Thread: IPW questions

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  1. #1 IPW questions 
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    Really dumb/newbish question, but how does the PCM read the IPWs? Is it at the point of the injectors spraying, point of fuel entering the combustion, or after it leaves the exhaust valves? Reason im asking is because since im running alky, my IPWs are spiking to 21mS on stock injectors with the 3.2” pulley running 18* of timing. My wb is also at 10.5 but after talking with a few alky users, that’s where I should be at. I asked a few members and they say usually when running 3.0” pulley is when the stock injectors are maxxed. If the IPWs are read at the injectors spraying then my tune is bad and needs a better tune.
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    Bastard Reptile's Avatar
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    A pulley really has no meaning to where your injectors should be. If you're running at 21ms to keep your afr at 10.5, then you're in need of upgrading your injectors.

    The PCM commands the current to the injector milliseconds for a given air fuel ratio. If you're keeping your intake charge cooler with the methanol, then you're moving more air into the engine. If you sit and think about it, moving so much air at a certain temperature is going to differ from application to application. Just because you've read that "oh, I'll be ok down to a 3.0" doesn't mean that you can hold to it. You're moving air into the LIM from say 280* down to say 200* because of the alcohol....which equals more fuel.

    I hope that I haven't completely rambled on aimlessly....
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    Quote Originally Posted by Reptile View Post

    I hope that I haven't completely rambled on aimlessly....
    No more than usual. Doesn't need to be said - but he is dead on - good info.

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    Quote Originally Posted by Reptile View Post
    A pulley really has no meaning to where your injectors should be. If you're running at 21ms to keep your afr at 10.5, then you're in need of upgrading your injectors.

    The PCM commands the current to the injector milliseconds for a given air fuel ratio. If you're keeping your intake charge cooler with the methanol, then you're moving more air into the engine. If you sit and think about it, moving so much air at a certain temperature is going to differ from application to application. Just because you've read that "oh, I'll be ok down to a 3.0" doesn't mean that you can hold to it. You're moving air into the LIM from say 280* down to say 200* because of the alcohol....which equals more fuel.

    I hope that I haven't completely rambled on aimlessly....
    The MAF reads X amount of air and commands X amount of fuel to reach X AFR right? If one sprays alky after the MAF I'm not seeing how this would change the IPW's to reach the commanded AFR. Regardless, I do agree the injectors need to be upgraded.
    Last edited by Nubraskan; 01-10-2008 at 12:56 AM.
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    good ****, thanks guys. :-)
    old setup-Z7 Turbo Kit w/T66, A2A I/C, stock cam & valvetrain/LS1 MAF/Ported 99TB/PowrTuner/AFC/Devils Own/LS1M Scanner/PRJ FP/42# Injs=12.3@118mph street tires -
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    Because the Alky isn't changing the air mass that passes through the MAF. It keeps it at a manageable temperature after it goes through the supercharger. Which it will still expand reasonably, but not as much as if you're trying to cram so much air into the engine that you're boost stacking. If anything, it's acting like unmetered fuel. Which is part of the reasons I've read about why it's so difficult sometimes to tune a car with alky. You can still run smaller pulleys after running methanol, but you've still got to keep your fuel trims in check regardless what size pulley you are running.
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    Quote Originally Posted by Reptile View Post
    Because the Alky isn't changing the air mass that passes through the MAF.
    The alky isn't changing the mass of anything, its just changing density. All air that makes it into the engine is seen by the MAF and the mass of air can't change after the MAF without additional air going through the MAF. So whatever amount of air the MAF reads is the amount of fuel needed to match that regardless of whether the density of the air changes later on.

    Quote Originally Posted by Reptile View Post
    If anything, it's acting like unmetered fuel.
    I'll agree with you on that.
    Last edited by Nubraskan; 01-09-2008 at 06:53 AM.
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    hmm makes sense, got me thinking a bit more. thanks
    old setup-Z7 Turbo Kit w/T66, A2A I/C, stock cam & valvetrain/LS1 MAF/Ported 99TB/PowrTuner/AFC/Devils Own/LS1M Scanner/PRJ FP/42# Injs=12.3@118mph street tires -
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    Quote Originally Posted by Nubraskan View Post
    The alky isn't changing the mass of anything, its just changing density. All air that makes it into the engine is seen by the MAF and the mass of air can't change after the MAF without additional air going through the MAF. So whatever amount of air the MAF reads is the amount of fuel needed to match that regardless of whether the density of the air changes later on.
    You're correct. Density was the word that I was looking for. Same principle, different word. LOL
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    What you see on a scan tool is comannded IPW's.
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  11. #11  
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    isnt 10.5AFR a tad bit too rich?
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  12. #12 Re: IPW questions 
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    normally on forced induction you want to keep it around 11.2- 11.5.......
    2001 GTP- PT76 turbo, Intense Drag cars old engine, Stage 4 Intense turbo cam,FMIC,150 wet,Double roller timing chain,Diamond forged coated pistons 8:0:1,Diamond piston rings,Cryoed L32 connecting rods,Cryoed crank,Clevite77 main bearings,Clevite77 cam bearings,Clevite77 L32 rod bearings,ARP Everything, Intense/meizere true billet Flexplate,Intense Wilson UIM/LIM,Intense oil pressure kit,Cometic,OE-R lifters,Cryoed L67 block,ATI turbo dampner,80# inject,Weldon 2035 fp,Aero Fuel Rails,AL cradle
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