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Old 06-17-2009, 12:09 PM   #1 (permalink)
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Intercooler Pressure Drop Theory - those last couple HP

As I understand it - pressure drop occures when the air "backs up" behind the intercooler and causes a higher pressure before the intercooler than at the manifold. Ok, I'm comfortable with that. This happens when the airflow through the compressor exceeds the max airflow of the intercooler right?

So how bad is the pressure drop on our stock I/C when running 22PSI at the intake manifold? 1PSI? 3PSI? Has anyone measured it?

The next (and bigger) question is are we more limited by the compressor or turbine flow on the stock turbo, stock hardware, and 22 PSI? I HPtuned my car myself and left a drop off of boost after 5500rpm for longevity of the turbo, but I'm wondering if I can free up other hardware restrictions, can I push 22PSI to redline? Is the cat and exhaust more restrictive of the system, or the intake and intercooler?

This may be a lot of speculation, but hardware upgrades have to start somewhare No matter what I do, I can't seem to break 32lbs/min on the MAF (usually around 5500 rpm incidentally), so if hardware upgrades are in order to push 34-35 lbs/min, so be it!

P.S. water-methanol injection is in my immediate future as well.
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2008 BRAZEN GXP - 5M Loaded Tuned to 22 PSI with HPT, AEM water/methanol injection kit - 4gph, Hahn Racecraft Intercooler. Solo street race exhaust, Catless, LE5 Throttle body, ZFR 6758, custom CAI 307whp on dyno dynamics - stock turbo (21 psi)


2006 SLY 2.4 Comfort and Power - TRADED 28-Aug-2008
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Old 06-17-2009, 12:59 PM   #2 (permalink)
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Quote:
Originally Posted by oldskool View Post
As I understand it - pressure drop occures when the air "backs up" behind the intercooler and causes a higher pressure before the intercooler than at the manifold. Ok, I'm comfortable with that. This happens when the airflow through the compressor exceeds the max airflow of the intercooler right?

So how bad is the pressure drop on our stock I/C when running 22PSI at the intake manifold? 1PSI? 3PSI? Has anyone measured it?

The next (and bigger) question is are we more limited by the compressor or turbine flow on the stock turbo, stock hardware, and 22 PSI? I HPtuned my car myself and left a drop off of boost after 5500rpm for longevity of the turbo, but I'm wondering if I can free up other hardware restrictions, can I push 22PSI to redline? Is the cat and exhaust more restrictive of the system, or the intake and intercooler?

This may be a lot of speculation, but hardware upgrades have to start somewhare No matter what I do, I can't seem to break 32lbs/min on the MAF (usually around 5500 rpm incidentally), so if hardware upgrades are in order to push 34-35 lbs/min, so be it!

P.S. water-methanol injection is in my immediate future as well.
As I understand it, the cat is the most restrictive. The exhaust has been proven to flow over 40lb/min (IIRC by BTF).
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Old 06-17-2009, 01:21 PM   #3 (permalink)
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Can't give you the hard numbers you are looking for. However, I can share what I have seen, heard, learned, and measured.

1) '07 Redline, Wester's tune, K&N air filter, Magniflow exhaust Solo catless downpipe.
2) The catless downpipe made a HUGE difference BEFORE the Wester's tune. I mean REALLY big. Yes, it threw a cat effieciency code, but the computer did NOT "learn down" the power, even after driving the car for days.
3) The stock turbo is built for max performance in the middle of the rev range. It loses efficiency above 5000 rpm.
4) At a recent autocross I used an IR heat gun to check inlet and outlet pipe temps after a run. The ambient was about 75 degrees. The inlet was about 145 degrees and outlet was about 90 degrees. I have spoken with some tuners who have said that they saw LOWER than ambient temps on the discharge side of a bigger intercooler on their 2.0 Kappa.
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Old 06-17-2009, 06:24 PM   #4 (permalink)
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Can't give you the hard numbers you are looking for. However, I can share what I have seen, heard, learned, and measured.

1) '07 Redline, Wester's tune, K&N air filter, Magniflow exhaust Solo catless downpipe.
2) The catless downpipe made a HUGE difference BEFORE the Wester's tune. I mean REALLY big. Yes, it threw a cat effieciency code, but the computer did NOT "learn down" the power, even after driving the car for days.
3) The stock turbo is built for max performance in the middle of the rev range. It loses efficiency above 5000 rpm.
4) At a recent autocross I used an IR heat gun to check inlet and outlet pipe temps after a run. The ambient was about 75 degrees. The inlet was about 145 degrees and outlet was about 90 degrees. I have spoken with some tuners who have said that they saw LOWER than ambient temps on the discharge side of a bigger intercooler on their 2.0 Kappa.
Thank you for this info, especially about the catless DP.

Regarding point number three - there are two reasons why it could be loosing efficiency above 5000rpm -either the backpressure on the turbine, or compressor efficiency. I was trying to get at if we have a 2-3PSI pressure drop on the stock IC @ 22PSI, then it would make sense that the power could carry out to higher revs if the IC is upgraded and the car is retuned.

Regarding point number 4 - i think it is physically impossible to have lower than ambient temps with an air-to-air intercooler. The lowest is ambient, and i'd call BS on those making other claims. If they were using an IC sprayer or meth injection thats a differnt claim altogether
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Old 06-17-2009, 07:14 PM   #5 (permalink)
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Originally Posted by oldskool View Post
Regarding point number three - there are two reasons why it could be loosing efficiency above 5000rpm -either the backpressure on the turbine, or compressor efficiency. I was trying to get at if we have a 2-3PSI pressure drop on the stock IC @ 22PSI, then it would make sense that the power could carry out to higher revs if the IC is upgraded and the car is retuned.

Regarding point number 4 - i think it is physically impossible to have lower than ambient temps with an air-to-air intercooler. The lowest is ambient, and i'd call BS on those making other claims. If they were using an IC sprayer or meth injection thats a differnt claim altogether
Retuning the computer can not overcome the correct assertion - turbo efficiency.

As for the lower than ambient temps, theoretically it can happen. Just look at what an expansion valve does in an A/C system. It is all about pressure drop.
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Old 06-20-2009, 08:31 PM   #6 (permalink)
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But in an AC system the expansion valve is allowing a refirgerant to go thru a phase change.
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Old 06-20-2009, 09:31 PM   #7 (permalink)
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Originally Posted by snaponbob View Post
Retuning the computer can not overcome the correct assertion - turbo efficiency.

As for the lower than ambient temps, theoretically it can happen. Just look at what an expansion valve does in an A/C system. It is all about pressure drop.
Theres no way you are going to get lower than ambient outlet temperatures on an air to air heat exchanger. The expansion valve in an AC system acts as a nozzle atomizing liquid refrigerant into the evaporator at low pressure. Allowing the refrigerant to more easily absorb the Latent Heat of Evaporation. In an intercooler there is no physical change of state of either the cooling material or the cooled material. At best you will probably be lucky to get within 10 degrees F.

Two laws of thermodynamics
1. Heat is Energy. As energy it cannot be created or destroyed only converted to another form of energy.
2. Heat will only naturally flow from an area with higher potential heat to an area with lower potential heat.( Like water seeking it's level!)
Because of entropy less energy is always received from a conversion than what is put in.

Last edited by P.Gadget; 06-20-2009 at 09:40 PM.
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Old 06-21-2009, 05:55 AM   #8 (permalink)
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True true. Forgot about that physical state change thing.
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Old 06-26-2009, 01:48 PM   #9 (permalink)
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I have checked my 2.4 DDM stage II boost pressure

On both sides. Right off the S/C manifold and then after the I/C and the DDM I/C is awesome!! it only dropped about 11/5 PSI and it keeps this baby cool!! It will keep your intake air at ambient temperature or because of physics "As air speed increases temperature decreases" sometime even cooler then that but not much . Now considering that the boosted air coming out of the S/C is supper hot it cools it a ton!! We My friend Gary "GaryH" and I took my car for a brisk drive and right after opened the hood and felt both pipes. The one coming out of the S/C and the one after the I/C and there is a huge difference!! The Pipe after the I/C was actually cool but the one on the other side going into the I/C was so hot you couldn't even put your hand on it. That tells me that the I/C is working great!

Last edited by Rickyd; 06-26-2009 at 01:57 PM.
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Old 06-26-2009, 11:06 PM   #10 (permalink)
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On both sides. Right off the S/C manifold and then after the I/C and the DDM I/C is awesome!! it only dropped about 11/5 PSI and it keeps this baby cool!! It will keep your intake air at ambient temperature or because of physics "As air speed increases temperature decreases" sometime even cooler then that but not much . Now considering that the boosted air coming out of the S/C is supper hot it cools it a ton!! We My friend Gary "GaryH" and I took my car for a brisk drive and right after opened the hood and felt both pipes. The one coming out of the S/C and the one after the I/C and there is a huge difference!! The Pipe after the I/C was actually cool but the one on the other side going into the I/C was so hot you couldn't even put your hand on it. That tells me that the I/C is working great!
As air velocity increases through the intercooler the delta temperature of the inlet and outlet of the intercooler will decrease because the air has less time to transfer heat.At the same time the delta pressure of the inlet and outlet increases The object would be to keep air velocity relatively low through the intercooler with as much coil surface area as possible to keep the delta temperature as high as possible.
Although if the intercooler becomes too large internally turbo lag could start to become an issue.Because on acceleration the compressor would have to fill a larger void before pressure at the throttle body can increase.
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Old 06-27-2009, 03:11 PM   #11 (permalink)
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Yes this is true but I really dont need to worry about that part to much.

You see I am running the DDM Stage II S/C so the throttle body is mounted on the back of the S/C. The DDM I/C is huge and it cools great! with only 1 1/2 psi drop in pressure it is one of the best around.
When I was talking about air speed I wasn't talking about the air velocity of the air going thru the I/C I was talking about the air passing thru the coolers fins. I took this picture of a digital temp meter I have mounted on the intake tube right before it goes into the manifold. As you can see at even only 40 MPH it runs cooler then outside air temp and NO I was not spraying Meth at the time either. I am not trying to disagree with you at all I am just saying this I/C works great! One thing that may help is having the RK ram air hood and also the side vents open. The air flows way better then stock. Ye Ye I know so I like to monitor things what can I say.
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As air velocity increases through the inter cooler the delta temperature of the inlet and outlet of the inter cooler will decrease because the air has less time to transfer heat.At the same time the delta pressure of the inlet and outlet increases The object would be to keep air velocity relatively low through the inter cooler with as much coil surface area as possible to keep the delta temperature as high as possible.
Although if the inter cooler becomes too large internally turbo lag could start to become an issue.Because on acceleration the compressor would have to fill a larger void before pressure at the throttle body can increase.
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Old 06-29-2009, 10:42 AM   #12 (permalink)
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Ah guys just so you know you are NOT talking about pressure drop, you are talking about flow. The pressure drop is the amount of boost lost in the intercooler do to it's size and design, this is why you can have to big an intercooler, if it slows the air down to much because it is to big or poorly designed you have pressure drop. The Dejon was tested against stock and the pressure drop was about 1 PSI over stock with a much larger intercooler and much cooler denser air at the outlet. This is the result of a good design by Garrett on the intercooler and decent end tanks by Dejon.
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Old 06-29-2009, 12:28 PM   #13 (permalink)
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No We do mean pressure drop of PSI between the inlet and outlet of the I/C.

Yes we are aware of flow but on this post my self anyway are talking about true boost pressure into the engine. I am worried about flow as well but I am mainly talking about pressure drop from in and out.

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Ah guys just so you know you are NOT talking about pressure drop, you are talking about flow. The pressure drop is the amount of boost lost in the intercooler do to it's size and design, this is why you can have to big an intercooler, if it slows the air down to much because it is to big or poorly designed you have pressure drop. The Dejon was tested against stock and the pressure drop was about 1 PSI over stock with a much larger intercooler and much cooler denser air at the outlet. This is the result of a good design by Garrett on the intercooler and decent end tanks by Dejon.
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Old 06-29-2009, 03:40 PM   #14 (permalink)
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I have the Dejon intercooler and see no pressure drop at all.
In 3 th gear temperature under full boost stays the same as outside temperature
In 4 th gear with stock intercooler temp raised with 23 degrees celcius
In 4 th gear with Dejon temp raised with 10 degrees celcius,so 13 degrees better than stock intercooler.
I have the BSR tune because with stock tune temperature won't raise so high.
Bigger intercooler is not always better...That's why I bought the Dejon,because I don't like the pressure to drop..
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Old 06-30-2009, 03:01 AM   #15 (permalink)
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Guys, pressure drop is the pressure difference between the hot side of the IC and the cold side of the IC. A smaller, lower flowing IC will have a greater pressure drop when it is taxed with more flow than it can handle. An IC that is too large will not have a pressure drop, but will cause more lag because of the higher volume to pressurize. Don't confuse the two concepts.
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2006 SLY 2.4 Comfort and Power - TRADED 28-Aug-2008
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