92 corvette tuning tips and questions.

[BlackW1dow]

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.

[2xls1]

Post your bin file.

[BlackW1dow]

Here is the bin file for the 1992 vette.

[NomakeWan]

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-Injection/showthread.php?341-16159278-ECM-Information-DA2-DA3&p=29337&viewfull=1#post29337

[BlackW1dow]

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-Injection/showthread.php?341-16159278-ECM-Information-DA2-DA3&p=29337&viewfull=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.

[BlackW1dow]

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.

[NomakeWan]

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!

[BlackW1dow]

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

[NomakeWan]

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.

[BlackW1dow]

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.

[NomakeWan]

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.

[steveo]

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...

[BlackW1dow]

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..

[NomakeWan]

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.

[LeMarky Dissod]

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.

[NomakeWan]

According to the stock BIN, the fan thresholds for the '92 Corvette are 219F Lo 227F Hi for 0MPH, and 227F Lo 235F Hi for any speed over 0 MPH.

[LeMarky Dissod]

219°F Lo 227°F Hi = 0MpH
227°F Lo 235°F Hi >0MpH
GM's $EE Y-LT1 fan-on thresholds are identical. The $EE F-LT1 & $EE B-LT1 fan-on thresholds do not change based on MpH, but are also too hot for me.

Given that:
LT1 cars' OE programs lead to running hotter in stop'n'go than on the highway
LT1 sedans and wagons with V08 mech fans run cooler than LT1 cars with electric fans

I don't see a reason against lowering the fan-on thresholds so that coolant temps remain consistent across environments, especially if this can be done without a mech fan.

[BlackW1dow]

So after throwing all my logs into trimalyzer, thank you steveo, I came out with this graph. i know there is a smooth button on tuner pro, but what's the best was to smooth it? do I smooth everything up on the right side to match the rest or should I leave it the way it is and do some more logging?

Does the logs just never touch those cells and that's why it isn't changed? I have attached the graph from trimalyzer as a reference to what I'm working with after about an hours worth of logging.

[lionelhutz]

I'd keep the fixed part for now. The rest that never got touched I would pull up. Pick those cells only and multiply them all by 1.13 first so they all come up close to the corrected part. If that correction isn't right then do another one until you get them close. After that, hand blend them into the corrected part to make the whole curve look nicer in the area transitioning between the corrected and the not corrected parts.

As for the corrected part, it looks pretty good. It doesn't have to be smooth, factory VE tables aren't. Just hand knock off any big peaks or valleys a bit which you really don't have to do here right now.

[NomakeWan]

What lionelhutz said is correct. Once you take the suggestions from Trimalyzer and put them into your tune, open the graph in Trimalyzer and just smooth any sudden jagged edges by hand. It may help to open a stock BIN and look at how its 3D graph is laid out to get an idea of what GM deemed acceptable. Getting the suggested changes from Trimalyzer is science. Smoothing the table transitions visually, that's art.

[BlackW1dow]

going back to the temperature scalers, how do yall know that the low MPH is based on 0 MPH and the high is anything greater than 0? Just experience or is there something that says it?

Also what is too hot relative to coolant and oil temp? oil temp stays about 219F

[kur4o]

BlackW1dow,

Can I ask you to make a eprom dump of ccm, using steveo flashack tool over aldl line. It will help us decode one more piece of the ccm puzzle, maybe add support of editing some of the eeprom stuff too.

I am sure it will work with dumping the pcm too[If you haven`t already try it].

[LeMarky Dissod]

going back to the temperature scalars, how do yall know that the low MpH is based on 0MpH and the high is anything greater than 0MpH?
Just experience or is there something that says it?

Also what is too hot relative to coolant and oil temp? oil temp stays about 219°F / 104°C.
My experience is with $EE '(94 & '95).
'vettes make use of a separate scalar: 'Fan Vehicle Speed Boundary' in TunerPro, or 'Fan Hi/Lo Vehicle Speed Threshold in TunerCAT.
The vehicle speed boundary / threshold is 0MpH, so anything OVER 0MpH uses the higher speed fan-on settings.
Although GM did not bother to use this feature with F- & B-cars, they can also use this feature by specifying different 'High' fan-on settings.

To answer your 2nd question:
examine oil & coolant temps while cruising on the highway, then use the fan-on settings to maintain similar temps in stop'n'go traffic.
If the coolant is clean & the radiator heatercore & cooling fans all work properly, I see no reason why the coolant should get hotter than
221°F / 105°C.
I prefer lower temps - I typically turn on the primary fan @ 203°F / 95°C & the 2ndary (meaning both) @ 212°F / 100°C (coolant temps).

[steveo]

i have to say that a VE correction table like that reeks of a bad constant. it tells me that injector size (or a related input such as fuel pressure) or engine displacement does not match the calibration. i wouldn't apply that correction from trimalyzer - i'd fix the botched constant and run more logs. not saying that correcting the VE table wont work, it's just bad practice. when your engine VE changes, it changes shape, it doesn't just move the entire table up.

[NomakeWan]

going back to the temperature scalers, how do yall know that the low MPH is based on 0 MPH and the high is anything greater than 0? Just experience or is there something that says it?

Also what is too hot relative to coolant and oil temp? oil temp stays about 219F
In your XDF, you will find a parameter called "Fan Low/High MPH Threshold," which will be set to 0. This means Low is 0 MPH, and High is anything over 0 MPH. You can change this value if you want to change this behavior.

Coolant temp is up to you. The OEM thermostat is designed to actuate at 180F. Due to the reverse cooling of the LT1, this means the engine tends to operate in the 195F range.

Oil temperature is a factor of the oil itself. For Mobil 1 Full Synthetic 5W-30, the stock factory fill, it can more than happily handle oil temperatures of 356F. It will, for short durations, handle temperatures above 392F. This property of the oil is why the oil cooler was removed when GM switched the Corvette over to this oil in 1992.

[lionelhutz]

i have to say that a VE correction table like that reeks of a bad constant. it tells me that injector size (or a related input such as fuel pressure) or engine displacement does not match the calibration. i wouldn't apply that correction from trimalyzer - i'd fix the botched constant and run more logs. not saying that correcting the VE table wont work, it's just bad practice. when your engine VE changes, it changes shape, it doesn't just move the entire table up.


That's a good point Steve, change the injector constant only first maybe and try logging again until the error isn't as high. Then start adjusting the VE table.

[BlackW1dow]

i have to say that a VE correction table like that reeks of a bad constant. it tells me that injector size (or a related input such as fuel pressure) or engine displacement does not match the calibration. i wouldn't apply that correction from trimalyzer - i'd fix the botched constant and run more logs. not saying that correcting the VE table wont work, it's just bad practice. when your engine VE changes, it changes shape, it doesn't just move the entire table up.

After pulling my stock tune it matches the bin I was tuning with. I can about 99% sure rule out the cylinder volume as the issue which leads me to the injector flow rate. The rate in the bin I was using matches the stock rate. That being said I know the injectors have been changed but I have no idea what brand or flow rate they are.

I have looked up the numbers on the injectors but it comes up with like 10 different options. how do I determine their flow rate so I can correct in the bin?

[stew86MCSS396]

After pulling my stock tune it matches the bin I was tuning with. I can about 99% sure rule out the cylinder volume as the issue which leads me to the injector flow rate. The rate in the bin I was using matches the stock rate. That being said I know the injectors have been changed but I have no idea what brand or flow rate they are.

I have looked up the numbers on the injectors but it comes up with like 10 different options. how do I determine their flow rate so I can correct in the bin?
Well gee...perhaps someone who's more web savvy can search the make and part number if you would post it.

Edit: If any one caught what I had posted/edited out, hind sight thought...if you're running lean based on the trim graph^^^you posted then my suggested increasing the injector constant is going to make you leaner.

[steveo]

That being said I know the injectors have been changed but I have no idea what brand or flow rate they are.

I have looked up the numbers on the injectors but it comes up with like 10 different options. how do I determine their flow rate so I can correct in the bin?

see? you've changed a fundamental fuel parameter without accounting for it in your bin, but you're calibrating a table that represents airflow. you will get better results if you start over and fix that constant. from your trims i'd say they are about 15% smaller than the stock injectors. so you could simply multiply your injector constant by 0.85 and get close. ....but this works better if we get proper specs. what numbers are on the injectors

[BlackW1dow]

see? you've changed a fundamental fuel parameter without accounting for it in your bin, but you're calibrating a table that represents airflow. you will get better results if you start over and fix that constant. from your trims i'd say they are about 15% smaller than the stock injectors. so you could simply multiply your injector constant by 0.85 and get close. ....but this works better if we get proper specs. what numbers are on the injectors


Okay so I have found which injectors I have. The number is 280 155 703 (tel:280 155 703). They seem to be Bosch injectors commonly swapped in Jeeps. I didn’t swap them out the previous owner did. Thank y’all for your help again, I am slowly learning this art.

[NomakeWan]

Okay so I have found which injectors I have. The number is 280 155 703 (tel:280 155 703). They seem to be Bosch injectors commonly swapped in Jeeps. I didn’t swap them out the previous owner did. Thank y’all for your help again, I am slowly learning this art.
So those injectors are from a bunch of Dodge products, primarily the Neon. They're 22.5 (23) lb/hr at 43.5 PSI. Stock '92 Corvette injectors were 22 lb/hr at 43.5 PSI. However, even though the 1992-1993 Corvettes came with 22 lb/hr injectors physically, the stock BIN is programmed for an injector rate of 23.79 lb/hr. Very curious choice by GM.

For comparison, the '94 Corvette came stock with 24 lb/hr injectors, and is programmed for a rate of 24.873 lb/hr.