Is relocating the MAT sensor really worth it? :confused:

 

Well, you may as well just do it, it's cheap if you do it yourself Don't spend $30 bux for the real kit, you can make it look just as good for around $3. There won't be any gains in power, but you may as well just do it cause everyone else is :D

 

C490Vette,

I do not know the actaul gains that can be obtained by this mod, however I feel that they can only be positive results. On my L98 I wanted to perform the same mod for one reason; the upper plenum got darn hot. Since the whole sensor case is all metal and it threads into the upper plennum, the plunnum heats up the sensor pretty good, and reading the air to be warmer than it actaully is. How much does it effect performance? Don't know. That was just my reasoning for the mod, to obtain more accurate air temp readings.

A cooler reading will help perforamce. I this case it happens to be a cooler reading by relocating the MAT sensor away from the heat source for more accurate readings.

LT1's have the Air Temp Sensor in the air duct to the throttle body, away from any heat sources for what I beleive is a truer reading.

Good Luck,
Victor

 

Now before anyone cooks me this is just my opinion. I think there is a huge increase in transient performance. I say this because by moving in your measuring the temp in the stack and not the preheat of the throttle body. The ecm calculates injector duty cycle pulse rate by the air temp coming in. Some say that the stock location is ok but I tend to disagree do to convection heating radiated by the captured heat of the throttle body from the block and manifold adding heat to the sensor. Just by its name MANIFOLD AIR TEMPERTURE not THROTTLE BODY TEMPERATURE sensor says that as close to the air intake would be best. Again I'm not say you'll have 20 HP, use a sticker for that :spam . But when you step on it the response time of the car seems to be "more responsive" because the injector duty cycle is calculated for the right air/fuel ratio and delivery of a higher fuel dump into the cylinders from an "enrichment" curve of colder air MAT readings from the sensor.
Again this is my experience and only an opinion. Others may chime in

Kitt

 

I feel it was worth it. Like 89 bowtie stated, the plenum area gets hotter than ambient air temp, and that is the temp the computer uses to calculate fuel/air mixture. I noticed more throttle response, especially down low, where our L98's are at their best. It can have the same effect as the throttle body bypass - cooler air means more HP. It also can enhance the effect of future mods. The little bolt-ons can add up, and this will help IMO and experiences. Real easy to do, also. Good luck!! :seeya :steering: :cheers:

 

Man, good question! I've swung 360 degrees on this one after moving the sensor back-and-forth several times. In the final analysis, I saw no hard evidence (i.e, E.T.s) to suppor moving the sensor under WOT conditions.

Argument FOR: "Tricks" the ECU into thinking the air is colder than it really is, so more fuel is added. You will only see a performance benefit if your car was running lean at WOT prior to the switch. I think far more cars run on the rich-side rather than lean.

Argument AGAINST: With the sensor relocated to the air box, when starting a hot motor your car's ECU does not realize how hot the air has become from hot soak, so your car runs much, much too rich for the first few minutes. I saw this problem manifested much more so with the Haltech ECU than the GM ECU. Say what you want about the GM ECU, I happen to think it's pretty darn good.

Here's my take: It is irrelevant what temperature the air is way out there at the front of the car. What your ECU needs to know is the temperature of the air at the point where it is mixed with the fuel. For that to happen, it makes sense to position the sensor where the General put it.

Please don't flame me if you disagree, realize this is just one of many opinions!

 

Hi Bill,
You brought up some good points that made me think.....especially about the hot engine restart.

On another note, One thing I was never too certain about is wheather or not the ECM compensates for the heat soaked temp sensor with any type of change to values. I highly doubt it, however, it was a thought. I am certain the reading the sensor is providing to the ecm is off due to the heat transfer into the plenum and sensor body. How much off I do not know...

However, it is interesting that the LT1's have the sensor relocated the tb duct and the updated sensor with plastic body rather than metal.

Hmmmm...
Victor

 

I dont like it, why would you want to fool the computer? its not like youre going to get 5-10HP out of this.

 

I agree 100% with ELEVENS, and that is why I have never bothered to do this mod, even though I have spent thousands on other mods. It just doesnt make sense! Trying to trick the car into running richer????? I think GM engineers are pretty smart guys, if you are pretty much stock, dont fool yourself with these free mods. The only one that works is the frisbee removal and the K&N open lid.

The best not so free mod is to gut your cats!

 

The LS1s also have the MAT sensor before the TB. There must be sufficient reason for it to be moved there. :seeya

 

GM could probably put the MAT in the glovebox, and with some ECU programming make it work. But move it out of there without touching the ECU calibration is when you begin to have issues.

Cheers!

 

I considered this mod but my concern is one that has not yet been mentioned and that is detonation. If the ECM thinks the air is cooler than it really is, wouldn't it bump up the timing curve causing detonation followed by spark retard? If this happens, you definitely wouldn't see a performance gain.


[Modified by vetracer, 10:41 PM 1/30/2003]

 

As was already mentioned, the ECM is programmed for the MAT to be located there. The L-98 are not programmed, so trying to fool the ECM can have adverse effects, unless you reprogram it. Regardless, this mod is USELESS and if anyone has proof to back-up anything other than SOTP, which we all know is misleading, please present evidence as Exhibit A!

 

Oh fudge. You guys are making good sense and I just recently re-relocated my IAT sensor lower down into the cold air stream for my Forced Air kit. :crazy: :)


[Modified by Red 90 L98 Coupe, 7:48 PM 1/31/2003]

 

Not that I am a proponent of the MAT relocate because I did it, I'm just tossing out ideas. Here's one. Does the Throttle body bypass not lower the air temp with no ECM augmentation? Agreed, the Mat location at the back of the plenum may give more precise air/fuel mix at the point of mixture, yet the drop in temp may not be that great. With this mod it seems even small drops in temp, like re-routing coolant away from the TB, have a positive effect based on track times. I have this mod also, like many of us, and it seems tried and true. How different is it compared to moving the MAT?
I have an 85, and according to the hot rod article that dealt with timing and track runs FOR AN 85 ONLY, with the ECM bumping up timing then retarding, it retards to 2* then goes up. I have mine set at 2*, where the article stated that because of this corrective effect 0-2* will improve track times, which it did for them. So, if you found out where the bottom baseline timing is when your year ECM corrects improper detonation, that may overcome too much retard based on false MAT readings. I hope that made sense.
Also, what about the issue of temp and pressure, as through Boyle's law they are related. With the BLM trying to attain the perfect mixture of air/fuel for 14.7 lbs/in, it can be seen that our barometric pressure varies with temp, and even though the point of air/fuel mix is a "closed system" to some degree, pressure is still a factor. They list air pressure on time slips. So what if the relocation helped to correct the difference between actual air temp and pressure, versus air heated by engine/plenum heat, while the pressure is different based on ambient air temp? Is this possible? :seeya

 

I also did the TB bypass, although I know it did nothing for my performance, I saw value in removing the extra bit of plumbing, and heat in the TB.

Take it from someone who has done all the freebies, and then spent some money on real mods..........
The freebies are just a fun way to get introduced into modding your Vette, you wont do any damage, and you may get a little SOTP or maybe a tenth or two in the right conditions and with your driving improving.

Great subject matter for the Forum, and a great way to get introduced into modding your Vette, the Forum community and such, but for performance that really works - THERE IS NO FREE LUNCH!!!!!

SPEED is directly proportional to $$$$$$$$$$ no big secret.

 

:iagree: Well said, Gus :cheers: :seeya