Currently I have the intake air temperature sensor mounted after the turbocharger, so it's measuring hotter air from the turbo than the surrounding abient air. Is this the ideal location for it ? What are the pros and cons of relocating it before the turbo near the filter instead? Maybe you tuner/chip programmers would have some insight on this.

I would keep it where you have it for better computer readings. The computer makes changes to the timing and what not based on this sensor so I would think you'd want it reading actual temps just before the TB.

Although I could be misunderstanding the idea.

My DS1 system had it mounted in the rubber hose between the turbo intake side and the OEM Fiero air cleaner. It worked there for 7 years just fine.

quote Originally posted by LordBoOsT: Currently I have the intake air temperature sensor mounted after the turbocharger, so it's measuring hotter air from the turbo than the surrounding abient air. Is this the ideal location for it ? What are the pros and cons of relocating it before the turbo near the filter instead? Maybe you tuner/chip programmers would have some insight on this.

yes, this is where you want it. the closer to the throttle body, the better. the ECM doesnt really care what the air temp outside is, it needs to know the temp of the air entering the engine.

quote Originally posted by Pyrthian: yes, this is where you want it. the closer to the throttle body, the better. the ECM doesnt really care what the air temp outside is, it needs to know the temp of the air entering the engine.

yeah I was just about to type that - the computer needs to know the temp of the air thats in the engine

Then you need to be able to remap your computer to take proper advantage of having the correct information going to the ECM.

quote Originally posted by Will: Then you need to be able to remap your computer to take proper advantage of having the correct information going to the ECM.

Do I need to remap the chip if its before(cold air) or after(hot air) the turbo?

What chip are you using now?

Any turbo app will require remap from the stock program.

Using a chip from Wester's Garage. Where you suggesting that the ECM needs different programming in regards to where the air intake temperature sensor is located? If so, please elaborate.

[This message has been edited by LordBoOsT (edited 07-14-2005).]

The intake air temperature will vary in a very unpredictable (edit to say that it's unpredictable for your application. It's already known what will cause an IAT to go way up or how to keep it low) way when turbocharging, as it would be functions of turbine and compressor size, any intercooling, etc. So while there may be a very steady intake temp before the turbo, it could be wildy fluctuating after being compressed, based on how efficient your turbo is. Right now, your car is probably running too rich to be of any use, as the ECM is reading the IAT to be very low, around ambient air temp, while the air exiting your turbo is nothing close to that, especially if you aren't intercooling. To get the most performance, etc. out of it, you really need to have it retuned.

Nate

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My Web page | The Turbo Super Duty Build.
You know that little voice that says it can't be done? I duct-taped mine's mouth shut and pushed it down a flight of stairs.

[This message has been edited by FastIndyFiero (edited 07-14-2005).]

re-tuned? no. if the chip was done proper, it will not need to be re-tuned. the air temps are actual temp the engine is seeing, and the ECM will adjust the fuel mix correctly based on correct MAP, MAT, TPS & O2 signals.

if you have the MAT before the turbo, the ECM will think you have ambient temp air going thru the intakes. and no way on earth can you correct for this, other than relocating the MAT sensor. also, if you have an intercooler, you want the MAT after that also. the MAT sensor should be right in front of the throttle body. Thats why its the Manifold Air Temprature, not the Outside Air Temprature sensor. This is what the ECM needs to know - the temp of the air going in the manifold.

I appreciate everybody's input but I have to ask...Is the original MAT sensor even capable of measuring the high temps a turbo can put out? I mean the original N/A engine and programming would never of seen such high manifold temperatures so I question if it's even relavent anymore where the sensor is located. Maybe I should take a hairdryer to it and see what values I get. Btw, reason for all this is that I want to use the MAT bung for mounting a water injection nozzle instead.

quote Originally posted by LordBoOsT: I appreciate everybody's input but I have to ask...Is the original MAT sensor even capable of measuring the high temps a turbo can put out? I mean the original N/A engine and programming would never of seen such high manifold temperatures so I question if it's even relavent anymore where the sensor is located. Maybe I should take a hairdryer to it and see what values I get. Btw, reason for all this is that I want to use the MAT bung for mounting a water injection nozzle instead.

I would strongly advise against putting a water injection point upstream of the turbocharger. The water spray tends to errode turbo compressor wheels fairly easily.

[QUOTE]Originally posted by Pyrthian:

re-tuned? no. if the chip was done proper, it will not need to be re-tuned. the air temps are actual temp the engine is seeing, and the ECM will adjust the fuel mix correctly based on correct MAP, MAT, TPS & O2 signals.

QUOTE]Thinking you can use an off-shelf chip on a modified engine is a bit of a misconception. Whereas you could get it close, especially if you informed the person burning the chip of all your mods and he was good at it. If you want it right, the car will have go a dyno with a wideband. Then you can get the A/F and the timming right otherwise you'll likely be leaving HP, drivability, or reliabilty on the shelf. You can get some awesume HP gains on an engine that seems to be right-on by just getting that chip spot-on.

I doubt the values governing the MAT need to be tampered with. The Fiero binary file shows correction values up to 200 degrees Celsius and the turbo Grand Prix up to about 156 degrees celsius which = ~ 312 fareinheit. It's very unlikely that you are reaching temps that high below 10 psi boost especially not with an intercooler. relocating the MAT sensor is the best thing you could have done because now the computer will make more accurate corrections regarding timing retard and base pulse width where as before ahead of the turbo you will have more advance and fuel than you should relative to the actual temperature of the air coming out of the turbo, the added fuel maybe desireable but not the degree of advance that would be reduced as the intake air temperature increases.

I did however notice that the values in the tables are constant througout the temperature span suggesting that one might consider changing the values a little beyond a certain temperature to introduce more reduction as the temperatures reach into the above natural aspiration range since the uniformity suggests to me that GM only incorporated a value that would support the highest temperature the intake is likely to experience naturally aspirated. I could not find the like table in the Syclone code (didn't look very hard) but did find where the MAT temp is tied into timing and it shows a 7 degree retard at wide open throttle around 105 deg C. There is no doubt in my mind that the MAT sensor for the Syclone is placed after the turbo so you can imagine what could happen if the sensor was moved to the inlet side of the turbo where high flow rate intake air is likely to cool it below the actual ambient air temperature and make the error even worse kind of like the wind chill factor, 32 degrees ambient plus wind means an even lower temp being felt.

I did find the MAP sensor instead of the MAT tied into timing retard in the Fiero bin; at 116 deg C, timing is reduced a max of 6 deg. So with these facts given that moving the sensor to the airstream behind the turbo to give a more accurate reading of the temp the intake is actually experiencing wil require no adjustment if compression ratio is stock and you are running no more than about 7 psi on 92-3 octane. Any higher for safety sake maybe an additional 2-3 degrees off the top maybe warranted.

[This message has been edited by Joseph Upson (edited 07-16-2005).]

Oh that's great info thanks, everybody's info/opinions help put things into better perspective but one importamt factor has been overlooked though, the water injection will bring down the air temp coming out from the turbo and I have to agree now that the MAT sensor is in the best location where it is now between the turbo and throttle body but this creates another potential problem. The spray nozzle would have to be located before the MAT so that sensor can accurately read the now cooled air but that would douse the sensor with water and really give it an artificially lower reading, lower even than the ambient air I think and most probably ruin the MAT sensor. So maybe the best comprimise would be to relocate that MAT sensor near the air filter only because of the cooling benifits of water injection.

It's not likely that water will ruin the sensor, but if you are concerned the sensor used on the TPI V8 should work and since it inserts in the upper manifold plenum of the TPI unit it has a metal casing that protects it from any gas that might reach it from reversion. I think it would be safer to put the water injection down stream of the sensor because the water hitting it and evaporating off of it may again give a lower than actual temp reading though probably not by much. If the intake air is a little cooler than what is actually being sensed that will work to your advantage against the risk of detonation.