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Cadillac Tech Tips - How to fix it Discussion, Performance modifications for the 4.x engines. in Item Specific Cadillac Discussion; Hey illumina, do you know if any other adjustable FPR's will fit the 4.9? Such as one of these ? ...
  1. #16
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    Re: Performance modifications for the 4.x engines.

    Hey illumina, do you know if any other adjustable FPR's will fit the 4.9? Such as one of these? I'm not worried about modifying the location of mounting or anything, just if it will work properly...

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    Re: Performance modifications for the 4.x engines.

    Ah, I'll enjoy this ONE bit of experience I have over Illumina... Don't bother with the Iridiums...they're just...well...the best I can describe them is in one word..."eh..."

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    Re: Performance modifications for the 4.x engines.

    Aeromotive makes an LT1 FPR, and Illumina said that the LT1 FPR would work with very minor mods. It is around $130ish at Summitracing.com

    And the Aeromotive one will handle alcohol (aka, E85) if you should ever want to use it.

    Here is some info on how to properly tune your engine with a fuel pressure regulator:
    http://www.aeromotiveinc.com/largedetail.php?ref=69

    Here is a FPR for the LT1 from Aeromotive.

    http://www.aeromotiveinc.com/pdetail.php?prod=13

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    Re: Performance modifications for the 4.x engines.

    I know the LT1 will fit, but I was asking about that particular one because I've been offered a deal to get the "Sport" SARD regulator for very cheap for my car, and it is brand new. I'm not worried about modifying things to make it fit, that's no big deal.

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    Re: Performance modifications for the 4.x engines.

    Ghost, if the price is right and you want to tinker with all of that, without having any serious leaks, then give it a shot. But remember this: the Aeromotive is boost referenced, i.e., if you also do any forced induction, then make sure you get thr right regulator.

    Happy fueling that 4.9 liter

    Tom, I haven't had any time, but I will tinker with the fuel pressure and adjust accordingly to see what can be done. I'll post the results.

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    Re: Performance modifications for the 4.x engines.

    Also, the P/N 13106 Aeromotive is the one that fits our engines. That's the one that I have on there now.

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    Re: Performance modifications for the 4.x engines.

    I'm not that familiar with MSD ignition systems...nor am I in a position to buy one right now lol..but just wondering. Does it allow you to fine-tune the timing on each cylinder?

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    Re: Performance modifications for the 4.x engines.

    Quote Originally Posted by Tailfin
    I'm not that familiar with MSD ignition systems...nor am I in a position to buy one right now lol..but just wondering. Does it allow you to fine-tune the timing on each cylinder?
    The "7 series" MSD ignitions allow fine tuning for each cylinder. The "6 series" that I used does not.

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    Re: Performance modifications for the 4.x engines.

    I have read that around 0.88v is optimal power for most cars. so for tuning, you can run WOT with the diag display on O2 volts and read it.

    It isn't super accurate, as it isn't a wideband O2, but it does give some reasonable reliability for this type tuning.

    Really have to dial it in with some controlled acceleration runs and run 3 runs to be consistent, then change fuel at WOT, then run again. Hell on the car, but it would give good data. Takes lots of time.

    Quote Originally Posted by illumina
    Ghost, if the price is right and you want to tinker with all of that, without having any serious leaks, then give it a shot. But remember this: the Aeromotive is boost referenced, i.e., if you also do any forced induction, then make sure you get thr right regulator.

    Happy fueling that 4.9 liter

    Tom, I haven't had any time, but I will tinker with the fuel pressure and adjust accordingly to see what can be done. I'll post the results.

  10. #25
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    Re: Performance modifications for the 4.x engines.

    Quote Originally Posted by N0DIH
    I have read that around 0.88v is optimal power for most cars. so for tuning, you can run WOT with the diag display on O2 volts and read it.

    It isn't super accurate, as it isn't a wideband O2, but it does give some reasonable reliability for this type tuning.

    Really have to dial it in with some controlled acceleration runs and run 3 runs to be consistent, then change fuel at WOT, then run again. Hell on the car, but it would give good data. Takes lots of time.
    Hey, I make my car go through Hell every day! Or at least on some days...

    I have a road that I can likely get away with doing that...But what you are saying is that I should adjust fuel pressure accordingly and find the best / optimal pressure by doing the runs, right?

    As for the o2 sensor, is it possible to connect a voltmeter inline with it to help get the most accurate readings?

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    Re: Performance modifications for the 4.x engines.

    I did just that on my Cutlass, it worked well. Just make sure it is a digital volt meter, I used a Fluke 87 from work, the analog ones aren't high enough impedance and will load down the O2. And make sure you don't put voltage on the O2, I have heard they get cranky when you do and blow. I don't buy it really, but that is what THEY say. I have played with mine, and the PCM gives a .45v reference to it anyway. I was trying a voltage divider and later a op amp to try to shift the voltage down 0.1v to try to richen cruise. And nothing would work, as there is only a REFERENCE VOLTAGE there, no current can be sourced from it, any load at all will drop the voltage and make it think it was lean and it would compensate by richening it up.

    Try a run where there is no shift, and you are at peak acceleration before you hit the stopwatch. Say 45-75 in second gear. Start your run so that you are already at WOT in second when you cross 45 (or whatever speed works). You don't want traction to be a variable, and you don't want trans shifts to be a variable either. I find my runs in 2nd gear from 35 to 85 work for my data logging runs (not timing it, just looking at airflow data and such).

    One could get creative and connect a LT1 or Vortec MAF to a RS232 port and calculate airflow (I have charts of what these 2 MAF's output) and start doing what it takes to peak it, that might show some good results too. It won't show rich/lean improvements, but it will show other airflow changes like air box, K&N, etc.

    Quote Originally Posted by illumina
    Hey, I make my car go through Hell every day! Or at least on some days...

    I have a road that I can likely get away with doing that...But what you are saying is that I should adjust fuel pressure accordingly and find the best / optimal pressure by doing the runs, right?

    As for the o2 sensor, is it possible to connect a voltmeter inline with it to help get the most accurate readings?

  12. #27
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    Re: Performance modifications for the 4.x engines.

    I could always run in manual 2nd / 3rd for a run to avoid shifting...

    But I am having trouble understanding something: the higher the voltage, the richer the mixture? Please explain this to me...

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    Re: Performance modifications for the 4.x engines.

    He said the opposite I think...


    Quote Originally Posted by NODIH
    I was trying a voltage divider and later a op amp to try to shift the voltage down 0.1v to try to richen cruise
    The more oxygen the sensor picks up, the lower the voltage will be. So if there is high voltage, that means there is less oxygen in the exhaust, so the ECM commands a lean mixture such that not as much of the oxygen gets burned up.

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    Re: Performance modifications for the 4.x engines.

    Higher voltage = Richer (commanding LEAN is the result)
    Lower voltage = Leaner (commanding RICH is the result)

    So if I dropped cruise O2 voltages by 0.1v, the PCM would command it to richen to come back to 0.45v.

    If you watch the BLM values in the PCM, and then disconnect a vacuum line, the BLM climbs. Integrator does momentarily till BLM climbs, and Integrator returns to 128ish. The Integrator is the high res computer representation of the O2 readings. Much easier to read. BUT, it is disabled at WOT (not technically, it goes to a fixed value is BLM is averaging 128 or LESS, if higher, it should pickup the BLM value), so you have to read the O2 off the FDC display in diagnostic mode.

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    Re: Performance modifications for the 4.x engines.

    it is now 4 years later.

    updates to this great thread?

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