Im awaiting the arrival of my diacom software but in the mean time I have been monitoring the fuel pressure in relation to how my car runs.

FWIW, I have converted to a GM '730 ecm. I previously had the fuel pressure set @ 37 psi and the car would run lean at idle, so I bumped it up to 40 psi. Now it runs better and does not run lean at idle but when I hold 2000 rpm fuel pressure drops back to 37-38 psi and at 3000 rpm 39 psi.

The car now is running at its best when first started up (open loop?) and will hesitate sometimes and I can hear popping outta the exhaust under heavy throttle.

Any idea where I should go when I begin to burn my own proms and get some diacom data?

I have a pocket programmer, definition files and eprom eraser.

Spare eproms and diacom are on the way.


TIA!

------------------
1985 355 S/R V8

 

Get some good fully warmed up idle data with diacom. I don't know what your car has in it(heads, cam), but from what i've gathered, aluminum heads like about 20d of timing , TOTAL timing that is. The very first thing to do is get those VE tables down pat!
You don't want to run too rich nor too lean. Once you get the VE tables close. No need to get them perfect, then you'll need to experiment with the spark tables.
I've also found that with the 58mm TB and the Superram, that you need some more pumpshot. Alot of Miniram guys also find the same things.

Those a few of the key things, get your idle basically perfect first, then you can build on that.

Brendan


PS. Do some searches on this board about "P730" and you'll find alot.

------------------
1987 IROC-Z L98,SR,EB 6085's,LPE 219/219 SR Cam, Crane 1.6RR, EB TPI Base, 58mm TB, Stock T5, 30lb SVO, AFPR, K&N, EB TES, Catco Cat, 3" Borla Cat-Back, Accel cap,rotor,distro/other crap, Aluminum DS, 94 Disk Rear, Adjustable Prop Valve, Precision 3.73 Gears, Weld in Sub-Frame Connectors, Hotchkis LCA's, KYB Shocks/Struts, Poly Bushings all over the place, Moog Upper/Lower Ball joints and Tie Rods ends/Idler Arm, Big stereo, 730SD Conversion.

To see the ROC, Check out the webpage Here

 

Thanks for the feedback.

My set up consist of AFR 190 68cc heads
Holley 58mm t.b.
Comp Cams 270HR cam on 112lsa
1.6 lunati r.r.
Hooker 2149 headers.... 1 3/4"
a.f.p.r. K&N, true duals w/random tech bullet cats, etc, etc, etc.....and of course the s/r

Assuming my diacom arives, i'll provide more data later this week.

------------------
1985 355 S/R V8

 

If your fuel pressure isn't holding, or even dropping when hitting the gas, then you probably need to replace your fuel pump. You can get a Walbro pump from Ron Gregory for a little over $100. DIY_PROM content: I'd hate for you to burn up your engine by running too lean before getting it tuned up. You're better off replacing the fuel pump first (also make sure your fuel pressure regulator is working and the vacuum line is hooked up and not leaking) so you don't tune your VE tables and then have everything change with the new pump.

------------------
Greg Westphal
'87 IROC 355TPI/A4

 

If you are programming the eprom, fuel pressure becomes a non-existant tuning issue. You just pick the fuel pressure you prefer to run (I recommend somewhere between 44-50 psi...depending on YOUR personal preference), and then tune the eprom accordingly.

If you HAVE to run over 50 psi and still maxing your VE Tables, this is a good indicator that you need larger injectors. More than 50 psi gets hard on the fuel pump and tends to shorten it's life.

 

Actually, I use fuel pressure sometimes as quick tuning. I have leanred (Glenn) and found out that that increasing FP tends to effect the high KPA areas. I have used this if I noticed that I was lean under hi loads. Pump shot has been very important for me. I have a miniram which I still hate and continue to have tip in problems no matter what I do. Although I have to say that I have gotten rid of all the tip in except after adding throttle while in Decel mode. If I did not have decel mode, then I would have no tip issues.