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a recent technical paper from OE supplier Behr on charge air cooling technology indicates that keeping internal air volumes small for the sake of throttle response is an important consideration when designing CAC systems for OE applications --- Eric
True, but first that states for OE applications, which of course any tuned car would not fall under.
Second, this is a quote from www.thedodgegarage.com:
Myth # 17 Big intercoolers cause lag
Answer- False!
I'm guilty of this one, you would think the extra mass of air and the long hose runs would cause lag no? Well it doesn't, as a matter of fact in the K-car after I installed my double size intercooler the throttle response and spool up was NOTICEABLY better.
Now not to offend the folks at Behr, but they ARE trying to sell you an intercooler. Presumably if they can get you to pay more for a cheaper to make, smaller one, they would make more money, no? I do agree though, that unnecessary piping is well ... unnecessary.
But a larger intercooler really won't hurt anything but your wallet at worst, and in the very warm weather we have here in California I think it's not at all bad idea. I'm not just talking about better flow, but more cooling surface area.
For some physics, while air velocity and density should be taken into account, one would assume that in a very large intercooler at low rpm the air mass is travelling rather slowly. Giving it much more time to cool. In a smaller intercooler it has to travel through it more quickly and has less time in contact with the metal surface to cool. At high rpm not only does the air go slower, but its initial temperature is lower because the turbocharger doesn't have to work as hard to compress the air, which also takes load off the turbo and helps give it a longer life.
As for turbo lag ... it's really not that big of an issue. Perhaps 99% of the Saaber's out there like instant turbo response, but honestly I'm willing to wait for a second. If I'm in THAT big of a hurry I'm going to pop it down a gear anyway, and believe me at 4500 rpm you won't notice any turbo lag even with the largest thing of an intercooler you can fit in the front of your Saab.
However, if one does not want to spend the big $ on a larger intercooler, and one is also satisfied with the flow of the existing one ... water injection will take the average 70% efficient intercooler and get it to about 90%. This means that while perhaps you'll be missing out on a few hp as a result of some backpressure before the intercooler, you won't be worrying too much about heat soak. A home made water injection system can be fabricated for a fraction the cost of an intercooler upgrade. So it might be the best possible solution. Nevertheless, if I had the dosh to spend, one of my first upgrades would be an intercooler ...
Cheers,
Dubbya
edit: Here's some interesting reading from the Dodge Garage: http://www.thedodgegarage.com/turbo_myths.html
And of course ...
http://www.thedodgegarage.com/turbo_intercooling.html
To be fair the stock intercooler does start do have a fair amount of pressure differential between the inlet and outlet once the boost starts going up. I'm told less then a pound or two is ideal and at 15 psi the stock one is about 2 psi, however... -- G. Donovan
That was on a 350 CFM intercooler ...
Very good reading indeed, from someone with a great deal of performance 4 cyllinder experience.
True, but first that states for OE applications, which of course any tuned car would not fall under.
Second, this is a quote from www.thedodgegarage.com:
Myth # 17 Big intercoolers cause lag
Answer- False!
I'm guilty of this one, you would think the extra mass of air and the long hose runs would cause lag no? Well it doesn't, as a matter of fact in the K-car after I installed my double size intercooler the throttle response and spool up was NOTICEABLY better.
Now not to offend the folks at Behr, but they ARE trying to sell you an intercooler. Presumably if they can get you to pay more for a cheaper to make, smaller one, they would make more money, no? I do agree though, that unnecessary piping is well ... unnecessary.
But a larger intercooler really won't hurt anything but your wallet at worst, and in the very warm weather we have here in California I think it's not at all bad idea. I'm not just talking about better flow, but more cooling surface area.
For some physics, while air velocity and density should be taken into account, one would assume that in a very large intercooler at low rpm the air mass is travelling rather slowly. Giving it much more time to cool. In a smaller intercooler it has to travel through it more quickly and has less time in contact with the metal surface to cool. At high rpm not only does the air go slower, but its initial temperature is lower because the turbocharger doesn't have to work as hard to compress the air, which also takes load off the turbo and helps give it a longer life.
As for turbo lag ... it's really not that big of an issue. Perhaps 99% of the Saaber's out there like instant turbo response, but honestly I'm willing to wait for a second. If I'm in THAT big of a hurry I'm going to pop it down a gear anyway, and believe me at 4500 rpm you won't notice any turbo lag even with the largest thing of an intercooler you can fit in the front of your Saab.
However, if one does not want to spend the big $ on a larger intercooler, and one is also satisfied with the flow of the existing one ... water injection will take the average 70% efficient intercooler and get it to about 90%. This means that while perhaps you'll be missing out on a few hp as a result of some backpressure before the intercooler, you won't be worrying too much about heat soak. A home made water injection system can be fabricated for a fraction the cost of an intercooler upgrade. So it might be the best possible solution. Nevertheless, if I had the dosh to spend, one of my first upgrades would be an intercooler ...
Cheers,
Dubbya
edit: Here's some interesting reading from the Dodge Garage: http://www.thedodgegarage.com/turbo_myths.html
And of course ...
http://www.thedodgegarage.com/turbo_intercooling.html
To be fair the stock intercooler does start do have a fair amount of pressure differential between the inlet and outlet once the boost starts going up. I'm told less then a pound or two is ideal and at 15 psi the stock one is about 2 psi, however... -- G. Donovan
That was on a 350 CFM intercooler ...
Very good reading indeed, from someone with a great deal of performance 4 cyllinder experience.