I had friend over this week to do some tuning on his HD truck. It has a fully built motor with ported heads/cams. He is using the Pro Racer tuning but hasn't received his datalogger yet, so he brought it up to my house to do some datalogging and tuning.
While tuning I noticed that the timing didn't appear to be where it should. The lower end timing was pretty low so we bumped that and that made quite a bit of improvement on the initial WOT. But as he pulled through the gears the timing still wasn't coming close to reaching what we wanted. I noticed that the IAT2's were very high also.
He runs basically an open element air filter. It can be enclosed for fresh air outside the engine compartment, but wasn't at the time. The temps were in the upper 80's but his IAT1 was between 115-125 with normal cruising, reaching 150+ at longer idles. His IAT2's would then be about 25-30 degrees higher. When he'd floor it the IAT1's would drop and the IAT2's would climb. Before he hit 3rd gear his IAT2 temps had exceeded 170 degrees and would hit 180+ by the time it shifted into third gear at WOT.
He had a stock heat exchanger on the truck, and the intercooler pump is working fine. We were looking for 15 degrees at WOT and only getting as low as 9.75! The computer will pull timing due to air temp just like it will add timing with low air temps. Most of you know that in winter several guys have blown up their trucks due to the added timing with the cold air. Well, this time of year it's the opposite. Once you hit 150 degrees on IAT2 it starts pulling timing. At 150 the factory modifier on my truck will pull between 2.2 degrees to 5.5 degrees depending on rpm at WOT. When the temp hits 174 degrees it jumps to 5 to 12.5 degrees of timing, again depending on rpm.
All of this can be tuned out, but that's not a good idea. A better idea would be to try to cool the air temps so the computer doesn't have to pull timing for safety. I took my truck out after his and datalogged the same things. I have an AIRRAID enclosed air filter, and even though the air temps were up to about 90 degrees (ambient) my cruising temps were only a few degrees above ambient (95 degrees IAT1 and 115-120 IAT2). My truck did the same thing as his at WOT, the temps climbed. But since I started at 25-30 degrees less I didn't reach the 150 threshold to pull timing until about 5400 rpm in 3rd gear, basically at the end of a 1/4 mile run. Now if I slowed down and immediately ran the truck again the air temps hit 160 which pulled a couple degrees, but that was without any cooling of the temps, just slowed from the first run and immediately hammered it again.
I do have a larger heat exchanger which would account for a bit of this. But I believe the biggest part of it is the air filter setup, enclosed versus the open filters many use. The reason I think it's the filter is because my temps were lower everywhere by a bunch, even idling still in gear where the heat exchanger wouldn't help as much (no fans on mine).
Anyway, the point of this thread is to shed some light on a big reason our trucks feel doggier in the heat. Do some datalogging on yours, you may be surprised at your IAT2 temps, especially once the truck is up to temp. Plus it was only 87 degrees with his, what will they look like at 95-100 degrees which many of us get?
Jody
While tuning I noticed that the timing didn't appear to be where it should. The lower end timing was pretty low so we bumped that and that made quite a bit of improvement on the initial WOT. But as he pulled through the gears the timing still wasn't coming close to reaching what we wanted. I noticed that the IAT2's were very high also.
He runs basically an open element air filter. It can be enclosed for fresh air outside the engine compartment, but wasn't at the time. The temps were in the upper 80's but his IAT1 was between 115-125 with normal cruising, reaching 150+ at longer idles. His IAT2's would then be about 25-30 degrees higher. When he'd floor it the IAT1's would drop and the IAT2's would climb. Before he hit 3rd gear his IAT2 temps had exceeded 170 degrees and would hit 180+ by the time it shifted into third gear at WOT.
He had a stock heat exchanger on the truck, and the intercooler pump is working fine. We were looking for 15 degrees at WOT and only getting as low as 9.75! The computer will pull timing due to air temp just like it will add timing with low air temps. Most of you know that in winter several guys have blown up their trucks due to the added timing with the cold air. Well, this time of year it's the opposite. Once you hit 150 degrees on IAT2 it starts pulling timing. At 150 the factory modifier on my truck will pull between 2.2 degrees to 5.5 degrees depending on rpm at WOT. When the temp hits 174 degrees it jumps to 5 to 12.5 degrees of timing, again depending on rpm.
All of this can be tuned out, but that's not a good idea. A better idea would be to try to cool the air temps so the computer doesn't have to pull timing for safety. I took my truck out after his and datalogged the same things. I have an AIRRAID enclosed air filter, and even though the air temps were up to about 90 degrees (ambient) my cruising temps were only a few degrees above ambient (95 degrees IAT1 and 115-120 IAT2). My truck did the same thing as his at WOT, the temps climbed. But since I started at 25-30 degrees less I didn't reach the 150 threshold to pull timing until about 5400 rpm in 3rd gear, basically at the end of a 1/4 mile run. Now if I slowed down and immediately ran the truck again the air temps hit 160 which pulled a couple degrees, but that was without any cooling of the temps, just slowed from the first run and immediately hammered it again.
I do have a larger heat exchanger which would account for a bit of this. But I believe the biggest part of it is the air filter setup, enclosed versus the open filters many use. The reason I think it's the filter is because my temps were lower everywhere by a bunch, even idling still in gear where the heat exchanger wouldn't help as much (no fans on mine).
Anyway, the point of this thread is to shed some light on a big reason our trucks feel doggier in the heat. Do some datalogging on yours, you may be surprised at your IAT2 temps, especially once the truck is up to temp. Plus it was only 87 degrees with his, what will they look like at 95-100 degrees which many of us get?
Jody
