So who does their own tuning on the LS4?
03-17-2008, 12:01 AM
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So who does their own tuning on the LS4? Last fall another tuner and I were playing around with some temperature models to replicate how the ECM estimates manifold air temperature (MAT) from IAT and ECT. Over the course of a couple of weeks of playing with the model, I logged something like 30 hours worth of data.
Understanding MAT is kind of important, as that is an input into speed density airflow calculations - our ECM's still reference speed density data even with the maf hooked up, at least under 3600 rpm. When looking at the data, it was obvious that the IAT sensor was becoming "heat soaked" in city driving, especially when crawling along at 5 kmh or less in bumper to bumper traffic for 20 minutes at a time.
When I finally got up to speed, it would take the IAT sensor perhaps 10 minutes to return to a normal temperature. So when operating in open loop, the engine ran a bit lean until the IAT sensor cooled off.
Anyone else notice this?
To try to combat this, I insulated the MAF and intake bellows. This did extend the time it took for the IAT sensor to heatsoak, and decreased the time for it to cool off, but looked like **** so I removed it.
I'm considering replacing the stock IAT sensor with a quick acting Omega sensor located in the airbox. Anyone tried that? Has this helped reduce heatsoak?
Understanding MAT is kind of important, as that is an input into speed density airflow calculations - our ECM's still reference speed density data even with the maf hooked up, at least under 3600 rpm. When looking at the data, it was obvious that the IAT sensor was becoming "heat soaked" in city driving, especially when crawling along at 5 kmh or less in bumper to bumper traffic for 20 minutes at a time.
When I finally got up to speed, it would take the IAT sensor perhaps 10 minutes to return to a normal temperature. So when operating in open loop, the engine ran a bit lean until the IAT sensor cooled off.
Anyone else notice this?
To try to combat this, I insulated the MAF and intake bellows. This did extend the time it took for the IAT sensor to heatsoak, and decreased the time for it to cool off, but looked like **** so I removed it.
I'm considering replacing the stock IAT sensor with a quick acting Omega sensor located in the airbox. Anyone tried that? Has this helped reduce heatsoak?
03-17-2008, 01:07 PM
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I do my own, and the first thing i did was set it to not make any timing changes due to IAT readings till its well into the 130's. I use the fender well intake and moved maf twoards the strut tower more and it only reads 15-20 above ambient, not like it really matters, i know its getting air thats cooler than engine bay air anyway.
All i did was smooth the VE table and dial the maf Hz into always be about + 2 trims at all times ( my car runs stronger with slightly + trims than neg trims in part throt). Thing is snotty as hell no matter what the temps are.
All i did was smooth the VE table and dial the maf Hz into always be about + 2 trims at all times ( my car runs stronger with slightly + trims than neg trims in part throt). Thing is snotty as hell no matter what the temps are.
