Measuring heatsoak vs actual AIT?
 

I was at the track on the weekend doing some datalogging and saw some AIT's of 180odd fahrenheit. I really wonder if this is accurate.

On the dyno I dont see these numbers so I want to know how to accurately test AIT and eliminate heatsoak. The sensors are in stainless or alloy tubes right before the throttle. Regular GM sensors.

Can I dangle a sensor in the pipe or something to eliminate any chance of heatsoak? Run a hose over the pipe?

Pls help me get accurate AIT data.

Thanks,
Dann

Run a thermocouple into the intake and compare?

So how can this be done @>20psi, 7500rpm?

Dann

A really tight fitting rubber plug with a tiny hole for the wire. Cram the plug in as tight as you can, then trust it a few times, so the tube cuts into it and holds on.

180°F. Your IC is broken.





I'm going to say this for the 10,000th time: STOP PUTTING AIT SENSORS RIGHT BEFORE THE TB SO YOUR HOT ASS RADIATOR *RADIATES* +200°F OF FURY ALL OVER THEM.

seriously, if I could enforce it, I'd make it illegal and fine/jail all offenders on this site.


move your AIT bung to your IC endtank.



But, with that being said, if this is while driving, I'd trust the readings. So long as you have airflow over the sensor element, it's going to report back fairly actual temps. Sounds like your IC is severely undersized/poorly designed for your application.

The throttle body intake elbow houses the IAT sensor and its right behind the 210* radiator.

Dann

Just go to an electronics store and do what you say and wire it to the ecu and go racing?

Dann

N/A miatas can see well over 190-200°F intake temps

This is why someone invented this thing called a cold-air intake, to source air outside the hot-ass engine bay.

Its turbo. It has an intercooler.

How do I test?

If your set on not moving it, then yeah. Put a harbor freight cheapo multimeter with a thermo couple and a rubber plug. It's 20 psi, not 120.

30 bucks worth of science equipment.

Maybe it's a top mount intercooler.

Is this, or is there, an industry standard way to do this?

Best idea so far, it was all I could think of also.

Dann

https://www.miataturbo.net/attachmen...ine=1458044949

Certainly not an industry standard, I'm sure. But this is how I measured the air temp output on an air compressor. In this case, I had a steel pipe. Drilled a hole in the plug, dangle the probe wire in the airstream (don't touch the pipe wall) RTV, and done. This didn't leak at 120 psi.

Champion, thanks.

Dann

Mazdaspeed 3/6 style ;)

Really though, is 180F not feasible for a heat soaked intercooler, on track @ 20psi?

I feel like that could be possible especially if ambient temp is 80-90 outside.

Or still would that just implicate a crappy intercooler?

It was 95f, 22psi.

I can't answer any of your questions but id like to.

Test your sensor. I run a GM open element sensor. On mine, I can have the car running at idle, and heat the end of the sensor with a heat gun and it doesn't change the readings. Because the element is measuring the air temp in the pipe, not the body of the sensor. I keep my sensor close to the intake manifold since heat soak doesn't affect it much. When the ait sensor is showing say, 30*F over ambient, I can grab the IC pipe and yeap, it's warm. Put it on the highway and both drop close to ambient.

Just test and see if heat soak changes the readings.

So heat the whole sensor, then remove the heat gun and see if.it registers atmospheric?

Sounds like an easy and good test.

Try it. On my car I used a heat gun, AIT sensor, and infared temp gun on a black pipe.

With the SC, if I let it heatsoak at idle, the AITs dropped if stomped it and went into boost, as there was a rush of cool air from the intercooler that cooled everything down. AIT sensor would show this, and infared temp gun/hand test confirmed it too.

It's feasible, ez, go slap on a MSM IC.

but if those temps are accurate, I think it's time to look into a more efficient core/system for that particular setup. I wouldn't be quite happy with a core that can get so heatsoaked that it loses that much cooling efficiency.

Vlad,

That's great and all and does look like a super efficient intercooler setup. But just going by the picture, that looks like it could have just been a simple 1-2-3 gear pull on a nice cooler 78f day.

Put that car on the track for a 20 minutes session and then the results would be more applicable.

Last time I measured my IAT at the track, I got it up to 160f @ 14psi and it was also probably 90f ambient air temp. Temp sensor end of my larger crappy ebay intercooler.

This was at AutoClub Speedway where there's a front straight you can go full throttle for probably 10 seconds in 5th or 6th gear. That builds a lot of heat in every system (turbo, coolant, oil, etc). My IAT was highest consistently at the end of this straight.

At the time I had my oil cooler in front of my intercooler and have since moved it.

Didn't get around to logging last time I was out, but I'm sure it's better.

I'll find more relevant logs, but IMO the post IC AIT's should not be hovering at 180+ with a proper (non-ebay) core and sufficient (properly ducted) airflow.

But I'm no trackday bro so I'm not 100% sure what is normal on track. Just sharing data

We need @Savington in here with Theseus logs.

he had a precision core with decent ducting so yeah

Theseus ran max IATs of maybe 30*F over ambient doing 20 minutes of 4-5-6 pulls in 100*F weather. I doubt your IATs are actually 180*F.

I'm with Braineack, though. Putting your IAT sensor in the coldside pipe behind the radiator is an awful idea and I don't understand why anyone does it. Move it to the coldside IC endtank where it belongs.

:dealwithit:

:bigtu:

Got that same intercooler headed my way.

I've asked before, but will you post a datalog showing this?

I think I still have a datalog of Splitime's 1/4 drag pull.

as he goes through the gears his AITs get cooler than when he started.

That's not possible (the air getting colder when you go in boost). That would mean his intercooler is over 100% effective.

But I've seen this before on my car. Heat soak raised the temps of my air going into the intake manifold at low speed (charge pipe between intercooler and intake manifold heat soaked bad) so AITs dropped when going into boost. This is why I run my AIT sensor close to the intake manifold, so it actually measures the temperature of the air going into the engine. :idea: Sticking it in the intercooler exit tells you the air temp exiting the intercooler, sure.

well it just means his ait was a little hot in staging.

iirc his ait was screwed into his IM.


here's one:

Sure, just as soon as you dyno your car.

:laugh: well played

:rofl:

Its a slow corner big straight track with an average speed of 80mph and a top speed of 150 in this particular car.

It really sounds like the right place for iat sensor is in the inlet manifold.

The end tank location is to prevent heatsoak?

Comments?

end tank is best for everything

Do you want to know the air temp coming out of the intercooler? If so, absolutely put sensor in end tank of intercooler to measure that.

Moving a sensor does not actually prevent the charge pipes/intake manifold from heat soak. That's going to happen no matter where the sensor is.

The sensor location will change what temperature you measure (air temp pre-turbo, post turbo, air temp exiting intercooler, air temp exiting charge pipe, air temp in intake manifold plenum, etc).

If the sensor body temperature skews the air temp sensor's reading, then you need a better sensor since it's not doing its job (measuring the air temp it's designed to measure).

Test sensor, if heat soaking the body does not change its reading at the element, the sensor is good. Place it wherever you want to measure air temperature.

May I please have a more detailed answer Vlad.

;)

I don't have easy access to them, or else I would. I've changed hard drives and computers a few times since then. I have posted the raw data copied straight from the logs before on the forum, though (here) so hopefully that satisfies your curiousity.

This is engineering myopia at its finest, dude. Why bother measuring the IATs in the plenum when they have to travel down the runner? Why bother measuring in the runner when the air has to pass through the port and past the smoking hot valve? Where do you draw the line?

The coldside IC endtank is easy to install, on the correct side of the heat exchanger, and highly resistant to heatsoaking. It's fine, certainly accurate enough for 99% of applications.

I'd argue it more, but I have to go install an IAT sensor in a prototype intercooler. :party:

:yippee:

Uh....

The further the sensor is from the valve, the more error there will be. Putting the sensor as close as possible will reduce the error the most. Common sense. You measure EGTs close to the exhaust valves, coolant temps close to the water outlet on the engine, oil temps close to the sump, all for the same reasons. To get an accurate measurement.

Your "argument" is that putting the sensor by the intercooler is accurate enough, same BS you accuse me of for "where to draw the line" regarding accuracy.

The whole point of having an AIT sensor is to do fuel and timing corrections based on the temperature of the air going into the engine, not the air exiting the intercooler. Two different things, two different temps, and your entire argument is to ignore it and call it accurate enough.

For anyone that's ever had a lean or rich hot restart after a brief shutdown, you've experienced what a change in air temps do to fueling when the temperature correction is not accurate.

Pat, your heat soak test only determines if the heatsoaking is occuring because of the metal that the sensor is screwed into is heating up.

What if the sensor element is heatsoaking, it may be the same temp as the air around it, but what if it isn't responding fast enough when a bunch of cold air is sucked in when restarting.

Id say, then its a crap sensor.

1.8L engine = 1.8L of air ingested per engine cycle (RPM/2) @100%VE

850rpm idle = 425 engine cycles per minute, or 7 cycles per second.

Assume 40% VE at idle, the engine ingests 5 liters of air per second at idle.

Let's guesstimate 2L total volume for the intake manifold. 2.5" OD pipe with a .080" wall thickness (standard IC pipe IME) has a volume of ~71cc per inch, with about 2ft of piping between the intercooler and the throttle body, so let's call that another 1.7L. IOW, the entire volume of air between my IAT location and yours is ~3.7L of air, or approximately the volume of air ingested in 3/4 of a second.

So yes, my argument is that it doesn't matter. :party:

You're looking at this wrong.

Consider the following two errors:

1: The change in temperature of the air (in a running engine) from the time it exits the intercooler to the time it enters the intake plenum having traveled about two feet at high velocity and encountered relatively little surface error, vs.

2: The error induced into a temperature sensor by being screwed into a hot piece of metal located behind the radiator vs. being screwed into a roughly ambient piece of metal located in front of the radiator.


Sadly, an AIT sensor does not measure the temperature of the air it's exposed to. It adds in a bias based on the temperature of the case of the sensor, and that error is far greater under most conditions than the change in the temperature of the air as it travels two feet at 50+ feet per second.

In the intercooler it takes a LOT less time than that to change the temp by 100f.

Who knows how much the valves and inlet tract can change the temp, especially considering the much greater Delta T.

Great, so you can definitely confirm that heat soak in the sensor body affects output of the sensor significantly?

Dann

Yes, I can confirm this definitely, for any commonly used OEM-type sensor. (eg: your J-type thermocouple mounted into a hollowed-out ceramic plug with aerogel used as the sealing agent doesn't count.)

So, the tubing you use to connect your intercooler to your intake manifold is filled with tightly-packed fins and has an equally large, finned external surface area?

No offense, but that's a pretty stupid design. You'll have much better results using smooth-bore tubing, and better yet if the tubing is plastic or silicone, which conducts heat less efficiently than aluminum.

Come on man, argue my point, not some absurdity. The valves are hundreds and hundreds of degrees and literally no one here has data on the heating effect they have on the inlet air temperature.

Thankyou for your info re: GM sensors.

Dann

Sure, but the intercooler is literally designed to transfer as much heat as possible. A round aluminum tube isn't. The difference in actual air-metal contact between the two is probably an order of magnitude.

And the delta T in an intercooler is <200* not >500*. Additionally the inlet air sits swirling around behind the hot valve for 3/4 of the time the engine is running. Im just saying that we dont know, and your maths example doesnt disprove this.

I can post up logs of the gm iat screwed into the cast iron manifold of a FFS supercharger pretty much sitting at 200f no matter what kinda driving the car did.

Ironically this same FFS I sold to Pat :likecat:

But who cares about any of my experiences. Let's talk about more theory :)

What's your point? I don't even know what your argument is.

This. No air temp sensor can measure air temperature accurately if it is heat soaked by something other than the air it's supposed to be measuring.


At wide open throttle, like you say the high velocity/high mass flow will result in the temps being practically the same.

Regarding the error you say the AIT sensor base temp affects the measurement, my testing showed otherwise on my setup.

At cruise/idle/not moving/etc, they will be different as the volumetric flow through the pipe is much lower.

I've measured this before, when the car had a SC on it. Intercooler stayed about 5-10*F over ambient at idle/cruise/highway cruise. Air temps near the throttle body changed depending on vehicle speed. At idle the engine bay heat soaked and AITs entering the engine were higher than what exited the intercooler due to heat from the engine bay entering the charge pipe.

A very good example of this is when I warm up the car, shutdown the car, let it sit for 15 minutes, and then restart the car. The engine bay heat soaks and the air temp entering the engine is typically 50*F+ over ambient easy. Why? Because EVERYTHING heat soaked when I shut it down. That is, everything, including the air in the pipe. It doesn't magically drop to ambient in 1 second as suggested, this thing called heat transfer happens.

AIT mounted near the intercooler reported a much lower temperature than what was actually going into the engine, resulting in a rich condition at startup. AIT near the throttle reported a higher value, and AFRs much closer to target.

Not hard to test if anyone is curious, it's just installing a second AIT sensor.

umm, I'm almost afraid to ask what your air density comps look like if the car is rich on hot restart with a heatsoaked sensor.

cause like 95% of turbo miata's on this site have to battle hot restart lean-ness.

also how would you mount the ait near the tb without heatsoaking it? we've had a whole thread about this before