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So... Learning odd things at the Dyno. Need input.
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.
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Heres a link to the original thread on LS1tech. Have pictures of spark plugs afterwards. https://ls1tech.com/forums/forced-in...eed-input.html