Overheating concerns based on reduced radiator airflow

[dragpack428]

Examing this picture, I have concerns regarding the impact these components would have on effective heat transfer/radiator efficiency. Are my concerns valid? It appears to block 30-40% of the surface area on a daily driver.

 

[evelrod]

I don't see any immediate concerns from viewing the photo. Of course it all depends on how much hp your trying to cool and under what conditions. There are worse conditions on OEM setups with water, oil, AC and, intake charge heat exchangers all stacked up behind very small grill openings.

For a street/drag car, I would not worry about it as long as you have a properly sized fan behind it.

Rod

 

[dragpack428]

Thanks Rod,

I took the other side of this discussion when it came up here. It's a basically stock, A/C equipped sedan with approx. 350 wheel horsepower. The car is equipped with the stock cooling fan. I couldn't imagine that hot spots along the condensor/radiator wouldn't have developed along with this reduced air flow behind the components. This seemed especially true considering how unforgiving aluminum engines are in terms of operating at temperatures above normal.

 

[MikeHalloran]

I'd be concerned about what are apparently bug deflectors over the air filters. I'd expect them to impede intake airflow.

But the presence of the intake air snorkels and filters probably wouldn't bother a healthy cooling system.



Mike Halloran
Pembroke Pines, FL, USA

 

[Deltona]

I would be concerned about the air intakes picking up hot air from the rad at low speeds and stationary...

If you have compromised a rad in any way then a simple converging duct can bring back some if not all (or more!) efficiency. Air will always take the easy route and go around, forcing it to go through can reap rewards.

 

[dragpack428]

Thanks Deltona.

What would this converging duct look like?

Mike,

I was concerned with the filter placement in terms of efficient flow as well. I intend to take temp readings across the radiator and behind the tubing/filters to determine if any significant differences are evident. I'm still concerned about this system sitting in summer traffic.

We did some work on a C6 Corvette some time ago and built a system that occupied much less area pre-radiator and placed thermocouples in various locations as well as measured using infra red/laser no contact devices. It was a concern however this certainly is not my area of expertise.

 

[evelrod]

I just do not see any problem with "picking up heat from the rad" under any condition where the "stock fan" is operating normally. As to the "bug deflectors"...I took a look at my KN after several years and the bugs have pretty much left it alone!;-) I'm with Mike, I'd take them off.
As to the "converging duct"...Maybe on a race application it might be worth the effort, it's just a simple matter with a bit of Al sheet and a couple pop rivets. For what I see from the photo, I'd just make sure the air cleaner ducts are fairly well sealed up where they pass the sides of the rad and leave it at that. There is no way the rad can pass the airflow available through that grill opening at any speed above a brisk walk! At a standstill, the OEM fan will pull enough air to cool the engine if it did so before your mods. The OEM fan, indeed, any fan (save a squirrel cage) has a stagnant area in the center of the rad, anyway.

Rod

 

[dragpack428]

I understand.

I have no intention of using the cotton gauze filters. I replace them immediately. In terms of restriction when loading occurs and particle pass through, these are not to be considered in any application. The new filter technolgy available is far superior in terms of flow/restriction and engine protection and no oil or cleaners are ever required.

 

[MikeHalloran]

Uh, what "new filter technology" is that?



Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

Maybe they are new selective filters that only allows cold air through and filer out the hot air. ;-)

Seriously, from the one photo how can we tell what the airflow into the radiator area is and where air might bypass the radiator and therefore how effective a converging duct will be. The converging duct is between the grill opening and the radiator, not between the filter and the engine.

It should help if the existing air ducts from the filter to the engine were simply shortened to get the filters as wide apart as possible. It might even be possible to install them facing straight ahead either side of the radiator.



Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Deltona]

Here is a good example of a converging duct, although in this case it is used on an intercooler:

Please note, I am only suggesting this as a solution to a problem you may not have unless you do some testing to prove otherwise or may not even have the room for.

The shields on the filters may be for water aswell, although does anyone know if a K&N will let water through? Something I have pondered on before....

 

[patprimmer]

Of course it will let water through. It has holes much much larger than a molecule of water.

It will keep out rain, but this is not a problem as it will easily pass through the engine and will in fact cool the charge and clean the chamber. It will not keep out water if you enter a ditch or creek or flood where the water level gets over the filter. You will then get hydraulic lock.

The real useful function will be to keep out bugs.

Water will be absorbed by the cotton fibre in the filter. This will then swell and reduce the pore size and therefore increase restriction.

That set up looks more like it was designed by a trendy stylist rather than by a competent engineer.



Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[dragpack428]

We rely on a new performance filter technology that was developed by a company that builds sophisticated military systems. We ran into these guys last year while submitting bid proposals. It's really well designed and engineered and the performance in all areas of measurement is first rate. They are called Greenlees/R2C in Illinois. I'm sure they can provide the technical details of the media they have patented.

 

[IceStationZebra]

The blocked airflow lowers the effective cooling capacity of the vehicle.
1. Air does not like to make 90° turns before entering the radiator. This is especially true just behind the filters, but is also true to items 1-2" in front of the radiator depending on air speed.
2. The engine will be ingesting air through the filters, taking air from in front of the radiator, effectively making the blockage worse.
3. The fan configuration also has some bearing here. If this vehicle has one fan, the filters are blocking a prime air flow area. But if it has two fans the flow is more evenly distributed therefore the filters are blocking a lower flow area so the downgrade won't be as bad.

What you are betting against is the worst-case condition that was used to design the system in the first place. If you don't drive in stop-and-go traffic with max AC in 120°F conditions you will probably be OK. You are taking away a chunk of the reserve capacity (relative to "normal" driving) that was designed into the package.

"There are worse conditions on OEM setups with water, oil, AC and, intake charge heat exchangers all stacked up behind very small grill openings."
True, but they are designed and tested in that configuration. The owner is not adding all that after they buy the car.


ISZ

 

[RossABQ]

Wouldn't it be a better design to stagger the filters vertically? The radiator appears to be a cross-flow design and in the present design, the filters are going to reduce the effectiveness of only the center rows, while the upper and lower rows are seeing "clean" air. I guess some testing would tell if it's better to have all the rows equally poor or some better than others.

Those seem like awfully big ducts and filters for a 350 HP engine (combined area of two).

 

[evelrod]

Yeah, but they really look racery!

I don't particularly like the setup either. Looks like something you would find on a rice rocket.

I still stand by my original post. They won't have much, if any, effect on the overall airflow pattern. The air behind that grill opening at even a slow speed will be stagnant because flow through the rads cannot keep up.

We just did a weekend test session at Willow Springs with our Lotus Cortina and were pitted with a NASCAR Taurus. 750 hp Ernie Elliot engine with all the heat exchangers stacked up in front. on a 90 degree day we ended up taping off almost the entire grill openings to get oil and water temps to stabilize.

I just don't see a problem...at least not from what has been posted so far. Drive the darn thing and see if it overheats. Don't "fix it" if it ain't broke

Rod

 

[IceStationZebra]

Just because you have satisfactory cooling during use does not mean you didn't lower the cooling capacity of the system. The question was "will these have an impact" not "will I overheat". I agree that the only way to judge if it will overheat is to drive it - short of doing a controlled cooling test on a dyno!

And how can you compare this home brew modification with a NASCAR?!? The production car is based on the lowest cost system that will work 95% of the time. The NASCAR teams have spent years and $$$ to perfect their systems, and if they overheat they just wasted a truck load of time, money, and advertising good will.

ISZ

 

[evelrod]

NASCAR setup is based on adequate cooling at MINIMUM air flow!

OEM's have no such constraints.

dragpack428 (Automotive)
11 Oct 08 12:17
Examing this picture, I have concerns regarding the impact these components would have on effective heat transfer/radiator efficiency. Are my concerns valid? It appears to block 30-40% of the surface area on a daily driver

My answer is still...(Condensed version)...NOT MUCH!

Rod