this question goes to everyone with 8-injectors...ok i know these injectors are bigger than stock which i have to compensate idle fuel pressure to idle properly. i also have RC440cc secondaries. now this puts me at 810cc's total per cylinder. now i know some of you have a little bigger primaries, like Corbin has 250cc's? i think someone has 310cc's. anyway, would i have to adjust the injector scaler a lot lower than it is. what do i have to expect when installing these injectors?

I can't think of a single good reason to upgrade your primary injectors to 370cc. What are you trying to accomplish?

stock primarys and 440c secondaries mathematically should take you to just over 500whp.

i dont see the need for larger primaries

I don't like the idea of using larger primaries. You will run rich out of boost, do nasty things to any catalytic converter between your turbo and the tailpipe, put black soot on your back bumper cover, turn on the check engine light, and make it so you will not pass on the sniffer next time you go for an emissions inspection.

Great idea, though, hacking a hack. I would recommend a solid fuel system. At one point, the EIC was the fuel system that was the least hacked. Nowadays, though, there are better options.

The only benefit I can think of when making the primary injectors this large would be the extra IAT correction.

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The 8 injector does not take into account temperature; this would help in that area.
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Increasing IAT correction will not significantly help. Remember, you still have the stock ECU trimming fuel based on o2 & MAP readings. Who needs more IAT correction anyhow? I can't think of a single good reason for that either, even with an 8-injector staged fuel system.

Either way you see it, the stock ECU does a great job with stock injectors out of boost. The 8-injector setup does a great job under boosted conditions even without IAT correction. If you need more fuel, install larger secondary injectors. That's the point, adding fuel where you need it (which you don't need out of boost). And yes, stock primarys and 440cc injectors are good up to about 500 HP.

Another thing I can't figure out is the recent fascination with you guys wanting to put more the 800cc worth of injectors in each port. I mean, good God, do you know something I don't? I'm running 720cc injectors and I run super rich at 28 PSI on the Super 20G with an injector duty cycle well below 85%. I hope you all know that bigger is not always better... get real.

The point is that the EIC will not compensate for air density. Density is a product of volume, pressure, and temperature. Without temperature correction, the EIC is only guessing, really. Think of how much a CAI helps a naturally aspirated engine. Now cram twice that much air in. What's the effect? More air = more power = more fuel. I just hope that you tune when it's cold.

Yeah yeah, I know all that. But you have to realize that the intake temperatures for a turbocharged engine on a very cold day is going to be comparable to a naturally aspirated engine's intake temperatures on a mild day. This means that the IAT correction is usually 0%. In this case installing larger primary's does no good.

Also take note that the stock ECU only uses IAT data during OPEN LOOP conditions only, to compensate for differences in air mass while the o2 sensor is not being used. If the stock ECU detects no IAT sensor or a malfunctioning IAT sensor, it uses the CLT sensor to make it's calculations. Before I started using the Accel DFI, I removed the stock IAT which forced the stock ECU to use CLT instead of IAT for fuel correction. I did this because I was getting 0% IAT correction in the mornings when it was cold due to the heated turbocharged air intake. The stock ECU, detecting no IAT sensor, used the CLT instead and enriched the fuel mixture on top of already enrichening it for CLT.

Do you see how installing 370cc primary injectors isn't going to give you more IAT correction on a turbocharged engine with the 420A/DSM stock ECU logic?

I see that. I know that 370s are not going to help. They will richen you up at WOT, when the O2 sensor is not referenced. Might as well richen it up with the EIC.

Not that I like the idea of an EIC, mind you. That was my primary point... 8 injectors is a hack. It's a better hack then fuel pressure tuning, but it is still a hack.

Using bigger injectors for primaries is just a hack of a hack.

those are all good points, i just wanted to know 'cause i have four 370cc's lying around and maybe these stock injectors might give out one day, and i can use a back up. either way, yeah that's a whole mess of fuel, but i'd see it as a safety margin with C16 when going 30psi, i have a SC34 turbo which is good to 525HP and no cat. i don't have emissions in FL BTW. i've chatted with Javad recently, and he's mentioned that he can make the 034EIC read IAT. you can send him the unit and he'll reprogram the EIC and it'll handle it. either way, i'm finally ready to dyno, i've been tunning like crazy, and i think my car is doing fine 23-24psi w/ racegas. it's freak'n scary fast now. i feel like i'm hitting 400WHP. my SPEC stage 4 is holding real well, it grabs like crazy and my left leg is freak'n tired. this clutch is a little harsh but i like that grab. but it'll be like next week till dyno, i'm so busy these days. but thanks for the input guys.

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I read it in the factory service manual, Dino.

Yeah, It dosen't make any since. The ECU will just adjust the LTFT way down to compensate, your never going to get more fuel through those injectors. The stock ecu will still control them, your just going to end up with a less consistant a/f mixture. If you want more fuel upgrade your secondaries. Sell those 370's and your secondaries for the money to get some 55#'ers.

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Originally posted by dougie2

Originally posted by MrSlick And BTW dougie, I'm not convinced at this point that the stock pcm doesn't look at the IAT sensor during open loop running...

I'm saying that it DOES use the IAT sensor during open loop. I think your confused.

Originally posted by MrSlick otherwise you would have to have your open loop tables VERY rich to compensate for the known problems tha you get with no IAT sensor.

Right. That's why it uses the IAT, MAP, and CLT during open loop. Closed loop uses O2, MAP, CLT.

Originally posted by MrSlick And please point out the page in the FSM where it states this for our stock pcm, because I don't see it

I don't understand why this is so hard for you guys to understand. I really honestly don't have time right now to go hunting through the FSM for it, that's why I've read the entire manual in the first place. There are actually lots of tricks you can do to the stock ECU if you'd read the FSM and get creative.

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Megasquirt powered 420A
Custom turbo system

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Here's what I found:

Originally posted by dougie2
Here's what I found:

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Originally posted by dougie2

Originally posted by MrSlick

Originally posted by dougie2 Here's what I found:

That's it does not say that it uses the coolant temp sensor allt he time.

C'mon Slick! You're getting off track, that's not what I was saying! I clearly stated that the CLT sensor is used if the IAT was disconnected... which I'm assuming you'll agree with now?

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Originally posted by dougie2

Originally posted by MrSlick Page I-16 of the FSM states that the IAT is used to determine the intake air temp (obviously) which is used to adjust injector PW and ignition advance... Now this is obvious evidence towatrds IAT use during closed loop and open loop.

Quote from page 1-16 that you're referring to: "The intake air temperaure sensor measures the tempurature of the air as it enters the engine. The sensor supplies one of the inputs the PCM uses to determine injector pulse width and spark advance." How is this "obvious evidence towards IAT use during closed loop and open loop"???

Originally posted by MrSlick Page I-17 of the FSm states that the CLT sensos is used for warmup enrichment, and adjustment of the IAC during warmup.

So... what's your point?

Originally posted by MrSlick Page I-43 also states that the IAT sensor is used in the calculations to determine the PW under closed loop operation...

I'll PayPal you $100 if you can even find the words "closed loop" or "open loop" on page 1-43. It really doesn't say that, does it Slick? It says: "Other inputs such as the TPS, RPM, ECT, IAT, VSS, and battery voltage all have varying levels of influence on pulse width, depending on the circumstances."

Originally posted by MrSlick Those are enough mentions for me to believe that the IAT is used for BOTH closed loop and open loop operation on a stock 2gnt/420a SBEC pcm.

It doesn't even come CLOSE to saying such a thing!

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I give up. I didn't believe this either, after an SAE certified technician argued with me about it while we tried to track down some issues I was having. So I found out for myself by malipulating the inputs and outputs of the ECU and logging & graphing along the way. I was able to force the ECU into or out of closed and open loop control states and adjust pulsewidth at the same time.

I know it for a fact, and I've experimented with the idea and found a way to fix a lean condition on my turbocharged engine that was never supposed to be turbocharged by modifing the IAT signal. IF you don't believe it, go test it for yourself... but making assumptions based on one generalized FSM paragraph is not the right way to prove a hypothesis. BTW- many Chevy, Ford, and Pontiac OBD-2 systems work the same way.

*edit: Also, by that last paragraph on 1-43, have you concluded that the ECU uses VSS data in both open and closed loop at all RPMs?

OK.

Well I'm open minded, so although the evidence that I have agrees with the FSM, let's talk about it open minded here for a bit.

Share with me some more in depth information on your testing and lets talk about it...

And I've done testing myself on forcing the pcm into open and closed loop and seeing the effect of the sensor.

The main point I would like to get acorss is that the pcm uses the IAT sensor in closed loop conditions as a major factor in determining ignition advance. If the IAT sensor isn't used in closed loop, then why does it factor into ignition advance?

So lets discuss your testing info.

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Originally posted by MrSlick

Originally posted by dougie2

Originally posted by etx It dosen't make any since. The ECU will just adjust the LTFT way down to compensate

Actually it won't.

Indeed... remember the stock pcm can only go +/- 25% on the LTFT... and bseides, that's only during closed loop operation... open loop is another matter And BTW dougie, I'm not convinced at this point that the stock pcm doesn't look at the IAT sensor during open loop running... it would be very stupid if it didn't. Every standalone system that uses an IAT sensor uses it for lookup and enrichment during both open and closed loop operation... otherwise you would have to have your open loop tables VERY rich to compensate for the known problems tha you get with no IAT sensor... And please point out the page in the FSM where it states this for our stock pcm, because I don't see it

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Indeed? I'll have to poke around and see that. Cool. learn something every day.

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'95 Eclipse TurboGS (garage deco)
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'97 Talon ESi-T (poor impulse control)
'99 Eclipse RS-T (daily beater)
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'17 Sienna (Middle Aged Dad Mobile)



Factory Service Manuals: http://nawdu.de/files/