<anorak mode=on>

Always thought these mesh coverings for intercoolers were a bit naff, but I actually had a good look at one yesterday fitted to an STi (owner is on ScoobyNet, and he can jump in if he likes).

I compared the area of exposed core in standard setup compared to the amount of core covered by this mesh and it's supporting surround.

Would you be suprised to hear that the reduction of surface area with one fitted was 25.16% ? 25% I hear you ask ? Yep, that's right.

So, by fitting one of these items you may save your intercooler having a few fins bent over (that takes a few minutes to straighten now and then). But is a 25% reduction in airflow through the intercooler worth that ?

<anorak mode=off>

OK, I'm not sure of the maker of this guard (owner jump in here if you like) but the others I have seen are a similar design.

Needless to say, the owner did remove the guard before going home

Bad thing ? Discuss.

Cheers

Ian

[This message has been edited by IWatkins (edited 13 May 2001).]

 

I thought it was 25.17%!!!!!!

 

Go to B&Q and buy a sheet of mesh Ali. and make your own!
JohnD

 

get an inlet temp gauge and test - why guess.........?

Martin

 

Its not 25%, its about 12% (note that each grid wire is shared by TWO grid cells)

But also note that the scoop entry cross sectional area is considerably less than the ca of the intercooler matrix.

Not sure what all this means - bigger scoop a good idea?

JD

 

JD,
Spent a while measuring this properly and the number was 25% not 12%. Maybe it is 12% on the one you have seen.

Deep,
25% to you.

Martin,
Fair point, but it's for a Scooby, so I don't actually care that much


All,
My point was, would you go out and tape over 25% of your IC on a standard car ?

Cheers

Ian

 

I wondered why the mesh on these guards is so tight. I put 6mm square grid over mine after some pebbles got in and caused quite a bit of fin bending. I think the restriction to air flow with this size is negligable and whilst protection might not be absolute, anything small enough to get directly through a hole would not do much harm.

Couple more points - I should say that the aerodynamics of the car (and scoop size)determine how much air goes through the intercooler space. The grill may give the air 25% less space to get through but the air will just compress and go through faster at a higher pressure (and of course very very slightly decrease fuel economy to overcome the resistance .)

Secondly I dont think air flow over the intercooler has any where near as big an effect as the size and specifically surface area of the intercooler itself. The heat is lost by radiation and all the air flow does is stop the surroundings warming up and maintain a temperature gradient for the heat to be transferred. In other words as long as heat is removed from the surrounding air (ie blown away) faster than heat is radiated from the intercooler it should not matter that much anyway.

<Anorak Mode = Off>

[This message has been edited by Boost II (edited 13 May 2001).]

 

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>
Intercoolers lose their heat predominately by convection, not radiation (all though a small amount is inevitable).
[/B]<HR></BLOCKQUOTE>

Oops, thats what I meant. I was thinking to myself the intercooler works like a "radiator" which is obviously misnamed!

 

On the other hand, the fins of the intercooler itself provide approx a 90% (guessing) restriction.

Provided that the area of the intercooler, less any reduction for the area of the wire is greater than the area of the scoop opening, it is not actually a restriction.

Eg, you have air been fed in through a hole of 20,000mm2 that they goes through a duct opening to 60,000mm2 (on the surface of the IC). If the duct opening is reduced by 25% to 45,000mm2, you still get 20,000mm2 (x flow rate) of air passing through the intercooler. The figures are not the actually sizes.

Intercoolers lose their heat predominately by convection, not radiation (all though a small amount is inevitable).

When the water spray is used the heat loss process is part convection, part conduction. Water droplets contacting the IC conduct heat away and more heat is conducted as the airflow evaporates this water.

 

would u recommend them fitted?

i have been thinking about getting one...

do scoobysport supply some? Easy to fit?
invalidate warranty? :P

 

Water spray kits tested on Cossie's do nothing.....waste of money...

Stick a Charge Air Temp Gauge in before and after and see......

Very funny to see the results.

 

Not true dingy if its designed properly.

They dont make a huge diference, but they do make some difference. Thats why they are installed on some of the groupA cars.

WI is much better though, makes a big diference on a restricted turbo engine running a proper mapped WI system.

The biggest gain from an intercooler is not the entry design, its the exit design. Most people apreciate the inlet design as thats what you see and its easy to visualise the airflow going in. If you really want to make it work however you need to have good flow charicteristics on the outlet.

The Impreza is really crap from this point of view. Fitting a front mounted intercooler will help a lot but still not be ideal. You need something like what is on the WRC car, where the outlet is huge and has a good duct design that speeds the airflow up on its exit.

Best i have seen is on the RS200, take a look at the exit duct, it's the dogs.

As to answering the original question, do some charge temp tests and find out, dont guess.