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Thread: $OD Corvair bin file - Got any advise?

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    Fuel Injected! corvairnut's Avatar
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    $OD Corvair bin file - Got any advise?

    Got any advice? OK.. some of you may know that I have been working on a Corvair bin file for a couple of years using at 6395 ECM with DIS. The starter bin file usually does not resemble anything after I get through with what it takes to make the engine run. The offsets that you see (55 degrees initial) is for the DIS. I wanted some real smart people to look at this file and tell me if you see any glaring errors that I have created with testing over the years. I use a romulator to change bin files on the fly so Im sure I have made a few whopper mistakes that I didnt change back. BLMs are pretty close all around and timing is about 5 degrees from ping just about everywhere.

    The Engine specs: 164 ci, 110 HP, stock cam, dual GM TBI-700 throttle bodies. Automatic Trans but cant signal ECM when shifting from drive/park, etc. Used engine with about 100K miles. Heated O2 sensor.

    The engine runs pretty good under all situations. I have good smooth power and pretty good cold performance.

    What I dont like:
    Idle is a little bouncy in N at 750 RPMs but less in gear, but I might be a little too critical. I see the AE pop on and off and have mad many attempts to change that, but never succesful. I would love to have a real smooth idle.
    When shifting from N to D, the Idle drops to around 450 and takes about 4-6 secs to get idle back to 750. RPM recovery was better in the past, but I'm sure I have made changes that killed that.

    The log file I have is with AFR loopup disabled for BLM recording. The xdl is too large for uploading, but I have posted to my website http://www.corvair-efi.com/upload/102312.xdl As you can see from this bin file, I learned with I know from the school of trial and error and wished I had been on the forum a couple years ago.

    Thanks for your time to look and I will put my "tough skin" on.

    Ted
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    Ted Brown
    Anderson, SC
    68 Corvair EFI
    61 Corvair Loadside Pickup (Future EFI)

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    Fuel Injected! gregs78cam's Avatar
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    The hunting at idle may be due to your "Idle Underspeed Spark Advance vs. RPM Error" (L44F9) being so high. I am guessing that you might be trying to get the idle speed to come back up after P->D with this parameter. Try making these values smaller for a more rock solid timing at idle. And actually I would think that you would want it to idle around 450 to 550 in idle, no? Also without the PCM knowing when you go into gear it will be more difficult for it to get the idle to recover faster. If you could get signal to the PCM, there a whole bunch of parameters that would fix it.

    What BCC did you start with? The reason I ask is the "IAC Counts vs. Desired Airflow" table seems to be really limiting the PCMs abilty to react to required airflow changes, i.e. 100% airflow in just 60 IAC counts doesn't seem quite right. Factory shows 100% at 150 counts.

    After writing all that I got the DL playing back and is the MAP supposed to be that high? Lower 60s? Seems kinda low on vacuum.
    1978 Camaro Type LT, 383, Dual TBI, '7427, 4L80E
    1981 Camaro Z-28 Clone, T-Tops, 350/TH350
    1981 Camaro Berlinetta, V-6, 3spd
    1974 Chevy/GMC Truck, '90 TBI 350, '7427, TH350, NP203, 6" lift, 35s

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    Fuel Injected! corvairnut's Avatar
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    Greg..thanks for looking. The reasoning on the IAC counts is that I have dual throttle bodies, so when the ECM commands and IAC opening, Ive got two (2) IAC motors, which is double the vacuum leak. so I divided the IAC counts by 1/2 and that part seems to work pretty well.

    At Idle, N..... the MAP is about 50, when in grear is about 60. Engine is worn and has some blowby. No vacuum leaks. You are right about the idle underspeed correction. I wanted it to try to keep the engine running during the shift to D from N.
    On the Idle speed... when I set it any lower than 700 RPM, when shifted into gear, the engine stalled, so i settled on 750 which is about as much RPM as I want at Idle.
    Ted Brown
    Anderson, SC
    68 Corvair EFI
    61 Corvair Loadside Pickup (Future EFI)

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    RIP EagleMark's Avatar
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    Quote Originally Posted by corvairnut View Post
    At Idle, N..... the MAP is about 50, when in grear is about 60. Engine is worn and has some blowby.
    Kind of hard to tune and diagnose a worn out engine showing that kind of MAP at idle?

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    Realistically, there's a good chance that's what many Corvair owners are running.

    Is the MAP sensor connected to both intakes or only one? If only one then time between pulses is greater. Signal filtering could making the average MAP read higher even though peak is correct. Could compare vacuum gauge readings at idle to MAP to check that.
    Last edited by 1project2many; 10-25-2012 at 05:24 PM.

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    driving 2 IAC motors, you may need to mess with the IAC PID settings, assuming there are still PID loops done with the newer TBI PCMs.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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    Fuel Injected! gregs78cam's Avatar
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    There are a bunch of IAC PIDs in $0D. As I am sure you know, the Crossifre Dual TBIs had issues with running two IACs and they get out of synch over time. I run both mine off of one IAC, but they are on a common plenum. There was a guy modifying the Crossfires to run on one IAC, and they apparently work pretty well, you could try that.

    The Idle Underspeed table is for a stable idle, and I don't think it will help much in the P/N to D transition (doesn't sound like it is), really need an trans input to take full advantage of that MaskID. What are you using for a shifter in this? You could maybe come up with a shifter mount/assembly with the P/N switch in it to get the signal to the PCM.

    And yes your tired engine is probably making both these issues harder to fix.
    1978 Camaro Type LT, 383, Dual TBI, '7427, 4L80E
    1981 Camaro Z-28 Clone, T-Tops, 350/TH350
    1981 Camaro Berlinetta, V-6, 3spd
    1974 Chevy/GMC Truck, '90 TBI 350, '7427, TH350, NP203, 6" lift, 35s

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    Fuel Injected! corvairnut's Avatar
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    Newly rebuilt engines are not much better, maybe by 5-10 MAP average. The MAP is connected to the crossover tube because of the pulsing issue you mentioned before. Using one (1) IAC motor would be much simplier, but I cant make a big enough hole (vacuum wise) with the crossover tube connection for the IAC to be effective. Running one (1) IAC leans out so much on one side the engine stumbles and dies, but since I went back to two (2), the problem is minimized. The engine is worn, but not worn out and the other Corvairs that have it installed have approx same results. Factory transmission shifter makes designing a shifter switch difficult at best, but who knows... one night it might come to me. (Im thinking already about magnet and a reed switch). The cool part is that the Corvair only had a "N" and no "P".... but then again, do you really need one?

    Thanks to everyone that looked and offered advice and I will play with it some more over the next few days.
    Ted Brown
    Anderson, SC
    68 Corvair EFI
    61 Corvair Loadside Pickup (Future EFI)

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    I've been running my Crossfire intake since '92 or '93 and the IAC's have never given me reason to believe they're out of sync. I realize this is a common belief but I've been repairing Crossfire equipped vehicles since about '98 and I've only seen a few IAC issues which are generally caused by a faulty IAC. But if the IAC's work then they'll stay in sync. At key off they're fully closed then opened back up a specific number of counts. From there all counts are known. It's really no different than an engine with a single IAC in that regard.

    What usually happens to Crossfire intakes is that the throttle blades either don't get aligned properly or the bores wear so the plates don't seal properly. You'd be amazed at how many Xfires I've worked on that suffered from throttle blade misalignment. There's only one TPS and there's no way to know if the plates close equally and you can run into some really poor idle situations.

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    RIP EagleMark's Avatar
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    Could the cross fire ECM have more voltage/amps available for 2 IACs?

    corviarnut log shows the IAC count low at idle, I was going to suggest opening throttle blades a little more to run one IAC, but seems they are open now. There are many changes to IAC parameters below, some I disagree with but then I didn't have my hands on this different animal.

    I had no idea the corvair engine was that low a vacuum at idle? But I'm guessing a little old cam wouldn't hurt the engine of the time and it would sure help cooling at idle. Was also surprised to see VE fueling at idle of 65%ish, I saw at cruise the MAP was actually better then idle at 2300 RPM. This explains some of the strange shape to your fueling table that you have BLMs really dialed into.

    There's two areas of your tune that would help stabilize idle. Idle VE and Idle Spark. Both have flat areas in Idle range, but neither is over far enough to left of tables to include your MAP at idle of 50-55. With that done you may be stable enough to avoid the AE blipping on and off at idle which will also be a big help in fueling!

    Another issue with this conversion may be O2 sensor placement. How far is it from head? Similar to what that system was stock? If you move the O2 sensor farther from stock like say to a header collector? You would need to adjust the INT Delay vs airflow (May be another name in this mask) as much as 30%. If not the INT can adjust faster then it gets feedback from O2 sensor, creating an oscillating idle.

    Proportional Gains Vs O2 error (again not sure of name in this mask) can also greatly improve idle with this low vacuum. Since they don't get much better with tight engine I'm assuming this is do to cam specs.

    There's a bunch of changes in your bin compared to BJYL which has many same settings as yours. V6 CPI bins are horribly different. Couple need work and a lot I'm not sure of why.

    One is Injector Offset, it is still 5.7L injectors and your bin is set to 50lb injectors which I assume are 5.0L so grab those offsets. Really important on conversions as the old charging system is lower at idle.

    The other is Spark Latency. Yours is still stock 5.7L distributor and now you have DIS. After you get them right check timing because you could be off by 10 degrees now or 10 degrees after.

    You also have 14.4 charging while driving and 14.ish fuel pump. but at idle I saw fuel pump drop to 12.ish. But your fueling is still in order. I didn't note how low voltage goes at idle. Drop into 12s and you can have all sorts of idle issues.

    MAT is checked and shows a reading in your log but none of the tables for it's compensation are filled in.

    Temperatures vary on this and I'm assuming it's placement of CTS on air cooled engine. But sometimes they creep up into Spark CTS compensation table, so your loosing timing.

    Here's a picture of some of the changes made, some I think are issues and other I'm not sure why you changed them.

    HTH!

    Post some pictures of this so we can see what a cool project it is!
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    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

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    Could the cross fire ECM have more voltage/amps available for 2 IACs?
    Maybe. But my truck's used a 7747 from 2000 until this summer and it's had a 7427 since July. Several others have used different ecm's with Crossfire successfully.

  12. #12
    Super Moderator Six_Shooter's Avatar
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    I'm running a crossfire off a '7427 without issue. Dual IACs are not a problem. This is yet another myth that needs to go away.
    The man who says something is impossible, is usually interrupted by the man doing it.

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    Fuel Injected! corvairnut's Avatar
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    Quote Originally Posted by Six_Shooter View Post
    I'm running a crossfire off a '7427 without issue. Dual IACs are not a problem. This is yet another myth that needs to go away.
    Since I have only heard of Crossfire and never seen one. How does it control two (2) IACs?.... I wired my in parallel and tested. After about a week of heavy use if figured the IAC control in the ECM could handle two (2) IACs on one circuit and that was 3 years ago.
    Ted Brown
    Anderson, SC
    68 Corvair EFI
    61 Corvair Loadside Pickup (Future EFI)

  14. #14
    Super Moderator Six_Shooter's Avatar
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    In the original configuration they were wired in parallel, IIRC. I wired mine to be in parallel, and has worked flawlessly.
    The man who says something is impossible, is usually interrupted by the man doing it.

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    i imagine if they were wired in series, they wouldn't be driven very accurately.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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