Jim bailey - 928 International

the L jet swinging door is pegged wide open at around 3,500- 4,000 RPM so the brain is working on the stored map by rpm with wide open throttle . It has no aditional adjustment for additional air once the door is fully open so lacking any way to pulse the injector longer (and they may be near continuous already) bumping the pressure is a reasonable "fix" .

Weissach1982

So am I going to have to buy Fuel pressure regulators to get full benefit out of the Euro intake stuff or the car won't run right? So what kind of tuning needs to be done in order for everything to work right so I don't have to do another motor rebuild?
Thanks,
Cory J

John Struthers

Cory,
I'd still wait for a 5-7lb SC boost, or just load up a used Euro engine
w/ECU. Mix and matching is cool if you have the time but there is a lot of cash to be spent doing it a piece at a time.
The swap is a one time deal and your already mapped -so to speak- with 80 - 100+ HP that wasn't there before and from what I've read those engines are no less reliable than our mild 4.5L 's.
Failing the swap I'd go SC with 5lbs of boost not a track car you are making, right? Just something with a bit more oomph to rip up the local camaro's stang's, and bird's right? If you want to tangle with the big game, late model vette's and sniff at the viper's, M-5's, Z 8's- you need a 5.0L or better and will still have to SC.

Weissach1982

-John S.
Well in the future I'm probably going to wind up buying a SC kit for my car...but I haven't found a direct bolt on kit yet, . I'd be willing to dish out the money for one though, if anyone knows of someone who makes a complete kit. As of now..i'm going to do minor bolt ons like the Euro intake and remove smog pump and add 85-86 manifolds. So I should be getting some good power results out of those, but until I find a SC kit for my car which I can't wait, I'll stick with these parts and retain my US parts just in case the SC won't flow well with the Euro Intake parts.
Cory J.

PorKen

Cory,

I picked up 10 horsepower on the dyno by richening the mixture with the AFPR ($165 for 10 HP?). Torque was unchanged; the stock fuel pressure must be OK up to at least 3900 RPM.

I still couldn't get over 200 RWHP (dammit!), so this whole intake business is intriguing.

...

This morning I was re-thinking about re-engineering the plenum and I was wondering about when the 'barn-door' is fully open. I look here and Jim B. says 3500 RPM or so!

How about a smaller (vacuum operated?), second throttle body, that would open after the barn door is fully open.

Bell-mouths on the entrance of each 'leg' would be nice too...

PorKen

I think I'll put in a vacuum gauge today and see how much, if any, full throttle vacuum there is.

Weissach1982

Hey Porken, who did you get your AFPR from and what mixture did you set it too? Also, what are bellmouths and explain what you are doing with this vaccum idea.
Thanks,
Cory J.

PorKen

I bought the AFPR from Huntley Racing. Seems very nice, all machined aluminum.

Stock pressure is 36 PSI. On the dyno I ran 41, 43, and 50 PSI, 43 made a couple more horses than 41, but 50 was too much and lost HP. At full throttle, 41 showed 13:1 on my air/fuel meter, 43 about 12.5:1.

I couldn't adjust the AFM so that the oxygen sensor would work properly over 41PSI and it would surge while cruising.

...

Bellmouths help transition the air from one pressure zone to another. Something to do with the shape.

They are cast into the S4 intakes:


On individual throttle bodies, they are tuneable, ie. by changing the length, you change the rpm range of the engine:


...

I want to check if there's vacuum when at full throttle. Ideally there wouldn't be, but if there's intake restrictions, then there will be some vacuum.

The vacuum remaining could control a second throttle body that would open as the rpms rise after the AFM door is full open.

toofast928

Hey PorKen what exhaust set up are you using? So AFPR, fuel pressure set at 40 psi should put me in 13:1 ratio. cool...........

ViribusUnits

Really Jim?

If this is the case, how does the L-jet computer make up for part throtal actions at high rpms?

Doing a few back of the envelope math, I figured that at 5500 rpm and WOT for my 83, I'd have much much more fuel than at 3500. OK, so the comptuer map takes care of that. It checks the RPM, and acts like it's WOT. Then I got to thinking. Is would be possible in part throtal opperations to have as much mass of air flowing through at 5500 rpm, and part throtal, as would be flowing through at 3500 rpm and WOT. That would mean horridly rich conditions at 5500 rpm and part throtal. That would mean a flat spot of sorts. Something I haven't experenced.

I'm not saying it's not true, but it's hard for me to belive.

PorKen

toofast928,

Stock exhaust manifolds, Flowmaster Delta 50, 3" single pipe: See here.

Also an open airbox (with stock paper filter): See here.

The pressure will probably be different for your particular setup, that's why, if you don't have one, an air/fuel meter is a must.

Weissach1982

Is an Air/Fuel meter necessary for tuning the 928 with an Ajd Fuel Press reg or Rising Rate?...what is the difference between the two?
Thanks,
Cory J.

PorKen

I suppose you could do timed runs, until you start going slower.

It easier with an air/fuel meter to set your WOT fuel setting. But after you set the minimum fuel pressure to be rich enough for full throttle, it's not as vital.

For setting the full throttle mixture you can use the stock sensor (or sensor location) for a meter, because past 60 degrees throttle, the ECU ignores the oxygen sensor.

After I set the WOT pressure, I found I just had to adjust the AFM bleed screw out a turn at a time until the car stopped surging while at part throttle with the oxygen sensor connected to the ECU. In my case at 41 PSI, I had to go 12 turns (of a maximum 14).

The O2 sensor circuit does a good job correcting for the richer setting.

Even when the car was stock, it was definately running too lean.

...

A rising rate FPR ups the fuel pressure at a higher ratio when on boost. It's a crude way of programming the fuel curve.

toofast928

Thanks PorKen. Your still using the USA heads and camshafts right?

PorKen

toofast928 - "It's got stock heads, stock cams, stock manifolds. It's a model made before high compression so it'll run good on regular gas."

...

I checked the vacuum at full throttle in first up to the rev limit, no vacuum.

Upon further thought, a secondary TB wouldn't need to be variable anyway, just go wide open after a certain rpm...