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

 

talk with wydopnthrtl. He's been doing data logging all summer and has some very interesting information regarding timing and engine temp and tip in.

 

Hopefully Rich will share this info with his thoughts. Thanks Jody for the good data. Time to think about enclosing my filter, or venting the engine compartment.
I have not run in extreme heat yet, and do have lower iat2 temps lower than most due to the MP blower and full exhaust. I will do some experimenting with ducting and possibly fender vents.
Jim

 

And both these trucks run KB's and full exhausts also. Getting the heat out from under the hood would help a lot.

Jody

 

Enclosed filter setup, ram air hood and vents in the fenders would help. A lot of money too (mostly for the hood and fender work).

The vents in the fenders would look killer if done right

Steve

 

I think SloeTruk on NLOC has the fender vents on his truck. Just check his gallery. They look pretty sweet.

 

I have a stock long block, Apten ported eaton, a 4# lower, and a open conical filter. With those things in place I see 129-130F IAT2 temps at the top of 3rd gear. And the ambient temp does't seem to effect it as much as does how hot & hard the motor has been run right before the run.

Also worth noting; I see the opposite when going into boost. My IAT1 temps go up 5-10 degrees and my IAT2 temps go down to right at about 20 degrees hotter than what the IC fluid temps are. (Gotta get into moderate boost for it to do that. Like 8psi)

After driving one hour and then being shut off for 20 minutes I saw 150+ IAT2 temps. Took it a good 1/2 hour more of normal driving to get them back down to the 115 area (85F ambient)


I'll be driving it more this summer than I did last so I'll make sure to collect lots of data.

Rich

 

Thanks Rich. So far the two I've datalogged do exactly the same thing; climb under WOT. They will climb under decel or anytime the throttle shuts, then fall with some throttle opening and resultant airflow. But under WOT they climb period, only difference being where they start. The enclosed air filter starts 25-30 degrees lower than the open. This is on trucks that are fully up to temp and have been driving normally, idling and cruising. If the truck is started cold and immediately hits the freeway the IAT1 stays much lower on the open element. Once it heat soaks and hits lower speeds/idling it take much longer to recover when moving than the enclosed system, never reaching the temps of the enclosed unit.

Jody

 

good info guys
i was thinking a nice cowl hood and ( maybe not ram air) enclosed filter set up with some tubes running down to the grill. but not that scoop that fits under the bumper

 

Found them. Um, it's definitely a different look.

Not sure I'm too sold on the look of that particular style of vent on the fenders.

 

WTF!!!!!!

 

 

Id rather have high IAT2's

 

Jody,

My SCT tune pulled 2 degrees out of my tune even when the outside temp was 70 degrees. I datalogged my truck at 76 degrees ambient temps and the IAT2 temp would toggle between 99 and 100 degrees (I have an old JDM Fluidyne heat exchanger). It was still pulling 2 degrees of timing.

The base tune that came from SCT with all the injector and MAF parameters added had a peak timing of 19 degrees. That was after 5000 rpm. I never saw more than 16 degrees of timing. That 16 came in at the point 18 degrees of timing should have came in and never climbed the extra degree at 5000 rpm.

Leaving the timing to move around on it's own is a recipe for disaster. I have a feeling it would have seen 19 degrees of timing when the ambient temp hit the the low 50's or upper 40's. This would be the temps where I wouldn't want it to see more than 16 degrees.

If you think outside air induction kits are the holy grail then think again. Dealerjim and I both ran them and saw zero reduction in ET or an increase in MPH. He had one brand (his was removed after 6 months) and I have the other. I can say it brings the IAT1 down. Ken800 on NHTOC did a bunch of data logging on this. The bottom line was the IAT2 only dropped 2-3 degrees using the ducted filter setup. I knew it from the track and Ken datalogged to no end to figure out what was happening.

Do yourself a favor and lock the timing with the Max Allowable Spark Table. I have a 16 degree slope timing tune for the winter, 18 slope timing tune for the warm weather and 18 degree no slope timing race tune. No monkey motion in these tunes no thanks to SCT.

 

My understanding is the "Borderline Knock" table is the one you want to make sure is correct. The "Max Allowed" table is not the one you want to adjust (this is according to a couple tuners and SCT).

I set my "Borderline Knock" tables to where I want them to be and when I datalog my spark doesn't exceed those parameters.

Steve