Fueling issue: 100VE at idle, 94VE in boost
#1
Fueling issue: 100VE at idle, 94VE in boost
Figured I'd post this here too just in case:
https://www.miataturbo.net/build-thr...a-94287/page2/
Re-Tuning OP's car, ran into a really weird issue and posting up to try to speed up diagnosis:
After his new engine, VE map is really odd. Car requires a LOT of fuel up to 100kpa, then requires VERY LITTLE VE in boost. We already diagnosed and replaced a dying fuel pump (or more likely just way too weak for this setup), but now his latest log shows a requirement of 100VE at idle, and only 94VE at 4k/10psi (or thereabouts).
Faulty FPR? (though logic dictates that the symptoms would be backwards if that was the case).
I will post a log when I get home.
Car has a DW200 pump now. NA return-style regulator. ID725's. I double checked injector dead times, offset like 5 times now, as well as re-calculated REQ_FUEL.
Could an exhaust leak be throwing off the o2 at idle?
Could the FPR be somehow inverted?
Could an injector be getting clogged/stuck at low PW?
What are we missing?
He's picking up a fuel pressure test kit in the meantime to hopefully rule that out.
https://www.miataturbo.net/build-thr...a-94287/page2/
Re-Tuning OP's car, ran into a really weird issue and posting up to try to speed up diagnosis:
After his new engine, VE map is really odd. Car requires a LOT of fuel up to 100kpa, then requires VERY LITTLE VE in boost. We already diagnosed and replaced a dying fuel pump (or more likely just way too weak for this setup), but now his latest log shows a requirement of 100VE at idle, and only 94VE at 4k/10psi (or thereabouts).
Faulty FPR? (though logic dictates that the symptoms would be backwards if that was the case).
I will post a log when I get home.
Could an exhaust leak be throwing off the o2 at idle?
Could the FPR be somehow inverted?
Could an injector be getting clogged/stuck at low PW?
What are we missing?
He's picking up a fuel pressure test kit in the meantime to hopefully rule that out.
#6
Starts and idles pretty good, no raw gas smell at exhaust. i checked for exhaust leakes, cant see, hear, or feel any pre-o2. There is one about a foot downstream, maybe more, after the o2, mentioned this to vlad and he didnt seem concerned. FPR was tested today and it was good. 40psi at idle, and 65 in boost.
NA8 block, 84mm 8.6cr, bp4w head, ported with backcut and tapered stock size valves, ST double lite springs, FM Mani and DP IC pipes and IC, GTX2860r gen 2, NB fuel rail, 94 FPR(just tested today to be good) NB IM, ID725, DW200, LS2 Coils
NA8 block, 84mm 8.6cr, bp4w head, ported with backcut and tapered stock size valves, ST double lite springs, FM Mani and DP IC pipes and IC, GTX2860r gen 2, NB fuel rail, 94 FPR(just tested today to be good) NB IM, ID725, DW200, LS2 Coils
#7
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Was the fp tested at the rail? I would't think the car would even run with 100% req-fuel (or there-abouts) at idle. What does total fuel correction look like at idle?
Edit: what is the injector high side voltage at idle? Measured from the injector plug, back to SGND on the MS
Edit: what is the injector high side voltage at idle? Measured from the injector plug, back to SGND on the MS
#11
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Also, fuel pressure should not vary by 25psi on a car running 10psi of boost unless you have a rising rate regulator. It should be a base of 43psi, idle at 39ish, and run ~53psi at WOT. I suspect that's just a measurement error, but it's also why I despise FPR-mounted analog gauges with a passion. Do yourself a favor and buy a 5v sender and wire it to the MS3 so you can actually see what's going on.
#12
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I don't use incorporate AFR (no particular reason, just never have), but even with that factored in, it still sounds low. For reference, Rover's fuel system is very similar (stock '94 rail/FPR/FF640s) and I am at 138%VE at 4000rpm and 170kpa. The idle cells are at ~82%. Even if you factor in inc.AFR and lean the VE table out by ~25% to compensate, that still only gets you to ~110 or so. 94 is still low by a good chunk. If incorporate AFR is not on, then it's way low.
Back on topic a bit...
100% VE at idle for what I am accustomed to on the Miata would result in an afr somewhere around 7. The only factor I can think of off hand that would explain these results is a voltage drop between the injector and the MS, assuming the dead times are setup right, which I am sure they are.
#14
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Or a turbo blowing most of another atmosphere's worth of air into the motor. Are you compensating for boost in your car with some sort of 2D table? I know the old AEMs had a 2D table which scaled injector pulsewidth with boost, but it always seemed like more trouble than it was worth.
#15
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Or a turbo blowing most of another atmosphere's worth of air into the motor. Are you compensating for boost in your car with some sort of 2D table? I know the old AEMs had a 2D table which scaled injector pulsewidth with boost, but it always seemed like more trouble than it was worth.
honestly man, I have way too much respect for you, what you have done and continue to do for this community to get in a silly difference of opinion arguement. I yield.
#17
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With that in mind, 40psi at idle and 65psi in boost on a 43psi FPR is bullshit. It's 33-34 at idle, 53 in boost, and the gauge is junk.
#19
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honestly man, I have way too much respect for you, what you have done and continue to do for this community to get in a silly difference of opinion arguement. I yield.
If everything is perfectly dialed, then logically, you are right. Empirically, from my experience, all my fuel maps end up with in-boost VE figures north of 100%VE. I set dead times per the manufacturer's suggestions depending on which injectors I'm using, so I would love to know why that is. There's also the oddity of all EV14 injectors seeming to want far more VE than a similarly-sized EV1 or EV6, and I would really love to know why that is as well.