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Old 06-28-2012, 06:26 PM   #1
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Default Confused on IAT

I'm about to install a MegaSquirt into my 2000 normally aspirated autocross car and am a bit confused on GM air temp sensors.

First, do I understand correctly that I _need_ a GM sensor rather than a regular Miata sensor?

Second, there seem to be at least two types of GM IATs - open and closed tip types. Which one is needed? Will this one (Tomco 12001) work?: Tomco 12001 Intake Air / Engine Coolant Temperature Sensor ECT IAC GM | eBay If not, can someone recommend a specific part number that's easy to get locally or order online?

Finally, where should I install it? I want to keep the stock IAT sensor in place for future OBD2 inspections with stock ECU (yep, will be swapping once a year). Have RB intake in the car now and it has this steel elbow between filter and MAF. Should I drill that and have a bung welded there? Is there anything less intrusive?

Thanks in advance! I'm sure there will be more questions
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Old 06-28-2012, 06:29 PM   #2
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you can keep your stock ait. but you gotta fit it into boost pipes if you go turbo... and should be open element.
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Old 06-28-2012, 10:28 PM   #3
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I'm staying naturally aspirated no matter what. So should I forget GM sensor all together? Will tuning be any different between a OEM sensor and GM sensor if I decide to go to GM later on?
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Old 06-28-2012, 10:47 PM   #4
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it wont report as fast as an open element.
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Old 06-28-2012, 11:12 PM   #5
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Thanks. I understand that it's not as fast. But what does it mean in real life for an autocross car? Acceptable, unacceptable?

I'm curious, if I use this maybe it'll fit right into the OEM opening?: http://www.summitracing.com/parts/SMP-AX32/?rtype=10

If not, something like this?: http://www.ebay.com/itm/Chevy-GMC-Ho...ht_3208wt_1177
or
Amazon Amazon
or
Amazon Amazon

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Old 06-28-2012, 11:32 PM   #6
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Or maybe even this one that I can pick up locally?: Duralast/Manifold Air Temperature Sensor (SU113) | AutoZone.com

Although if I can get a GM sensor that would fit into OEM hole with a grommet that would be great!
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Old 06-29-2012, 02:35 AM   #7
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Old 06-29-2012, 03:00 AM   #8
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Oh, good, thanks! So this one locally should do the trick: Duralast/Manifold Air Temperature Sensor (SU113) | AutoZone.com

Still a question on whether anybody tried to used a sensor that fits in grommeted OEM location instead of thread-in bung. Anyone?
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Old 06-29-2012, 01:07 PM   #9
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For NA, just drill a hole in the intake pipe and screw it in. I have a ~.5" hole in a silicone elbow with the sensor hanging out of it. It's not going anywhere and boost leak isn't a concern without boost.
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Old 06-29-2012, 03:16 PM   #10
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Mine's an NB with RB intake (elbow). Not sure where to drill the hole.
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Old 06-29-2012, 08:19 PM   #11
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No reason to use any particular intake. The RB intake was sold to adapt the stock cross-over pipe to the afm to a cone filter element, and allow use of the stock ecu. You no longer need it. In fact, it is heavy and in order to use it you must leave the restrictive element-style AFM in place.

I took my RB intake out when I installed my MS. I just ran an intake tube from the crossover pipe to a filter element and drilled a hole in the rubber tube near the filter. The RB sits in a box. Just remember to tape over your open connectors.

Depending on your knowledge level you may have a huge learning curve ahead of you with the MS.
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Old 06-29-2012, 09:08 PM   #12
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Jonathan, I'm not sure I understand clearly. First, I need AFM to pass OBD2 inspections (i.e. to connect stock ECU once a year and ave the car run and drive with it). Secondly, I'm not sure what you've done with your intake. I understand that you took the elbow out. Is your filter still behind the driver's headlight?

Finally, did you just drill the hole in the tube and stuck the standard 3/8" thread GM sensor in instead of screwing it in?

My knowledge level is pretty low. However the guy who will be dyno tuning the car has done MSs before so I'm hoping for some help.
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Old 06-30-2012, 01:31 AM   #13
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Are you attempting to run in parallel?

If you are, ignore my above advice and you can't use a gm iat with the stock ecu.

If going standalone, just leave the afm/rb intake/Mazda iat together and remove it. Replace section with flexible 2.5" tube and cone filter, insert gm iat into tube. If you put it in plastic, tap it. If you put it in rubber just make the hole slightly smaller. My filter is behind the headlight and my iat is in a 90 before the filter.

When smog comes switch it back, shouldn't take 5 min.
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Old 06-30-2012, 08:47 PM   #14
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I'll run MS as a standalone. But once a year I'll be disconnecting it and putting stock ECU back to pass OBD2 reading for inspection. At least that's the plan.

i see that you are saying swap the whole RB intake with AFM out and only put it back in with stock ECU? Interesting, I was thinking of just leaving it there. What you are suggesting might make better sense.

Do you have a pic of your intake i could look at? And what size drill for the GM IAT hole in what should be a silicone/rubber elbow?
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