LT1 intake air temperature question

[Pranav]

Guys, those that can read this from their computers at hot idle with the hood up, what kind of IAT temperatures are you getting?

Long story short, we all know I've been through all kinds of hell with misfires when I put in a new motor last year, and chasing my tail on all kinds of components and even lost that motor over running with those misfires too long. I've done an opti job a couple of times, swapped out ICMs/Coils, re-done all of the plug wires, new plugs, etc. I thought I had this nipped in the bud at TWS, but then again I only made 5-6 laps at 50% pace before I popped the motor.

Yesterday on the dyno the car with a fresh new motor, new plugs/wires, freshly cleaned injectors, it again started breaking up above 5k RPMs after a couple of pulls. Instinctively I remember some comments that were made about my aluminum intake elbow, which was put in with the new motor last year; it was piping hot to the touch. It would break up above 120-125*F IAT. We put a small fan right on it, and then were able to get the IATs much lower and make 6-7 back to back pulls with no problem with the oil/water temps going up as expected.

Went home, couldn't find my old plastic/rubber piece, so I insulated and wrapped the hell out of it with 15ft of gold tape. I saw an improvement in IAT and the elbow is now just warm to the touch, but it will still 110-115*F at idle. (90*F outside, probably 100*F in my garage, coolant at 195-200).

Later on I found and put on a stock plastic elbow, and was getting 115*F-120*F at idle compared to my super insulated metal elbow; so it actually was a little worse.

I then punched a small hole in the plastic assembly right after the filter and put in a second IAT sensor there and moved the wire over to it, IATs readings are now down to 100-105*F, the starting temps under which I was able to get solid pulls. Yes I know this actually is just fooling the computer, just wanted to see if it would sound less rich at idle and decel, and it does so for longer now.

I think I may be good now, but to be safe I'm getting some more gold wrap and insulation, and a heat shield for the air filter. I will likely re-dyno later this week to make sure this all works before I go to Hallett.

The only other issue I can think of is I'm picking up a lot of heat from the oil cooler/lines that are near/below the filter. Attached are pictures of everything I just talked about. Those of you not familiar with the LT1s note that the elbow/TB is right above the waterpump/neck, and the stock IAT sensor location is right in it.

Can you guys with running LT1s and scanners see what your IATs are at hot idle with the hood up?

Wondering if I have just been cooking my air filter the entire time or if something else is wrong with the system that is causing it to react so poorly to higher IATs.

[Pranav]

I can't get images to work, just click here and scroll down:

http://imgur.com/a/tMuVE

[GlennCMC70]

I see your problem..... Your feeding hot air off the oil cooler right to the air filter and the air filter is also pulling hot engine bay air into it as well.
You need to run a 100% stock set-up. The stock set-up pulls air from in front of the core support. You also now know why my oil cooler is on the passenger side. It was just the best place for it.

[Pranav]

Yeah, you're right. I've got an IAT issue, I could try to bandaid it with more wrap and heatshielding, but in reality I've got a big source of heat too close to the filter.

Already started pulling the cooler lines off, waiting for some more hose to come in so I can run it to the other side.

Found all my stock intake parts. Just going to wrap it all up to be safe.

[Pranav]

One more thing I can't believe I forgot to mention.

Morning after the dyno I got to work on the intake swapping and testing, and got the motor nice and warm in my corner of the garage. It was 90* outside but with little ventilation I'm sure ambient temp near the front of the car against the wall was close to 100*F. Needless to say things were toasting, but the car should be able to handle it at idle as it always has.

Anyways suddenly the car started stalling and dying, in some cases attempting to restart would cause backfiring thru the intake, and it refused to start. No codes as usual. Went out for lunch and let the car cool off for a couple hours, started right back up, once it got warm it started acting up again. With it hot I swapped out the ICM and it fixed it right up, has been starting up and staying running while hot since.

Took a close look at it and there's a big crack in the plastic case near the connector.

So I'll be going back to the dyno with an all stock intake wrapped with gold tape, relocated oil cooler, and a replaced ICM. This better work or I'm throwing in the towel for Hallett.

[y5e06]

wow, what an incredibly frustrating collection of problems. Good look man.