I think your example makes sense David but the hair dryer trick might put the last nail in the coffin for this discussion.

 

So there is a difference in the AEM ait sensor and the GM one? Is worth changing if you have the AEM one?

 

Oh yeah I'm sensing a polishing bearings / dyno fan speed type of video coming Those were hilarious. You are a good actor DB.

Autronic come with a GM IAT sensor if I recall.

 

Say you put the sensor in a confined airspace that is 200F. It will take X time for the sensor output to reach an equilibrium point and read the actual temperature. We were defining that time as a lag in previous discussion.

Since the response time (lag) could be several seconds to reach equilibrium, you're already done with your gear pull before the sensor could catch up. It's no longer being heated, so you clip the true peak value off your measured data. Using some pretend numbers; instead of seeing 110F sweeping to 140F you only see 110F sweeping to 120F. That air might have been 140 degrees for just a short moment at high RPM but you wouldn't be able to measure it as the sensor isn't being exposed to the peak heat long enough to read the true peak temperature.

That being said, the same effect could be seen on the old core. Instead of me seeing ~215F on my old setup it may really have been around ~250F under the same conditions. Groc mentioned that the mass/thickness of the sensor which directly affects how quickly it can notice a change in temperature is probably that way for durability purposes of the sensor. No one would want to run a GM IAT if it broke up and flew into your shiny new Indy intake manifold...

You are 100% correct in saying that the IAT works well for comparing intercooler cores though. Its output will be repeatable, and consistent. I just wouldn't necessarily call it accurate. There is no doubt in my mind that your new core is leaps and bounds better than the old one, which was also great in its time.

 

I think I hear David's hair dryer...listen closely

 

David, I KNEW the answer to the schit-from-shinola IC vs the Buschur Race FMIC. I was giving that as an example of two truly different temps but would we be able to 'measure' the difference effectively. My answer also lies in my logs. When Tony lifted in 4th the temp was 118.4 degrees at time frame 22.440, then the temp dropped to 114.8 at 22.800. That shows a nearly 4 degree drop in .360 seconds. It didn't go to 116.6 first, it logged 118.4 then 114.8. That at least shows the quickness of the sensor responding to input air.
As to the ambient temps, the 70 - 110 would be a reasonable assumption. It was 95 at 5:00. The radio said 97 but that depends upon where they measure from. If they were at the starting line, ambient is much higher.

 

9sec9, with the temperatures you listed, I think it is safe to say resolution could be affecting things here as well. Basically, the AEM seems to only report in 1.8 degree increments. You could be at 117.5 degrees and it would report either 116.6 or 118.4 and likely will bounce around between the values despite the value never changing.

Point being, a change from 117.5 to 115.7 ( a change of 1.8 degrees) could effectively show as a change of 118.4 to 114.8 degrees (a change of 3.6 degrees). Gotta love analog to digital conversion. This is where the Motec 32-bit processor comes into play. Also, if I recall, the AEM has a pretty large time resolution anyway, something like 100msec between samples unless you turn it to a high speed log parameter. The thermal mass of the sensor is still the dominant item in the system though.

David, I'd love to see a little one of your videos. Unfortunately, I already have the data on the GM IAT sensor, I'll have to see if I can dig it up again. A couple Honda guys already made a post about this quite some time ago on Honda-Tech. It's SLOW in an absolute sense, but for an automotive sensor, it's not too bad.

The Autronic sensor IS NOT a GM IAT sensor. It is actually a pretty nice little sensor. Much more compact then the GM piece. I suppose it could be a thermocouple out of a GM sensor potted into an 1/8" NPT fitting. But that seems pretty wasteful to go to that extent to put a half *** sensor in there.

 

Thanks 03, I agree about the resolution, but that's also where 'trending' comes in to play. The trending coincides with expected results and time frames. Still, the sensor is what it is. It's probably more than adequate for what and how we use it.

 

Hmm I could have sworn one of the sensors that came with my Autronic said GM on it... maybe it was the water temp sensor or a relay or something. Anyway yes it is 1/8 NPT.

 

I knew you knew 9sec9 Your example of the temps falling that quickly is a very good indication of the speed the sensor reacts.

I was going to do this tonight when I got home but I cleaned my car and put a cover over it, I was too lazy to take it back off.

Maybe tomorrow at the shop.

 

Also, one more thing to remember. Extremes may be a possibility, but the law of averages changes not only the liklihood of the temps being .9, but also the time frames to be 50 milliseconds on the actual temp change being missed. Using the extremes doesn't really show the liklihood of what the true temps and time frames would be. The trending of the numbers give a more accurate example of what is truly happening. CAN the extreme's occur, yes. Is it likely that those are indicative of what is happening on every read? Not even close. That's why the law of averages and trending become important when looking at data like this.

 

Bosco says hello, and are we there yet. Indy

 

Get the baby Bosco. Tell Indy to get you a cookie. Indy, Here's the latest pictures of the trailer and car. I worked on it all day. It sure makes it easy to work on the car when pop, pop, twist and the radiator is out! Changed out the front fan, pulled the entire exhaust system off, including the O2 housing, changed the oil and filter. Did some port matching in critical places (3 hours of hard work), added the new sponsors decals to the trailer and car, then crawled into the shower on all 4's.

 

Lookin' Sweet.. Trailer has all the right names on it!! Nice!!

 

car and trailer look great...