ken800

I decided to do some testing with my JL ram air to measure the intake air temp sensor... I have a 20 minute long log file so I won't post it... I'll just post the summary.

Started the engine, let it run until temp was up to about 2/3 normal operating temp. At this point, intake temps started to rise. So, I took off for work. At 15-25MPH through my neighborhood, the intake temp stayed within 1 degree of ambient. At full operating temp I slowed at a light (didnt' stop, down to 20MPH) briefly and temps jumped 7 degrees quickly. Back up to freeway speed and temps stayed at ambient for next 10 miles or so. I hit a patch of traffic and dipped into the 10-30mph ranges and temps climbed about 8 degrees very quickly. Single digit MPH and the temps jumped to 16-20 degrees over ambient and were still climbing. I rolled at a constant 30MPH for about a 1/2 mile and temps maintained 13-14 degrees over ambient. Maintained 40 mph for another 1/2 mile or so and maintained 12-14 degrees over ambient. Back down to 10 mph and back up to 16 degrees over ambient. The cooling fans now kicked in and hot fan wash complicated things. I sped up again and the fan went off right before I parked. I let it run in park with the fan off and peaked at 33 degrees over ambient. The fan kicked in and the fan wash made temps jump very quickly. I let the engine run for a couple of minutes and reached 142 degrees intake temp. Ambient was 83-84 degrees the whole way which meant I was at 59 degrees over ambient sitting there.

Summary:

While engine is cold, low MPH will keep intake close or at ambient. Once the engine bay is completely heat soaked, it takes at least 30MPH to keep intake temps down within 10-15 degrees of ambient. In stop and go traffic, it's going to be just plain ugly. I'll test again this afternoon when the truck has been sitting in the sun and I'm running around at lunch. I suspect the heat and difference between intake and ambient will be quite large....

Assuming the adage that a 10 degree change in intake temp is worth 1%, it stands to reason that in stop and go traffic, until you get up to speed, those little quickie throttle jumps are missing (on my truck at 380HP) around 1.5-3% HP which equates to 5.7 to 11.4 HP. I am assuming a 10-15% ambient vs. intake temp which is somewhat conservative because I hit a 39 degree spread sitting there this morning for just a couple of minutes. Keep in mind this test was at 83-84 degrees ambient with the sun on a low horizon. At noon, that number may climb very high. I suspect that if given enough stop and go time that the engine bay will approach the operating temp of the engine... we'll soon find out eh?

This doesn't mean JL's box is bad. Quite the contrary. Without the ram air setup, I don't think intake temps would come down nearly as quickly or ever even reach ambient. The fact that ambient can be reached with a hot motor is good, but the ultimate question is how much HP off of launch and through the early part of first gear am I losing due to heat soak and hot air being ingested?

An even bigger question that always begs: Is more warm air better than less cold air? And what will the stock airbox look like?

I'll keep you guys posted as I'll be doing the same thing with a stock airbox and K&N panel filter in a week or two.

Ken