TMIC fan mod Q&A

Alin

Diehard Car Enthusiast!
Cruising on highway gets you close to ambient. Standstill i have seen as high as ~160. This was done sometime last year. Nothing logged this year. The fans are mounted but NOT hooked up. They are eye candy until George sends the modulator and hook ups.
 

Batmobile_Engage

Squirrel Meat Aficionado.
Staff member
Nice, nice...good info. My readings should be pretty low then right? What should post IC temps be like?
 

Alin

Diehard Car Enthusiast!
Not a damn clue. George should know. He knows everything! :lol:
 

HolyCrapItsFast

Drinks beer!
I don't want this to head off topic but I wondered... Have you measured or logged intake air temperatures? If so, what seems to be normal while driving? Also, this one is probably best answered by @HolyCrapItsFast but anyone can feel free to chime in: What sensor measures IATs and where is it located? Also, is the Cobb AP an accurate measure of IATs? I know it can be shady in some measurements, but if it's only displaying what a sensor is sending (via the ECU) then I suppose it's accurate.

The reason I ask is because I'm curious what the temp differences may be between TMICs and FMICs. Also, I wondered if you logged any of that data before you installed the fans, Alin. That data, and the data taken after installing the fans would be interesting to see, if the sensor is in the intake manifold or throttle body.

Lastly, I've heard about "sub-ambient post IC temps". Is this true or even reasonable? I've never really measured IATs and I'd love to now, but my AP shit the bed and I need to send it back to Cobb for repair/replacement.

IATs are measured and MAF. IIRC? Not the best place IMO. I think they should be measured after the IC.

Yes the IAT is in the MAF sensor. This is the best place to put it for a MAF based vehicle because temperature must be taken at same location as flow to properly calculate the mass of air going in. Once the air passes the MAF sensor. the system does not care what the temperature is because the mass never changes... only the volume and density does. In a speed density system the temperature is best taken closest cylinder at the most common source of absolute pressure which is usually the intake manifold and after any intercooler
 

Alin

Diehard Car Enthusiast!
Yes the IAT is in the MAF sensor. This is the best place to put it for a MAF based vehicle because temperature must be taken at same location as flow to properly calculate the mass of air going in. Once the air passes the MAF sensor. the system does not care what the temperature is because the mass never changes... only the volume and density does. In a speed density system the temperature is best taken closest cylinder at the most common source of absolute pressure which is usually the intake manifold and after any intercooler

So does this mean temperature does not matter? Regardless if the IAT is 60 degrees or 160 degrees, how does temperature come into play, in regards to ANY aspect? (Im not sure what fundamental the temperature actually plays) what does it affect/whats its purpose?
 
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Spamby

Meat Product Toy
Yes the IAT is in the MAF sensor. This is the best place to put it for a MAF based vehicle because temperature must be taken at same location as flow to properly calculate the mass of air going in. Once the air passes the MAF sensor. the system does not care what the temperature is because the mass never changes... only the volume and density does. In a speed density system the temperature is best taken closest cylinder at the most common source of absolute pressure which is usually the intake manifold and after any intercooler

Ah ha. That's where I'm wrong. Speed density vs. maf vehicles, SD being better measured after the IC and at the manifold.

SD relying on the actual density of air rather than the mass of it.
 

Spamby

Meat Product Toy
So does this mean temperature does not matter? Regardless if the IAT is 60 degrees or 160 degrees, how does temperature come into play, in regards to ANY aspect? (Im not sure what fundamental the temperature actually plays) what does it affect/whats its purpose?

I do know temperature affects the density of air. Colder air is more dense and thus more oxygen molecules per measured volume. I think that's right? Lol
Colder air being more dense makes more power. Hence the reason why an intercooler is used to cool the air charge temps.
 

Alin

Diehard Car Enthusiast!
Ok well i have this question now and i dont know how much sense itll make but here goes: so do they make an intercooler for the intake? (I dont know how an intercooler works EXACTLY so could you fab up a separate intercooler for the intake? For example in the right foglight spot. The tdi has a side mount intercooler and its small as hell)
 
I'm kind of confused about your question.

The intercooler is already cooling your intake charge. The air that enters from your intake flows into the compressor side of the turbine and then forced through the intercooler into the manifold. The compressor side is completely separate from the exhaust side so temperature don't rise that much.

It wouldn't really help to have another intercooler at the beginning of the intake tract because it's already pulling in air that's close to ambient anyway.
 

Spamby

Meat Product Toy
An air to air intercooler, what we have, cools by allowing ambient air to flow over the tube and fins and cooling the warmer compressed air inside the intercooler.
An air to water intercooler works by using a liquid to cool the air temps.
Heat is generated when compressing air so in our case, when your intake air is compressed by the turbo, the result is a hotter air temp at the discharge side of the compressor. This is why an intercooler helps create a cooler charge temp allowing you to gain performance. [MENTION=1172]Alin[/MENTION], your thought of an intercooler on the pre turbo side is interesting and may be plausible. It would have to be post maf to avoid any skew of maf readings. I should think? Another thought would be to add heat sink fins to the intake tubing to maybe help transfer heat.
 

Alin

Diehard Car Enthusiast!
[MENTION=9]HolyCrapItsFast[/MENTION] please tell me if its possible to do what [MENTION=1507]Spamby[/MENTION] suggested in the post above!
 

Batmobile_Engage

Squirrel Meat Aficionado.
Staff member
That's an interesting idea Alin, but I don't think a pre-turbo intercooler would be efficient enough to warrant it's use in the first place. As for the MAF, it would read okay as long as you didn't put it too close to said IC and set it in the straightest section of piping possible, with no tapers. You would want the flow to be even with little turbulence for an accurate reading.
 

Batmobile_Engage

Squirrel Meat Aficionado.
Staff member
I think fins on the pre-turbo side would be less effective than wrapping the entire section in thermo tape with a reflective surface. Also, focusing more time on optimizing air flow through the engine bay would probably yield the best results.
I've often considered putting a small scoop on the hood above the filter, but I can't bring myself to cut the hood.
 
I agree with [MENTION=662]Batmobile_Engage[/MENTION] with the inefficiency of it. The reason why it's placed post turbo is due to it's efficiency to cool. Luckily the turbo is forcing the air through it. I think it would be a huge obstruction in the intake tract. I don't think enough vacuum could be pulled to not make it a restriction. Maybe it's not as much of a restriction as I think though. Flow tests could prove this...
 

Batmobile_Engage

Squirrel Meat Aficionado.
Staff member
I agree with [MENTION=662]Batmobile_Engage[/MENTION] with the inefficiency of it. The reason why it's placed post turbo is due to it's efficiency to cool. Luckily the turbo is forcing the air through it. I think it would be a huge obstruction in the intake tract. I don't think enough vacuum could be pulled to not make it a restriction. Maybe it's not as much of a restriction as I think though. Flow tests could prove this...

Exactly. If you made the pre-turbo IC with the least restrictions possible, there would be little to no temperature drop. If you designed it for a noticeable temperature drop, the opposition to flow would be terrible. If you really wanted to get crazy with this, you could design a metal jacket to wrap the intake in and spray the interior of the jacket with CO2, kind of like a CO2 IC sprayer. Once again, it's effectiveness pre-turbo might be crap.
 

HolyCrapItsFast

Drinks beer!
I think fins on the pre-turbo side would be less effective than wrapping the entire section in thermo tape with a reflective surface. Also, focusing more time on optimizing air flow through the engine bay would probably yield the best results.
I've often considered putting a small scoop on the hood above the filter, but I can't bring myself to cut the hood.

Agreed... The thing with a heat sink is the transfer goes both ways unless it has an active heat pump behind it like a peltier junction. Otherwise you could potentially transfer heat from the engine compartment into the intake tract. The laws of thermodynamics suggest that heat will always flow toward the coolest point and where the air inside the intake tract is cooler than the air under the hood, the heat will transfer from the engine room into the fins of the heat sink and then into the tract causing the opposite effect to what is desired.

A reflective surface will simply reflect the heat radiation from the underlying pipe surface preventing heat transfer into the pipe. Reflective tape is your best bet.

As for an pre-turbo intercooler? It wouldn't be at all efficient because you are trying to cool ambient temperature (or close to ambient) air with air that is also ambient. Why? :tup:
 

Alin

Diehard Car Enthusiast!
I was thinking 30 min ago. What if you did a fan mod for the intake as well? A small 4-5" fan that kicks on at a certain temp. Wouldnt that be a better solution to the intercooler thought? (Im probably going to wrap the intake)
 

Batmobile_Engage

Squirrel Meat Aficionado.
Staff member
I was thinking 30 min ago. What if you did a fan mod for the intake as well? A small 4-5" fan that kicks on at a certain temp. Wouldnt that be a better solution to the intercooler thought? (Im probably going to wrap the intake)

That would be interesting. Maybe mount it inside the top of that ducting you did and run it all the time maybe....with a toggle on/off switch.
 

HolyCrapItsFast

Drinks beer!
I was thinking 30 min ago. What if you did a fan mod for the intake as well? A small 4-5" fan that kicks on at a certain temp. Wouldnt that be a better solution to the intercooler thought? (Im probably going to wrap the intake)

Stop Thinking!!! :tard:
 
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