I'm chasing my tail all over the place using fuel temp. Maybe I'm missing something but I don't recall ever seeing this much variation while using gmiat. So which method should conclude to better adjusted and more consistent wideband readings? I tune for 11.5 and next run is 10.9... Then I'll see a 12.

Can fuel temp heat soak on 90 + degree days?

 

I've used both and get better results with the GMIAT in the UICP......

 

Fuel definitely heat soaks. Thats the point of the sensor in stock form. It measures how much the fuel has heat soaked and the ecu adjusts accordingly.

The problem you are having is a result of the actual intake air temp changing at a different rate than the fuel temp.

John Bradley refers to fuel temp as a constant average.
https://www.evolutionm.net/forums/ec...d-density.html

I only used it for a couple months, it was spring time and the temps werent very hot. Which means the SD calculated temp was directly related to engine bay temp, not so much ambient temp.

I like actual IAT. And I like seeing the temp curve during a pull. You dont get that info with the fuel temp sensor.

Not taking anything away from the guys that use fuel temp. It certainly works under certain conditions.

 

Ok well that confirms I'm not crazy!

 

I feel the same way,i think with the iat you can more acurately compensate for different air temps and compensate faster also,it's my favorite method for tuning SD by far.

 

Yeh Ive literally been going bonkers using fuel temp and I never really put two and two together and last night making some wot pulls 28 psi I hit 12.3 I was utterly baffled.

 

one thing to keep in mind using the GMIAT is that you will have to rescale all your air temp based compensations, I've just zero'd all of mine out to it isn't pulling timing or wgdc based on air temp, Once I get my tune sorted I will try and put them back in.

 

Yea I'm zeroes I was on gm iat last year. Thing is they seem real fragile I've killed two of them installing? Or something else caused the cage to break and lock the iat reading. So as a quick fix I went fuel temp and I've been battling ever since ..

 

fragile but cheap..... I haven't had mine long but it hasn't broken yet

 

GM IAT heat soaks as well. Sit in traffic with a stock turbo and let me know how that works out for you. If the Air temp/baro correction hasnt been played with I have seen 130* sitting in stop and go traffic with ambient temps around 85*. In stock form the ECU would globally pull 3-4* and richen up a fair amount as well.

How much have the fuel temps varied at this point? I never see more than 3-6* more than what the MAF would measure pre inlet, so if the fuel is heatsoaking it would have to be 60* or more to drastically affect AFRs and/or trims (60*F=1.0 AFR).

No wiring changes have been made and that input is still stock to the ECU? I have locked it out and had cars fairly consistent as well.

 

Interesting. I never knew the stock sensor was so bad during heat soak from start/stop traffic.

I always figured it was just hot so let's run less timing and more fuel. But your post above seems like the stock tune is being a little too conservative under heat soak. I've also noticed the car seems to lose a lot of power after sitting in traffic for awhile. I always thought that was just part of the game.

So even though I'm not running SD, this post suggests I could make the switch for the IAT sensor just to get better readings during traffic? Seems worth it considering the price.

 

Maybe unzeroing my iat ign trim will help. Is it as easy as logging fuel temp in evo scan? The only ecu change I made was to pin the sas from egr.

I see 25• avg ambient change on average but we also have been seeing 50 or better on some days.

Is sd sensitive to back pressure changes? My dynomax vt could be varying back pressure too much you think? It rattles crazy from the gsc cams

 

Log air temp since the programming hook should switch fuel temp to interpreted IAT. The other thing would be the temp scaling needs to be correct or that could throw it off. Backpressure hasnt seemingly affected the fuel temps.

If your swings are that large, then I would presume there is something else at play but that is only based on what I have seen. I will go log an SD car here, heatsoak it, and report back. I may not have results until next monday as today is full and i am leaving for a race tomorrow.

Aaron

 

I noticed that at idle my silencer in the magma flow ti richened it up significantly in ol. I'm gonna take this damn vt off just to clear that off the list .. Plus I miss the noise

 

Ok I'm a blooming idiot. I was on 0E with no gmiat. So I plugged my gmiat in and it's just froze at 105. Wth? Set back o 03 and im getting 89 which is pretty close. I mad have made that error somewhere trying to get back to an old map and being an oversight. Crikey