Author Topic: How hot is air from turbo? (Read 4457 times)

jimfoo · « **on:** May 23, 2007, 01:51:00 pm »

How hot is the air from the compressor of a turbo? I called a place that sells silicone tube, drove down to the address and found a Walgreens. I called them up, and the a-holes are in California even though the phone book says CO. Anyway, I stopped by a NAPA and bought some straight Gates hose which is rated to 135C. Will it work, or at least for a little while?
Thanks.

jtanguay · « **Reply #1 on:** May 23, 2007, 02:08:11 pm »

all depends on the amount of air you are flowing, and the pressure at which it will be compressed.

on some big trucks the air would be much hotter than 100C... and the system would use an intercooler that ran off the engine coolant... very interesting!

I would say that for 15 psi it should be fine. maybe someone else can give a better idea though...

xud9te · « **Reply #2 on:** May 23, 2007, 05:11:33 pm »

simple formula for this one;

(P1*T1)^(0.283)=(P2*T2)^(0.283)

So for the ideal turbo outlet temp, T2 = T1*((P2/P1)^(0.283))

where P1 is the absolute pressure atmos (14.7 psi), P2 is absolute pressure after turbo (14.7 + 15 psi boost = 29.7psi), T is temp in 'degrees R' which is degrees f plus 460.

For 15psi at 20 degrees c (68 f) you have an ideal outlet temp rise of:

((68+460 * ((29.7/14.7)^0.283)-460)-68 = 115 deg f.

If your turbo is about 70% efficient at this boost level and airflow (figures taken from the compressor map) then the rise will be 115/0.7 = 164 degrees f, 73.33 degrees c. Adding this to the inlet temperature; 164+68 = 232.3 degrees f, 111.3 deg c.

This is of course not assuming any conduction heat from the turbo itself (small in comparison anyway). I have found in practice that these numbers are a little bit high anyway. All depends on what humidity the air is etc.

I bet the rating of the silicone hoses is alot higher than the stated numbers anyway, they want to be careful that a bad batch can still make it to 135 degrees!

I would say they would be fine!

(I think.... :? )

jimfoo · « **Reply #3 on:** May 23, 2007, 05:56:15 pm »

Thanks. It is actually regular rubber hose, not silicone.

jimfoo · « **Reply #4 on:** May 23, 2007, 08:25:37 pm »

So thinking about it, it doesn't do much good to run a air/water IC unless you are running a lot of boost, not that I was anyway.

lord_verminaard · « **Reply #5 on:** May 24, 2007, 08:54:47 am »

Not really. Air to water I/C's have the advantage that they do not need a constant flow of air over the core to cool the pressurized air. Most Air to water units have their own reservoir of coolant separate from engine coolant- likewise, they also usually have their own small "radiator" that cools the water. This makes them nearly immune to heatsoak, and depending on the rate of flow for the water pump in the system, the "cycle time", or how long the water used to cool boosted air makes a complete cycle in the system is usually longer than what any car will ever run on full continuous boost at one time. Might be a good option on your 4x4 project since you really will not be hitting speeds high enough to work on an air-to air cooler.

Brendan
84 Scirocco 8v
81 Scirocco 'S w/ 3A and 4k
01 Jeep TJ 4.0

jimfoo · « **Reply #6 on:** May 24, 2007, 09:25:45 am »

Guess I was thinking engine coolant "cooled" the air. That makes more sense. I will have a separate fan for my IC. I think a separate air/water system is too complex for what I need.

jtanguay · « **Reply #7 on:** May 24, 2007, 07:36:53 pm »

Quote from: "jimfoo"

Guess I was thinking engine coolant "cooled" the air. That makes more sense. I will have a separate fan for my IC. I think a separate air/water system is too complex for what I need.

well 5 psi @ idle speed will probably get you heat soaking... only big rigs used engine coolant to cool the charge air on some models...

you should at least get a thermostatically controlled fan for the IC, or a water spray system to help eliminate heat soak...

jimfoo · « **Reply #8 on:** May 24, 2007, 08:32:02 pm »

I may run the fan all the time as it is a small one. After a waste of a day trying to plumb the air & IC, I got smart and bought ABS to design a prototype so I could easily change things before spending money on the good stuff. I also got an idler pulley mounted so I can run the h2o pump by itself off the crank.

burn_your_money · « **Reply #9 on:** May 24, 2007, 08:55:05 pm »

Thanks for the tip on ABS, I definitly would have overlooked that option

jimfoo · « **Reply #10 on:** May 25, 2007, 08:08:09 am »

Now what I think would be cool is all lexan tubing. Too bad they don't make it in 90's. Although I'm sure metal would help take a lot more heat out. Lexan takes close to 500 degrees F, so wouldn't melt, and it isn't brittle. Guess it wouldn't look good though if your turbo leaks oil. :lol: