Automotive Air Conditioning Information Forum

ice-n-tropics wrote:As Bohica indicated the a CAC, a hefty charge air cooler, is pretty basic for your higher temp and pressure intake air if you expect that HP and any engine life.
You said lower ram air is for the radiator which leaves upper ram air for CAC and then Radiator.
But not enough height for condensers w/o preheating and restricting air for the rad CAC pack.
That may leave just wheel wells and trunk for condenser location?
E. G., Porsche 911 rear lid mounted condenser (with ambient air temp) scoop. Just brain storming.
hotrodac

My car only has one source of ram air....the lower air dam.

What is CAC?

If the constant running fans on each 13 x 13 condenser is sufficient then I will do this. The two condensers will not be in direct flow of ram air. The fans will be their only source of air flow.

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Given the dribble of information on the vehicle, I can only assume it is a Gen 2 Firebird T/A.

Those cars had large, one pass Tube & Fin condensers, which were not as efficient at transferring heat.

A modern, dense fin parallel flow condenser has a big advantage. Consider that the entire condenser for many pickup trucks on the road today is 17" x 14" x 1"

The heat exchanger stack, placement & airflow all fit in the equation. The A/C condenser needs to be first in line for cool air because of the needed discharge temp. The engine cooling radiator can easily tolerate 150f air, to maintain a 190f fluid temp.

As Ice already mentioned. you can put the high side loop almost anywhere - the liquid will always return oil. Porsche & the Pontiac Fiero have both proven this.

On Pike's Peak with the Oldsmobile we learned a lot about engine cooling. Much of what is said today in forums & magazines has little basis in fact. Wild stories about "cavitation" - with not one damaged impeller to demonstrate it as a fact. Cooling system theories that are easily proven wrong, etc.

One place you can always get rid of engine heat, is the oil. With turbochargers this becomes more important. Because oil should be over 200f, it is easier to put the oil cooler in the hot air from the backside of the radiator. This speeds warm up as well as offering cooling under load. Just need to size the heat exchanger properly.

Please give us some more details about the systems you propose.

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bohica2xo wrote:Given the dribble of information on the vehicle, I can only assume it is a Gen 2 Firebird T/A.

Those cars had large, one pass Tube & Fin condensers, which were not as efficient at transferring heat.

A modern, dense fin parallel flow condenser has a big advantage. Consider that the entire condenser for many pickup trucks on the road today is 17" x 14" x 1"

The heat exchanger stack, placement & airflow all fit in the equation. The A/C condenser needs to be first in line for cool air because of the needed discharge temp. The engine cooling radiator can easily tolerate 150f air, to maintain a 190f fluid temp.

As Ice already mentioned. you can put the high side loop almost anywhere - the liquid will always return oil. Porsche & the Pontiac Fiero have both proven this.

On Pike's Peak with the Oldsmobile we learned a lot about engine cooling. Much of what is said today in forums & magazines has little basis in fact. Wild stories about "cavitation" - with not one damaged impeller to demonstrate it as a fact. Cooling system theories that are easily proven wrong, etc.

One place you can always get rid of engine heat, is the oil. With turbochargers this becomes more important. Because oil should be over 200f, it is easier to put the oil cooler in the hot air from the backside of the radiator. This speeds warm up as well as offering cooling under load. Just need to size the heat exchanger properly.

Please give us some more details about the systems you propose.

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Sorry, that info would help. You're close, its a 1998 Pontiac Trans Am (4th Gen). Iron block 390ci with about 450 HP Normally Aspirated. It will be getting 20psi of boost so we are expecting a little over 1,000 RWHP.

So from what you said about my factory condenser being an inefficient design.....maybe its possible to just use a "dense fin parallel flow condenser" the same size as my factory condenser and it will work out ok. I can still fit a pair of pusher fans on the front of the condenser too. And keep the two factory puller fans on the back of the radiator. I have 1 inch between the condenser and radiator, as set up by the factory.

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My red Trans Am.....

http://s263.photobucket.com/user/lilmac ... .html?o=24

By 1998 those cars already had Parallel Flow condensers.

Your OEM unit is 25" x 15" . Just make sure it has enough airflow.

Your car was an OEM electric fan vehicle, so make sure all of the seals, dams etc. are still in place for best airflow from the OEM fans.

The pusher fans can be good or bad, depending on application.

The Gen II LT1 has a decent water pump. Avoid any underdrive schemes.

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bohica2xo wrote:By 1998 those cars already had Parallel Flow condensers.

Your OEM unit is 25" x 15" . Just make sure it has enough airflow.

Your car was an OEM electric fan vehicle, so make sure all of the seals, dams etc. are still in place for best airflow from the OEM fans.

The pusher fans can be good or bad, depending on application.

The Gen II LT1 has a decent water pump. Avoid any underdrive schemes.

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My entire system is perfect, just like the day I bought it new from the dealer. My problem is I went to an iron block 390ci LSx engine, instead of aluminum. Its also a fully forged race engine with more cubic inches than the stock 346ci. So its going to run a little hotter. But when the A/C is OFF....it runs just as cool as the aluminum engine did. As soon as the AC goes ON, and I am sitting in traffic or a lot of stop and go traffic.....it will overheat. If I'm on the highway cruising at 65-70 it stays cool as the aluminum engine did also......

There are literally thousands of turbo and supercharged 1998-2002 Trans Ams running around, some of them have figured it out and they never overheat, most have issues. But what works for one guy just does not seem to work for the next guy with the same exact set up.

My specific turbo kit uses a large single turbo mounted dead center in front of the engine, right behind the radiator. So the puller fans have to go.....to make room for the turbo. So pushers are added. But then there's no room up front for the condenser. So this is why i'm trying to use 2 smaller condensers in series.....I have room to do that. But they will only get air flow from the fans I attach to them.

One guy, with my exact car, moved the condenser into his front bumper with two puller fans.....so the ram air from the lower factory air dam feeds only the radiator. But he had to fab a lot of stuff and do some welding......I just can't do all that.

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And there it is.

3 to 5 times a year, every year for the 12 years I have been on this board the same series of questions happens.

1)" My A/C sucks at ide / overheating at idle"

2) Questions about engines, parts, etc. - this can go on for pages.

3) "I got rid of the OEM fan(s) for space / efficiency / because it looks cool"

Finally. The real answer. The incredibly well engineered OEM cooling system has been compromised. Engineers spent significant time on that system. Wind tunnel time. FEA. Testing & refinement.

You have an LS swap. OK, easy enough to understand. Be faster to get answers with that info up front. Any other radical departures from stock? Waterless coolant? Radiator support relocated in car?

Like I said before, internet lore is worse than speed shop customer tech info. A cast Iron block does not "run hotter". The heat you have to get rid of at idle is simply the fuel it takes to spin the assembly. And at WOT, the heat load is still the fuel burned. Aluminum transmits heat better, so an alloy head has a slightly cooler combustion chamber. The Iron block is actually a bonus. It keeps the cylinder walls a little warmer, which reduces friction. In an ideal engine model the cylinder walls would be 275f while the heads would be 200f

Make sure you have enough bypass flow in the coolant path. Blocking a bypass circuit on an engine swap is a common mistake. The cooling system flow within the engine can be significantly higher that the radiator flow.

If the ONLY problem you have is idle cooling with the A/C on, you need to increase heat exchanger airflow. A bone stock car with a bad fan does the same thing at idle. A missing air seal & dead fan clutch in a V6 Ranger would make you look for a blown head gasket - except on the freeway it is cold as ice.

All of us here will be glad to help you through the process. We like Hot Rods. Ice literally wrote the book on Hot Rod A/C. I have done enough engine swaps in my lifetime to make every possible mistake. I was designing Turbo Systems in the late 1970's

bohica2xo wrote:And there it is.

3 to 5 times a year, every year for the 12 years I have been on this board the same series of questions happens.

1)" My A/C sucks at ide / overheating at idle"

2) Questions about engines, parts, etc. - this can go on for pages.

3) "I got rid of the OEM fan(s) for space / efficiency / because it looks cool"

Finally. The real answer. The incredibly well engineered OEM cooling system has been compromised. Engineers spent significant time on that system. Wind tunnel time. FEA. Testing & refinement.

You have an LS swap. OK, easy enough to understand. Be faster to get answers with that info up front. Any other radical departures from stock? Waterless coolant? Radiator support relocated in car?

Like I said before, internet lore is worse than speed shop customer tech info. A cast Iron block does not "run hotter". The heat you have to get rid of at idle is simply the fuel it takes to spin the assembly. And at WOT, the heat load is still the fuel burned. Aluminum transmits heat better, so an alloy head has a slightly cooler combustion chamber. The Iron block is actually a bonus. It keeps the cylinder walls a little warmer, which reduces friction. In an ideal engine model the cylinder walls would be 275f while the heads would be 200f

Make sure you have enough bypass flow in the coolant path. Blocking a bypass circuit on an engine swap is a common mistake. The cooling system flow within the engine can be significantly higher that the radiator flow.

If the ONLY problem you have is idle cooling with the A/C on, you need to increase heat exchanger airflow. A bone stock car with a bad fan does the same thing at idle. A missing air seal & dead fan clutch in a V6 Ranger would make you look for a blown head gasket - except on the freeway it is cold as ice.

All of us here will be glad to help you through the process. We like Hot Rods. Ice literally wrote the book on Hot Rod A/C. I have done enough engine swaps in my lifetime to make every possible mistake. I was designing Turbo Systems in the late 1970's

My car is factory original as it sits right now, 19 years after I purchased it. Its not an LS swap. The car came with an LS engine and it still has an LS engine. Its just made out of iron instead of aluminum. The only change this car has seen is an iron block was installed to replace the aluminum block. Nobody touched any part of the cooling system. The factory radiator and condenser, lines, shroud, air dam, every single factory part remains untouched on the car.

The aluminum engine was pulled out......every single accessory part was swapped over to the iron block (heads, intake, throttle body, fuel rails, every single factory part that came on the car when I bought it.....except this short block is a 1,500 HP capable fully forged engine. Callies crank and rods, Diamond pistons. And its even a lower compression engine than the factory aluminum block, at 10.2:1.....because its built for boost. The only difference in the factory engine is the metal......its now iron. The day I picked it up at the shop who swapped the engine.....I've had these overheating issues only when the AC is ON.....anywhere other than highway cruising.

So the iron has to be the problem.....iron gets deep heat soaked, aluminum doesn't. Everyone who owns this year model car that goes to iron has higher engine bay temps, and so do I. Everything under the hood is hotter now also. I used to be able to lay my hand across my factory plastic intake after its up to operating temp, about 200*F.........now when the temp gauge still reads 200*F, my hand cannot be laid on the intake or I will get burned. Its because of the iron getting heat soaked and heating everything else up thats under the hood.

The factory cooling system is the same as it was for the last 19 years I've owned the car and never had a overheating issue....I changed to a iron block, and now I'm overheating. Its 114 pounds more dense metal, than the aluminum block.

What else could it be thats causing the overheating when not a single other item was touched or disturbed in any way.....?

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This is a similar single turbo set up in the same exact car I own. He only has this single puller fan on the back of his radiator....no shroud at all. But all of his lower ram air is dedicated to flowing through the radiator while hes moving. No condenser in front of the radiator.

This works on his set up. But other people have tried and it does not work. I may have to try this, with a 2,700 cfm puller....but absolutely with a completely sealed sheet metal shroud.

Then my condenser will have room up front with two large Derale pusher fans attached.

https://cdn.discordapp.com/attachments/ ... /image.jpg

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Measured the air 6" off the asphalt in LV at 165F. OEMs often use belly pans these days to stop recirculated idle air.
Bohica's PP experience for severe rare air and temp paramaters w/ turbo would be worth considering.
So you are attempting 20 psi boost w/o a charge air cooler (CAC). Somewhat counter productive even with a detuned compression engine.
Cooling the intake air after the turbo is effective for 20 to 30% HP increase and engine durability is a big +
Big Rigs locate the CAC across the bottom half or sometimes the full radiator height with the condenser covering only the upper half so the CAC entry air is not preheated.
OEM's normally use a air to air CAC heatX but have used air the liquid CAC.
Dragsters have used ice on the exterior surface of the CAC
Happy Thanksgiving
hotrodac