. Not to bad. Also my torque converter is letting me down because of slippage. Its not a horrible converter but not the best for my application. Its probably whats allowed the transmission to survive as long as it has. So, take away TC slippage, hone in on timing, and add a little more boost, I should get to 1000 whp if not a hair more.

Moving along, during dyno session, tuner tells me my fueling components are to big for my application. Hmm? Why? Whats wrong? Says the VE table will have to be flatlined to continue maintaining the 1:1 fuel ratio. Never heard of this and quite a bit to take in, when I've spent years now learning about how boosted applications need a boost referenced FPR.

So my thinking is this. Even if fuel pressure gauge starts at 43.5, and in boost the pressure starts showing higher and higher, the actual output of the injector doesn't go higher and higher, they are just maintaining the same output as they would at 43.5. If I go unreferenced, and add 20lbs boost, now the injector is putting out whatever it would at 23.5 fuel pressure. Given all this, is my tuner telling me that these injectors can support the power goals while running at 23.5 psi pressure? Engine is good to 25lbs if not more. 25lbs will be a stopping point. Now my fuel pressure would turn into 18.5psi.

In a nut shell, none of this makes sense.

So I would like to know, whos out there running unreferenced FPR's, on 85% Ethanol, 25lbs of boost, and the engine is happy about it.

 

I know the P59 has an injector limit, the table can be scaled to work well at idle or WOT, but not really both once the injectors get large enough

that said, I would not unreference the FPR. You want the injectors to be able to "drive" thru the boost and atomize fuel, not dribble it

 

Ive been doing road pulls up to 14lbs and I dont see anything crazy with my fuel system being over kill. My open loop fueling is within 1-2% off at most. Close enough for narrow bands to take over. Honestly dont think I could get much closer with the resolution of the P59 3 bar VE. The higher Boosted region of the VE isn't as aggressive as the lower region but its doing a good job targeting my commanded. Commanded is .794 Lambda. Starting at 155 KPA (about 8lbs) my multiplier is 1.26 on out. That leaves me about 5-6 rows to run up to 25lbs. I could see the VE start to level off and not be as aggressive looking. The VE does rise but not at a crazy rate.

 

The VE table is just one factor in a whole list of things that are multiplied together. If you think about the physics, the actual volumetric efficiency of the engine does not change strongly with boost. The density of the air going into the engine goes up with boost, but volume wise it is pretty constant at a set rpm.

Now on a REFERENCED setup the FPR maintains the same pressure differential across the injector, so the VE table typically carries the same value with higher boost, assuming the pump can keep up. This leads to the UN-Referenced case, that looks exactly the same as the pump NOT being able to keep up. The VE table on this setup will need to increase with boost to compensate for the lack of fuel. This is the same thing as a stock returnless (unrefernced) fuel system as well. If he is saying the table value is maxed out then something is seriously wrong with the tuning and the scaling is all over the place. The IFR table, VE, MAF, stoich, enrichment, etc. all multiply together to get your final fueling. You can fudge any or all of those to get the final "what the wideband reads" fueling correct with varying consequences for touching each of them.

High duty cycle (25-85%) for injectors is their happy spot, above and below that you may run into issues on huge injectors (like 500lb/hr ones), but I have never seen a normal injector less than 250lb/hr that needed anything crazy done with the regulator.

The 07+ trucks got better since they incorporated a factory fuel pressure sensor and closed loop fuel pump control, basically eliminating the need for a referenced regulator. The issue then becomes the factory filter and pumps ability to flow enough fuel, but the factory flex trucks are typically good for ~600hp on gas.

So, lot of rambling, but your tuner has no good reason to not want to run a referenced regulator when available. You could make it work unregulated but thats kind of stupid if you have the ability right in front of you along with plenty of pump. Either way the tune needs to match the actual setup or its not going to be happy.

 

I have my tune and latest log uploaded. Im about 60% duty cycle on the injectors at 14lbs boost with 64%E. Is .794 Lambda a little aggressive starting at 8lbs of boost though? Clearly this would prevent the flat shelf look on the VE if this was lowered. Engine seems to be fine with it the way it is. I wont really know until I get it back on the dyno, if fuel can be pulled a little in this area.

I assume with the injectors Duty Cycle, once I turn the pump on high, this will give my injectors some more room to run. Or will the Duty Cycle just stay high but the pump is just making sure the volume is there?

I'll be finding out this week once I get it back on the dyno. I had to stop short because of a bad coil and my wastegate had failed and also turned out to be to small.

Also now that I remember, I've been told that, setups that are running a referenced FPR need to flat line the Offsets vs. Volts vs. Vac table. (For the Injectors) Copy 0 column and paste throughout in the table. From the few forums I found discussing this, is the a Greg Banish thing? 99% of people are telling me it doesn't matter, and the 1% is saying to do it. I'm not getting a clear answer on this. Currently haven't made this change.

 

The 1% would be correct...

 

The regulators job is to keep things constant so the injector always sees the same.preasure differential. So then why would the offset change with manifold pressure if the regulator is negating that? Hint: it wouldn't.

With your pump, it shouldn't matter if the regulator is sized properly as long as pressure is maintained.

 

Heres my update.

Made it back to the dyno past weekend and ran with reference connected and will continue to do so. I think with the coils going bad it was leaving him endless possibilities on what the problem could be. Was able to get it all ironed out and had a good day with everything functioning.

We stopped at a nice even 900 tire, just enough to get the tires to begin out running the roller. We left off with a graph line that was headed up and to the right. We had 17 degrees, 23 lbs at 6700rpm's, running with 70% ethanol.

The next day I made it the track to do some test and tune passes but was challenged with traction issues. I seem to be able to take off from the line fine but when I get 60-100 foot out I start loosing traction. Rear suspension is 100% stock with the exception of Speed Engineering traction bars. Which actually do a nice job of stiffening the rear end but I don't think my rear end is getting loaded. Curious if I need to remove a leaf and add some good shocks. I'm running 3.73 gears with the Hoosier quick time pro 28" tire. All this is in a fully dressed extended cab 1500. I'm thinking I need to get the rear to squat more while getting the front up.

 

Relocate the rear shocks and go with some adjustable shocks as well

 

should I mount booth shocks behind the rear?