6G Celicas Forums

Hey guys,
Since I have a Gen III in my st204 w/o a GTFour body kit I've been watching my intake temps carefully. (Autronic brand IAT is mounted as close to the engine as I can get it without it being directly above the engine). When I first finished building the engine for the car I still had the insulation on the hood and had a semi covered enclosure for the air filter. The hottest my air intake would get was 80C (crazy!) and that was sitting in traffic with no airflow over my I/C (front mount). Then driving it was around 65C. At night driving it would go down to 60C.

After pondering what to do and talking with some drifting friends, I ended up raising up the rear of my hood 4mm, which isn't even noticeable, removing the weather stripping. And also removing the insulation from the hood and making a full enclosure around the airfilter out of plastic and Plexiglas . NOW my air temps are 60C on a hot day sitting in traffic with no air flow over the I/C, and 45C moving on the freeway on a hot day. At night on the freeway it is 40C.

relevant intake info(shortened from above): big fmic (air/air), and Autronic brand IAT mounted two feet from TB inlet, not directly above engine. Numbers below are before and after a full air filter enclosure and raised rear of hood 4mm.

-------------------------Before-------After
hot day in traffic------80C---------60C
hot day on hwy-------65C---------45C
night on hwy----------60C---------40C

(80c is 176f, 65c is 149f, 60c is 140f, 45c is 113f, 40c is 104f)

So now that I've mentioned my numbers, I would like to know what your numbers are. I'm expecting it to be cooler once I get the hood vents. I would like to know what the norm is for this engine. Also please mention if you have the fmic or tmic

This post has been edited by match220: Aug 3, 2013 - 5:13 PM

my temps are getting up around 40-50c and its winter here im not liking it at all, so im changing to front mount to try and get rid of this heat soak

i can tell 40c is bad heat soak because the turbo only makes tutu on high boost setting, usually it tutu on low boost too when intake manifold temp lower than 30c

Yeah, and I have rigged my radiator fans to be on all the time because I don't have any ventilation on this engine. It still runs hotter than I would like it to run even with the fans on all the time. And my air intake temp suffers because of this. A friend of mine has an extra GTFour bumper that I'm trading him some car parts for, but I really need the hood to vent some heat out. I may raise up the rear of my hood more for now just to release heat from the engine bay.

yes the vent could have alot to do with it, i have mine mostly blocked off as i dont want water to build up in my manifold.

its strange you get such high temps even with a front mount .. its almost discouraging, i was thinking my w2a was responsible for my heat soak as in once the water gets hot theres it just takes so long to cool down again

what about your water T? my stock sensor is reading 84c around town and not going back to 82

I believe it is due to not having ventilation. I have a pretty large front mount, but with the front mount I only have the small opening in the stock st204 bumper. So the large i/c is only getting a small amount of airflow over it. I also want to put a water sprayer on my i/c and set the Autronic to trigger it when I go over a certain air temp. Between putting a GTFour bumper and hood on the car, and adding the sprayer to the i/c, I should see the temps drop considerably. Once I add the bumper and a sprayer I'll try to remember to update this thread with the info.



My normal water temp is around 90C, and that is reading straight from the Bosch sensor that is recommended for the Autronic. It fluctuates around that.

You should pretty much ignore any intake air temps at idle or slow traffic. Thats not really the true air temperature, its just the air temp sensor getting heat soaked.

In my car I see temps around 10-15F higher than ambient temp. So if its 80F out, Ill have an AIT of about 95. The highest I have seen was 150F, and thats after turning the car off on a hot day and letting it sit for 10 mins. Once I fire the car up and idle it for 3min, the temps drop right back down. This is with a 29x9x6 front mount IC.

Even though most of those extreme temps are just heatsoak, it IS a good idea to fix the problem, as the ECU is programmed to retard a fair bit of ignition timing when the AITs rise.

Yeah, I'm not too concerned with the temp sitting in traffic, and the Autronic is very good about retarding based on air temp, and that is also customizable. It is the moving the running air temp down. I do have heatwrap that I can put on the intake piping, but that would make it ugly I think. After I put a sprayer on the i/c, I'll see what the temps are and then still plan on getting the GTFour bumper/hood.

How are you measuring your air temp? Do you have a standalone also?

Yes, I'm running on Megasquirt. IAT sensor is mounted on my intercooler pipe, and I also have a gt4 hood/bumper, so that might have a lot to do with the lower temps I'm seeing.

I'm curious to see what the temp difference will be when I finally have a hood and bumper on. A friend of mine has the full GTFour body kit on his car, he says the hood is aluminum. Is it really? I'm sure that helps with the engine staying cool as well, since the aluminum is able to transfer heat very well.

This post has been edited by match220: Aug 5, 2013 - 7:43 PM

Yeah its all aluminum and extremely light weight.
What really helps is the huge vent over the exhaust manifold. On a summer day you can see all of the hot air pouring out of there as the car idles.

After realizing how hot this engine gets is a normal engine bay that is sealed, I see why toyota added all of the extras to the ST205, and I don't believe anymore that is for looks like I used to think. Aluminum hood, exhaust vent, bumper vents, and an engine oil cooler. Does anyone know how hot this engine gets in the MR2?

Some people also recommend to actually mount the IAT in the fender, away from the engine bay.
The theory behind this is that inside of the engine bay the sensor is going to get heat soaked and actually read higher than the air flowing through it.

I actually had to fudge my MAT correction table to get mine to display correct a/f ratios in hot weather, due to the temp sensor getting hotter than the air flowing through it.

yeah, I've been trying to avoid heatsoak the best I can while still mounting it close to the inlet. It would definitely throw off calculations and a/f ratio a bit. I would have to have another bung welded on just to experiment. Or I could wrap that section in heatwrap for an ugly solution

You can also fudge the idea gas law curve in your mat temp corrections table. Thats kind of how I did it.
The best way to know if you need to do that is to shut the car off after you were driving, let it sit for 5min so that the mat temp goes up as high as possible, and the restart the car. If your a/f ratio goes really lean right after the restart, then the sensor is heatsoaked and not sending the correct air flow temperature. If thats the case, you'll have to fudge your temp curve.

in the stock setup theres a temp sensor in the air box and a temp sensor in the manifold. most likely the stock ecu uses both

my powerfc plug-in ecu however only has correction table for the manifold temp sensor, the one in the air filter is just for datalogging

manifold is where it needs to be



and yes, everything on the st205 bonnet is functional and all from rally. the little nostril thing is the cambelt cooler, apparently the st165 rally car snapped cambelts from excess heat, hence it first appeared on the ST185RC

I don't think I have the expertise that would trump a team of technicians that have decided to put the air temp sensor in the manifold, that is my disclaimer before I say everything I am about to say. Maybe they can get away with one AIT on the mani since there is a second AIT elsewhere. They could perform a calculation similar to... [airbox AIT + mani AIT / 2 = x]..or instead of averaging the two sensors they may have a percentage of [x] that is used depending on the runtime, RPM, MAP, etc. The ST205 stock ecu may have a separate table specifically for the two sensors and how fuel mixtures are calculated with those two depending on the RPM, MAP, etc., during testing I would imaging that they placed other air temp sensors throughout the systems and deduced that (if airbox AIT is at this temp, mani AIT is at this temp, and RPM or turbospool is at _____, then they can fill out a range of average temps under those conditions. There are a whole range of calculations that can be done with a car that has two sensors under completely different temps and pressures, especially when calculating that info with other sensors. From what I've seen on the GenIII setup, it isn't in the airflow stream on the manifold, it sits off to the side of the airflow. I would think it is more susceptible to heat soak there. With that in mind I would say that the manifold alone (without the airbox AIT) is not the best place for the sensor unless you can add a second sensor and mimic whatever calculation they have that averages the two sensors. It is for that reason that I didn't put it in my manifold and instead chose to put it in the intake tubing. My Autronic doesn't accept two AIT sensors either, so I have selected the best possible place to mount the AIT. Which is not directly above the engine, but as close to the TB inlet that I can get it. I may move it closer to the fender about a foot away from the I/C as someone mentioned above, but that will come when I decide to pay an aluminum welder again and buy another bung to go in my tubing.

Yes, the reason why the stock engine has a second sensor in the air box is to figure out the difference between the two sensors and determine what is heat soak and what is not. With just one sensor in the manifold, your a/f ratio is going to be thrown off due to heat soak unless you tune your compensation curve.

On an aftermarket ems the best place to put it is really in the fender, just after your intecooler. This way you get a general temp of the air rushing by, without the engine bay soaking the sensor to death.

midnight winter run log, just loading up 3rd, 4th, 5th gear to 6000rpm / 1.30bar

s358.photobucket.com/user/nzcelica/media/345boost_zps4dc14ae9.mp4.html



This post has been edited by delusionz: Aug 7, 2013 - 1:58 PM

how hard would it be to start an "engine management" sub-section on the forums here? I can see how this topic would go under forced induction, but if we had an engine management section it would be a great way to have a lot of consolidated information similar to what we've been discussing here.