Insulate your CAI?
 

I've been having some troubles this summer with my IAT sensor getting heat-soaked by the AL pipe when idling or caught in stop n' go traffic. I started thinking about the thermodynamics involved and concluded that insulating the outside of the CAI would help reduce the amount of heat being disipated to the intake air stream. When you think about it, the pipe picks up all of it's heat from the hot air under the hood and transfers that heat into the much cooler, faster moving air inside it. Only when the air under the hood is cooler than the pipe will any heat be disipated through the outside of the pipe and that only happens when the engine has been off for a considerable time.

The most commonly used material to insulate intake piping seems to be header wrap. I considered this but header wrap isn't very good at reflecting radiant heat. For that we need something reflective. But wait, my CAI is already polished and reflective. Hmmm... what if I used a reflective material with a boundary layer behind it? Searching the performance shops turned up lots of reflective tape and only one insulating sleeve. I didn't like the sleeve because it's laced up and looks like it would be hard to form around bends and protrusions. I ended up choosing Reflectix home insulation from Lowes for $15 a roll and a $6 roll of AL foil tape. Reflectix is class A/1 fire rated, tested in direct contact with a 250F heat source for 96 hrs without damage and the manufacturer rates it for 180F contact use or up to 300F air temp.

Anyway, here is the finished product. It's going to be nearly impossible to provide controlled test results due to changes in ambient air temps but I'll do my best to provide my subjective impressions backed up by the best data I can provide by comparing before and after scan tool IAT temps.

http://a.imageshack.us/img196/718/cxrredux001.jpg

http://a.imageshack.us/img843/662/cxrredux002.jpg

Ok, it's not as pretty as polished, powder coated or painted but it's not that ugly is it?

Well, I'm probably coming from left-field here with my home-brew CAI, but yes, insulation from engine compartment heat (together with associated damping of metal intake tube resonance) is a definite factor in what's under my hood :)! Of course, the specific solution to the issue may vary, but I think the problem is genuine!

http://i8.photobucket.com/albums/a33...eBrewCAI_1.jpg

i've got mine wrapped also, it stays almost at outside temp.

The purpose of a CAI is to add the metallic piping that can dissipate heat easier. Now, if you insulate it, you might as well have a stock intake. You would be better off insulating the exhaust manifold to lower temps.

Thanks for the interest and replies. SL members must be smarter than the average car forum member becasue I could hardly believe some of the arguments I read elsewhere while researching this. Some claimed that insulating the CAI would only trap the heat and make it hotter, others claimed that there is so much air flowing through it that there is no reason to insulate it. The second argument makes more sense but ignores the fact that if it were true, the CAI would never get hot in the first place and we know that they do.

My initial impression is very good. On my first test run I tried to dupilcate a scenerio from yesterday when I drove ~10 miles, stopped and idled for 5 minutes. Ambient air was 75F and the IAT climbed from 90F to 126F while idling. Tonight the ambient air temp was 71F and the IAT climbed from 85F to 108F. Not bad for $20.

Your first statement is false. The purpose of a CAI is 4 fold. First it draws intake air from a cooler air location than oem. Second it allows for greater airflow than oem. Third, it adds measurable WHP and TQ gains. Fourth, it adds engine noise that people who buy performance parts appreciate hearing. It kind of makes your car 'feel' faster. :)

Your second statement is also false. If the air outside the bare AL pipe is 150F and the air inside is 90F, where is the heat being transferred to? I submit to you that since all of the heat in the CAI metallic pipe is being absorbed from heat sources inside the engine compartment and all of the cooling is being accomplished through intake air flow, insulating the outside of the CAI results in less heat being absorbed by the intake air.

Granted the benefits of insulating the CAI are only significant when stopped or moving slowly when the only air moving inside the engine compartment is from the fans blowing 200F air off the radiator and the intake air is less and slower moving but these are the times when a metallic pipe with very high thermal conductivity is actually worse than the oem plastic materials with very low thermal conductivity.

Insulating the exhaust manifold is a great idea but addresses slightly different concerns. I highly doubt that insulating the exhaust manifold can reduce engine compartment temps enough to have as much effect on the heat absorbtion rate of the 4th most thermally conductive element as insulating it from the heat source will.

Sorry, but that makes no sense whatsoever to me. If the intake air is cooler than the engine compartment (the whole point behind a CAI), it doesn't need to dissipate heat, it needs protection from being heated under the hood. Hence the insulation!

I think you're missing the point of a CAI. If you have cool air coming in, how is it possible to dissipate the heat in a hotter pipe? Doesn't work that way dude.

I think the insulation is a great idea ...

As for insulating your exhaust manifold/ headers ... I'll agree.

It will keep some heat out of the engine bay and keep your exhaust gasses hotter.

Nice Brett, I like it.

Thanks Don. It's helped to keep IATs down a little but didn't solve the hot engine/lean idle issue. I can only guess that the IC is reducing the IAT enough to cause the lean condition. Another good reason to go with a blow-thru MAS.

Ive been away for a while Fred. What are you using to tune(piggyback) the ECU with?

Welcome back. I'm using a Split Second Enricher to add fuel in closed loop at the on-set of boost and 440cc injectors. AFR is 14.7 in vacuum, 12.3 in closed loop with boost and 11.5 in open loop.