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Intercooler before or after the rad?

Old 06-08-03, 06:30 PM
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Intercooler before or after the rad?

Hey, Im making a shroud for my rad and intercooler that will direct the air through both and then out a vent in the hood.
What Im wondering aboot is whether it matters or not if the intercooler is before or after the radiator?

Before: cooler air flowing through intercooler...

After: a LOT easier to mount and plumb...

Anyone done this or have an opinion on which would be better?

PS- car will mostly be street driven with occational track days

Thanks
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Old 06-08-03, 07:08 PM
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Hey snuff..

Imo I would always mount the rad first. For a strictly street driven car or drag car (where your engine is not running peak temps for long periods of time) the front mount is a more practical way to go. But for anyone that is running even one track day a month, I would put the rad first without a second thought! All it takes is one track day to melt that sucker. That's the last thing you wanna be worried about when your just trying to have some fun on the track. I can't remember what your running currently (if you could refresh my memory) or how much boost your running, but I personaly would suggest a nice big oil cooler also. Unless you plan on coming in to cool it off every few laps or have money to blow . I like to spend a good 20-30 mins at a time out there to get a good rythem going.

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Old 06-08-03, 07:25 PM
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hey man, i got a 88 turbo engine w/ a to4e and running a max of 15psi (not all the time...)
I will probably be mounting a second oil cooler inline with my current one this winter.

If the car is mostly driven on the street and the ic behind the rad, would it increase the intake temps because of the hot air comin through the rad?
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Old 06-08-03, 09:00 PM
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Mount the intercooler so it gets the coolds air possible - It cna be either in front of or behind the rad - But if you do mount it behind the rad give it its own duct and fresh cool air, if you front mount the IC build a split duct so that at least the bottom half of the rad gets cool air (or the cooler end if its a custom cross flow rad).
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Old 06-08-03, 10:27 PM
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Putting the rad in front will always increase the intake temps as opposed to putting it behind. You will sacrifice some performance. But the air coming through the rad isn't gonna be hot!.. Its not gonna be cold, but not hot either. Think of it the other way around thought. Do you want less then cold air running through your rad when your at the top of every gear for 20 mins straight ?..
Since your running a vented hood if you gonna mount it behind I would make it V-style (if you weren't already gonna do that) so the all the air will have nothing to do but be sucked through the IC and out through the hood with a little help from some ducting. Another good idea is to direct all the air from the two side vents as well as take out the secondary bumper lights and direct that as well straight to the IC. That should give it more then enough cool air to get the best of both worlds. At high speeds the air should rush in there and have the same effect.

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Old 06-08-03, 11:43 PM
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Damn Snuff!!..

Think you posted in enough forums! lol...
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Old 06-09-03, 01:20 AM
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Originally posted by Mld>7
Putting the rad in front will always increase the intake temps as opposed to putting it behind.

Think of it the other way around thought. Do you want less then cold air running through your rad when your at the top of every gear for 20 mins straight ?..

Since your running a vented hood if you gonna mount it behind so the all the air will have nothing to do but be sucked through the IC and out through the hood with a little help from some ducting. Another good idea is to direct all the air from the two side vents as well as take out the secondary bumper lights and direct that as well straight to the IC.
no, air coming through the rad will be significantly hotter (even if by a few degrees) than ambient air... the point of the intercooler is to lower temps AS MUCH AS POSSIBLE, if not for performance than for longevity's sake. always, always, always get fresh, cool air to your IC, otherwise you're just hurting yourself in the end. you can make comprimises with the radiator, and its rate of exchange, etc (even if it means running a slightly higher operating temp), but to PURPOSEFULLY run a hotter level of boost is, well, not a good idea. i'm not trying to be a jerk, but it's a BAD BAD idea to have anything less than the coolest air hitting your IC, not to mention the coolest air at a reletively low velocity (ie: using ducting which diffuses and slows down the air, increasing its static pressure, closer to atmospheric)... making sure that your IC can be as effective and efficient as it can at reducing boost temps is absolutely paramount, and a single digit difference in rad, engine, and coolant temps comes second, by a lot.

the difference between the rad and IC in terms of importance of temps is that the rad, as a far larger piece of hardware, will still have some cooler air coming at it, not to mention that the temps neccessary for heat exchange in the rad are higher than that of the IC. trust me, it's no where near as bad for your engine to run a hotter rad (say, with another 1 or 2 psi on the cap) with a big *** intercooler in front, than to HAVE to run a larger/far more efficient (than one that would do the job in the right place) IC to make up for the temp difference.

yes, front mounting is NOT your only option.
there is the old TII/Boxer style, where air is vented down onto a top mounted IC (which lends itself to a shorter intake tract, which increases throttle response time), there are the (rather strange) bottom mounted ones which need significant ducting as well, along with some pretty serious rock protection (would NOT recommend this solution for a road car), the "behind the wheel" version (utilized more often in rear-engined, twin or single turbo setups, like a Porsche), which although you need to protect it from rocks, ducting is simpler, less drag and lift inducing, and is a safer place than right beneath your sump. hmmmmm...
you can be as creative as you like, but you NEED the COOLEST air possible... make sure you've ducted/shrouded it correctly (as in first, you have some, and secondly that your "in" side of the shroud is slightly less than the total area of the intercooler core... for the diffusion)

Last edited by wakeech; 06-09-03 at 01:22 AM.
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Old 06-09-03, 05:17 PM
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Originally posted by wakeech
no, air coming through the rad will be significantly hotter (even if by a few degrees) than ambient air... the point of the intercooler is to lower temps AS MUCH AS POSSIBLE, if not for performance than for longevity's sake. always, always, always get fresh, cool air to your IC, otherwise you're just hurting yourself in the end. you can make comprimises with the radiator, and its rate of exchange, etc (even if it means running a slightly higher operating temp), but to PURPOSEFULLY run a hotter level of boost is, well, not a good idea. i'm not trying to be a jerk, but it's a BAD BAD idea to have anything less than the coolest air hitting your IC, not to mention the coolest air at a reletively low velocity (ie: using ducting which diffuses and slows down the air, increasing its static pressure, closer to atmospheric)... making sure that your IC can be as effective and efficient as it can at reducing boost temps is absolutely paramount, and a single digit difference in rad, engine, and coolant temps comes second, by a lot.

the difference between the rad and IC in terms of importance of temps is that the rad, as a far larger piece of hardware, will still have some cooler air coming at it, not to mention that the temps neccessary for heat exchange in the rad are higher than that of the IC. trust me, it's no where near as bad for your engine to run a hotter rad (say, with another 1 or 2 psi on the cap) with a big *** intercooler in front, than to HAVE to run a larger/far more efficient (than one that would do the job in the right place) IC to make up for the temp difference.

yes, front mounting is NOT your only option.
there is the old TII/Boxer style, where air is vented down onto a top mounted IC (which lends itself to a shorter intake tract, which increases throttle response time), there are the (rather strange) bottom mounted ones which need significant ducting as well, along with some pretty serious rock protection (would NOT recommend this solution for a road car), the "behind the wheel" version (utilized more often in rear-engined, twin or single turbo setups, like a Porsche), which although you need to protect it from rocks, ducting is simpler, less drag and lift inducing, and is a safer place than right beneath your sump. hmmmmm...
you can be as creative as you like, but you NEED the COOLEST air possible... make sure you've ducted/shrouded it correctly (as in first, you have some, and secondly that your "in" side of the shroud is slightly less than the total area of the intercooler core... for the diffusion)
Thanks for the responces guys.
I still have to decide what Im gonna do... I might end up putting the ic behind and making seperate ducting for both so that both get fresh air.
I dunno...

And I posted in so many forums cause... well... I was bored
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Old 06-09-03, 06:25 PM
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but to PURPOSEFULLY run a hotter level of boost is, well, not a good idea.
Maybe I was unclear with my ideas on IC placement. If I in any way came across as suggested that you should purposefully run a hotter level of boost, which I thought I was pretty clear on, I am sorry. As I said earlier putting the rad in front will always increase the intake temps sacrificing some performance.

Since your running a vented hood if you gonna mount it behind so the all the air will have nothing to do but be sucked through the IC and out through the hood with a little help from some ducting. Another good idea is to direct all the air from the two side vents as well as take out the secondary bumper lights and direct that as well straight to the IC.
to have anything less than the coolest air hitting your IC, not to mention the coolest air at a reletively low velocity (ie: using ducting which diffuses and slows down the air, increasing its static pressure, closer to atmospheric)...
I cant help but feel like you are contradicting me and agreeing with me at the same time.

To clear things up I never meant to give the impression that intake temps are not important. But for road racing conditions generally you put the rad first. Both Intake and rad temps will have a negative effect on engines. To put the rad behind in those conditions would effect the rad more then just a few psi. Besides you said yourself that if it is ducted right it will work just as well. In the end I guess it is snuffs decision. But from what I have seen road racers get the best results this way.

Last edited by Mld>7; 06-09-03 at 06:27 PM.
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Old 06-10-03, 08:38 AM
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Originally posted by Mld>7
But from what I have seen road racers get the best results this way.
*nod* fair enough.
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