Power FC Air Temp Sensor Idea...
03-02-03, 01:08 AM
#1
Air Temp Sensor Idea...
It may be too late and I might be thinking retarded, so let me know if this doesn't make sense.
With that said, upon considering options for relocation of my air intake sensor, I thought about what remains a constant on the car in terms of air temperature in relation to the actual charge temperature. Basically, once you have all of your modifications set and are ready to tune your car for safety and power, you want to make sure that the variables considered by the PFC are accurate and this seems to be the biggest disadvantage with the air temp sensor's stock location.
My solution (theory, haven't tried it): Come up with a mount for the air intake sensor that will measure ambient air outside of the engine bay the best possible. Heat soak is no longer a problem and it will accurately reflect outside air temperature as long as you don't drive under some water which would really cool off your charge temp... but I digress. Once you have ambient air temperature, the air goes through the same route every time and that's through the intake, to the turbo, then intercooler, up to the intake manifold and in the engine. The way I figure it, this can be accurately measured as I'm sure we have all been cruising down the highway and know exactly how efficient our intercoolers are by comparing it to ambient with different boost conditions. The stock location as well as the intercooler outlet location are not going to be able to adjust fast enough for no boost to max boost for the air temp increase, so that would be another factor you would have to add to the equation. Anyway, since we're able to adjust fuel in relation to temperature range, you simply add the "my intercooler is x degrees above ambient air" to ambient air temperature and when you tune your car, make that temperature as close to 1.0 as you can. Then either retune at different ambient air temperatures (time consuming and expensive for some) or figure out the math and physics of it all for the rest of the factors.
I understand this makes the most sense for front mount intercoolers that don't tend to heat soak as bad as a stock mount, but intercoolers cool off relatively quick and I don't see the I/C outlet location being more accurate or a better way to do it if the only reason is intercooler heat soak. I just decided that I need to relocate because it was around 45F the other day when I went to the drag strip and my intake temp read 55C from the heat soak of waiting in line and it was time for me to go full boost from a standing stop??? No wonder we have a reputation for engine's being unreliable, this sensor could be a major achilles in terms of the engine.
Am I too tired and need to shut up or does this make sense? I would like to hear some input to the idea and nothing like, "Just drill the I/C out and thread it in, it's the same thing..."
Richard
With that said, upon considering options for relocation of my air intake sensor, I thought about what remains a constant on the car in terms of air temperature in relation to the actual charge temperature. Basically, once you have all of your modifications set and are ready to tune your car for safety and power, you want to make sure that the variables considered by the PFC are accurate and this seems to be the biggest disadvantage with the air temp sensor's stock location.
My solution (theory, haven't tried it): Come up with a mount for the air intake sensor that will measure ambient air outside of the engine bay the best possible. Heat soak is no longer a problem and it will accurately reflect outside air temperature as long as you don't drive under some water which would really cool off your charge temp... but I digress. Once you have ambient air temperature, the air goes through the same route every time and that's through the intake, to the turbo, then intercooler, up to the intake manifold and in the engine. The way I figure it, this can be accurately measured as I'm sure we have all been cruising down the highway and know exactly how efficient our intercoolers are by comparing it to ambient with different boost conditions. The stock location as well as the intercooler outlet location are not going to be able to adjust fast enough for no boost to max boost for the air temp increase, so that would be another factor you would have to add to the equation. Anyway, since we're able to adjust fuel in relation to temperature range, you simply add the "my intercooler is x degrees above ambient air" to ambient air temperature and when you tune your car, make that temperature as close to 1.0 as you can. Then either retune at different ambient air temperatures (time consuming and expensive for some) or figure out the math and physics of it all for the rest of the factors.
I understand this makes the most sense for front mount intercoolers that don't tend to heat soak as bad as a stock mount, but intercoolers cool off relatively quick and I don't see the I/C outlet location being more accurate or a better way to do it if the only reason is intercooler heat soak. I just decided that I need to relocate because it was around 45F the other day when I went to the drag strip and my intake temp read 55C from the heat soak of waiting in line and it was time for me to go full boost from a standing stop??? No wonder we have a reputation for engine's being unreliable, this sensor could be a major achilles in terms of the engine.
Am I too tired and need to shut up or does this make sense? I would like to hear some input to the idea and nothing like, "Just drill the I/C out and thread it in, it's the same thing..."
Richard
Last edited by Roadracing7; 03-02-03 at 01:13 AM.
03-02-03, 09:36 AM
#2
You are spot on. We've mentioned this intake air temp sensor as a sure time bomb under such conditions. If your tuning was based on actual air inlet temps you would have been several tenths lean on your target AFRs during your drag run.
I have thought about simply reading ambient air temp, car would simply run a bit rich at times. Wonder what all the tuners or owners of different cars do? Are not other turbo or sc'd cars experiencing the same challenges?
I have thought about simply reading ambient air temp, car would simply run a bit rich at times. Wonder what all the tuners or owners of different cars do? Are not other turbo or sc'd cars experiencing the same challenges?
03-02-03, 10:35 AM
#3
About other cars, I would believe our biggest problem is the sensitivity of our apex seals to lean conditions like knocking and detonation. A friend of mine is running a supercharger at 8psi on his S2000 with no problems. Remember the Z31 300ZX Turbo? 7psi with no intercooler... Those pistons I guess can handle small issues like differences in intake temp.
Richard
Richard
03-03-03, 12:36 PM
#5
Rotary Enthusiast
Concept has merit for FMIC's, especially for drag use.
Air density diff at 55C vs 45F is 17% ! Actual error is mitigated by base PFC air corrections that leave some xtra fuel in as temps rise, but .8+ a/f ratio leanout could occur until sensor reads correctly.
Any acceleration checks for IC temp rise will include some thermal mass heat sink effects of the IC. If you roadrace, would need to confirm similar results.
SCC tests on M2 SMIC showed 158F actual max intake temps at roadcourse, and just 90F temps for some accelerations runs, 12-13 psi on 80F day, iirc.
Still seems best to just put sensor on IC tank/exit pipe. Esp true for M2 SMIC with mixed track use ... using fan and insulation near sensor to minimize heat soak.
Either way, would need to be sure idle and transitions were still ok.
Air density diff at 55C vs 45F is 17% ! Actual error is mitigated by base PFC air corrections that leave some xtra fuel in as temps rise, but .8+ a/f ratio leanout could occur until sensor reads correctly.
Any acceleration checks for IC temp rise will include some thermal mass heat sink effects of the IC. If you roadrace, would need to confirm similar results.
SCC tests on M2 SMIC showed 158F actual max intake temps at roadcourse, and just 90F temps for some accelerations runs, 12-13 psi on 80F day, iirc.
Still seems best to just put sensor on IC tank/exit pipe. Esp true for M2 SMIC with mixed track use ... using fan and insulation near sensor to minimize heat soak.
Either way, would need to be sure idle and transitions were still ok.
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