Thucydides

Greetings.

I'm finally getting around to removing the stock MAF meter after several months of fun and games. With spring in full bloom here in northern California it's time to get rid of the far too easily heat soaked stock IAT sensor and move to the GM unit just upstream of the throttle body.

My question is, is there any difficulty using my existing tuning file, which I've already got pretty well set up for my 460 cc injectors? The base maps for both the stock MAF installed and the stock MAF removed appear to be identical. If so, it should be simply a matter of flashing the proper firmware to the ECU (after disconnecting the coil pack) and then reinstalling my existing tune file.

Anyone see any problems with this approach?

Jim

Thucydides

My son and I swapped out the MAF and are now reading IAT in the intercooler tube between the intercooler and the throttle body. In answer to the my original question you can re-use your tuning file after you've re-flashed your firmware, and there is absolutely no need to go back to the base map and re-input the data you want. The Megasquirt manual confirms this, though not necessarily where it would have been easiest to find.

Best of all, by not taking temperature measurements at the MAF sensor, which is quite close to the turbo, the measured IAT were so much lower, and so much more stable, that at first I thought the sender wasn't working. The weather's cooled and so I can't say it won't still heat soak to some degree, but I'm pretty sure this was a major step in the right direction.

I probably should have done what most folks do and simply have gone to the GM IAT sensor when I originally installed the turbo kit. But even later in the game, the way I did it, the swap was painless.

Braineack

iTrader: (62)

probably wont have to change the tune too much, unless corrections came into play.

Thucydides

I think you're right, Brain; the car runs beautifully and the IAT readings are tens of degrees lower. It was stupid of me not to have done this simple modification months ago.

Braineack

iTrader: (62)

you reflashed the firmware for the GM AIT sensor though right?

Thucydides

Good question.

We reflashed the firmware to "MM9495 without MAF", but you raise what I suspect is going to be an important point....how does the MSPnP know what temperature sensor is in there unless I tell it.

I couldn't find anything in the drop down Megatune menus or within the configuration files that would allow me to specify a type of IAT sensor, and there were no options during the firmware reflashing procedure either. Perhaps the GM IAT sensor supplied with the DIY kit is the default sensor for the "without MAF" firmware with current version of MSPnP?

As it is the IAT gauge is responding in what seems to be an appropriate fashion; starting at ambient in a cold motor and climbing eight or nine degrees above ambient with a fully warmed motor in the 55 degree weather we're having tonight. With prolonged idling the IAT will climb twenty degrees above ambient, will climb a few degrees under boost, and returns to the eight or nine over ambient with light load cruising. So it seems to be working properly, but I can't be sure.

I'll search the manuals for a definitive answer, but so far so good.

Braineack

iTrader: (62)

because the firmware file is already setup to be used in conjunction with a GM AIT sensor.

Thucydides

Agreed. I found the info in the Wideband section of the MSPnP Manual last evening. It doesn't exactly spell it out for you, but the hint is pretty strong. Anyway, thanks for keeping an eye out and for the confirmation.

Jim