Gridlock Mikey

GULP!!!

Scary in here when you don't know

OK here's my first attempt of sussing out whether a particular mod is worth doing or not.

I reckon i'm gonna be told by someone somewhere that it's a waste of time and not worth doing. I wanna be able to argue my case. In order to do that, i need to know in simple terms, what that bloody great box under my scoop actually does . There i've said it

Now i understand that it is cooling air and not liquids like a radiator or heat exchanger. If having the intercooler mounted on top of the engine is SOOOOOOO ineffective, why did Subaru do it?

There must be a benefit to sticking it where they have.

When i look at the intercooler (Inspecting for bumpf in the fins ) only the rear 3rd seems to recieve the forced airflow. Does this mean that the front 2/3rds is not being used properly and can be improved on OR is it simply that the whole intercooler face IS being used, just not having air rammed into it all over?

Does anyone know about the ACTUAL airflow once it has entered the scoop? I have watched my bonnet on the Autobahns and it's quite scary watching ya bonnet flex because of the aerodynamic effects of the scoop. Now i fail to believe that even at moderate speeds (40+ ) the scoop is that innefficient that it can't gather enough air to cover the face of the entire intercooler. I mean...REALLY have a look at the size of the scoop in relation to the size of the bonnet, it's bloody massive.

Anyways, so the intercooler cools air, why? is it all about this dense air explodes better than warm air?

Fingers hurting now,

Actually it's home time. I'll leave it with you. Go discuss

Mikey Genuinley interested this time

NBW

Mikey,

Take a look here http://www.howstuffworks.com/turbo4.htm

Cheers
Tim

Shark

Mikey

Simply put - the cooler the air going into the engine the more dence it is. The more dence it is the more you can get in on any given stroke of the engine. The more air you get in the more oxygen you get in. The more oxygen the bigger the bang

I'm sure there are many more tech minded than me on here, but I would guess that a front mount intercooler that goes the whole front of the car must restrict the engine cooling rad and A/C rad if fitted.

Perhaps Subaru decided that a top mount one was right for the Impreza for one or both of the following reasons - it looks good with a bonnet scoop, or it is a workable solution because of the flat 4 engine layout leaving room for it at the top of the engine.

Ford boys may disagree but IMHO a top mount intercooler would be imposable with an upright 4 layout, without a huge bonnet buldge.

Hope this helps and I'm not talking crap

David

[Edited by Shark - 2/15/2002 9:17:18 PM]

Infinity

Mikey,
There is another good reason for having an intercooler. When you compress air it generates heat. When using a turbo to compress air you not only gain heat from this process, but the exhaust side turbine gets very hot aswell, this will add to the overall heat gained by the air inside the turbo. When this hot air enters the cylinder it can increase inlet valve wear, and also cause pre detonation of the fuel, which in a bad enogh case will hole your pistons,or blow head gaskets or warp heads, or shatter valves. Not very nice. A charge cooler works with water. Pace products do made to order units.

[Edited by Infinity - 2/17/2002 6:24:31 AM]

GavinP

There is some good stuff on Autospeed:

Air/Air Intercoolers

Air/Water Intercoolers

According to the "Training WRX" book, the reason that the intercooler was top mounted was simply low cost. I would think that after a while, the bonnet scoop became a "trademark" of the Impreza so they haven't moved it.

Pace do produce chargecooler kits or you can adapt a RS Legacy heat exhanger yourself: Like this

Thanks

Gavin

evo kid

An air /water intercooler is often refured to as a Charge cooler
these are not usally worth the extra weight penatly they carriey as the need a separte raddiator in front of the car and a pump to pump the water round the system .

i do not own a scoob (have evo 6 ) but if you plan on modding the car i would recomend fitting a front mounted intercooler as a worth while mod , as the original sits (as you already know )on top of the engine soaking up the heat .

GavinP

It all about what type of driving you do - an air/water intercooler has a "small" advantage in that water can carry FOUR times the amount of heat away as air....

Yes it does weigh more (in my case about 15Kg) but don't be too quick to dismiss it....

Thanks

Gavin

Bitten Hero

In answer to your questions about why only a third of it seems to be used - that's because at higher speeds that's pretty much the case! Basically, the air gets forced into the scoop, hits the back, and goes down through the intercooler fins. The faster you go, the more the air gets pushed up against the back of the scoop (lifting the bonnet as it does so) and the less area of the intercooler gets used.

To get around this, buy or make an intercooler splitter (there were posts on this recently in one of the forums - this one maybe?). This device is basically a mini-scoop that sits inside the main one, and diverts the bottom half of the air downwards into the front half of the intercooler. The top half of the air carries on like normal and goes through the back half.
There's a chap called Bladerunner that will make you and send you one for £25. I've got one, and it definitely feels better, particularly at higher speeds - more steady urge right through the rev range. I'd recommend it (and others do too).

Another point. Front-mounted intercoolers (FMICs) often suffer from greater turbo lag than top-mounted ones. Can't remember why this is, but it's probably to do with the much greater length of piping that's involved in connecting up the turbo (back of the engine bay) with the intercooler (front of the engine bay) and back again.

Bet you've never learnt so much so quickly in your life Why didn't they teach us this stuff at school? Would have made Physics much more interesting

Cheers
Richard

[Edited by Bitten Hero - 2/18/2002 6:54:07 PM]

submannz

The Subaru water/air intercooler are very expesive to make, and they are some of the most efficent intercoolers of any production car being able to carry the most mass and less restriction

BladeRnnr

Hi all,

Try

http://freespace.virgin.net/michael.ferries4/splitter.htm

for an explanation.

regards

mike f.