Figured I'd post this here too just in case:
https://www.miataturbo.net/build-thr...a-94287/page2/

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.

 

NM....dumb question

 

Did he check for vaccum leaks?

 

How does it idle/start with the current high ve? Do exhaust gasses smell of fuel?

 

Does actual VE in datalogs follow this trend? How about injector pulsewidth? 4k/170kpa should need way, way more than 94%VE

 

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

 

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

 

hate to disagree... but with incorporate AFR turned on, this may not be too far off.

 

Cam timing out?

Dann

 

Waiting for tune and log.

 

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.

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.

 

Idle at 82% would be flag for me. Anything over 100% is also usually an indicator of error compensation in the fuel table on a Miata head except the wild cammed, ported, OS valve, tuned intake manifold versions. But hey, you can't argue with the results! If it runs the way you want it to, that is all that really matters.

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.

 

Don't forget that at idle the pressure will be lower than with engine off, pump running. a 25psi difference sounds pretty close to what I would expect between idle and 10psi boost.

Dann

 

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.

 

with speed density, the additional fuel is added by the load factor. So at 170kpa, you get 1.7x the pw.

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.

 

Im running a 14psi wastegate, seeing a little creep to 15.5psi

 

I could have sworn it was a smaller difference, but looks like I misremembered. My datalogs from Acamas say that on a 60psi base, it idles around 51psi. Peak of 87psi at 27psi of boost. In a car running 10psi boost, it should vary by 19-20psi if the motor is healthy.

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.

 

Yeah, 10psi vacuum at idle then 15psi boost =25psi change. So i would say that is normal.

Dann

 

I had no idea Megasquirt did this automatically. I always assumed the >100% VE figures were "accurate" once rising fuel pressure was taken into account. I never really thought about it very hard beyond that TBQH.

Sorry if I came across as hostile above at some point, I absolutely did not mean to. I respect you as well and I value your input/experience, even if (especially if?) it conflicts with my own. I'm learning here

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.

 

Id say the FPR/gauge is **** or the pump is overwhelming it. Regardless it's close enough that the VE table should look normal. Again I guess cam timing.