Question re intercooler and cooling airflow

Emission · Emission's Garage

I removed my condensor (or evaporator, whatever it was) from the rear decklid when I pulled my A/C.

Air used to get pulled through the grill and either go through he condensor, or the intercooler before going into the fan. Now, with the condensor gone, I have a feeling the air is taking the path of lease resistance (open grill) on its way to the fan - mostly bypassing the intercooler.

Does it make sense to put a blocker (sheet of aluminum or something) over the open grill to force all air through the intercooler? Will the engine run warmer with less airflow, or will I not be able to tell the difference?

- Mike

ZLP · ZLP's Garage

Yes, it will help the i/c if you block off the rest. Many people here have done it already.

beepbeep · 10-30-2006, 03:33 AM

OEM 930 has a plate on rear decklid that isolates intercooler somewhat so air drawn trough it is drawn trough it.

Arguably, making additional blocking plate will improve efficiency somewhat but will also load the fan little more.

sand_man · 10-30-2006, 07:22 AM

I've been meaning to do this. Ever since completing my engine rebuild (which inclued the removal of the compressor and condensor), I just haven't had the "garage time" (or energy) to fab something to up to close off the passenger side of the tail. Maybe that'll be my next project...close up the gapping hole!

Emission · Emission's Garage

Quote:

Originally posted by beepbeep
OEM 930 has a plate on rear decklid that isolates intercooler somewhat so air drawn trough it is drawn trough it.

Arguably, making additional blocking plate will improve efficiency somewhat but will also load the fan little more.

To me, engine cooling is more important that intercooler cooling - what did you do?

Jim2 · Jim2's Garage

Hmmm, interesting that the topic has come up guys.

I did some tests you can mull over, though they may not give you exactly what you want.

Pressure differential from top of intercooler surface, to bottom side surface (ambient air), no A/C condensor, half bay Andial/Garritson intercooler 4" core - 65mph 0" (zero!) differential, at 130mph 0.5" water column. This indicates the air is taking path of least resistance through the opening where the A/C condensor was.

Pressure on top of intercooler (wing deck) relative to atmospheric - at 65mph 0" (a little positive). At 130mph 1.5" water column.

Next test, I cut out a carboard insert which fit tightly around the perimeter of the I/C and the underside of the louver opening in the wing with a 6" wide gap along the passenger side. Unfortionately at this point I also added a forward facing cardboard scoop on top of the wing which was 3.5" tall and the same width and depth as the I/C. Top to bottom pressure differential - 65mph 1.5" water column. 130 mph 5.5" water column!.

Maximum recoverable pressure at 130 mph is about 6" water column.

I remain concerned about fan staravtion in racing applications, but also about dumping hot I/C air into the fan.

Here are some other numbers:
After a few hard track laps with a stock 930 at 1 bar, with stock turbo, stock I/C and A/C condensor in place, turbo discharge 375F, post I/C 275F - yeouch! (Temps taken on a 85F day)

After a few hard track laps with a modded 930 at 1 bar, with a K28, Andial I/C, no A/C condensor, turbo discharge 360F, post intercooler 225F.

As above with the dumb cardboard scoop mentioned above, intercooler discharge 195F. (30F reduction in temp from the scoop)

I could go on here for a while, but the moral of the story is, you need some form of block off on the right side of the wing. Just remain aware that at some point you could begin to starve the fan and possibly see increased engine temps.

Jim
Planning my next mod...

Emission · Emission's Garage

You almost want something to block the air flow through the grill that has a "shutter" than can be opened or closed based on engine temps.

sand_man · 10-30-2006, 10:37 AM

My car is a daily driver and thus far, with the passenger side of the tail completely open (no condensor) , I'm amazed at how cool the engine appears to run...I know the oil temp gauge is far from an optimal indicator, but my needle usually stops right before the middle line in the gauge. I'm sure this isn't optimal for the IC, but maybe a partial block-off would be a good compromise between engine cooling and IC cooling. Or a block-off that was maybe perforated...

turbodog · 10-30-2006, 03:15 PM

I mounted a 9 inch SPAL fan on the stock intercooler. Fits pretty good. Tapped the power from the rear wiper motor which I had already removed. I turn it on at the track or when I get ambitious. No test data, but the fan works on an oil cooler.

Emission · Emission's Garage

Quote:

Originally posted by turbodog
I mounted a 9 inch SPAL fan on the stock intercooler. Fits pretty good. Tapped the power from the rear wiper motor which I had already removed. I turn it on at the track or when I get ambitious. No test data, but the fan works on an oil cooler.

Can you post a picture?

I wonder if that is more effective than a water mist?

hobieboy · 10-30-2006, 05:21 PM

Quote:

Originally posted by turbodog
I mounted a 9 inch SPAL fan on the stock intercooler. Fits pretty good. Tapped the power from the rear wiper motor which I had already removed. I turn it on at the track or when I get ambitious. No test data, but the fan works on an oil cooler.

IMHO, on track, I think an oil cooler without fan might actually be better since the fan will end up blocking the air. Similarly, the way factory did the intercooler - air has to go thru it (& the A/C condensor) to get into the engine bay, hence the great air flow (engine sucking air in). If air can go around it, then the cooling effect on the intercooler will diminish. But I'd still think a fan on top will block air flow at track speed.

turbodog · 10-31-2006, 09:28 AM

I disagree. The fan on my front fender mount oil cooler provides much more airflow than ambient. If I had my oil cooler in the front spoiler, a different story. Direct air flow. The intercooler is tucked away from direct air flow. When I turn the intercooler fan on I know I am passing/forcing a lot more air than ambient. It just makes sense. When the fan is off, sure it may reduce airflow a little, but not block it off. If things get warm I turn the fan on.

Emission · Emission's Garage

Quote:

Originally posted by turbodog
I disagree. The fan on my front fender mount oil cooler provides much more airflow than ambient. If I had my oil cooler in the front spoiler, a different story. Direct air flow. The intercooler is tucked away from direct air flow. When I turn the intercooler fan on I know I am passing/forcing a lot more air than ambient. It just makes sense. When the fan is off, sure it may reduce airflow a little, but not block it off. If things get warm I turn the fan on.

Please post a pic. I think your idea makes sense - I may try it.

Craig 930 RS · 11-01-2006, 10:42 AM

I am absolutely convinced that shrouding is a must for any track work.

The very highest post-IC temps I have seen are 150 - on a hot day, with 1.0 indicated boost with race gas. And 3 oil coolers.

Craig 930 RS · 11-01-2006, 10:46 AM

The 930:

Note small cutout for air filter.

Next step will be to shroud the airfilter - air inlet temps are consistently 14 degrees above actual ambient

turbodog · 11:23 AM

I don't like the idea of restricting airflow into my already hot
engine compartment. The fan just moves a lot of air. This started out as a temporary solution while i worked toward a
Blownsix or other monster ic upgrade. I'm still gonna upgrade, but i'm going to look for a way to attach a fan(s).

Craig 930 RS · 11-01-2006, 11:15 AM

Excellent idea. I also have a large puller SPAL fan for under my new 965 IC - TBI

hobieboy · 11-01-2006, 01:03 PM

The engine sucks a lot of air in. If the only air passage thru is the intercooler, that's where it will go thru; with or without the fan.
The "downside" is the argument where the ambiant air sucked in by the air filter is now hotter. I'd be curious to know the real difference of air flow through the intercooler with fan + non-blocked off shroud vs intercooler only with a blocked off shroud like Craig's.

Craig 930 RS · 11-01-2006, 01:24 PM

Believe it or not........a 'hot engine compartment' is somewhat of a myth.
Besides the IC, there just isn't much in there to create heat - think about it for a bit.
-------
Hobie brings up a good point whether he knows it or not - and that is:

A fan which pushes air UP and out through the tail. Yes, that's right. Virtually no high pressure exists in this outside-of-the-tail area. If one could rig up a set of fans to push air from, say, the bottom of the IC and up through the IC and leave the rest of the tail open........every component 'wins'. Cooler air for the engine heads, pistons, and cylinders - and efficiently cooled air for the IC.

jt1 · 11-01-2006, 01:40 PM

How about some sort of ducting for the air cleaner so the engine pulls cool air from outside, thru the previous condenser area, rather than picking up air from inside the engine compartment?

John