Fastest928

You tune with Fuel pressure for peak hp.full throttle over max lh voltage reading, and with piggy back for ther rest of the curve.

Strokers max the maf at about 4000 rpm.

Marc

MarkRobinson

Hi Marc,

I suppose that's for the '87 on up...I've never had one of those, all mine have been '85-86 cars as I like the sharper body lines.

The 415rwhp dyno was at 2psi below stock FP, using 30# injectors in lieu of the stock 24#. Assuming my MAF ran out like the '87 cars, this HP number would not be possible. I get my AFC-R tomorrow..will do some voltage testing at WOT before I program the unit as it's fully programmable to accept a variety of ranges.

Mark.

mspiegle

No doubt the stock fuel system can handle some boost. Andy's lower-priced kits are able to run with very little modification to the fuel system (no RRFPR or piggyback).

I'm just saying that once the MAF voltages go over 6v, bumping the signal up wont gain you fuel because the LH has already maxed out the injectors.

If you can take that fuel curve of yours from 5000+ and get it to 11.0:1 with only MAF voltage changes, I will definately be scratching my head.

mspiegle

The MAF from my 85/86 was identical (bosch pn#) to a 928GTS MAF, so I can only assume that nearly all the MAFs are the same.

Let me know how your data logging goes. I'm very curious.

Also, those are some kick-*** numbers for that level of boost. Are you intercooling? Any other mods?

John Speake

Y, we actually lowered FP by 2psi to compensate for the 30# injectors (stock are 24# on the '85-86 cars), '87 on up are 19#, so it's not as large of a difference. FP at WOT was about 41psi or so.
>>>>>>>>
Mike, if you have data logging it would be very interesting to know what the injector duty cycle and MAF volts were at max torque and max power.

MarkRobinson

My last monitored dyno run was that one: 415rwhp, 380rwtq, 30# injectors, 28psi at idle, 41psi @ WOT. That run was our first run on the car, & customer requested extra-rich for high Texas temperatures, so we left it there. He's got my first exhaust (same style) off my grey car, + 5psi, no intercooling (a real bear on the pre-87 cars).

I'll let you guys know what I find. BTW, Marcus' car made 525rwhp on our kit + S4 intake + a/w intercooler @ 12psi through a '91 automatic on his '85 car...all w/o FMU or such on 30# injectors, drawing through a stock MAF.

Mark (Thanks to you guys for sharing your thoughts)

Jim bailey - 928 International

Marc Reviel and Mark Robinson and F.A.S.T. (Forced Air Systems Texas) have a lot of history. Which reminds me Reviel (as I recall)was at his wits end several months ago when he stuffed a USA 32 valve 85-86 engine into a Euro 16 valve L H and the ignition was out of phase. He offered a reward for HELP and yes I did tell him that the two wires to the secondary stage of the ignition were flip flopped USA to Euro .......I never did see that check

MarkRobinson

Hi Jim,

That was me. Yes, that did get it running but still had other ignition issues that were never fully solved as it ran "lopey". I was hesitant to congratulate you since I wasn't sure that it fixed the problem rather than semi-patched it. I few more months of testing/diagnosing did nothing to fix the issue. ...I now think I know what they were, but then had no clue. the old LH sure is finicky. I don't want you to feel like you were gyped on your advice, but still don't know if that indeed was the final ticket. 1/2 the reward with you to make peace? ...it's obvious it still bugs you. I can understand. I do appreciate the help.

Mark.

Fastest928

Mark,
I am not sure of the early 32 v electrionics ... all stokers use the stock ecu programming and higher rate injectors and rrfr.

I would suggest that you use a non intercept box with an additional injector that is map programmed and inject into the manifold at the TB point. Distribution may not be perfect, but it will work and allow you to work around the stock system. "Might" need to dientify if the maf and ecu has a similar limit as the later ecu/maf.

If anyone can keep it running string in the heat, it is you!

Keep up the good work.

Marc

Jim_H

Jim bailey - 928 International

Mark the Euro 84-85 did NOT have an idle stabilizer valve so quite possibly the Euro LH brain has no such provision. The USA 85-86 does have the LH control idle speed although you also have a manual adjustment once you override the LH function then let the brain handle it from that point forward. The Euro LH engine runs OK on a USA brain just not sure about the opposite....

MarkRobinson

Wish you would have forwarded that info before I sold the car. Christine's happy in Alaska I hope....

Jim bailey - 928 International

Did you ask ?

John Speake

Marc,
The MAF fitted to the 85/86 32v is identical to the one used on all the later 928s.

Jim bailey - 928 International

John do I recall correctly that the "mixture control screw" on the MAF is only active on 85-86 and NOT wired for the 87> ?? Which although the same MAF it's features are used a bit differently ?