Subaru WRX Forum banner
1 - 10 of 10 Posts

·
Registered
2010 Subaru WRX Limited Hatchback 5MT
Joined
·
232 Posts
Discussion Starter · #1 ·
Stock intake and tune except AEM Dryflow filter on my 2010 WRX. Seeing 30F+ above ambient (60F) IATs in stop and go traffic, as high as 60F while sitting in a drive thru, and 10F on highway.

Having read all the cons of aftermarket and IATs i.e. Cobb w/ Airbox I thought the stocker would be an icebox. I guess aftermarket is even worse. Should have started monitoring IATs a while ago...

What are you guys seeing? Perhaps the stock airbox has gotten leaky after all these years. Or I’ve seen filters mentioned as a cause.
 

·
Registered
Joined
·
65 Posts
I tend to think your readings are pretty normal. Considering coolant temp is 200°+, underhood temps will be a good bit higher than atmo. I've worked on a lot of stock vehicles and have seen what you are describing pretty regularly with the vehicle just idling in the shop. Being a turbo car our underhood temps are subject to being a bit higher than an NA car by nature. Stock airboxes typically yield lower IATs than short rams or the "airboxed" intakes that are more or less open to the rest of the engine compartment. If you want near-atmo IATs you're gonna have to risk sucking up water and get a down-in-the-fender "cold air intake", or fab up a way to get a ram air function air scoop to bring atmo air straight into the airbox while driving.

Some solutions to help reduce underhood temps are installing hood louvers to draw out engine heat, keeping heat shields installed/upgraded, install a turbo and up-pipe blanket, and/or wrap the rest of the underhood exhaust with heat wrapping. I just wrapped my manifolds today, and while I didn't have my scanner to check IATs on the way home, and it's cooler atmo today than previous day's, my only way of seeing temps is by the coolant temp gauge. I saw about a needle width's cooler on the way home.. Whether that was due to atmo being cooler or the wrap is beyond me. The wrap also seems to have muffled some exhaust noise from under the hood.

P.S. If you're gonna do ANY heat wrapping, I highly recommend wearing rubber gloves, a thicker long sleeve shirt you don't really care about, glasses that cover your eyes well, and some form of mask to prevent breathing in the gnarly fiberglass strands. You'll be glad you did. Or you'll be itchy for the next three days.
 
  • Like
Reactions: a5m

·
Super Moderator
Joined
·
11,784 Posts
Stock intake and tune except AEM Dryflow filter on my 2010 WRX. Seeing 30F+ above ambient (60F) IATs in stop and go traffic, as high as 60F while sitting in a drive thru, and 10F on highway.

Having read all the cons of aftermarket and IATs i.e. Cobb w/ Airbox I thought the stocker would be an icebox. I guess aftermarket is even worse. Should have started monitoring IATs a while ago...

What are you guys seeing? Perhaps the stock airbox has gotten leaky after all these years. Or I’ve seen filters mentioned as a cause.
The factory intake pulls air directly out of the front of the car not the engine bay. What do you think is going to improve with an intake that has the filter drawing air from IN the engine bay?
 

·
Registered
2010 Subaru WRX Limited Hatchback 5MT
Joined
·
232 Posts
Discussion Starter · #4 ·
I tend to think your readings are pretty normal. Considering coolant temp is 200°+, underhood temps will be a good bit higher than atmo. I've worked on a lot of stock vehicles and have seen what you are describing pretty regularly with the vehicle just idling in the shop. Being a turbo car our underhood temps are subject to being a bit higher than an NA car by nature. Stock airboxes typically yield lower IATs than short rams or the "airboxed" intakes that are more or less open to the rest of the engine compartment. If you want near-atmo IATs you're gonna have to risk sucking up water and get a down-in-the-fender "cold air intake", or fab up a way to get a ram air function air scoop to bring atmo air straight into the airbox while driving.

Some solutions to help reduce underhood temps are installing hood louvers to draw out engine heat, keeping heat shields installed/upgraded, install a turbo and up-pipe blanket, and/or wrap the rest of the underhood exhaust with heat wrapping. I just wrapped my manifolds today, and while I didn't have my scanner to check IATs on the way home, and it's cooler atmo today than previous day's, my only way of seeing temps is by the coolant temp gauge. I saw about a needle width's cooler on the way home.. Whether that was due to atmo being cooler or the wrap is beyond me. The wrap also seems to have muffled some exhaust noise from under the hood.

P.S. If you're gonna do ANY heat wrapping, I highly recommend wearing rubber gloves, a thicker long sleeve shirt you don't really care about, glasses that cover your eyes well, and some form of mask to prevent breathing in the gnarly fiberglass strands. You'll be glad you did. Or you'll be itchy for the next three days.
Thanks so much for your reply and the tips!

I went back and re read some of those threads on aftermarket intakes and IATs. It’s clear they see much higher temps than the stock airbox. Say if the stocker is 60F above ambient, then the aftermarket one are 60F on top of that! Makes sense though since like you said even with an Airbox like the Cobb they aren’t completely sealed from the heat in the engine bay.

I’m in the ceramic coating camp vs wrapping so decided to coat my ELH which will be going on soon. We’ll see how it does compared to the stock heat shields. Thought about getting a turbo heat shield, either a ceramic coated one or getting it coated myself. Apparently people put heat shielding under the stock air snorkel since it sits right over the radiator. I’m sure that’s a major contributing factor.

As much as I like the sound of aftermarket intakes like the Cobb, I decided to stick with stock for now. Maybe in the future I’ll take on the task of getting the Cobb with the Airbox and getting it all heat shielded. Worried the effort will not be worth the time or money, and all the shielding will quiet things down, hence achieving the opposite of what I’m going for in the first place haha.

The factory intake pulls air directly out of the front of the car not the engine bay. What do you think is going to improve with an intake that has the filter drawing air from IN the engine bay?
I think you may have misunderstood? I’m saying the factory airbox with the snorkel is seeing some pretty high temps, higher than I was expecting. I thought it would be much cooler based on what I was reading about aftermarket “cold air” intakes and high IATs. As I realized, the aftermarket intakes are seeing even higher IATs, even if they utilize the stock air snorkel like the Cobb Intake.
 

·
Registered
Joined
·
65 Posts
While it's true lower IAT is ideal, the main idea behind the aftermarket units is increasing volume of flow by reducing restrictions typically seen in factory units, namely the sharp turns and accordion tubes, as I'm sure you've read. This concept is slightly more important than temps because more volume can overcome higher temps when it comes to oxygen content of the charge, which is the main focus of performance and overall efficiency. That's pretty much the bottom line of forced induction. Think of an engine like an air pump, the more air in = more air out = more power + higher volumetric efficiency.

And besides, all the air goes thru the turbo which is way hotter than a couple hundred degrees, hence the need for an intercooler. The IAT you are reading is from the MAF in the airbox, which is only the very beginning of the system. As air travels thru the turbo it picks up a ton of heat as it's compressed, before picking up more heat as it makes it's short trip to the TMIC. Obviously the intercooler does it's thing, but temps going into the throttle body are going to be higher than what you're reading at the MAF, especially with a TMIC sitting on top of a hot engine. I'm experiencing some heat soak issues in stop and go driving so I'm down this path of reducing temps myself.

Something to help with heat transfer thru the charge pipes is swapping them out with silicone hoses and shielding them from nearby heat sources where possible. The silicone hoses work well at keeping intake air insulated from engine bay heat, and are usually smoother on the inside further reducing restrictions. I've read that the turbo inlet silicone hose requires a tune, unsure on truth to that. I've also seen some heat reflective film at several sites, I have to imagine putting some in strategic areas would help also, like directly on the inside faces of the turbo heat shield.

I've also read about tilting the IC to increase air flow thru it, by slapping a few washers and longer bolts in the rear mounts. The post was on an older model, and mine is newer than the OPs, unsure about yours.. Idk if it's possible on mine as the scoop under the hood looks like it might not allow hardly any tilting of the IC, but I haven't tried yet either. That might be a tomorrow's lunch break project. It may or may not require modification of the scoop under the hood..
 
  • Like
Reactions: a5m

·
Registered
2010 Subaru WRX Limited Hatchback 5MT
Joined
·
232 Posts
Discussion Starter · #6 ·
That’s true, IAT is just a part of the bigger picture but I think the main reason it comes up is because of how the ECU uses it to do it’s calculations and adjustments. Something for me to research more. In addition, trying to maximize efficiency of the stock TMIC would help since it doesn’t take much for it to get heat soaked due to the size, and more importantly, location.

According to your signature you have a 2012 WRX? Our TMIC bolts directly to the turbo compressor outlet so I’m not sure if the tilting trick would work. I think best option would be to shield the downpipe and do a dissipating coating on the TMIC. Whether or not the cost is worth the gain is the question.
 

·
Super Moderator
Joined
·
11,784 Posts
Thanks so much for your reply and the tips!

I went back and re read some of those threads on aftermarket intakes and IATs. It’s clear they see much higher temps than the stock airbox. Say if the stocker is 60F above ambient, then the aftermarket one are 60F on top of that! Makes sense though since like you said even with an Airbox like the Cobb they aren’t completely sealed from the heat in the engine bay.

I’m in the ceramic coating camp vs wrapping so decided to coat my ELH which will be going on soon. We’ll see how it does compared to the stock heat shields. Thought about getting a turbo heat shield, either a ceramic coated one or getting it coated myself. Apparently people put heat shielding under the stock air snorkel since it sits right over the radiator. I’m sure that’s a major contributing factor.

As much as I like the sound of aftermarket intakes like the Cobb, I decided to stick with stock for now. Maybe in the future I’ll take on the task of getting the Cobb with the Airbox and getting it all heat shielded. Worried the effort will not be worth the time or money, and all the shielding will quiet things down, hence achieving the opposite of what I’m going for in the first place haha.


I think you may have misunderstood? I’m saying the factory airbox with the snorkel is seeing some pretty high temps, higher than I was expecting. I thought it would be much cooler based on what I was reading about aftermarket “cold air” intakes and high IATs. As I realized, the aftermarket intakes are seeing even higher IATs, even if they utilize the stock air snorkel like the Cobb Intake.
The conditions you described are specifically known for increasing intake temps. You've got a blazing hot radiator next to the actual air intake by the grill. Its like that with most vehicles. Whats important is the air while the car is moving.
 

·
Æternum
Joined
·
16,157 Posts
It is expected that stop and go or sitting in traffic will produce higher IATs.

In those conditions your engine is drawing very little air and therefore there is more time for air to heat up within the airbox itself.

As soon as you start moving at a reasonable pace, you should expect IATs to drop signficantly.

Do not worry - this is all by design.
 
  • Like
Reactions: a5m

·
Æternum
Joined
·
16,157 Posts
While it's true lower IAT is ideal, the main idea behind the aftermarket units is increasing volume of flow by reducing restrictions typically seen in factory units, namely the sharp turns and accordion tubes, as I'm sure you've read. This concept is slightly more important than temps because more volume can overcome higher temps when it comes to oxygen content of the charge, which is the main focus of performance and overall efficiency. That's pretty much the bottom line of forced induction. Think of an engine like an air pump, the more air in = more air out = more power + higher volumetric efficiency.
Yes, except that most modern systems have very little restriction and you will not see ANY improvement in power in relatively stock form.

I have covered this in depth in other posts, but the primary reason that Aftermarket Intakes "make more horsepower" is that they lean out the OEM fuel curve. This has nothing to do with a reduction in restriction.
 

·
Registered
Joined
·
65 Posts
That’s true, IAT is just a part of the bigger picture but I think the main reason it comes up is because of how the ECU uses it to do it’s calculations and adjustments. Something for me to research more. In addition, trying to maximize efficiency of the stock TMIC would help since it doesn’t take much for it to get heat soaked due to the size, and more importantly, location.

According to your signature you have a 2012 WRX? Our TMIC bolts directly to the turbo compressor outlet so I’m not sure if the tilting trick would work. I think best option would be to shield the downpipe and do a dissipating coating on the TMIC. Whether or not the cost is worth the gain is the question.
Yes you are right - it didn't dawn on me until I popped my hood on lunch that the TMIC is bolted directly to the turbo outlet, so tilting the TMIC is definitely not an option on our cars without causing more problems.. so I just checked oil level and closed the hood.
 
1 - 10 of 10 Posts
Top