adjusting richness

[roscoscott]

I'm new to the forum thing but I'll get it eventually sorry for my improper etiquette. here's what I have, what I have in it and the problem I'm having. 75z, 3.0 pistons, bigger cam, 240sx turbo injectors, 240sx turbo mass air flow meter with the guts out of my stock air flow, 240sx turbo throttle body, the intake has been honed (board out), header, 2 1/4 exhaust, 80 something zx turbo fuel pump, adjustable fuel pressure regulator on the rail. I have the stock ecu and harness.

I adjusted the fp to 35 psi and it flooded on cold starts but if you could keep it running at the red lights it would run good wide open. The 02 was reading 1.00-1.50v so I adjusted the tension on the wheel in the air flow meeter and got the 02 down to .5v-.8v. I took it for a ride and had restricted throttle response because there was to much tension on the wheel. I dropped the fp to 25 psi, unplugged the cold start injector and re adjusted the meeter. I lost alot of hp but it started cold and idled at red lights.

now the questions;

1. is there any way to lean out the fuel other than the mass air flow?

2. do I have to replace the stock ecu or efi with an after market one?

3. is it flooding when it's cold because of the bigger injectors?

thanks for any help ~Rosco~

I'd like to run it at 35psi or better

[roscoscott]

is it ok to start a new thread lik I just did?

[Zed Head]

This thread should be informative for you - http://forums.hybridz.org/index.php/topic/95316-braaps-l6-efi-induction-advice-and-tips/

The Air Flow Meter (AFM) only handles part throttle fuel enrichment (as you've discovered) until the vane is wide open from air flow, after that it's all rpm and temperature based.

The cold start valve (CSV) only squirts gas when the key is turned to Start. After the engine starts, it does nothing.

[roscoscott]

ok thx I'll look at that web sit

[FastWoman]

Well, yes, there are ways to lean out the mix electronically. Although Atlantic Z shows how to adjust the AFM spring tension to alter the mix, I personally don't think this is a good approach. A better approach is to keep the AFM's mechanical response correct (per the "beer can" calibration procedures on Atlantic Z) and then the do other adjustments as needed.

But first, you should ask why you're running rich. These are a few common things to check first:

*Bad coolant temp sensor or faulty connection

*Bad air temp sensor or faulty connection

*Stuck cold start valve

*Bent AFM vane ('75 problem only. As there was no backfire relief valve, the vane could be bent from backfire.)

If you've ruled those out, and if you're sure everything else on the engine is in proper working order (and especially no vacuum leaks, correct valve lash, correct timing), then you can lean out the mixture by adding resistance in parallel with the coolant temperature sensor. As you have an adjustable FPR, you can also lower the fuel pressure -- but I wouldn't think any lower than maybe 20 psi.

But first, check the above. I bet you'll find something out of whack. These EFI systems tend to drift lean, rather than rich.

Edited February 7, 2011 by FastWoman

[roscoscott]

Thanks fast Woman

I put a new temp sen in it when I put the motor in, but that doesn't mean it's good I'll check it. I smoked the intake and there were no leaks. I need to double check the timing. I'll get back to ya on this thx ~Rosco~