Placing ICE on the exterior of the plenum

[red92]

....I have a supercharged intercooled V8 with a MAF and an IAT at the air box. Last weekend I had this vehicle at the drag strip and between runs I opened the hood so the motor would cool. Someone in the pits suggested that I put a bag of ice on the plenum "because thats what he dose -cause- cooler intake equals more power" .....
I told him I did not see how that would help when the OAT, humidity and altitude are unchanged?

You don’t have to be an engineer to know that temperature and altitude affect air density (as well as humidity).
My question is ...Will a pysically cooler plenum create a HP increase.

 

[NickE]

I know that the WRX guys with Top mounted Air->Air intercoolers put crushed Ice on the intercooler to help prevent /alleviate heat soak.

 

[patprimmer]

A colder manifold will give a very slight improvement in air density, as the air will not heat up quite so much when flowing through the manifold. The actual improvement will be very dependant on a few variables, but mostly manifold design and routing.

After all, an intercooler is an efficient heat exchanger in the inlet duct. a cooled inlet manifold is just a pretty louse intercooler

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
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[rmw]

red,

While the theory behind the suggestion is valid, the practicality is a real stretch. Post this question in the heat transfer forum, and the members there will use a lot of heat transfer terms that all boil down to the fact that with the large volume of air going through the plenum, and the plenum's inherent poor design as a heat transfer device, flat surfaces, no fins, etc, (because it is an air flow device, built to minimize flow restrictions) that while it might feel good to try to do all that can be done, the actual incremental decrease in air temperature through the plenum is probably not measureable with standard instrumentation.

Look at it differently, When you want to pass a large volume of air across a device to remove heat from an engine, what does it look like?? A radiator. Want one of these in your plenum. Anything less is just spitting into the wind.

Maybe that is just what patprimer just said.

rmw

 

[patprimmer]

rmw

You said pretty much what I said, but quantified at an even lower efficiency than I implied, but i think you are correct.

I had in mind a turbo system with long ducts, but without the intercooler, and was thinking about the entire length of air-duct being cooled, like maybe 5 or 6 feet of 2.5" tube to a plenum, then maybe 14" of 1.25" tube, but in reality that would be a very extreme case, and I still would expect maybe less than 1 deg drop at wide open throttle high rpm. The word minute seems more appropriate than small, and on a V8 with a typical compact manifold with virtually no air-ducts, the word infinitesimal might be more appropriate.

Regards
pat pprimmer@acay.com.au
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.

 

[rmw]

As hard as those of us who deal regularily with heat transfer work to get as much as we can efficiently get, I can assure you that we would never select an automotive air intake plenum (at any temperature) or an intake manifold system as our device of choice.

I have been trying for years to figure out a way to use the cold (40-50F) suction side vapors of the A/C system piped through a heat exchange device in the intake air. Whether possible or not, the BTU balance at 70 mph on a 95F day would me much akin to the ice bag on the plenum on a hot race afternoon.

rmw

 

[icguy]

red92

Logic would indicate that you don't leave the ice on the intake during a pass, therefore, NickE hit it on the head...your friend is merely trying to cool the intake system to a degree and prevent heat soaking. It is effective, but there are many variables involved. Such as...time between passes, time the ice is on the intake, is the car pushed or driven through the staging lanes, length and agressiveness of the burnout, staging time, etc. CAN it help...sure...does it help...possibly...will your ET be erratic and unpredictable...you bet! If you're ET racing, a consistent power output is FAR more important than having more power ocassionally. Just a racers opinion.

 

[ejit]

Been done for 40 years on NA cars, it works.

 

[ruggedscot]

I once saw a system that utilised some water and antifreeze mix and an off board chiller.....

The mix was cooled down to around -20 degrees and kept in an insulated tank. This was then pumped round through an air to water charge cooler, result good drop in intake air temperature to engine.

Of course could not be used as a long term aid but more to short drag bursts as having to tow the required chiller would mean that a substansial weight penalty would be incurred.

Kinda neat seeing the ice on the pipes though feeding the cooling system.

Rugged

 

[TTmotors]

I think what most people experience from putting a bag of ice on the plenium, is that all map sensor cars have a intake air temp sensor on the plenium (mayby not all but alot)and it causes this sensor to read a lower temp and that sends the timing up a bit. Does increase power. I dont think youd see quite the gains on a maf car or a carb`d version.