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Old 03-21-2011, 11:40 AM   #1
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Default Hot little compressor: Constant 20-40* AIT delta

I have a hot little compressor housing. Regardless of the ambient temperature, my AITs are consistently 20-40* higher. My AIT sensor is not messed up. After a drive yesterday, I put my hand on the compressor housing and it was actually hotter than the valve cover. My guess is that it is heatsoaking from radiant heat coming off the turbine.

What would be the best way to keep my compressor housing cool?

A metal shield?

A blanket?

A duct? Regarding ducting, FWIW I have to undertray on now and judging by the way my hood moves around there is plenty of airflow in the bay. I plan on putting a tray back on.
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Old 03-21-2011, 11:42 AM   #2
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Didn't you remove your cold air box and install filter directy onto the compressor recently?
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Old 03-21-2011, 11:45 AM   #3
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Didn't you remove your cold air box and install filter directy onto the compressor recently?
Yup. Thing is, I had the exact same delta when I was using the cold air box. BTW the housing was too hot to hold my hand on it without getting burned.
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Old 03-21-2011, 11:50 AM   #4
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I don't think thats abnormal at all.
I highly doubt ANYONE here can touch their comp housing with bare hands after a pull or driving
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Old 03-21-2011, 12:17 PM   #5
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Your Intercooler should take care of any heat the turbo might add from heatsoak during out of boost driving/cruise, it's still >80% efficient out of boost.

where is your AIT sensor located? Are you sure it's not the sensor itself that's hot?



Noggin. Use it.
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Old 03-21-2011, 12:21 PM   #6
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Brainey is correctomundo: my AIT heatsoaks frequently as well. Too lazy to relocate it to the IC end tank. lol
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Old 03-21-2011, 12:23 PM   #7
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Your Intercooler should take care of any heat the turbo might add from heatsoak during out of boost driving/cruise, it's still >80% efficient out of boost.

where is your AIT sensor located? Are you sure it's not the sensor itself that's hot?



Noggin. Use it.

AIT sensor is about 18 inches or so after IC outlet.

By "the sensor itself that's hot" are you implying that the metal body of the sensor is heatsoaking? Hmm... I actually have this copper pipe fitting attached to the IC outlet tube and the AIT sensor screws into it. Maybe the tube and the sensor body is heatsoaking. The sensor bulb itself does not extend into the air stream so maybe this is what is going on. Hmmmmm
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Old 03-21-2011, 12:29 PM   #8
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So it's outside the engine bay more or less? or is it still behind the radiator?

These GM AIT sensors like to heatsoak. If I idle, I can watch the AITs raise a good 10-20F. As soon as there's airflow it drops right back down to about 5-10F over ambient. Same thing if you park the car and then come back after 20-30mins, the AIT will show an increase, and why a lot of guys complain about hot starts. When I had it just before the TB, when the a/c fan would turn on at idle, I'd see a jump in AIT temps too.

Moving my AIT sensor outside the engine bay, just after the IC significantly reduced this effect.


But like I said, since it's after the IC, if you're driving, you should not be seeing AITs much greater than ambient.
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Old 03-21-2011, 12:52 PM   #9
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No, it's still behind the radiator.

Let me try moving it right next to the IC or on the end tank. Thanks!
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Old 03-21-2011, 12:58 PM   #10
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I would say get a turbo blanket and heat shield on the manifold to help block heat build up on the comp housing. Also like they said relocate your AIT, I had a problem when i had my NB. I placed my AIT in my intercooler pipe right before my TB. This made it heat soak fast, I also noticed my intercooler piping heat soaking as well. So i put a metal plate where the A/C fan was. I dropped my AIT a good 25 35 degrees when idling and when driving a good 40-50 degrees.

Im wondering if it would be good to put the AIT in the back of the manifold. My manifold has a spot for it so im going to try it and see how it works.
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Old 03-21-2011, 01:05 PM   #11
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Probably a better spot than in front of TB, will have airflow when idling and the IM will do a good job of removing heat from it. But eventually the IM will heat up to same temp as underhood temps.

That Audi AIT sensor looks like an interesting alternative.
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Old 03-21-2011, 01:09 PM   #12
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The plastic AUDI AIT that uses o rings to seals? Thats the one you talking about.
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Old 03-21-2011, 01:17 PM   #13
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yeah that guy.
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Old 03-21-2011, 03:17 PM   #14
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I've always put my AIT sensors in the intake manifold. It was recommended by Motec and Autronic. Downside is that after shutdown, heatsoak causes inconsistent hot start issues. Seems like the worst is about 10 or 15 minutes after shutdown. I have a 30 second decaying post-start enrichment that is rich enough to get it going when it's heatsoaked, but not so much that it has problems when it isn't. I spoke with a Honda EFI engineer, and he said that most OEM's just ignore the AIT sensor for hot starts anyway.
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Old 03-21-2011, 03:47 PM   #15
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Yeah, I'd love to get Ken to revise the Megasquirt code in this regard.
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Old 03-21-2011, 04:15 PM   #16
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Which ATS is the smallest fitting in diameter? Most accurate?

Delco
Ford
Miata
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Old 03-21-2011, 04:33 PM   #17
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Smallest diameter is to pull the sensor component out of whatever sensor you prefer, solder some wires on it, put it through the fitting of your choice, and fill it with epoxy (leave the sensor body sticking out into the airstream).

EDIT:
Note that the 'official' sensor here is made out of a hose barb, and they added an additional support 'hoop' soldered to a sensor lead and embedded into the epoxy.
http://www.mrm-racing.se/shop/produc...t=45&id_lang=1
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