IAT Transfer curve LS3 to LS1

[ctd]

I'm running a large air intake with an LS3 MAF in my 2001 C5, it is a 416 stroker. I started chasing the AFR swings last summer, opening & closing the hood was all it took. So I loaded the bias & filter tables from the LS3 Corvette, re tuned the MAF with reasonable results.

Now I would like to get the IAT transfer curve correct but I'm at loss as to how to do so. I've searched & have found some discussion about this but no help as to how to go about correcting it. Maybe it is one of those closely guarded , I'm hoping it is just me missing something.......I was not very good in school.

Some have choose a number & applied that to the LS1 transfer curve, the characteristic of the LS3 looks very different so I'm sure this isn't the correct way. Any idea's?

[LSxpwrdZ]

The problem is we don't know the resistance reading of the axis on the table... without that information it is hard to accurately copy the transfer curve to the gen3 tune.

From all of the setups I have done the temperature was off by ~20deg F. So I applied that to the entire stock curve and have had good results. One of my to-do's is to calculate the breakpoints in ohms of the gen3 table.

[MikeOD]

I've got a to do of wiring both sensors and logging both at the same time to get the correct table...haven't gotten there yet though sorry.

[LSxpwrdZ]

I spent some time tonight after I got the idea of using current existing calibrations to back calculate the Gen3 breakpoints. If you look the Gen4 ECM's give the IAT scaling in resistance. There are Gen4 and Gen3 applications that share the same IAT within the MAF. C5Z06 has an 85mm MAF which is the same as the MAF used in the LS2 C6's and LS2 GTO's. So I created a spreadsheet to back calculate the resistance of each breakpoint on the Gen3 table so that I could then lookup/calculate the temperature from other calibrations like the card MAF IAT sensor or the IAT2 charge temp sensor found in the LSA/LS9 applications.

I don't have a gen3 application here currently to test this out on so if any of you with Gen3 applications running a Gen4 card MAF sensor and utilizing it's built in IAT sensor, I would like you to try these values in the IAT sensor calibration and see if the readings are sane.

[ctd]

Very nice & I will give it a try! Sounds like a very good idea!

In my searching of the net I found this from Justin Abbot, he talks about this issue specifically. I'm not sure if he is willing to share his solution.

http://justinlabbott.com/programming...-pcm-part-iii/

We have had two feet of snow in the last couple of days, yesterday mother nature decided to add rain in the mix & just above freezing temps. That raises havoc with trees & power lines unable to take the weight. We have been without power coming up 18 hours & this is our third outage, highways closed everywhere blah blah.

[J Alper]

can you list the link for part 1 and 2 of http://justinlabbott.com/programming...-pcm-part-iii/

[LSxpwrdZ]

Report back your findings if you can. I did find out that the CTS-V/ZL1/ZR1 IAT2 manifold temp sensor is the same scaling as a stock LS1/2/6 IAT. So using those temp sensors from a LSA or LS9 can be done on our older gen3 cars as well without any scaling of the IAT table.

For reference the bung for that IAT2 sensor is M14x1.5...

[ctd]

Report back your findings if you can. I did find out that the CTS-V/ZL1/ZR1 IAT2 manifold temp sensor is the same scaling as a stock LS1/2/6 IAT. So using those temp sensors from a LSA or LS9 can be done on our older gen3 cars as well without any scaling of the IAT table.

For reference the bung for that IAT2 sensor is M14x1.5...

I had considered the external sensor, some are suppose to be very fast acting. Wanted to explore this avenue first, little more plug & play. Good info on the CTS-V & the ZR1 I will check out the repository for a look!

Loaded your values into the table this morning & it looks very promising, different, thank you for that! I'm trying to hit the key this weekend & see how the values compare to the ECT & Outside air temp. Bottle of WB test gas to calibrate that as well.

[ctd]

IAT MOD LS3 MAF.jpg

I don't have a gen3 application here currently to test this out on so if any of you with Gen3 applications running a Gen4 card MAF sensor and utilizing it's built in IAT sensor, I would like you to try these values in the IAT sensor calibration and see if the readings are sane.

Took me a couple of try's, did not realize the impact the heater had. I'm referring to the heater in the card, assumption on my part. So for this test I unplug the card until the scanner was logging, you have 15 seconds before the temperature is skewed.

So very nice! it is within 3*F, this car has not been fired since Nov. Our ambient temp has been very stable, the ECT agrees with the outside air temp in car.

I've included the transfer curve used based on your values, just want to be sure I've done this correctly.

[LSxpwrdZ]

Here is the table with the Card MAF IAT values applied

[ctd]

Would you bother to apply an overall correction & correct the 3* or just call it good? Having the transfer curve more accurately reflect the sensor is so cool, thank you!

How do I buy the beers

[LSxpwrdZ]

At that point I'm not sure which is more accurate. We do not have the scaling on the ECT sensor and who's to say one is more accurate to the other without physically calibrating both of them...

Good method of testing temp sensors is boiling water on the high side and crushed ice on the lower end.

[ctd]

We may get another -20C shot this winter, I will do that one when it happens. Two reference points ECT & EXT air temp, both agreed.

[RonSSnova]

I doubt you would want to dunk the Card MAF in water though.

[Jabbott]

I just looked at the attached file, they are really close. I converted the new data that is resistance to temp into A/D count to temp which is what the LS1B ecu reads. No tricks, just some math.

[DSteck]

For those curious, the axis on Gen III is voltage across the temperature sensor as a percentage of the reference voltage. There's a pull up resistor in line, and based on the calibration values, I'd say it's probably about 2450 ohms.

So, to convert the axis in Gen IV to Gen III, take the resistance (Rt) and use it with the pull up resistor (Rp).

% = Rt / (Rt + Rp)



The extremes don't line up that well, but they never do on analog signals anyway, so I'd assume there's some other factor in the conversion. For the actual usable area, it's a dead nuts conversion.

[Jabbott]

I've got 2490 as the pullup.

[DSteck]

I've got 2490 as the pullup.

That works too. Pushing the numbers around between 2450 and 2550 changes where it fits better. 2450 seemed to have a better overall R^2.

[MikeOD]

I've got no problem converting the axis...but I fail in excel with creating the trendline and then using it to find the temps ont he Gen 3 axis breakpoints . I'll keep messing with it later on.

[ctd]

Thanks for the response I do have to ask the reason for pull up resistor..........sorry to ask but rode on the small school bus.