Battling high IAT's on a LSA
Thread Starter
Teching In
Joined: Oct 2015
Posts: 10
Likes: 2
Battling high IAT's on a LSA Long time lurker, first time poster. I have a 71 Impala with a 6.0 and a ported LSA, have been battling high IAT's since the install a couple of months ago.
While I was waiting on a custom intake tube I originally just had a K&N filter coming off the TB sitting right above my fans. IAT's while street cruising would be 130ish-140ish. If I hammered down then obviously they would climb to 160ish+. On the highway doing 75mph, they would lower and sit about 120. Put the new intake tube on over the weekend to get the filter away from the fans. It now sits near drivers wheel well and I was seeing them at 160ish while just street cruising. It was probably 85 degrees and humid out on Monday when I saw those temps. But I assumed moving the filter away from the fans my IAT's would go down not up. Listing engine/blower info below. let me know if I missed something. Reading the IAT's off my Dakota digi dash which is getting info from my Holley Terminator. IAT sensor is on the lid. Also, I'm seeing coolant temps climb to 220 once in a while, they seem to coincide with the high IAT's. They get hotter when the IAT's are hotter. If I'm sitting idle though, the IAT's and coolant drop.
Thanks in advance
LQ4 10.3-1 compression
Aftermarket pistons/rods
Borowski LS3 CNC ported heads
Mild blower cam
Ported LSA blower with 2.45 pulley (ZL1 lid)
Stock brick (I know I should have did the re-enforced and I will)
Boost District upgraded heat exchanger/pump
Flex sensor but running E85
While I was waiting on a custom intake tube I originally just had a K&N filter coming off the TB sitting right above my fans. IAT's while street cruising would be 130ish-140ish. If I hammered down then obviously they would climb to 160ish+. On the highway doing 75mph, they would lower and sit about 120. Put the new intake tube on over the weekend to get the filter away from the fans. It now sits near drivers wheel well and I was seeing them at 160ish while just street cruising. It was probably 85 degrees and humid out on Monday when I saw those temps. But I assumed moving the filter away from the fans my IAT's would go down not up. Listing engine/blower info below. let me know if I missed something. Reading the IAT's off my Dakota digi dash which is getting info from my Holley Terminator. IAT sensor is on the lid. Also, I'm seeing coolant temps climb to 220 once in a while, they seem to coincide with the high IAT's. They get hotter when the IAT's are hotter. If I'm sitting idle though, the IAT's and coolant drop.
Thanks in advance
LQ4 10.3-1 compression
Aftermarket pistons/rods
Borowski LS3 CNC ported heads
Mild blower cam
Ported LSA blower with 2.45 pulley (ZL1 lid)
Stock brick (I know I should have did the re-enforced and I will)
Boost District upgraded heat exchanger/pump
Flex sensor but running E85
Yes, that seems quite high. I think the delta to shoot for is 15-20 degrees above ambient temperature when cruising. My first thought is if you have an air pocket somewhere in the system. If you are running e85 and getting those high temps, there is definitely something wrong. Another thing to check is the routing of your hoses. Make sure that you are sending the coolant coming right off of the heat exchanger and into the lid. I also noticed a huge difference in IAT's when I added a reservoir. I think it helped to add more volume to my system as well as help purge air from the system.
Thread Starter
Teching In
Joined: Oct 2015
Posts: 10
Likes: 2
I have the small reservoir that came with the pump. I'll add checking the routing of my hoses to my checklist along with an air pocket in the system.
Is there a specific way to try and bleed the air pocket out without the coolant vacuum bleeder tool? Or should I look to borrow one from someone?
Is there a specific way to try and bleed the air pocket out without the coolant vacuum bleeder tool? Or should I look to borrow one from someone?
You need to step back and ensure there is an in/out flow path for air under the hood. Then route cold air to the inlet.
I’d put it back the way it was to verify the temps actually drop back to 130-140. Something sounds odd there.
Personally I’d run a decent amount of water meth at the inlet to help fight those temps.
FWIW I run a twin setup with no intercooler. Turbos hung out in open air. I see within 10* of ambient cruising and 225 or so at 15lbs at the 1/8th mile. The gm sensor is only good for 250 and its pretty inaccurate around there. But I will bury the IAT sensor @ 255 plus by the end of the ¼. E85 seems to handle it well, so I wouldn't' sweat your temps too much.
I have since installed 4gph of 50/50 at each turbo inlet.
I’d put it back the way it was to verify the temps actually drop back to 130-140. Something sounds odd there.
Personally I’d run a decent amount of water meth at the inlet to help fight those temps.
FWIW I run a twin setup with no intercooler. Turbos hung out in open air. I see within 10* of ambient cruising and 225 or so at 15lbs at the 1/8th mile. The gm sensor is only good for 250 and its pretty inaccurate around there. But I will bury the IAT sensor @ 255 plus by the end of the ¼. E85 seems to handle it well, so I wouldn't' sweat your temps too much.
I have since installed 4gph of 50/50 at each turbo inlet.
Thread Starter
Teching In
Joined: Oct 2015
Posts: 10
Likes: 2
You need to step back and ensure there is an in/out flow path for air under the hood. Then route cold air to the inlet.
I’d put it back the way it was to verify the temps actually drop back to 130-140. Something sounds odd there.
Personally I’d run a decent amount of water meth at the inlet to help fight those temps.
FWIW I run a twin setup with no intercooler. Turbos hung out in open air. I see within 10* of ambient cruising and 225 or so at 15lbs at the 1/8th mile. The gm sensor is only good for 250 and its pretty inaccurate around there. But I will bury the IAT sensor @ 255 plus by the end of the ¼. E85 seems to handle it well, so I wouldn't' sweat your temps too much.
I have since installed 4gph of 50/50 at each turbo inlet.
I’d put it back the way it was to verify the temps actually drop back to 130-140. Something sounds odd there.
Personally I’d run a decent amount of water meth at the inlet to help fight those temps.
FWIW I run a twin setup with no intercooler. Turbos hung out in open air. I see within 10* of ambient cruising and 225 or so at 15lbs at the 1/8th mile. The gm sensor is only good for 250 and its pretty inaccurate around there. But I will bury the IAT sensor @ 255 plus by the end of the ¼. E85 seems to handle it well, so I wouldn't' sweat your temps too much.
I have since installed 4gph of 50/50 at each turbo inlet.
Putting the filter back to the TB is on my list to confirm that as I agree that it sounds odd. When I was cruising after getting it away from the fans I was like WTF.
I thought about meth as I ran it on my Pro Charged 2008 Grand Cherokee SRT years back. However, I'd much prefer I get to the root of the issue before throwing meth at it.
Once I get her right, then meth is a viable option
Yup, I've had guys tell me not to sweat it as I'm on corn, But as mentioned above, I'd like to get to the root of the problem just for piece of mind.
Thread Starter
Teching In
Joined: Oct 2015
Posts: 10
Likes: 2
Yes dual fans, see below.
https://www.brphotrods.com/p/313-904...with-fans.html
Trending Topics
Theres always the Killer Chiller which uses the ac to cool a brick which the water runs through before going to your intercooler. If your interested I have one that was used for mock up but never got the system together and decided to go a different route.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo The car running a little warm at speed could be a few things... low cruising timing advance, could be air in the system etc...
Last edited by Pro Stock John; Jul 5, 2023 at 07:17 PM.
There are generally high and low pressure zones under the hood that make pockets of hot air. Even though air temps are less than ideal behind the radiator near the TB, the air is defiantly moving there.
Can you tip the top of the radiator back and snake in some ducting in front of the radiator? Those intake tubes they use on c5-c6 vettes have a nice compact shape to them. You can get some 5” alum dryer duct as well. Oval it out and shape as necessary. Then fiberglass over it when you are done. Done that on several setups.
Can you tip the top of the radiator back and snake in some ducting in front of the radiator? Those intake tubes they use on c5-c6 vettes have a nice compact shape to them. You can get some 5” alum dryer duct as well. Oval it out and shape as necessary. Then fiberglass over it when you are done. Done that on several setups.
Thread Starter
Teching In
Joined: Oct 2015
Posts: 10
Likes: 2
Yup, I actually read that on here while searching my high IAT issue and did that a couple of weeks ago. IAT, coolant and Ambient were within a few degrees of each other
Thread Starter
Teching In
Joined: Oct 2015
Posts: 10
Likes: 2
So I ordered a coolant vacuum tool and it will be here today. Its probably something I should have anyway.
Can someone tell me the proper way to re-fill the HX system after I drain it and pull vacuum on it?
What I was going to do and not sure if its the proper way. Refill with the vacuum system until full. Disconnect the vacuum system, put the lid on the HX reservoir, start the car and let it cycle thru. Turn the car off, open the cap and top off, does that sound right?
Can someone tell me the proper way to re-fill the HX system after I drain it and pull vacuum on it?
What I was going to do and not sure if its the proper way. Refill with the vacuum system until full. Disconnect the vacuum system, put the lid on the HX reservoir, start the car and let it cycle thru. Turn the car off, open the cap and top off, does that sound right?
Thread Starter
Teching In
Joined: Oct 2015
Posts: 10
Likes: 2
Just a follow up in case anyone cares or if it helps someone else out.
I drained my HX system, thru the vacuum on it. Filled with the same tool. Just took her out for about 20 minutes. 4-5 WOT pulls, a couple of hard launches. IAT’s never went higher than 145ish. However the part that gives me confidence that air might have been the issue. The IAT's dropped immediately, pretty much as soon as I let off, they dropped and dropped fast. From 140 to 130 in a blink of an eye. That never happened, when they dropped it would be very slow. I know the true test will come when it’s hot AF out again, as its only like 70-75 degrees this morning. But fingers crossed.
I drained my HX system, thru the vacuum on it. Filled with the same tool. Just took her out for about 20 minutes. 4-5 WOT pulls, a couple of hard launches. IAT’s never went higher than 145ish. However the part that gives me confidence that air might have been the issue. The IAT's dropped immediately, pretty much as soon as I let off, they dropped and dropped fast. From 140 to 130 in a blink of an eye. That never happened, when they dropped it would be very slow. I know the true test will come when it’s hot AF out again, as its only like 70-75 degrees this morning. But fingers crossed.
Thread Starter
Teching In
Joined: Oct 2015
Posts: 10
Likes: 2
They were cruising around for hours last week Saturday. But it was only like 75 degrees out as well. Havent driven her since then as I sheered the PS pulley of the PS pump on a hard launch Saturday evening. Called CVF Racing, sent them pics and they sent me a new one free of charge. I should have the new PS pump and pulley today.
Good deal! Another thing that helped lower my temps was some shrouding to force the air through the heat exchanger. I found that the air was flowing around it instead of through it. I made some quick shrouds out of aluminum and it made a huge difference.