7427 VE Table lower values in entire table

As I said in my other thread, I still have a VE spike at about 1600rpm/40-60kpa where the VE wants to be >100. Surrounding cells are mid-80s.

Engine is a 87 454, basically stock. It has an aftermarket dual-plane intake and the exhaust is factory manifolds to dual 2.5" pipes that eventually merge into a single 3" through a muffler and full length exiting behind the rear tire. So really nothing should be creating these high numbers. Running stock 85lb injectors and aftermarket FPR with vacuum reference (15psi at idle, and it will crest 30 at WOT). I am running the later high-pressure pumps in both tanks. NV4500 manual trans. I did start with a 7.4/manual bin.

The spike used to be higher than the ECU could compensate for. I've made adjustments to the overall fuel calcs to try to bring the number down by increasing engine displacement (currently sitting at 496) and dropping the injector flow rate to 80. And also mechanical change by increasing the fuel pressure. This has gotten me to a point where at least the BLM isn't hitting its max if I keep things in that cell. But still, it has an occasional lean stumble right there. Currently the cells are at 99.

I have noticed that the majority of my VE is >50, with just a few high-40 values. With that, I think I have enough space to play with the fuel calcs even more and drop the overall values again, to try to get that high spike down to like 90.

I've checked fuel pressure and it is not losing pressure. EGR is non-existent and disabled in the code. Same with AIR. TBI base was rebuilt a few years ago with bushed shafts and there is no detectable vac leak there (and yes I checked at the VE spike).

So I guess this is really just a sanity check before I go in and drop my injector flow rate to like 75 and start tuning again. 95% of the time it runs fine...but that 5% is aggravating, especially if I'm trying to smoothly pull out with a trailer.

Sometimes increasing the surrounding cells to a specific VE cell wants to be >100 will help.

Are you using a VE Fixer spreadsheet?

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Originally Posted by dave w

Sometimes increasing the surrounding cells to a specific VE cell wants to be >100 will help.

Are you using a VE Fixer spreadsheet?

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I am using the spreadsheet. I'll try bumping the surrounding cells first. Thanks!

Typically the increase in fuel pressure, related to intake vacuum, is only 4 to 10 psi. I have thought for years that that was to compensate for the difference in intake manifold vacuum versus fuel pressure across the tip of the injector. I hope that makes sense. On the later model cars with returnless fuel system it is compensated internally with the PCM programming.

Quote:

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Originally Posted by MO LS Noobie

Typically the increase in fuel pressure, related to intake vacuum, is only 4 to 10 psi. I have thought for years that that was to compensate for the difference in intake manifold vacuum versus fuel pressure across the tip of the injector. I hope that makes sense. On the later model cars with returnless fuel system it is compensated internally with the PCM programming.

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Thanks for that.

Through a lot more driving and data logging and smoothing of the VE, it is driving nicely except for the stumble. But now I can reproduce the stumble pretty consistently and believe it to be AE related, like I need AE to stay active longer. I'm working on that part right now.