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Thread: 92 corvette tuning tips and questions.

  1. #1
    Electronic Ignition!
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    92 corvette tuning tips and questions.

    Good afternoon,

    I hope yall might be willing to help me.. I'm currently trying to tune my 92 corvette, and am struggling tuning out code 26 after doing a AIR and EGR delete. I'm using $DA2 as the definition file, but it doesn't show to have any flags to toggle for any codes except for VATS. I could tune out the EGR by setting all the values to max for the EGR scalers, but cant seem to crack the code 26.. Any help is greatly appreciated.

  2. #2
    Fuel Injected!
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    Post your bin file.

  3. #3
    Electronic Ignition!
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    Here is the bin file for the 1992 vette.
    Attached Files Attached Files

  4. #4
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    Quote Originally Posted by BlackW1dow View Post
    Here is the bin file for the 1992 vette.
    That's your XDF, not your BIN. Your BIN is your actual tune, the thing that you're putting on the chip/Ostrich/Romulator/etc.

    But if that's your XDF, then there's your problem. Please use a proper XDF from here and you'll find it has the flags you seek: http://gearhead-efi.com/Fuel-Injecti...ll=1#post29337
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  5. #5
    Electronic Ignition!
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    Quote Originally Posted by NomakeWan View Post
    That's your XDF, not your BIN. Your BIN is your actual tune, the thing that you're putting on the chip/Ostrich/Romulator/etc.

    But if that's your XDF, then there's your problem. Please use a proper XDF from here and you'll find it has the flags you seek: http://gearhead-efi.com/Fuel-Injecti...ll=1#post29337
    God Bless you, this is exactly what I was looking for. I downloaded the XDF from tuner pro and was confused at how little it allowed me to tune. I ordered the adapter to actually pull the bin from the factory chip and it should be at door by Friday. I will attempt tuning it out with this XDF as a starting point and update yall on where I get.

  6. #6
    Electronic Ignition!
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    Good news, I was able to tune out the EGR and code 26 from my 92 vette. now i have another question. What all do the companies change when they say they can send a custom chip to gain 10-15HP? how do they do that without datalogging?

    after i datalog what are my first steps to tune? is the ultimate goal to get the BLM to 128? Theres soo many scalers and tables that are able to be changed but i would think a sorta simple tune would only require changing a few things like VE tables, Spark Advance, and fan temp turnon.

    Thank you greatly for the help on finding the right XDF.

  7. #7
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    Quote Originally Posted by BlackW1dow View Post
    Good news, I was able to tune out the EGR and code 26 from my 92 vette. now i have another question. What all do the companies change when they say they can send a custom chip to gain 10-15HP? how do they do that without datalogging?

    after i datalog what are my first steps to tune? is the ultimate goal to get the BLM to 128? Theres soo many scalers and tables that are able to be changed but i would think a sorta simple tune would only require changing a few things like VE tables, Spark Advance, and fan temp turnon.

    Thank you greatly for the help on finding the right XDF.
    Woohoo! Glad to hear you're sorted. Yeah, the XDFs available directly from TunerPro are woefully out of date compared to those created by the community here.

    Anyway, the "magic sauce" that legitimate companies (like pcmforless) charge for are tweaks to ignition timing and fuel maps based on their experience with others who have had similar work done in the past. Since they have experience with several similar vehicles, they can create an "average" improvement that should work for any other similar vehicle. It won't be as nice as a tune with proper datalogging, but if your vehicle falls within the specifications of one that the company has experience with, you should still be able to see some improvement.

    Hypertech is not a legitimate company, so just ignore them.

    Tuning on these older ECMs is a little more involved than newer ones, and I don't have direct experience with your ECM specifically, so I can't walk you through every single step. But in general, you'd want to adjust fuel to get the BLMs to 128, yes. If you feel spicy you can then start tweaking ignition timing, but you'll want to be sure to keep track of knock counts and all that. There'll be a falloff point where adding timing doesn't actually net you a benefit, not to mention it'll make you more prone to knock, so start slow.

    Hopefully some others with more experience with the '278 can chime in here. For general tuning-related stuff though, plenty of folks around here should be able to help, and there are entire online courses that are applicable to all engines (though the actual nitty-gritty of how to log the data, make adjustments, and apply them to your specific ECM are not covered). Good luck, have fun!
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    Last question before I start data logging. After reading this fantastic article by Eagle Mark I need to know if the 10% 20% 30% tps logs are separate logs or are one long one. Do I stop the log, save it then start another or just enter and exit with different throttle positions all on one. Thanks again

  9. #9
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    Quote Originally Posted by BlackW1dow View Post
    Last question before I start data logging. After reading this fantastic article by Eagle Mark I need to know if the 10% 20% 30% tps logs are separate logs or are one long one. Do I stop the log, save it then start another or just enter and exit with different throttle positions all on one. Thanks again
    You can do it either way. If you log one giant drive with all the throttle positions, you just need to account for that in whatever program you're using to analyze the data, whether that's an Excel spreadsheet or a tool like Trimalyzer.
    1990 Corvette (Manual)
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  10. #10
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    Okay so I have logged a few times now. about an hour of driving i think. went to put it into a history table and lucky me $da2 doesn't have any made yet... Followed a tutorial by eagle mark to create one and I couldn't figure it out. When making the History table i put Right BLM in the (Z output), RPM in the (X AXIS), and MAP in the (Y AXIS). it doesn't populate VE it only puts BLM in the table.

  11. #11
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    Quote Originally Posted by BlackW1dow View Post
    Okay so I have logged a few times now. about an hour of driving i think. went to put it into a history table and lucky me $da2 doesn't have any made yet... Followed a tutorial by eagle mark to create one and I couldn't figure it out. When making the History table i put Right BLM in the (Z output), RPM in the (X AXIS), and MAP in the (Y AXIS). it doesn't populate VE it only puts BLM in the table.
    I don't use the Excel method, I use Trimalyzer, but generally the VE table isn't "populated," it's something you yourself have to define based on your tune. For example, in Trimalyzer, you can select from "low VE table" and "high VE table" because on $EE there are two separate VE tables. But I would expect an Excel spreadsheet to work the same way, in that you would have to define the layout of the VE table(s) present in your tune yourself so that the spreadsheet can populate it with recommended changes to each VE cell.

    Also, if it's at all possible, I would like to ask a favor of you since you own a '92 Corvette. Over in another thread we are working on reverse-engineering several aspects of the Corvette CCM. We generally know how a 94~95 works, and we know how a 90 works. But a 92 is a question mark. If you wouldn't mind terribly, would you consider downloading a program called EEHack and then recording an Idle Module Scan? It would create a text log, which if you could share would be really cool. If you are interested in helping out, the program can be downloaded here: http://fbodytech.com/eehack-2/download-eehack and the Idle Module Scan is located by clicking "Raw Cmd" and then "Idle Module Scan (TEMPORARY)". Do make sure that the correct COM port for your ALDL cable is selected in Settings.

    If not, totally understandable, and I thank you for reading anyway.
    Last edited by NomakeWan; 09-23-2021 at 07:25 AM.
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  12. #12
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    Quote Originally Posted by BlackW1dow View Post
    it doesn't populate VE it only puts BLM in the table.
    one thing you need to understand about tuning fuel is you're rarely populating a table with new values, you are adjusting the existing values based on feedback.

    in simple terms the ECM says "5!", but your o2 sensor says "...but we had to add 2% of fuel there" so you might change the value to "7" and then try again.

    in real terms, since you're tuning a VE table, the ecm actually says 'for 2000 RPM and for 50KPA of MAP, the engine is 43% efficient'.

    it then injects its fuel on the assumption that the engine is actually 43% efficient at that RPM (there are other things affecting fuel but just worry about the VE table for now)

    you then get feedback as a BLM from the trim system that says "trim in this area is 150"

    since 128 is 0% trim, we can calculate the trim as 150/128=1.171 (17%) (in other words 150 is 17% higher than 128)

    so the ECM had to add approx. 17% extra fuel to achieve the proper mixture.

    since we had to add 17% of fuel, we can assume that instead of being 43% efficient at that RPM/MAP value, it is actually 50% efficient. so you could change that value to 50.

    but a better way to tune would be to get multiple data points from that area and average them together, because big piston engines are not a precise instrument.

    you then have to 'interpolate' or 'guess' the values to smooth the table in between your adjustments, because there's no way you'll have good data for the entire table.

    if this sounds time consuming, and like it's something a computer could do for you with way less effort, that's why i wrote trimalyzer (but then you have to learn to use that properly, too, and have some common sense in case it makes a mistake.)

    the other reason tools like trimalyzer are good is because you can't always trust trims, you can only trust them once you are in closed loop, and the engine is warmed up, and you aren't in power enrichment, and whatever else. trimalyzer is good at filtering data.

    edit: it's also good at taking HOURS of logs and crunching the whole thing...

  13. #13
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    So I am messing around with the ve tables and my car is getting hotter than normal. Not sure if it’s bc I removed the EGR and air system or the tables..

  14. #14
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    Quote Originally Posted by BlackW1dow View Post
    So I am messing around with the ve tables and my car is getting hotter than normal. Not sure if it’s bc I removed the EGR and air system or the tables..
    Removing EGR and AIR should have nothing to do with engine temperature.

    If you want to know if your VE modifications are having an adverse effect, revert them back to what they were and see if the problem resolves itself. If not, then something else has changed. Is it hotter out? Did one of your fan relays die? Are you just doing a lot of testing while the car is sitting still rather than driving around at speed? The C4's cooling system isn't the greatest, and if any part of it isn't working at its full potential, things can get out of hand pretty easily. I found that out from experience, hahaha.
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  15. #15
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    Quote Originally Posted by NomakeWan View Post
    Is it hotter out? Did one of your fan relays die? Are you just doing a lot of testing while the car is sitting still rather than driving around at speed?
    The C4's cooling system isn't the greatest, and if any part of it isn't working at its full potential, things can get out of hand pretty easily.
    I found that out from experience.
    Don't know about the LT1 OE fan-on thresholds for '92 & '93, but they were set so high from '94-'97 that the powertrain usually runs considerably much hotter in stop'n'go traffic than on the highway. NomakeWan's observations about the cooling system are absolutely spot on.

    I can sort of get why GM would prefer LT1s to run 32°F hotter in stop'n'go than on the highway (except for sedans & wagons with big ol' mech fans that cost 10 peak horse), but this is easily fixed by lowering the fan-on thresholds to keep temps more consistent across driving conditions.
    If both fans are on by 212°F / 100°C instead of 235°F / 113°C, it's one less thing to worry about, and a much larger safety margin.
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