Air Inlet Temps
10-01-12, 11:13 AM
#1
Rotary Freak
Thread Starter
Air Inlet Temps
Lets talk about the effects of Air Inlet Temps on tuning and performance. We were running the RX7 this past weekend at Mosport and we were having substantial issues with the tune as the AIT sensor was reading underhood temps of 33C and adjusting the tune to reflect what the car would need at that temp. Ambient air temps outside the car were around 12C (approx 55F)Obviously the car ran like crap and was pig rich. We ended up leaning it down by almost 20% to get the A/F's back in to the high 12's low 13's, adjusting the throttle position enrichment leaner by about 5% and trimming the temp compensation a ton and turning it off above 4500 rpm.
The tune on the car was done with AIT's of around 85C and it had worked extremely well at those temps with ambient air temps of around 30C. The drop in ambients and AIT's threw the previous map out of whack and luckily enough we were able to compensate. I need to build an airbox to more closely control the AIT's as we are now just drawing from the engine compartment, but I can't believe how sensitive the tune is to temp. Anything else we should look at to help reduce the whole temperature sensitivity of the car? I can't have the car retuned every race, its like running a Weber Carb on it, LOL.
On a side note, we ran the car on Grand Am Conti's for the first time. Drooooollllll....... it would stick and go anywhere you wanted it to. Big thumbs up for the tires and I can hardly wait to get more track time on them as they do require a different setup on the car and we need to think about what we need to do.
Eric
The tune on the car was done with AIT's of around 85C and it had worked extremely well at those temps with ambient air temps of around 30C. The drop in ambients and AIT's threw the previous map out of whack and luckily enough we were able to compensate. I need to build an airbox to more closely control the AIT's as we are now just drawing from the engine compartment, but I can't believe how sensitive the tune is to temp. Anything else we should look at to help reduce the whole temperature sensitivity of the car? I can't have the car retuned every race, its like running a Weber Carb on it, LOL.
On a side note, we ran the car on Grand Am Conti's for the first time. Drooooollllll....... it would stick and go anywhere you wanted it to. Big thumbs up for the tires and I can hardly wait to get more track time on them as they do require a different setup on the car and we need to think about what we need to do.
Eric
10-01-12, 12:41 PM
#2
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it sounds like maybe you could find a better place to put the air temp sensor? maybe the difference in what it reads vs outside is a problem?
part 2 would be to build the air temp vs fuel map, so you don't have to do it. its kind of the point of EFI, but it is tricky. our honda has the MPG change pretty drastically with outside temp (we've raced from 110F to 20F!)
pic is the stock air temp "map" for the GSL-SE
part 2 would be to build the air temp vs fuel map, so you don't have to do it. its kind of the point of EFI, but it is tricky. our honda has the MPG change pretty drastically with outside temp (we've raced from 110F to 20F!)
pic is the stock air temp "map" for the GSL-SE
10-01-12, 01:01 PM
#3
Rotary Freak
Thread Starter
it sounds like maybe you could find a better place to put the air temp sensor? maybe the difference in what it reads vs outside is a problem?
part 2 would be to build the air temp vs fuel map, so you don't have to do it. its kind of the point of EFI, but it is tricky. our honda has the MPG change pretty drastically with outside temp (we've raced from 110F to 20F!)
pic is the stock air temp "map" for the GSL-SE
part 2 would be to build the air temp vs fuel map, so you don't have to do it. its kind of the point of EFI, but it is tricky. our honda has the MPG change pretty drastically with outside temp (we've raced from 110F to 20F!)
pic is the stock air temp "map" for the GSL-SE
Eric
10-04-12, 11:18 AM
#4
What system are you using? Temp compensation is pretty much a constant that can be calculated based on air mass v. temp. It's typically not something you "tune". You setup the table to reflect the mass v. temp and forget it. A rule of thumb to start with is 3.5% per 10*C.
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