Intercoolers

[Mihnea]

Guys, simply install a boost gauge before AND after the IC and compare boost at WOT.

Mihnea

[91_S2]

pressure drop will increase as the size of intercooler increases but the amount of cooling it can provide increases with size also. There is going to be a trade off between the amount of pressure drop and cooling capacity.

Greg

Greg,

That must depend on the configuration of the IC. Pressure drop is a function of resistance to flow. This would seem to be a function of the internal cross sectional area. Take 2 extreme cases.

A - A single longtube 5 meters long

B - 10 tubes of same cross section as A in parallel each 0.5 meters long.

Both has the same core size but B will have lower pressure drop.

[sorens2]

That´s what I thought. I must have misunderstood something before. Off course it has to be optimised for better flow. Then again.... can my IC get too big, these facts taken into consideration ? Volume ?

Søren S2

[Audi_CQ]

Guys, simply install a boost gauge before AND after the IC and compare boost at WOT.

Mihnea

Have you done that on many cars? Tested the same car with different IC's?
What about temp? A large IC will create a large temp drop and cool air = denser air. So even if boost is lower after the IC the air will have more O2 for the engine to burn.
Boost is not so important, power is the goal

[Greg_S]

Greg,

That must depend on the configuration of the IC. Pressure drop is a function of resistance to flow. This would seem to be a function of the internal cross sectional area. Take 2 extreme cases.

A - A single longtube 5 meters long

B - 10 tubes of same cross section as A in parallel each 0.5 meters long.

Both has the same core size but B will have lower pressure drop.

This is very true, didnt really explain it very well. example you have shown is like having a narrow double pass IC and a single pass version. Kinda stuck my foot in it a bit


Audi CQ I think mihnea was making the point that it wouldnt be an advantage to have a massive IC to get lower intake temps past a certain amount because the temperature drop would be insignificant in the extra work the turbo would have to do to make decent boost before the IC which could push the turbo it a bad area of the compressor map where the temperatures rocket.

Think i got that one about right



Greg

[Audi_CQ]

Audi CQ I think mihnea was making the point that it wouldnt be an advantage to have a massive IC to get lower intake temps past a certain amount because the temperature drop would be insignificant in the extra work the turbo would have to do to make decent boost before the IC which could push the turbo it a bad area of the compressor map where the temperatures rocket.

Think i got that one about right



Greg

Hi Greg,

My point is this: Why is it harder for a turbo to push air trough a big "pipe" then a small one? The difference in volume between a large and a BIG IC is very small compared to the amount of air the engine swallows so lag isn't changed either. So IMHO bigger is better

[Billman]

@ Audi CQ

Can we see your IM ?

[Audi_CQ]

@ Audi CQ

Can we see your IM ?

Hi Billman,

Posted some pictures earlier in this thread:

http://www.s2forum.com/forum/showthread.php?t=2585

Cheers,
Roger

[Greg_S]

yup I see your point roger.

[4WheelDrifter]

LOL. Guys. It takes a lot longer to get a large airbed up to a certain pressure, than a small balloon for example. Try it. The airbed has a lot more lag, you could say.

[audiman]

Agreed, the large IC gave my car more lag, not much, but a bit. The difference between the front intake manifold and the stock setup is about 200rpm less lag, so it is volume dependant. The more air you have to compress the more lag that you will get.

[Audi_CQ]

LOL. Guys. It takes a lot longer to get a large airbed up to a certain pressure, than a small balloon for example. Try it. The airbed has a lot more lag, you could say.

That's right, but have you thought about how much volume there is in an IC? The difference between a stock and a really large one is probably only a couple of litres. A 2.2 at 3000rpm uses 55 l/s of air with ve=100%. To make 1 bar of boost at 3000 rpm, it will take an extra 4/100 of a sec compared with stock......

Use a different manifold with front intake, and the total volum will be less then stock even with a huge IC

[audiman]

Agreed

[S2central.net]

Guys, simply install a boost gauge before AND after the IC and compare boost at WOT.

Mihnea

No need in this case !

Simply do the fundamental maths here for understanding Pressure Ratio.

The bigger the pressure drop across the IC then the harder the turbo will have to work to generate the same boost pressure seen at the inlet manifold. This means a loss in efficiency at the turbo for any given flow rate... which means increased air temp entering the intercooler.

IF the bigger intercooler can reduce air temp by more than what it was increased by the turbo then you are OK in terms of ultimate power as colder air always means more power.

You need to measure air temp before and after intercoolers to get any real view on their capabilities. OK we do need some guages then

An ideal IC has zero pressure drop and 100% efficiency.

Large pressure drop can result in lag and poor throttle response (regardless of any potentially lower intake air temp) - its a compromise like many things !



Paul

[4WheelDrifter]

That's right, but have you thought about how much volume there is in an IC? The difference between a stock and a really large one is probably only a couple of litres. A 2.2 at 3000rpm uses 55 l/s of air with ve=100%. To make 1 bar of boost at 3000 rpm, it will take an extra 4/100 of a sec compared with stock......

Use a different manifold with front intake, and the total volum will be less then stock even with a huge IC

Sorry. I wasn't calling the stock IC a party balloon! I just like to think of things in opposite extremes, to think about the difference.

LOL @ Paul with his maths, as usual.