So what I'm about to say is going to go against the 99% in here, but hang with me. I'm still questioning it and really not liking it.

Overview of setup: 370 10:1, Aeromotive 5.0GPM variable speed Pump, matching Fuel Regulator (Aeromotives Recommendation) Fic 1650s, 91 octane with 7% E, NGK 7 plugs. Return system. -10 feed and return, -8 through the rails, parallel feeding through the back of fuel rails and onto the regulator. 58psi fuel pressure.

My truck is on the dyno and tuner tells me he cant get the fueling to lean up without making the VE take a step down or leveling off. Never seen a VE just flat line or head lower as boost rises. At this point I'm stumped and slightly confused. I can hear the engine breaking up in the 4K region. He trys a couple other things and nothing is changing. At this point he double checks with me on fuel pressure and make sure he knows the regulator is boost referenced. He makes another run on dyno so I can watch gauge to see what pressure is doing. The fuel pressure rose in step with boost pressure. At this point Im thinking everything is working just as it should. Just adjust the VE and get on with it. Well at this point hes telling me the pressure is to high to start with and the boost reference is adding more of a problem. Well, from my understanding anything past pressure equilibrium (boost) what we witness from the pressure gauge is not what the injectors are actually flowing but is compensating for the pressure against the injector from the boost. If I see 68psi from the gauge because of the boost, the injectors are still flowing the same as they would at 58psi. Now without the extra 10psi (via boost reference) the injectors would actually be flowing 48psi, while the gauge still shows 58psi.

At this point he explains that my pump and injectors are over kill. ON 91 OCTANE. I can understand this. Wasn't expecting much out of 91 other than to have my truck function fairly well. The fuel system was designed to flow the correct amount of E85 at high boost. So we still have breaking up in the mid range and I cant think of anything that would be causing it. I explained to him I setup the injectors in the tune based on 58psi, FIC's data was based on that and I didnt want to go through the trouble of scaling. Truck ran fine cruising around. he suggests lowering pressure and I'm fine with that. I wont be stressing the pump at a lower pressure and I believe the injectors will work fine there. I lower to 43.5 best I can and he makes another run. It helped a little but still breaking up. Heres where it gets questionable. He says to unhook the Boost reference off the Regulator. What??????

I dont know what to think about this and he explains he has multiple people running around without boost reference making good numbers and no death to the engine. Tells me boost reference is only needed when the injectors are properly sized and the pump cant maintain the pressure. So he talks me into it, and make a pass. To my surprise it helps. But now the engine is breaking up around 5700 rpms.


So I'm completely stumped now. Trying to understand what the hell is going on. Is my engine beginning its death or is it happy with this.

We go ahead and mix in E85, bringing the blend to 55%. Motor is liking it and seems to be happy up to 5700 or so. I'm still getting a miss fire randomly so I decided to stop. Fuel ratio was maintaining. No recordings of spark knock. No spark being pulled.

I'm going to look at the plugs. I'll post images and the tune if anyone cares to look and see what the hell is going on. He said he was moving the VE 1% in the area trying to figure out the miss but clearly it seemed to be an ignition issue. I'm hoping coils. I dont think preignition because this was happening in the lower RPM's with the reference hooked up.

I want to go back to using the reference but unclear if its needed.

Truck made 860 at 16lbs so far. I want to work these issues out plus a couple more before going back.

 

What’s the gap on the plugs? If it’s not, try .019-.022 and see what happens. IMO the fuel system is set up correctly. Removing the boost reference from the regulator just ups the duty cycle so the injector can handle the fueling (not likely helping anything, just coincidence). If fueling is on track (AFRs staying where they belong) it’s either valve springs or ignition. I’ve never tuned anything with VE, but I do know it follows the torque curve so it definitely could drop as boost/rpm increases. I’d check the plug gap and start there.

 

should of mentioned I did remove plugs and gapped at .020. But nothing changed. I believe the springs are PAC 1218. I’ll probably change them just to make sure that isn’t an issue along with the coils. The unhooked reference line on the fpr is what worries me. Duty cycle I believe was 60% on the Emix. Fuel pressure at 43.5 and then the 16lbs boost makes them underperform. The injectors I believe are rated 180lb at 58psi. Are people making 900+ With smaller injectors on pure 85% ethanol?

 

 

There’s no reason to worry about duty cycle until you start to run out of it (and some guys don’t even care about it then!). What could are on it? It could a coil or even a single wire.

 

So I shouldn't be concerned with NOT running a boost reference line to the fuel pressure regulator? Is it possible for the Duty Cycle to show good (not maxed out) but the injectors still have pressure working against them leaving me blind on whats really happening. If thats the case then plugs are my last tell tell for a proper tune. I'll be the first to admit, I need to be knowledgeable on plug reading. I'd say mine look fine.

For my settings in the tune, I inputed FIC's data and ran the Flow Rate vs. Kpa at 180 across the board and set fuel regulator to 58psi.

Heres FIC's statement:

(All values listed in the tables attached assume you are running the OE GM 58psi system when applicable. You are NOT required to adjust any of the provided data because of our policy to list flow sizes at 43.5psi when advertising our injectors for sale.)

At 43.5psi they are rated at 155.88lb.

During the Dyno Tune the pressure was lowered to 43.5 and reference off. But now looking at the tune, my Flow Rate vs. Kpa was left at 180. Something isn't computing.

If my reference is off at 43.5 and add 20lbs boost against the injector my the new injector flow is now 114.5lbs.

This is what worries me. 114.5lb injector, 85% content, running 18 degrees. If I'm not doing this right. Let me know, but for the life of me I cant find one article or thread talking about how they didn't run a boost reference and got away with it.

I'm not really wanting to learn what works and what doesn't on a 7k short block, when I know or at least thought I had the fuel system taken care of past 1K HP.

I'm just wanting to get to the bottom of this.

 

I don't know VE tuning, but I do know that it's perfectly fine to tune without the boost reference line hooked up as long as one has enough injector to support it.

Your tuner is correct in that regard.

 

I’m not sure why you’re getting hung up on this fuel pressure/injector duty cycle thing. None of it’s an issue if AFRs are holding true. Here’s how it goes, you set fuel pressure per the manufacturer. Yes, most forced induction setups will use a boost referenced regulator and you’re correct in how it works. If you have a fuel delivery issue (clogged filter or you’re losing your fuel pump for example) duty cycle will go up to try and keep AFRs in check. If you try and push more power and realize your injectors are falling short by showing excessive duty cycle, you can up the fuel pressure to compensate. It’s done like this all the time. Personally, I’d leave the boost reference line hooked up. It’s not causing the issue you’re having with it breaking up. If the tuner thinks it is, well then…….it’s up to you how you want to deal with it and I know what I’d do.

 

I appreciate the help guys. Forums are my only go to for info and advice from people with experience. I hooked the reference line back up and changed the settings in the ecm to match my regulator pressure. Fueling shouldn't ever be a concern. If it is, the toggle switch is an arms length away. I'm currently logging VE Error and so far is going good. Well, my brake pads might not be worth a crap once I get it dialed in but they need to be looked at before racing starts anyways.

For the breaking up, I'm narrowing it down to the coils. I read the truck coils are the best performers in the OEM line up. Is that what I should stick with?

Also didnt bring it up but I'm going to have to add another wastegate. Boost kept rising running on the spring. My controller was shut off and when I turned it on, with 10% duty cycle, boost really ramped up. Its a 44mm placed in the direct path of exhaust flow. Exhaust will run right into the gate before it 90's up to the turbine. Would adding one more 44mm be good enough or is it okay to go bigger on the second waste gate? Either way I'm needing one.

 

Stick with the truck coils (don’t forget it could be a wire too). What’s the hot side consist of? Divided or merged setup? What’s the boost control strategy?

 

Bottom right is the gate. Plugs and wires was installed the same day I went to the dyno. Do you think 2 44 mm gates would solve the issue. Thought about buying a bigger one and seeing how that works and if that’s not enough I could finish off with 2 equal sizes that are bigger. Just not sure how 2 different size gates would work with each other.

 

I dont know how much it matters, but I have my 02 sensor in the down pipe about 16" from the turbo, not before.

 

That’s the narrow band. Had it after and the readings swing and wouldn’t match left o2. Given it’s a new engine it should of read close. Installed where you see and the reading became stable. With cam and open exhaust the o2 would pickup on outside air.

 

What's the lambda/AFR? Lot of talk about fuel pressure and duty cycle and "its not good", but what is "it".

 

what turbo? looks like a t4 flange?
i know every one likes to say making 1k on a t4 is no problem but your probably nearly there at the crank

 

Currently under boost its commanding .794 and the wide band is recording .73 or so. EQ error shows anywhere between 7-12% rich which looks to be accurate. The duty cycle hit 90% but I'm still pulling fuel.

 

2.5" crossover and T4 flange. At the crank it should be hitting 1K. Tuner said my converter is missing about 1K rpms. With a lockup I should be able to hit 1K at the tire. Maybe in the future I'll upgrade some trans parts and change the converter.

While at the Dyno the tuner was dialing in spark 1 degree at a time and was picking up power. If not for the miss and me questioning the unhooked reference line theory, we could of took it further.

 

That seems awfully fat. Are you sure your injector data is good? I run 4 bar of base fuel pressure with a 1:1 FPR and no issues seeing 70+ psi of fuel pressure in boost.

 

Fat on the commanded or my WB reading? Also FIC's data. If theres adjustments that need to be done there, then I'm completely ignorant in that respect.

 

are you logging/monitoring voltage? when i was toasting voltage regulators with my hot side, my voltage would drop in higher RPMs above 4k. easy box for you to check.

another vote to keep boost reference hooked up if you're already set up to run a boost reference to your FPR

just made 820rwhp on e65, deka 80's, stock 3/8 feed, 5/16 evap return. your fuel system should be more than adequate as others have mentioned.