Injector Quest

[Turismo]

Heretic -

You said you use the SAFC to help with idle with your big injectors. I guess I was under the impression that even with this kind of fuel controller "idle" is a closed loop function and any adjustments made with the AFC here would be corrected back to the OE parameter by the ECU.

If this is false as you state that this works, I shouldn't have a problem since the PMS has an idle only parameter that I can add/subtract up to 100% fuel out of.

I guess my main question to you is without the AFC how did your car idle and how much do you have it set to remove to obtain a normal idle?

If you remove the AFC's input does your idle return to being rough?

If this is a real solution I would probably go with bigger injectors then mentioned and try to run with as near OE pressure as possible (50-60).

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'96 JRSC GSR Sedan (Black Currant Pearl)
AEM CAI / PMS
J&S Safeguard / Walbro HO Pump
DC Strut Braces Skunkworks Rear Swaybar
H&R OE Sports Billstein HD's
(8psi pulley on deck)

[SC SiR]

I checked the type of injectors we have. It is the Saturated type. I used an ohm meter and measured the resistance at the two teminals. I got 12 ohms.

If we use the peak and hold type, the ecu might burn out.

Just my 2 cents.

[Turismo]

I'm at 6psi still with the 8lb pulley sitting here waiting for me to find my fuel solution before it goes in.

The PMS unit can add/subtract upto 100% in the fuel department and has tables for Idle, & Low, Med, & High throttle positions at 2200,4000,6000,7800 rpm (and everything is adjustable in 500rpm incrementif I get their windows software). I think it will be up to the task as long as what your saying about "closed loop" not being a problem, which makes sense, the ECU's already trying to do what I'm aiming for.

My main concern is I'm not going over 8psi and 440's are probably geared to be able to handle "big boost".

How many psi can 440's support? This should help me with my descision.

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'96 JRSC GSR Sedan (Black Currant Pearl)
AEM CAI / PMS
J&S Safeguard / Walbro HO Pump
DC Strut Braces Skunkworks Rear Swaybar
H&R OE Sports Billstein HD's
(8psi pulley on deck)

[1fstGSR]

at 43 psi they will support 268 CHP
at 58 psi they will support 311 CHP
at 70 psi they will support 342 CHP
This is based on 80% duty cycle and a
BSFC of .50
Will

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13.24 on a smokin' motor can't be bad!?!

[Heretic]

Ops, I meant I'm putting the extra 4 injectors into my intake runners just behind the stock location, not plenum.

Turismo: Yes, the ECU is closed-loop at idle. That's one of the reasons you can even idle with 33-50% larger injectors. The effect of the S-AFC at idle/low throttle is to decrease injector pulse width which is along the same direction as the ECU's adjustment. Thus they are both acting in the same direction, not against each other so that the car doesn't run too rich.

Kinda, neat since it actually works. There are a lot of factors that decrease my car's idle from stock: removed the dual stage intake switch in the plenum, (teg's don't have that), removed the switch-over from air-box, lower compression, cam tuning, bigger injectors, massive headword, etc, but my car idles just fine. It lopes and sounds fucking evil to be sure, but idles fine. My only problem is right when I start it sometimes I have to open the throttle a bit, but that's just nit-picky shit.

I don't think my car will idle at all without the AFC. I haven't really tried though. Of course, I run like 2.6 kg/mm^2 fuel pressure @ idle. I go between 2.6 kg/mm^2 @ -18 mmHg to 4.2 kg/mm^2 @ 15 psi. (that's like ~30psi idle to ~62psi @ 15psi).

You have a PMS, you can control injector width, yes? Get huge injectors, like ~440s. You can tune the injectors way down at low-rpm, low-load with it. Theoretically you can run injectors twice as big if it can adjust -50% duty cycle without problems. 50-60psi is still pretty high fuel pressure. Anything above ~70psi is saying, "Blow up my engine, I really don't need it." It'll be much nicer on your fuel pump. Ideally you'd just run like ~45 psi static pressure and do everything with your PMS, but I'm not sure if the PMS that tuneable/reliable. Remember, don't go over 80% injector duty.

How much boost are you running again? 8 pounds?



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Ryan Earl
'99 Turbo SH
NTPOG - North Texas Prelude Owners Group
My Page

[Heretic]

If your PMS works, 440s will absolutely not be a problem. Like I said, I've sat in an Integra with 720s that idle'd. 440s should be enough fuel such that you can run 8psi @ 45psi fuel pressure without a problem. Your pump will deliver the fuel much more consistently and be much happier all around. What are your stock injector sizes?

The Windows software would be a very good/wise investment. As would a good tuner. I know enough about tuning that I am comfortable tuning my own car, but I know more than most people about tuning. It's very, very important to get it tuned right. I'm sure you know this, but fuel is -the- most important part and hardest to get right. I only run ~4-5 degrees of retard at 15psi because I have a good fuel curve. Once fuel is right, ignition is really easy to get right. The J&S is invaluable for this tuning.

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Ryan Earl
'99 Turbo SH
NTPOG - North Texas Prelude Owners Group
My Page




[This message has been edited by Heretic (edited March 27, 2000).]