I recently installed a new intercooler (DFIC), and it has two bungs, pre & post core. I want to use the one after for monitoring temperature, which would essentially be IAT.

I see where AutoMeter has such a gauge:

http://www.autometer.com/cat_gaugede...id=3146&sid=11

It utilizes a Type K thermocouple. Not being an expert on this stuff, I decided to do some research...

I know that I want something accurate, dependable, and almost equally important, it must have a good response time (very little lag).

This link looks to contain some good info:

http://www.weedinstrument.com/produc...0response'

Within, it states that K thermocouples should not be used for accurate measurements below 900 degrees F. That being the case, I'm not sure why AutoMeter chose this type...

Also, the response times seem not to be dependent on the type (J, K, T, etc), but if it's grounded or not, and its diameter.

Is this something for which one can go here (http://www.mcmaster.com/) and build something pretty slick, possibly better than the AutoMeter one?

Thanks for any input!

 

K-type thermocouples are used in such cases simply because they have such a wide operating range, the same gauge used for EGT can simply be made more sensitive and recalibrated for lower temp usage such as IAT. Also, the same type of probe can be used for just about any purpose, EGT, IAT, oil/water temps, etc. Inherently a K thermocouple does not have a great deal of output voltage at lower temperatures as, say, a T-type. The output curve of a K-Type (voltage v. temp), while not very high with regards to mV/degree is more linear than some other thermocouple types, making scaling a bit cleaner and not needing signal conditioning. As long as the meter movement is properly calibrated, temperature compensated and the lead length (actually lead resistance) is matched to the gauge/tc combo, you can end up with a fairly accurate gauge setup. The lead length/resistance issue is something that many overlook. If your gauge comes with a ten foot extension, use all of it. Dont cut it back in an effort to make a cleaner install or you will end up with reading higher than actual. Also, never substitute wire of a different type, it will affect the readings.

A digital gauge, or analog gauge with powered amplification can give better results at lower temps than one directly powered by the TC. Ideally you would want a meter that has two inputs and a differential reading function for intercooler use and testing. Fluke has a couple nice handheld instruments with these functions. I have an older model 52 with these features. Granted, it cant be mounted in the dash like a typical gauge, but I only use it for temporary, testing situations.

 

TonyB,

you might just want to wait to see if M7 rolls out the twin temp gauge they are working on.

 

Bart, I've been talking with him about that for a while. The concerns he also has is the response times... I'll ask him again to see what he might be doing. I would love a SPA-like gauge!



http://www.spa-uk.co.uk/design/dualgauges.asp

 

Greatbear - thank you very much for the knowledge, and as always, your ability to explain things so clearly!

I found other forums where guys were recommending to cut the extensions if too long. Your information makes sense. The AutoMeter comes with an 8' lead...

I also PM'd Dr O to get his input, and he provided some good information on how to make such a device! He says that it would be fairly easy. Might be a fun project, but I would probably need his assistance along the way...

 

a twin temp in a single gauge would rock.

 

That's what Peter feels also. Personally, after the fun of testing efficiency, I'd just use the post core for IATs... and leave the pre one for something else, possibly.

 

Doesn't Sid's gauge read in and out?

Along with, distance to target, air speed, landing gear up or down, and status of radar deflecting panels.

 

Tony, some good thermocouple info here:
http://www.facstaff.bucknell.edu/mas...pThermCpl.html

 

Sid's shows "in" or "out" or the delta. I've seen them in Subaru's and other cars. I just don't know what kind of thermocouple it uses...

Thanks for the link. Checking it now!