ZERO Fuel at 2850 rpm

[thesupragod]

Ok, so after Trying to get the car tuned at IPS Motorsports in Columbus, OH, I found out that the issue is not ECU related (i think) Basically at 2850 rpm the fuel map just drops, NO injector pulse width... We tried adding 50% fuel at 3000 rpm with my SAFC NEO with no success.

Basically, does anyone have any ideas?

I tried swapping ecu's thinking that the Mines ecu i am using had a dead spot in it, but my stock ecu did the same thing.

I tried unplugging the Cam angle sensors individually and that didnt help...

Thanks!

Oh, still ended up making 453 hp and 373 tq at 15.1 psi!

[tsupra]

is your fuel pump wired to run at 12 volts all the time?

[thesupragod]

Yes sir, it is. Thats a really good thought though, thats right around where it switches from 8 to 12 v. I watched the FPR gauge while on the dyno, not a single fluxuation, until boost set in then it just went up...

Good thought!

[bfr1992t]

Maybe you're hitting fuel cut? Try -50% on the AFC.

[tlo86]

what are you using for your tach signal?

[johnd]

Just seeing the title of this thread I knew it was going to be a 1jz Q.
I've spent a year trying to flatten out my lean spot around the same
rpm.:nono: I think I got it now.
How do u know there's no injector pulse?

[thesupragod]

1. I dont think im hitting fuel cut, my ecu has no fuel/boost cut.
2. Im not sure, which wire is the tach singnal? my tach works and everything... not sure.
3. Im dont know that there is no injector pulse, i just know that there is almost no fuel, the wideband goes full lean, and the guy at the tuning shop was convinced that there was almost no pulse...

I am debating about going standalone to try to resolve the issue, but its just so damn expensive!

[johnd]

If you search this there's a couple different threads,
some guys "like me" just try tuning it with the piggy back,
other's upped there fuel pressure and it worked for them.
I guess that's the best result you'll get from a safc/pb.:3d_frown:

[tsupra]

Yes sir, it is. Thats a really good thought though, thats right around where it switches from 8 to 12 v. I watched the FPR gauge while on the dyno, not a single fluxuation, until boost set in then it just went up...

Good thought!
ok, i'm trying to work out a theory on this. if this is the rpm point where the ecu switches the fuel pump from 8 to 12 volts it may be expecting a surge in fuel delivery or sudden short lived increase in fuel pressure and therefore ease back on the injector pulsewidth. if this theory is correct it could explain your problem.

[tissimo]

It doesn't matter if the fuel pump is at 8v 12v or 40v, the FPR should do its job and keep the Fuel Pressure constant in the rail.

What fuel pressure are you running? A buddy had issues with his as well, we had to turn the fuel pressure up to 38-40 and add a little fuel to smooth everything out.

[tsupra]

It doesn't matter if the fuel pump is at 8v 12v or 40v, the FPR should do its job and keep the Fuel Pressure constant in the rail.

What fuel pressure are you running? A buddy had issues with his as well, we had to turn the fuel pressure up to 38-40 and add a little fuel to smooth everything out.

if the fpr is doing its job then there would still be a momentary surge in fuel pressure right when the fuel pump switched voltages. my theory is that the ecu is trying to compensate for something it thinks is going to happen but doesn't due to the fuel pump running at 12 volts all the time. would you did to fix your buddys car was a band aid. you added fuel to overcome the ecu cutting the injector pulse width.

[lintlars]

Do you have a fuel pressure guage? does it drop as well?
I does not state it anywhere just trying rule the simple things out.

[tissimo]

if the fpr is doing its job then there would still be a momentary surge in fuel pressure right when the fuel pump switched voltages. my theory is that the ecu is trying to compensate for something it thinks is going to happen but doesn't due to the fuel pump running at 12 volts all the time. would you did to fix your buddys car was a band aid. you added fuel to overcome the ecu cutting the injector pulse width.

The pressure would have to change drastically do do any major fueling changes.

The issues is probably more to do with the actual injector itself then anything else I would imagine. The ecu is tuned for the stock saturated injectors vs using peak and hold injectors (mkiv 550s or most aftermarkets).

[Cya]

Could it be the style of ecu, meaning from a chaser/soarer vs. Supra. Im personally running a Chaser A/T ecu. The reason im asking is because while searching on ebay for a few things I noticed the sc300 (soarer) has an ecu to control the fuel pump. That last person working on my swap before I had to complete it told me the Chaser/Soarer wiring was more round-about than the Jza70, which leads me to belive that this could be part of the problem.

With that said, my theory is that the ECU is "dropping" the fuel map in this one spot because this ecu is missing.

Does this make sence?

Are you running a Soarer/Chaser ecu as well? It just seems odd that a more than a few people are having this same issue.

[thesupragod]

Ive used 2 ecu's actually... one mines tuned ecu and one stock ecu, both to the same effect. Ive played with my fp a ton, from 35 to 55 lbs, same thing. I a have my walboro 12v modded as well. Oh, the ecus are from the chaser, it was a supra half cut from j-town.

Thanks!