Lean at part throttle transition from vacuum to boost ... feels like a wall

[chilort]

Need some assistance on where to set my fuel pressure.

I do have an AEM wideband so I'm sure of the AFRs

This is an '86 Daytona with a custom intercooled log setup (stock intercooler in a stock location) with a FWD Perf Stage III cal. Injectors are 804s (filed to fit the stock fuel rail) and I have an AFPR (Acufab).



I've been trying to fix an over rich problem (I guess I think it is a problem and you all can tell me). When at full throttle but pulling a hill or under load the thing is pig rich (10.0). I've been pulling base pressure using the AFPR. I had the base pressure at 48psi.

Full throttle runs are great. The AFRs start in the high 10s to low 11s and never go above the low 12s before I shift (around the first red light on the digi gauge or less).

Today I bumped the base pressure down to 46psi. Under load on a hill at full throttle the AFR goes down into the 10s but not to 10.0. But.....

When at part throttle as the car transitions from vacuum to boost the car goes super lean (17.0 or ---, the dashes meaning off the scale). Then, once the car hits 5lbs or so, the AFRs come back down. As the car is doing this if feels like it hits a wall until the fuel kicks in and then it is off again.

I hate the part throttle response.

I don't know what to do. If I bump the pressure back up then I risk washing down the cylinders with too much fuel when I'm running in hills (which is often). If I keep the fuel backed down like this, the car is a PITA to drive in city traffic (which is often).

Does the LM only look at boost/vacuum to determine fuel? I'm guessing no. And that means it is probably using the TPS too. Could the TPS be slightly off? I've got a spare. Maybe I'll throw it on today.

Opinions? Help?

[chilort]

Banged away on my dizzy some today to take the slop out of it and brought the base pressure back to 48psi or so. Seems to nearly make it through that dead spot now. On a flat or nearly flat the car runs high 10s to low 11s for AFRs. Pull much of a hill and it shoots down to 10.0.

[turbovanman²]

Your still too rich, have you talked to FWD about revising the cal?

[GLHNSLHT2]

When a friends are did that it was a bad map sensor. His was an 85 laser suckthrough. Same thing, a/f would go almost full lean from 0-5psi then come back at part throttle. At WOT it wouldn't do it.

[chilort]

When a friends are did that it was a bad map sensor. His was an 85 laser suckthrough. Same thing, a/f would go almost full lean from 0-5psi then come back at part throttle. At WOT it wouldn't do it.

Interesting. I thought maybe it was the vacuum tubing but I've replaced darn near all of it.

I've had my OTC scanner on it but never while driving. Might be time to figure out how to do that and take it for a spin to make sure the MAP really is reading correctly.

I've also not talked to FWD about revising the cal. It seems like most would rather stick a fork in their eye than work on an '86 cal.

[GLHNSLHT2]

You need to get a MityVac and check the vac system completely. Make sure you have ZERO leaks. What OTC do you have? The 4000E with the pathfinder 2 cartridge is sweet. You can watch, all 4 cylinders for knock, rpm, coolant temp, TPS and timing advance all at the same time. That's the way I have mine setup at least.

[chilort]

4000e w/ pathfinder 2 is what I've got.

[chilort]

Took the base pressure down to 47psi. It is quite a bit better now. I still need to drop it a little more. Now it is going rich up top and it never used to do that before I whacked my dizzy. Even leaning it out it still drives right through that dead spot now no matter what I do. AFRS are now in the low 11s until I get up there in the RPM. I would have liked to have played with this a bit more today but I got to fix my fan wire instead.

[chilort]

Base pressure is now at 45psi. Holds 11.5 AFR through the rpm band. Until I hit a grade, then it drops into the mid 10s. Still too much fuel?

My entire transition problem is still gone. Must have been a timing issue that we solved when we dropped in the "new" dizzy and reset the ignition timing.