AO

Sits in the merge collector, and yes, I did a free-air. So technically it's only measuring one head, but I've done that on my other (SCed) cars without any significant variability from one side to the other. I know ideally I should place it after the Y but I don't have an available bung there.

PorKen

The WOTpot is 1K pot with a 8.2K bridge resistor to cap it at 900-ish ohms. (I recall now that a little less than 1K ohms was the limit for the LH to register WOT. My code requires at least 30 ohms to determine if the pot is connected.)

So it sounds like you're good, there.

AO

I'm seriously suspecting the MAF.

I'm surprise others with the S300 chips (and a US-rebuilt MAF) have not had issues.

I'm going to try my other spare MAFs and see if there is any change. Will report result later today.

GregBBRD

I had a set of Ken's chips in a stock '85 which ran so lean the dyno operator refused to run the car, after the first pass. A different MAF did not solve the problem, with that vehicle. Ken sent me an adjustable potentiometer that Ken apparently supplied with his chips originally, but deleted because he decided it was not needed. I was under the assumption that he had "resumed" including this potentiometer with all his chips (after my experience), to allow people to fine tune the mixture, at full throttle.

"Generic" chips have always had limitations, simply because no two engines are exactly the same....especially 30 year old engines with 30 year old components! The 3.2 liter 911 Carreras, which also had Bosch injection (from a similar time period), had an adjustable potentiometer inside the brain to that allowed "fine tuning" of the engine.

Once you have the correct fuel pressure, the correct injectors, and a couple functional temperature senders, WOT mixture on the 1985-1995 vehicles, is almost completely dependent on the MAF and the computer (chip set).

You are on the correct path. A different MAF will tell you if you have a "chip issue".

PorKen

The stock chip is 'generic' and it works pretty well. If y'all can't get a car to fuel properly or there is a sensor or wiring issue that prevents returning the car to near stock condition, then don't blame the 'chip'.

The WOTpot was for folks that may have added a larger exhaust system (not just a X-pipe) or injectors that were much different than stock. Andrew is using the stock injectors and it is still lean with the stock LH chip with the higher pressure S4 FPR so there is obviously still a problem somewhere.

What is the idle AFR with B->C connected?

mark kibort

yes, from your video .. WAY too lean.. and i mean, 14.7 is very dangerous.. surprised you didnt have a ton of pinging.
figure that one out and you will have a bunch more power too.

AO

I tried that yesterday. It was like 10-12, but that was on a cold engine. But the WOT was definitely working. It was almost undrivable.

Do you think unplugging the O2 sensor would shed any light?

I'm going to try one other MAF, and if that doesn't solve it, I'll shark tune the bitch to get it safe and then go have some fun. I'm missing a track day tomorrow!

Agreed. There is power there for sure. It's already better, but WAY too dangerous.

PorKen

LH 2.2 doesn't learn, so the O2 sensor shouldn't affect WOT. How do the plugs look? Do you have any that are too clean? IE. bad injector or spark plug misfire? One jug not firing will dump a lot of air into the exhaust.

If it does come to down to using the SharkTuner, you can still use the S3.S300s EZF chip as long as you keep the AFR below 13 at WOT. (The brains don't communicate.) If using the S4 FPR, start with something like a 27# injector in the ST.

AO

Ahh yes. Thanks. I forgot there isn't an o2 adaptation like the S4s. I've not pulled the plugs, mainly because they're a PITA to get to, but I will try to tonight. The motor runs very smooth, so I don't think there's any issue there, but a weak or plugged injector could explain things. So I'll read the tea leaves and report back. (Daughter has flute lessons tonight, so not sure if I can get to it today.)

I might also try a different WBO2 just in case the one that I'm using is wonky.

I really appreciate all the support. Especially from the robots.

AO

OOooo... Ooo. Mr. Kotter! Mr. Kotter!

How about a weakish fuel pump? I could hook up the Go Pro and see if the Fuel Pressure falls (or fails to rise) on a full-pull. That would explain things, wouldn't it? I have no idea how old the fuel pump is, so it's worth a try and I happen to have a brand new fuel pump should it happen to be weak.

Thoughts before I chase my tail?

blau928

It is appearing that you might want to invest in a data logger. That way, you can monitor all aspects of the engine and check the logging files and data before and after something odd happens.

You could log fp, timing, fuel pulse, etc..

Aim pista, Motec etc....?

Just my $0.02

AO

I have an Innovate on my GT, but it's a PITA to hook up. Maybe over the winter. Now I see why guys buy cars with OBD2 and just get a dongle.

mark kibort

very easy to do..... just jack up the back of the car, mount the fuel pressure guage on the fuel rail, and then have someone watch the gauge as you use 4th gear at 3000rpm and then floor it slowly while also appling the brakes.... this way, you get no run away wheel spin, you get to see WOT,and you dont need to mount up a go pro and a light under the hood.

AO

On a whim, I measured the Temp II. Current ambient temp is ~80F and car is 100% cold.

On both sides I get ~1.9k Ohms. Seems a bit low doesn't it? I think it should be more like 3k. I'm going to dig around to see if I can find the one on my GT (it's in pieces) and measure that for reference.

Yeah! Way easier! I'll give that a try first.

PorKen

Temp II problems are usually over-enrichment when hot or lean when cold.

S4-up there is error correction for out-of-range temps - the LH switches to a warm default.