Quick Question regarding sensors

[z-ya]

You need a 3/8" NPT (national pipe thread). It's a standard pipe (tapered) thread. It seals as you tighten it. Be carefull not to over tighten these sensors as they will snap right off (done that). Also, don't go too deep with the tap. Start by taping 1/4 the way up the tap. Then try the sensor. You want to be sure that the sensor will seal before you run out of thread. I use teflon tape on the threads to ensure a good seal.

[RTz]

What he said

[24OZ]

Thanks very much.

[Matt Cramer]

You need a 3/8" NPT tap - these are pipe threads, and they are not 3/8" in diameter at all (kind of hard to say what the 3/8" actually refers to, but it's probably close to the inside diameter of one kind of 3/8" pipe). The 3/8" NPT thread has 18 threads per inch, and the nominal outer diameter is 0.675". So be sure it's a pipe thread tap with the right number of threads per inches - there are some other pipe threads like BSPT where the 3/8" tap has 19 threads per inch.

[Challenger]

 

So the bottom sensor is my IAT sensor. Its a GM sensor off of a early 2000s blazer, maybe late 90s. Being that it has a plastic body should I mount it on the manifold somewhere or just in front of the TB? I was considering attaching a small flange onto the sensor so I could could screw it onto the manifold being that there arent threads on it like the others Ive seen.

[letitsnow]

That sensor is meant to be pushed into a rubber grommet, I wouldn't use it. Buy the IAT sensor and bung from DIYautotune, it has a 3/8" npt thread and exposed element, you'll have to weld the bung to the j pipe or tap your intake somewhere, just make sure it's post turbo. I put mine in the J pipe and it works great.

[Challenger]

Well heres my effort to eliminate as much heat transfer from the intake manifold to the sensor..

 

Just cut up my old cold start injector. Drilled out the original hole, and slipped the flange over the IAT sensor. Ill be glueing the flange on for good tomorrow so when I tighten it it will actually pull the sensor down onto the o-ring and seal it. To bad the sensor wasnt smaller on the top where I could just slip it over the top and tighen it down.

[Tony D]

most N/A applications nowadays use the IAT from the air filter. If you are concerned about heat transfer from the manifold, mount it there, or in the cold air piping before the throttle plate. Problem of manifold heat transfer solved.

 

Turbocharged...well that's another matter entirely.

[Challenger]

Yeah, I found my IAT sensor would be perfect to fit into the stock boot going from the TB to the AFM but that was N/A. Im using it for a turbo engine so air will be a little warmer. haha

 

Anyways is there a way to mount two IAT sensors, say one in the manifold and one right before the TB? Would there be a way to watch both temperatures at the same time to see how much heat soak there is from the manifold and when it happens?

[letitsnow]

Yeah, I found my IAT sensor would be perfect to fit into the stock boot going from the TB to the AFM but that was N/A. Im using it for a turbo engine so air will be a little warmer. haha

 

Anyways is there a way to mount two IAT sensors, say one in the manifold and one right before the TB? Would there be a way to watch both temperatures at the same time to see how much heat soak there is from the manifold and when it happens?

 

Yes, but the MS will only use one for fueling calculations as far as I can remember. It's pretty much just setting up another ADC and probably a few simple lines of code to get a gauge reading correctly and the datalog to show. Do some research in the manual.

[thomas]

I have a turbo l28 and I have the (open element gm) temp sensor mounted in the third runner and it seems to work for me. ive tried switching it around but it seems like i can get the a/f a little more dialed in under boost with the sensor in the manifold. I might be wrong but when the throttle is closed (idle part throttle decel) there is a reserve of air in the manifold that heats up before its ever drawn into the engine, when there is a greater amount of cool air entering into the manifold (wot) the air is moving so much it dosent have a chance to match manifold temps, though it will heat up a little. It also seem when my intake manifold is cool the fuel demand increases but as it gets warmer and ambiant temp stays constant the fuel demand drops. I have a crappy intercooler out of a sabb9000 and i never see intake temp above 180, and that only happens when im at idle and decel. It also might come down to tuning preference, I dont know.

[Randall]

even though this an old topic i thought i would add to it...

 

I just finished my turbo setup with MS2 and i mounted the GM sensor in the manifold where the cold start injector was previously.

I was driving it around for the first time and had my datalogs to reference when i finally stopped the car. It was approximately 40F outside and after the car had warmed up even at WOT the air temp never went below 100F i find it hard to believe that on a 40 degree day that i would not see IAT temps below 100 degrees especially considering where my air filter is mounted.

 

 

 

[skirkland1980]

Your temp sensor is picking up heat from the turbo. I have mine mounted right before the tb. Do you have heat shielding under your intake?

[Randall]

no i took it off when i cleaned everything up and never put it back on...I plan on doing that sometime soon to see if the heat soak reduces.

[Randall]

well put the heat shield on and i would have to say that there was very little change. temp was still reading a minimum of about 100 degrees with 70 ambient. jw if its possible that the heat transfer from the turbine to the compressor could possibly heat the air that much. 

 

I was thinking about installing a 1/2 MPT to 3/8 FPT nylon reducer where the air temp sensor is to isolate it from the intake manifold using the nylon reducer.

[skirkland1980]

You're saying you have a 30 degree increase in ambient with the same temps? Sounds like an improvement.

[Randall]

Yeah but whether it is 40 degrees outside or 70 degrees the min temp I see once warmed up is 100. Before the manifold gets hot from heat soak I can see the temp register a few degrees above ambient and when I crack the throttle it immediately drops to ambient.

 

So although the heatshield did help some my minimum temp when fully warmed up is still off from the heat soak.

 

I am going to buy a 1/2 mpt x 3/8 fpt reducer made of nylon and use it to separate the sensor from the manifold. Ill report back any changes.

 

Btw when it is reading 100 degrees my charge pipes are super cold to the touch. Kinda hard to believe that the air would go from 40 or 70 degrees to 100 just by entering the manifold. The manifold even when hot should not transfer that much heat to the incoming charge.

[skirkland1980]

Are you using a GM coolant temp sensor? That sensor is made to test a very slowly fluctuating coolant temp. If you notice normal air temp sensor use a fine wire probe which can pick up temp changes quickly. Your sensor is feeling the temp of the manifold (which is heating up from the turbo, cylinder head and exhaust manifold) not the air. The charge pipe would be a better location for the sensor.

[Randall]

Yeah I understand that I just looked up the temp rating for nylon and its about 200 degree F working condition.

 

I would not think the manifold would ever reach that high of a temp considering the motor is usually around 200 max.

 

I really want to try to insulate with the nylon so that I do not have to re-wire and have a fitting welded in my j-pipe.

 

If this works fine if not I will resort to installing in the j-pipe right before the throttle body and just plug the hole in the manifold.

Edited March 10, 2013 by Randall

[NewZed]

Don't forget radiant heat.  It's line-of-sight.  Any hot parts will be radiating heat and anything that is in the view of them will be absorbing it.  Could be a hot spot on the bottom of the manifold.