Intake Air Temp. Critical Limit ?

[morgie]

Does any of you have any ideas / sheets / specs of what could be a Critical Intake air temp., the temp beyond wich we should consider installing an intercooler ?

I've installed a temp. sensor into my intake just in front of the throttle body, and in 4, 120km/h, WOT, i peak at about 55°C (ambient temp was -25°C) .. is it hot ? is it limit ? is it ok ? what's the limit ?

[Legacy777]

Limit sorta depends on whether your getting pre-ignition & detonation.....or whether the ECU is pulling timing to cure this......

[RaZor]

Very interesting!!!

In forced aspirated cars, the highest temp that you want to see - depending on how much boost you're running, of course - is about 30 degrees C above the day temp.

http://www.autospeed.co.nz/cms/article.html?&A=0360

[rallysam]

I would think that the limit would depend on your boost, also. High intake temps might be ok at low boost levels. Also, vice-versa is true: high boost levels are ok at low intake temps (that's why you get an intercooler). So there probably isn't one simple number to put on the temperature limit. Did I get that right?

[boostjunkie]

I've installed a temp. sensor into my intake just in front of the throttle body, and in 4, 120km/h, WOT, i peak at about 55°C (ambient temp was -25°C) .. is it hot ? is it limit ? is it ok ? what's the limit ?

Hey morgie, where did you get the temp sensor from? I'd like to install a temp sensor to monitor intake temps, especially since I would be getting that intercooler spray sometime soon.

[mile hi]

I wouldn't mind knowing the source on the intake temp sensor myself if it will withstand the higher temps that we have seen. One of the problems we have seen on the WRX and it's air to air is that after sitting at a stop intake temps can go to 350F+. I have a lot of info on our turbo's and we have studied this a bit but unfortunately the info does not deal with compressor output temps directly as there are variables involved such as turbo intake temp, humidity, and a big one for us altitude as the turbo does have to work harder here. It is tied to efficiency and and to complicate things this does not happen on a linear scale. It looks like the stock turbo does pretty well in general until 13lbs or so and then temps start to rise and at 15 they are rising fast but again there are variables to consider. I guess the best rule is to keep things cool as possible like some of the 1/4 mile people do and they will use containers of ice in the lines to get the temps down to ambient or lower. Spearco even has a chart on how much ice to use. (ALCO) al@iwtu.net

[morgie]

This was a low-cost, low-tech Mod, since it was mainly for 'fun' and to check how this temp vary with boost and ambient temp. Maibe the MaxTemp displayed may not be high enought for "hardcore" use, well see.

So i simply bought a cheap Electronic Termometer equiped with a metal Sensor (Wich i found for 10$ CAD at WalMart.).

Expect a lag of 4-5 sec in temp results.

here's a pic of the thing. In the foreground, you can see the probe.



I drilled a hole 2-3" from the throttle body, in the Plastic elbo (after removing it of course), and glued the sensor into place.

The Sensor has a nice "protuberance" so it cant be sucked in !

my only worry is that sensor is part-plastic, part metal. just let the metal part enter the hole ! so the plastic wont melt hehe , if it's not resistant enought .

[mile hi]

I know I have had a few start to melt on me. We have a custom built multi channel unit with thermocouples. It looks like thermocouples are the way to go but they are more difficult to use and more expensive.
AL(CO)
al@iwtu.net

[Gordo]

I've used K type thermocouple extension wire to a millivolt meter and then converted using the Omega temperature tables. The following is what I get, although I wonder at the accuracy a bit.
Regular running around town I have approx. 35 degrees F (0.0 mvdc); at WOT with 14 psi boost for 15 secs. I got 120 degrees F and I can see running any longer I'd be up to 140 degrees F. Ambient temperature was about 60 degrees F. Because I don't have a cold junction I think we have to add about 25 degrees.