Stephencs601

lean mixture was 14.49 to 15. Also, power was not steady. Went up and down then started dropping after 5100rpm

mark kibort

fuel regulator is the only thing that can take it from stoich to the 13:1 range under WOT conditions. cruise will always be in the 14+ range due to the o2 sensor and its hunting. if it is really lean, it will be down on power, big time, 16:1 and higher ! that can be caused by clogged fuel injectors, fuel filters, or you could have a bad fuel pump. check fuel pressure

mk

mark kibort

souds like you are right at stoich, and this is where bad stuff happens under WOT. fortunately, the 928 engine is underrated HP wise and it can handle the max heat that is generated at this mixture. detonation can happen here too. i would fatten it up by buying a fuel pressure regulator (RRFR) or you can crimp the return line on one of the regulators to raise the pressure slightly.

mk
make sure your WOT switch is working, but it sounds like it is, as if it isnt, it goes real lean under WOT conditions.

Stephencs601

So, it comes down to either fuel pressure or WOT, correct?

hacker-pschorr

Mark,
I did a lot of testing on the dyno with a manual switch on the WOT circuit. With the switch off the car was reaching scary lean levels, everything else on the car was 100% and fuel pressure was perfect.

Without a fuel pressure gauge any "testing" on the fuel system is all guess work. Sure ramping up fuel pressure will "fix" the problem (lean condition) it's not a good solution.

Crimping off the return line on each regulator is a good way to test each unit. But again, without a pressure gauge attached to the rail, you are just guessing as to what is really going on.

I would also get the car nice and warmed up, check the resistance on the Temp II sensor. If for some reason it's not a high enough resistance the car will run lean..........WOT switch is the easiest part to check, go from there.

It could also be the AFM, a short in the wiring, unless you are measuring vacuum or doing the carb cleaner test you have not 100% ruled out a vacuum leak.

mark kibort

being that close to normal, its not a failed AFM, could be fuel pressure due to a weak pump and a fuel regulator to raise pressure is a good solution. however if one cylinder is not firing, that will be a logical cause too. especially if you are down 50hp!

leaks in the vacuum lines cant do this. a big leak could , but then it wouldnt be able to idle

yes, the WOT makes the car go real lean (not that scary, as "way" lean is not as bad as 14.7 lean! ) if it is working, it will be obvious as you say.

post the dyno runs and we can take a look. if the afm is working, the fuel curve will be pretty flat.

Id shoot for the injector issue, as the big hp being down could be a big reason.
our cars still run kind of well, with one cylinder not firing

MK

hacker-pschorr

Mark, he's not down 50hp, at the most 12 or so even if that much.

My car will go from stoich to rull rich at idle if I activate the WOT switch.

AO

Assuming your WOT switch works and there are no vacuum leaks, I agree with Enzo/Hacker that without a Fuel Pressure gauge, you're kind of pissing in the wind. You need to know if you're losing pressure at WOT.

If you are losing pressure, it could be a weak pump, clogged fuel filter, etc.

If you are NOT losing pressure, then it could be a clogged injector, bad Temp II?, etc.

Not sure which cam a bad fuel damper or FPR fits in? Anyone?

SteveG

Is this the session that took place at Powersurge in Port Jeff on Sunday? Did they solve the no-start problem on the '94? If so, I'm curious what was causing it? Wish I could have hung around longer. If Wayne is reading this, how about a short report on the day?

Stephencs601

Yes this was the Dyno in Port Jeff, and no; Lexs' car had to be towed. We could not get it started no matter what we tried. Wayne helped soooooo much, a real great guy. Lex told me today he will get it going soon.

I hate being so lean and not knowing waht it was yesterday.

Fogey1

FYI, in 2001, mine was:

'83 US 928S 5-spd. #62013
Grandprixweiss over Brown leather.
New to me at an indicated 87K with broken odo and not run for more than a year, on its 2d tank of Premium & Techron, without intake tubes, it dyno'ed at:
192.3/192.0 rwhp & 232.2/234.0 torque.
AFR steady around 14-1 from 2750 RPM. 15.8 at idle.

Others told me I could get more with an adjustable FPR and richer mix.

mark kibort

I got your dyno run and plotted it against my 188hp with headers dyno run from my 1997 run from my stock US 84S. Yours is actually better in all areas. both hp and torque are either the same or slightly better.
the ONLY difference could be the fuel mixture, but i didnt have a meter on mine, until i did the 40hp adders. at that point i was 13.8 with the fuel regulator as they come and ended up at 12.5 with a 1.5turn advance of the RRFR screw.

so, based on my perfectly running 84, before big mods, and only headers and a cat removed, yours looks perfect. now, mine was a little weak compared to some 84s and earlier 928s, but certainly in the healthy range.

put a fuel regulator , or just clamp off the return line on the opposite fuel regulator, and you will probably pick up 5-7hp and get the fuel ratios in the 13s. If not, ill send you another stock fuel regulator.

MK

Stephencs601

Mark, Thanks for the reply. I am going to put an Adj fuel Reg on as soon as I can get one. But it is good to know I am where I should be. Now it is time to do some mods to pick up hp. Other than a blower, is there chips or other easy mods available.

hacker-pschorr

Why not find out where fuel pressure is now before doing anything, then test both regulators?

Here is the chart:

AO

I wouldn't say that's overly lean. Maybe slightly, but I wouldn't be afraid to run it as is...

Edit: However, something isn't quite right... I'd double check the WOT switch and check the fuel pressure.