IAT correlation

I've been doing a bunch of reading but cant find anything showing that lowering IAT1 has a direct correlation to IAT2. Considering the air is being compressed through a super hot spinning wheel, is there any info showing that colder air pre turbo actually makes a difference? Or are the gains found via new intake brought on by the design itself and improved airflow. If someone has the data showing lower IAT2 due to the intake itself please post it .

Civic17siYAY said:

I've been doing a bunch of reading but cant find anything showing that lowering IAT1 has a direct correlation to IAT2. Considering the air is being compressed through a super hot spinning wheel, is there any info showing that colder air pre turbo actually makes a difference? Or are the gains found via new intake brought on by the design itself and improved airflow. If someone has the data showing lower IAT2 due to the intake itself please post it .

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After putting on my map intake my iat1 gets hotter than stock box but iat2 is the same or even lower(10-20 above ambient). I also have a PRL Intercooler. From what I’ve read around on other forums etc the benefit of colder pre turbo air is that colder denser air is better for the turbo to compress, the turbocharger has to work less compared to compressing hotter air. I’m not sure how accurate that is on this scale of temp difference. I did a lot of research on it before getting the map intake cause I was worried about losing power with higher iat1. Also from drob instagram page he recently tuned a full MAPerformance bolt on car that made basically the same power as full bolt on PRL cars on his page. Hopefully someone can give us more knowledgeable info

2tone said:

After putting on my map intake my iat1 gets hotter than stock box but iat2 is the same or even lower(10-20 above ambient). I also have a PRL Intercooler. From what I’ve read around on other forums etc the benefit of colder pre turbo air is that colder denser air is better for the turbo to compress, the turbocharger has to work less compared to compressing hotter air. I’m not sure how accurate that is on this scale of temp difference. I did a lot of research on it before getting the map intake cause I was worried about losing power with higher iat1. Also from drob instagram page he recently tuned a full MAPerformance bolt on car that made basically the same power as full bolt on PRL cars on his page. Hopefully someone can give us more knowledgeable info

Click to expand...

First lets clarify the parameters IAT1 as shown on HONDATA equipped cars is referring to after intercooler temps that the engine is ingesting in the cylinder. IAT2 is the temperature at the mass airflow sensor pre turbo. KTUNED cars I am not positive but I believe from my readings that the above statement is opposite (someone else can verify this for us I am sure)

The "temperature delta" across the system is whats important. The short version of explaining this is colder air in = colder air out. Period. The intake starts colder it will end colder than it would given the exact same scenario with hotter starting temperature.

Would obsessing about this be beneficial to 99% of the owners? Not really. But I am currently obsessing about it myself anyway.

Seeing the lower temps is more placebo than anything else as it just eases my mind when Im preparing to lay in to the car.

If either number exceeds 120+ while stopped I never give it much boost if any until they plummet back down to closer to ambient when I start moving.

Fun facts:

1) The radiator fan blows hot air directly onto the maf sensor. this is part of the dramatic temp spikes people see when stopped. I have my sensor insulated to help with this.

2) The cooling fans rarely need to be on unless stopped, which dramatizes this effect.

3) It is not uncommon to see 140+ at the maf sensor when stock and vehicle not moving

4) On average a 20-30 degree difference between IAT at the maf sensor (iat2 with hondata) and outside temperature is fairly normal and close to what the stock box does

5) I have mine to 9 degrees different on 80 degree days... down to 6 degree difference when its below 60....these numbers are while car is in motion. Using a modified mishimoto short ram setup.

6) What is more important is to make sure there is not a huge difference between iat1+iat2, then we are doing our job.
If post intercooler numbers go up dramatically compared to pre intercooler than the system is working too hard to provide the commanded boost pressure. This can be helped with relieving pre turbo restrictions (race maf or any kind of intake)....relieving after turbo restrictions (intercooler/piping)....or lowering boost command until the above items are installed or a more efficient turbo is ran.

PowerPerLiter said:

First lets clarify the parameters IAT1 as shown on HONDATA equipped cars is referring to after intercooler temps that the engine is ingesting in the cylinder. IAT2 is the temperature at the mass airflow sensor pre turbo. KTUNED cars I am not positive but I believe from my readings that the above statement is opposite (someone else can verify this for us I am sure)

The "temperature delta" across the system is whats important. The short version of explaining this is colder air in = colder air out. Period. The intake starts colder it will end colder than it would given the exact same scenario with hotter starting temperature.

Click to expand...

Yea I have Ktuner so iat1 is pre turbo, and sorry my man but my hotter pre turbo temps has not given me any hotter after Intercooler temps. Maybe in colder areas where ambient temps and under hood temps have a bigger difference it’d be a different story Idk I’m not an expert or anything I’m just trying to learn but “colder air in = colder air out” is definitely not true in my specific experience. Also I’m only comparing stock temps to map temps not necessarily true cold air intake temps to hot short ram temps. But my Intercooler is still cooling down to 8-15(during pulls only) above ambient I’m not sure how close to ambient cobra/injen users are getting?

2tone said:

Yea I have Ktuner so iat1 is pre turbo, and sorry my man but my hotter pre turbo temps has not given me any hotter after Intercooler temps. Maybe in colder areas where ambient temps and under hood temps have a bigger difference it’d be a different story Idk I’m not an expert or anything I’m just trying to learn but “colder air in = colder air out” is definitely not true in my specific experience. Also I’m only comparing stock temps to map temps not necessarily true cold air intake temps to hot short ram temps. But my Intercooler is still cooling down to 8-15(during pulls only) above ambient I’m not sure how close to ambient cobra/injen users are getting?

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That is pretty good and I am not suprised at what your seeing. A lot of that result I believe is heat soak in the maf sensor itself but you are actually getting colder air from where the maperformance intake is drawing from.

The colder in=colder out statement is generalized and "in theory".

Would you see a 1:1 result? No. Its all about overall system efficiency at the end of the day and changes are more visually dramatic in the data-logs the colder the outside temperature which is the "start temp" for the system.

I wouldn't worry about any of it as much as I have. Outside of peace of mind/sound normal drivers wont notice the differences to this degree...pun intended...

The intercooler is still going to do its job. The difference is the time it would take. Its like this, take a car in 80 degree outside temp....lets say pre turbo we are reading 140* sitting at a stop light..you need to wot when light changes..would you rather be sending 140+ through the intercooler with little airflow vs 100? The before intercooler temp will definitely affect the efficiency across the board but will vary in intensity depending on conditions....

PowerPerLiter said:

First lets clarify the parameters IAT1 as shown on HONDATA equipped cars is referring to after intercooler temps that the engine is ingesting in the cylinder. IAT2 is the temperature at the mass airflow sensor pre turbo. KTUNED cars I am not positive but I believe from my readings that the above statement is opposite (someone else can verify this for us I am sure)

The "temperature delta" across the system is whats important. The short version of explaining this is colder air in = colder air out. Period. The intake starts colder it will end colder than it would given the exact same scenario with hotter starting temperature.

Would obsessing about this be beneficial to 99% of the owners? Not really. But I am currently obsessing about it myself anyway.

Seeing the lower temps is more placebo than anything else as it just eases my mind when Im preparing to lay in to the car.

If either number exceeds 120+ while stopped I never give it much boost if any until they plummet back down to closer to ambient when I start moving.

Fun facts:

1) The radiator fan blows hot air directly onto the maf sensor. this is part of the dramatic temp spikes people see when stopped. I have my sensor insulated to help with this.

2) The cooling fans rarely need to be on unless stopped, which dramatizes this effect.

3) It is not uncommon to see 140+ at the maf sensor when stock and vehicle not moving

4) On average a 20-30 degree difference between IAT at the maf sensor (iat2 with hondata) and outside temperature is fairly normal and close to what the stock box does

5) I have mine to 9 degrees different on 80 degree days... down to 6 degree difference when its below 60....these numbers are while car is in motion. Using a modified mishimoto short ram setup.

6) What is more important is to make sure there is not a huge difference between iat1+iat2, then we are doing our job.
If post intercooler numbers go up dramatically compared to pre intercooler than the system is working too hard to provide the commanded boost pressure. This can be helped with relieving pre turbo restrictions (race maf or any kind of intake)....relieving after turbo restrictions (intercooler/piping)....or lowering boost command until the above items are installed or a more efficient turbo is ran.

Click to expand...

I notice everyone posts pre turbo IAT temps being "x amount colder with y intake" but no one mentions post turbo IAT temps. That's why I'm curious about the correlation. If lowering pre turbo IAT doesnt do anything to post IAT than airflow and design characteristics are what cause the jump in hp/tq not drawing in colder air before throwing it through a hot compressor.

Not entirely convinced that lowering Pre turbo IAT by 10-20 degrees will cause post turbo IAT to go down at all. If it were, you would think that every intake maker would publish post IAT numbers and not pre.

And my obsession comes from being in this swamp called Florida where ambient air temp is 90 most of the year.

Civic17siYAY said:

I notice everyone posts pre turbo IAT temps being "x amount colder with y intake" but no one mentions post turbo IAT temps. That's why I'm curious about the correlation. If lowering pre turbo IAT doesnt do anything to post IAT than airflow and design characteristics are what cause the jump in hp/tq not drawing in colder air before throwing it through a hot compressor.

Not entirely convinced that lowering Pre turbo IAT by 10-20 degrees will cause post turbo IAT to go down at all. If it were, you would think that every intake maker would publish post IAT numbers and not pre.

And my obsession comes from being in this swamp called Florida where ambient air temp is 90 most of the year.

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Believe me I get it! I am not even in a known hot climate (Ohio) and I worry about it during the summer. I genuinely dont think you would see any sort of viewable difference in that climate after the intercooler even with a true cold air intake setup. Not to say it wouldn't benefit at all but your talking a super small difference across a nearly untraceable "delta" with far too many variables to outright say its worth it. The bigger benefit would be with intercooler upgrades for someone in a super hot and humid climate.

To use your numbers provided you would maybe be seeing 7-14 rather than 8-15 at best (just an example of how small of differences you may see)...with less time for the temp to drop...and thats basically it.

PowerPerLiter said:

That is pretty good and I am not suprised at what your seeing. A lot of that result I believe is heat soak in the maf sensor itself but you are actually getting colder air from where the maperformance intake is drawing from.

The colder in=colder out statement is generalized and "in theory".

Would you see a 1:1 result? No. Its all about overall system efficiency at the end of the day and changes are more visually dramatic in the data-logs the colder the outside temperature which is the "start temp" for the system.

I wouldn't worry about any of it as much as I have. Outside of peace of mind/sound normal drivers wont notice the differences to this degree...pun intended...

The intercooler is still going to do its job. The difference is the time it would take. Its like this, take a car in 80 degree outside temp....lets say pre turbo we are reading 140* sitting at a stop light..you need to wot when light changes..would you rather be sending 140+ through the intercooler with little airflow vs 100? The before intercooler temp will definitely affect the efficiency across the board but will vary in intensity depending on conditions....

Click to expand...

Very true I would always prefer to go with having coldest temps possible regardless and in situations like that(stop light low airflow) it probably is a more noticeable difference until you get up to a speed that’s giving good air flow. Thanks I didn’t even think about that much, I never launch the car so I’ve only really been paying attention to temps during pulls where I was usually already getting pretty good airflow. Thanks for that perspective! And to the whole colder in colder out thing that’s still a good theory to by in life in general. You get out what you put in

Yea I agree I think Intercooler is more important when you’re worried about temps, and I understand that Florida life lmao I’ve spent most of my modding research time on temps. Anyone worried about temps should also definitely do the eBay mesh grill, I saw some great results with lower temps on stock air box. Also @PowerPerLiter those are amazing temps on your modified short ram, do you have a thread or any videos on what you did??

Does anyone know about how the turbocharger itself reacts to intake temps? I read somewhere, I’m pretty sure it was a focus st forum, that turbochargers work harder/ are less efficient with hotter air. So would colder intake temps make a happier turbo, more efficient? Quicker spool? Better turbo reliability? Any turbo wizards out there that can chime in

IAT1 - Pre Turbo.
Temp is measured after the air is filtered (MAF / pre-turbo)

IAT2 - Post Turbo
Temp is measured after the charged air exits the IC and before entering the intake manifold (MAP / post turbo)

The variables that affect the actual Charge Air Intake Temperature (post turbo are):
* Type of IC
Fin vs Bar and Plate, Core Size and Flow, Inlet & Outlet Hose sizes, Material (Rubber / Plastic vs Aluminum) etc....
** Turbo Efficiency
% below MAX Pressure Ratio of the Turbo will determine how much heat is being generated/transferred by the compressor

CAI's work with NA engines; as the air is directly entering the Intake Manifold after the MAF.
FI engines are not the same. In order to achieve the optimum charge air temp at the intake you'll need:
1: Turbo Efficiency
2: Ability to cool the Charge Air (which is well past the MAF)

Hold on and I will go take some current pics with how its sitting. I am in process on all of it still but I do intend on making an elaborate thread on this topic eventually once all my findings are 100% duplicated and verified to my liking.

2tone said:

Does anyone know about how the turbocharger itself reacts to intake temps? I read somewhere, I’m pretty sure it was a focus st forum, that turbochargers work harder/ are less efficient with hotter air. So would colder intake temps make a happier turbo, more efficient? Quicker spool? Better turbo reliability? Any turbo wizards out there that can chime in

Click to expand...

100% yes to all the above.

This post is very convincing. I have been asking myself this question all weekend (is it worth making a CAI if I have a very efficient intercooler). I'm so used to making a CAI for N/A applications. This turbo it new to me.

So this is what I gather from these posts in here in a nutshell.

1. Making a CAI is a waste of money. Focus on getting a more efficient intercooler to cool post intercooler temps.
2. Heat wrap the maf sensor. This should help with temp spikes people are seeing at the maf sensor, especially in stop-n-go traffice.

If this is it, I feel like my SRI will be a beast with an upgraded intercooler and I will just be done with it. My SRI primary role is to reduce/eliminate any pressure drops the stock system may have had. I will only heat wrap my maf sensor.

Thanks for posting your observations guys in that your pre-turbo IAT temps had no bearing on your post turbo IAT.

Please forgive the ghetto-ness as there have been a lot of removing and adding different pieces moving towards the end goal.

This is the view basically from the filter itself looking forward to the front of the car. Circled in red is the air path straight from the grill.



This is the same airflow path looking through the grill opening toward the filter (same opening circled in red in previous photo)
Top left of pic is some foam, this is sealed along the edge of the guide plate that takes the air above the radiator against the middle of the grill. You cant make out the plate but it is thin gauge aluminum that is directly attached to the core support under the stock cooling plate and is one solid piece bent over the radiator/condensor and goes all the way forward to the edge of the grill opening. Everything that is metal is insulated and cool to the touch at all times now.


The cut opening in the airbox lid is almost completely contoured to the hood. (I am entertaining doing away with the lid completely and ultimately just sealing the hood to the lower part of the box when the hood is closed (via something like the moroso carb pan seals for old hot rod cowl induction)

Notice the foam in between the core support and lower box (this is right above the radiator hose)


When I close my hood it seals the box directly to the grill basically.

This setup has been daily driven through high and low temps rain etc. for about the last 6 weeks while Im gathering data before I rip it all out and start over with better materials and finalized/ simplified product in mind.