If i was doing it, i'd be looking into sourcing a sensor designed for the purpose. Most of the automotive sensor manufacturers would have a few in their arsenal that are tolerant of manifold heat, vacuum levels and also be airtight. The S2000 has one of those sensors, not sure who makes it though. Another benefit of using a sensor designed for the purpose is they're pretty cheap from a wreckers yard and you'll get the pigtail with it to make a secure connection too.
The next part would be getting the scaling/resistance vs temperature chart and syncing that with your datalogging gear/spreadsheet. If you were to run this sensor as the engine's IAT sensor then you'd need to pick one with scaling that's exactly the same as the OEM one, or very close to it. From comparing a few (Denso) sensors and their scaling curves with the OEM one, i'm concluding that an air temp sensor which has a Denso curve would be most suitable. They're used on a lot of Japanese cars and the curve is close enough to the OEM one - unless you want to buy the entire MAF sensor to avoid any slight variances.
The problem with these manifold tolerant sensors is that the probe is usually coated in plastic to ensure long term survival, which dulls its response time. You could melt the plastic off and use it temporarily but i wouldn't expect it to last in the long run.
The 370Z FSM states 1.8-2.2kOhm resistance @ 25*C/77*F air. 0.283-0.359kOhm resistance @ 80*C/176*F air.
Mazda3 FSM states 2.21-2.69kOhm resistance @ 20*C. No mention of what resistance at higher temps though. This MAF sensor is used in heaps of late model Mazdas (2/3/5/6/CX7/MS3) and the thermister is easy to cut off. This is the thermister i am using and that is probably why my IAT as seen by the ECU reads a little warmer than the onboard ambient temp sensor.
Air temp sensor as used on late model Mazda Proteges (looks like an stake-end) has a plastic covered probe. Mazda3 turbo diesel (non-USDM model) FSM states 2.21-2.69kOhm resistance @ 20*C water and 0.29-0.35kOhm resistance @ 80*C water. Figures are based on water temps because this probe is fully sealed. I've owned the Mazda3 T/D so that's why i had a spare sensor, which i hacked up to mount the above IAT thermister (remember my pics?)
Air temp sensor as used on RX7 (screw in type, with plastic coated probing end) has identical scaling to the Protege sensor. On the RX7, this sensor is screwed into the metal intake manifold.
Relocation i think for the Z is crucial as the area around the Bank 1 (MAF/stock IAT) side of the radiator is a lot hotter than the area around the Bank 2 side. Wrapping my MAF sensor with the neoprene stuff didnt make much difference. Sucks that the fans dont come on until almost 100*C coolant temp so there isnt air to circulate around the engine bay when you're at the lights - things keep getting hotter as the engine gets warmer. I contemplated Uprev purely for the fan control but it's not cheap to remedy something Nissan should've done - damn modern emissions restrictions!
I think i mentioned somewhere in another thread that there's some healthy discussion on the Corvette/GM forums (and the Holden forums in Australia) about HSRKs, choice of sensor location (behind fascias, at the mouth of the intake, the neck of a pod filter, just before the throttle body, etc etc). My stance on this part of the debate is that unless the engine is pinging, i'm not going to worry. Like yourself, i also think that the ECM does some massaging of the sensor output. The IAT reading you get on OBD2 readers is what the sensor sees, not the final (digested/processed) temperature used to determine ignition timing and fuel injection amount.
As for the throttle body coolant bypass... i'm on the fence on this one. It's quite an involved mod to do esp with air bleeding etc so i'm not that keen on this one. As for potential gains, it would be similar to wrapping the MAF tubes to prevent radiant engine heat affecting the MAF sensor. Removing the hot coolant from the TB is like blocking the radiant heat from the engine.
Although, if the ECM does indeed apply some calculation to the IAT detected temperature, the ECU won't even notice that the air passing thru the TB is now slightly cooler. Another argument is that the air doesnt spend long enough in the TB to get warmed - you can wave your hand thru a flame and not get burnt but if you hold your hand there then it'll be a different story.
Either way, I really doubt Nissan would use a different TB (a non-coolant warmed one) in regions where sub zero temperatures never occur (eg. UAE, Malaysia, etc) but it would be interesting to get some input from members from these regions. The Aussie 370Z has coolant passing thru the TB.
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