Blown87

iTrader: (1)

I have an 87 Z-28 305TPI with a paxton supercharger (8PSI). I have a mild cam (206/212 .480/.487), MSD-6BTM ignition, AFPR set to 40 PSI, Accell #30 injectors, Flowmaster cat back exhaust, and a chip that is calibrated to the above specs.
The problem that I have is the vehicle is running very rich. Black smoke out the exhaust, misfiring, and will not idle. I have checked all mechanical components (compression 100-115, exhaust back pressure 1 PSI @ 2000 RPM w/ stock exhaust manifolds, No fuel leak down after shut off, timing set to 6 Deg. BTDC). All seems to be good.
Now for my question: Does the MAF sensor need to be calibrated or replaced to compensate for the larger volume of air passing throught it? Has anyone had similar problems? Any advise would be appreciated.

P.S.- I returned the PROM once to verify that it had been properly calibrated. DFE motorsports did the programming. They checked it and assured me that it was set to my specs.

dgoodhue

It should be able to compensate. Do you have a scan tool? if you don't I would try to get access to one and look at your BLM's at idle and while driving around. I would guess the problem is youre chip isn't properly calibrate for 30lb/hr injectors.

Blown87

iTrader: (1)

I thought about the possibility that the injector constant was incorrect, but DFE checked and are sure that it is calibrated to #30 injectors. I would drive it but I can't get it to run enough to take it for a test drive. The only scan tool that I have is an OTC, that is really slow.

Blown87

iTrader: (1)

Well, I've got some numbers. The vehicle is idling well now. I replaced the plugs with NGK plugs that have a colder rating. I know having plugs that are not fuel fouled will make it run better for now.
When the vehicle is idling it goes into open loop. With the engine at about 2000 RPM the fuel integrator starts at 128 then drops to 113. Once it hits 113 it goes into open loop. After a few seconds it goes back into closed loop and the process starts again. The block learn is at 108 but that does not include any street time.
It can feel a slight misfire as the O2 crosses from rich to lean. I did not drive it because I know it is still running rich, and if the plugs foul it will probably start stalling again.

dgoodhue

Don't worry about the INT. If your BLM are at 108 your already taken the maxium amount of fuel, hence why your still running rich. Maybe try lowering your Fuel Pressure some.

drive it

iTrader: (1)

Ditto to above on fuel press.-what is it set at? If not unreasonably high....then they didn't set the inj. constant where it needs to be.....just because an inj. is "30lb" doesn't mean that is what the inj. constant needs to be set at.....
Are the blms at 108 at all maf gps and cells?
Give your scan #'s to DFE....if they don't reprogram then I would'nt give 'em any money.....

Blown87

iTrader: (1)

Here is an update if anyone is interested:
I replaced the O2 sensor. This eliminated the dropping out of closed loop at idle. The car runs much smoother now so I was able to put it on the street and get some more numbers. My OTC only gave me five BLM cells to read.

Cell 5: BLM: 109
INT: 130
O2 volts: .01-.70
MAF: 10g/s

Cell 6: BLM: 108
INT: 128
O2 volts: .01-.71
MAF: 10g/s
Note: Cells 5 and 6 were at idle with no throttle change.

Cell 7: BLM:117
INT: 128
O2 volts: .02-.70
MAF: 17 g/s

Cell 11: BLM: 108
INT: 100
O2 volts: .78-.81
MAF: 46 g/s

Cell 15: BLM: 108
INT: 100
O2 volts: .82-.83
MAF: 58 g/s

The vehicle is still running rich. My fuel pressure is at 40 and I can not get it any lower. If anyone has suggestions or similar expiriences, I would like to hear them. I think maybe this post should have been put in the DIY PROM or TPI section. Sorry if I placed it here incorrectly.

dgoodhue

If you can't lower the FP anymore, your injector constant in the chip need to be set higher. 2 of the 3 108 BLM you list are out of range for the ECM and 108 and 109 are almost their.

Blown87

iTrader: (1)

In my first post I mentioned that I had DFE check to see if the injector constant was correct. They said that it was, but based on my complaint they would set it to 32.5. Should it be set even higher?
What do you mean by two of the three 108's are out of range? Is 108 the most fuel that can be trimmed out?

dgoodhue

Unless they expanded the BLM range, yes 108 is the most fuel that can be taken out.