I'm not sure if there's more people like me out there. I've tuned the hell out of my car for part throttle but it still needs work at full throttle (and lots of it). I purchased an LM1 wideband O2 sensor setup but was too cheap/broke to buy the extra equipment for logging RPM.

Instead I planned on running the output of the LM1 to the PCM and using regular ol' datalogging software to record AFR along with other engine parameters. The A/C pressure was the most obvious choice as it will readily accept a 0-5 volt input however tuning by A/C pressure is hardly intuitive.

To help make the tuning process easier I've created a spreadsheet to convert A/C PSI readings to AFR and then input that data into a tuning spreadsheet that spits out the next PE values to try for the next run.

I haven't had the time to test this but there might be someone with the time. I do have some numbers collected a long time ago in it for demonstration. The equations used have not been verified. If someone wants to be a guinea pig than I will be more than happy to send it to you. If someone knows the ins and outs of the PCM code I'd be much obliged if you check my math. Maybe someone has suggestions or additions. Email is the easiest method to reach me.

If this works it should make WOT tuning a lot cheaper and easier for myself and any other cheap bastards out there

 

send it over jason@jandjspeedshop.com

 

Here's the equation for an LM1 that you're looking for Buttercup.

100*(((AC Pressure Voltage/.625)+10)

I'm not as savvy with the LT1 stuff, but we use that equation for the AC input in HPTuners. As long as there's a parameter in your scanner for commanded air fuel ratio, it should work out fine. If there's not, something like an EQ Ratio should be able to be calculated just the same.

Did you ever look over the spreadsheets for PE tuning that Chris Bennight set up a while back? I ran across them while trying to find some info on what the PE values mean in the LT1 PCM.

Oh yeah, and send me the spreadsheet if you don't mind, I wouldn't mind looking it over as well. I was going to set up something similar myself, but I still haven't got everything together to scan this stuff from my buddy's car.

 

Thanks for the help. I can only record the A/C pressure value so that's what I'm going off of. I'm working with these two equations

VOLTS = 5N/255
PSI = 1.833N - 14.95

I use those equations to equate A/C pressure (in PSI) to a voltage. From there I use linear interpolation to arrive at a certain AFR. I'm using the interpolation so that you can input a minimum and maximum voltage and the corresponding AFR's. I figured this method would be best as you can pick and choose what AFR and voltage values to use to increase the resolution.

I was trying to think who wrote that tuning spreadsheet, I got it from Christian Millard a long long time ago. I have integrated that same spreadsheet (although modified) into my spreadsheet. The AFR values I calculate are imported directly into the tuning section.

I'll send you a copy to look over.

Jason, email sent

 

Where do the values in your equations come from? I'm not familiar with 5N, 1.833N, etc.

Also, do we know what PSI is 0v and 5v?

If we don't know those, there was a nice guy in another thread about a similar subject (originally posted by fwiked I believe) who offered to custom tailor some parameters in freescan. If we could get that sensor to input raw voltage rather than psi, that would probably work fine as well.

 

Got them from some GM datastream documentation but I don't recall the source. The "N" is the raw value reported by the PCM.

Using those equations 0V = -14.95 PSI and 5V = 452.465 PSI I was going to check these against my manuals but if memory serves me correct, it's dead on

I sent you the spreadsheet. You'll see I also allowed for an offset should it be needed.

 

Send the spread sheet over here as well...i'm the guy that'll edit freescan. e-mail>darkmajiks at aol dot com
p.s. you guys'll have to do the testing for me as i cant find my converter box and dont feel like making another (or buying one)

 

Im ready to test away!!

 

I've sent you guys an email! There should be a few people out there now with this spreadsheet but I haven't heard back from anybody. I'm anxious to find out how well this works so as soon as you have some feedback, let me know.

I'll be out of state again for about a week starting this weekend so if anyone tries contacting me and don't hear back, that's the reason

Thanks for giving this a look guys. Hopefully I'll have the time to use it myself before too long.

 

Received the file...I'll check it out and work on freescan and let you guys know what I come up with, I'll be pretty busy with work for the next week but as soon as I get some free time I'll get something out, curious as to who wants a copy? PM me an e-mail address

 

Maybe we should wait until someone gets some time in on just the spreadsheet to validate the whole idea? I'd hate to see you put time into this if doesn't work well or if there are improvements or changes to make. This is just an untested first rev after all.

If it works well we should probably figure out what specs to use in Freescan. I'd like to know how the resolution really is in use. Some testing would be helpful. If it's sloppy we probably want a pretty tight AFR range, like 11.5-13.5 or something just for WOT tuning.

Sorry I don't have the time to be doing the testing work myself, I feel like a schmuck

Thanks again for the help! I'll let you know if anybody communicates with me on results. If it works well I'd definitely like a copy of your patched Freescan.

 

No worries, I was planning on doing it anyway and I'll just use the spreadsheet as a reference (depending on the feedback) and I'll also make it so they can select where they want to input the WB data from i.e. if they used the oil temp pins.

 

I'd like a copy! I just ordered my NGK wideband setup yesterday. I've know about the ability to log the 0-5 volt output thru the a/c for sometime, I was on the LT1edit mailing list some time ago. Your tool sounds cool, Ive actually been searching for the values of PSI vs Voltage and havent had much luck. Being about to basically use something like VE master on the logged data too would be a bonus! Please send me a copy to gex@tampabay.rr.com

Thanks Jason

 

That would be awesome. I'd like a copy also.

Sweetred95ta@hotmail.com

 

Emails sent guys. Haven't heard back from anybody yet. Once someone gets the chance to hammer away with this thing I'd really appreciate a detailed report on how well it worked, what could be changed, etc.

I'll be leaving for a little over a week starting tomorrow (Friday) evening. I may find the time to check on this site but won't be checking my email. I hope this thing proves hopeful!