Intercooler temps (again)

[Malcolm Robb, LC 0112G]

Yep, but the problem here is adding 3 sensors to the car (T2, T3, Ta) , 2 
of them in fairly hostile places (T1 & T2). Ta isn't going to vary much 
over a 15 minuite test I suppose, so a simple initial temp reading may be 
good enough. My car does have a MAT sensor which I could probably use for 
T3, but I can't make head nor tail of its calibration. The ALDL data stream 
seems to have a raw A/D value,  which makes conversion from raw (0-255) to 
real (deg C) a real pain. (it looks like it's on a 5V feed via a 1K 
resistor, whereas a constant current circuit would have resulted in near 
linear readings !!)

Also the air temp sensors seem prone to heat soak effects and poor response 
times, probably due to the lousy conductivity of air. That is why I thought 
measuring the water temp's in & out of the IC would be easier. A comparison 
of Ta and either water temp would tell you how much heat soak there was, 
and a comparison of water in and water out would tell you how good the 
radiator (core ?) is at dumping the heat, and the IC of picking it up 
again. If the IC water is at 90 deg C going in, it isn't going to be as 
good at cooling the air as it would be if it were at close to Ta. (It can't 
be at less than Ta unless you go for the 'beer cooler' approach)

But Shannen's idea of a water spray onto the rad's sounds like a good'un to 
me. Might try that next time I'm at the track. Should work for one lap at 
least.

Cheers,
Malcolm Robb, LC 0112G

-----Original Message-----
From:	Michael Hagopian [SMTP:mhagopia at vt.edu]
Sent:	Sunday, May 07, 2000 12:19 AM
To:	gmecm at diy-efi.org
Subject:	RE: Intercooler temps (again)

> This should tell you how much heat is being removed from the airstream.
> Measuring the temp's should be easy, but I couldn't work out a way of
> measuring the flow rate without spending $100 on a flow rate sensor. But
> like Mr Nacelp, I am amaised how good the IC is at cooling the intake 
air.
> I just wish there was a simple way of measuring how good it really is.

You can calculate intercooler efficiency by using:

efficiency= (T2-T3)/(T2-Ta)

where:
T2=Temp of air leaving compressor (supercharger or turbo)
T3=Temp of air leaving intercooler
Ta=ambient temperature

A comparison of the efficiencies before and after a system change
would allow you to determine whether the modification was
worthwhile.  You could also determine the heat transfer rate on a
per mass basis without knowing the flow rate:

q=1.01(T2-T3) (Temperatures in Kelvin or Celsius)

You'll get heat transfer in units of kj/kg.

Mike

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