MAT Sensor Relocate

[CharlesBrown]

Did a search on this and didn't find much detail. Maybe because it's too easy, which it is! The wire attached to the old sensor located under the rear of the intake manifold is easy to pop off. Plug in the new wire supplied with the kit (Mid. Amer. Mtrs). Drill a hole (7/8") in the inlet air intake (instructions indicate where) Reroute the wire and plug in the new (supplied) sensor and you’re all done... almost! A good thing to do at this point is remove the entire inlet filter housing and clean (blow) it out. To be sure, there will be shavings there from the aforementioned hole-drilling. Now you find out about the Mickey Mouse attachment used to hold the housing at its top...just ahead of the mass-air-sensor housing. Two carriage bolts in sheet metal slots. Could this be done any cheaper? As you get one tight the other comes loose and the reverse. Loads of fun there. If you have done this little relocating and found an answer to the carriage bolt issue I'd like to hear from you.

 

[boomdriver]

lol...it gets better yet.

The air filter box mounting bolts that you're describing and thier cheesy little metal tabs that twist around inside the top of the shroud DO tend to piss ya off as they turn and come loose and you don;t know it until you;ve screwed the bolt all the way down...
J&B weld fixed that. Got the tabs in place after having made the little detent bigger so it would grab something and set them in JB.

next, the air filter lid has the 2 similar bolts on each end on L-98 motors, and something similar later yrs, and those eventually crack around the bottom so that tightening just makes the crack bigger and the lid looser. I closed the crack and expoxied inside, removed the bolts, ground the excess material from the sides of the filter box and searched for 2 black rubber stretch cords that fit exactly from one bolt hole to the other with a fair amount of tension on the lid to hold it on the filter box. I then cut and shaped the hooks on the end so they fit better, and secured the whole assembly in place. My lid is opened and the edges ground smooth so the rubber straps do not get cut. It does not look bad at all, and keeps the lid on pretty tight. It helps to have the K&N filter with a good rubber seal. I used to have a so called "cold-air" induction on there that was a PITA, and required cutting of the old shroud top but after seeing that cold-air is a complete falacy I returned to the semi-stock filter box and its flawed mounts. The severe loss of cooling airflow thru the radiator was another reason to go back... Once the issue of the cheap mounting hardware was resolved, its good as new. Oh yeah, the spring clamps on the MAF cracked their mounts as well, so that got the hacksaw and the MAF and ducts are all silicone tubing secured with real hose clamps. Very solid arrangement with enough flex in the silicone tubing to handle engine torque.

 

[TedC]

Yep and yep. Happened on my both my 1988 and 1989. Used a screw driver to prevent the metal tab from turning. What a pain. Problem solved by riveting the metal tab down after I could see what was going on.

 

[aklim]

What again is the point of relocating the MAT sensor?

 

[LT4man]

You end up picking up cooler air (denser air mixture) to be read by the sensor.

Cooler air should be better compared to the hotter air at the position of the original sensor.

Cooler = denser = more power!

 

[boomdriver]

The "theory" is that the stock MAT sensor gets effected by the outside air temp in its stock location. MAT is one of several inputs that help determine fuel/air ratio and optimum for performance is slightly richer than the minimum for good emissions....So, moving the MAT to the airbox gets it away from the direct engine heat and allows it to exist in an ambient-temp world.
While doing some research on this I stumbled on some other interesting electronic control mods that can be done. One is a simple devise that sends an upgraded signal from the o2 sensor by way of an adjustment, and a little box that adds or subtracts volts that are essentially what the ECM sees from the o2 sensor. It can be adjusted for full lean or full rich depending on what you;re doing that day. It was a radio-shack build it yourself kinda deal, so I never got much past the drawings...but it seemed possible.

 

[aklim]

IIRC, and this has been forever, the stock location for the MAT is in the manifold itself. I know my current one with the HSR sits in the manifold. That means, it gets the air temp off the air just as it is about to hit the cylinders. Is that inaccurate at that point?

Now, lets say that it is inaccurate. What is the difference if you did a dyno tune where that was taken into account.

 

[89blackvette]

my thoughts on this. It is not worth the trouble and cost to reloacte the sensor. I have worked on motorcycles for years and have tested this on a Suzuki Hayabusa with dyno run before and after. It just did not cause ANY rise in Hp or torque. Just another pie in the sky that does nothing.
Mike

 

[TedC]

GM wanted the MAT sensor to be an integrated part of the engine for assembly line testing purposes. So the priority was assembly line priorities not preferred location. I tried the MAT relocation kit on my 1988 and it did make a small difference in responsiveness during hot soak conditions (long idle at red lights). I did not find any WOT advantages and did not install one on my 1989.

 

[CharlesBrown]

What again is the point of relocating the MAT sensor?

It seemed like the thing to do at the time.

 

[Rex S]

my thoughts on this. It is not worth the trouble and cost to reloacte the sensor. I have worked on motorcycles for years and have tested this on a Suzuki Hayabusa with dyno run before and after. It just did not cause ANY rise in Hp or torque. Just another pie in the sky that does nothing.
Mike

I have to agree. Both sensors are in place in my 90 ZR1 and while at Texas Mile last year I switched back and forth between them and found no difference in speed. Car actually turned best run with the stock locatiion used but only by 1 mph and there are to many variables to consider this a fact. One of those deals that sound good on paper and may work great on a dyno but in the real world ????

 

[Hib Halverson]

In most applications, just relocating the IAT (that's "intake air temperature") sensor makes little or no difference in performance if the testing is done properly.

 

[UNCLEBILL]

In most applications, just relocating the IAT (that's "intake air temperature") sensor makes little or no difference in performance if the testing is done properly.

I have a 1990 Vert. I put in the Bosch III injectors. Was running a 141 BLM. Put my AFPR back on and adjusted from 44# to 50# psi in stages and got it down to 133 BLM. I have speed density and found relocating the MAT sensor would cause a rich condition. Tried it out and got a 127 BLM. I am going to fine tune the AFPR and I will get the 128 BLM. These are my results on a "speed density" L98 only. MAF Vettes may not see these results as the MAF can adjust more easily.

 

[WhalePirot]

What again is the point of relocating the MAT sensor?

Money.. for the kit seller?

As Bill said in techno-speak, the ECM fine-tunes to optimize A/F ratio as measured by the O2 sensor(s). Aged components, variations in them and faulty inputs will throw it off, but block learn (BLM) will try to get back to optimum. S/D has less authority in that regard than MAF.

Upping the FP (greater amount of fuel) will cause shorter pulses and vice versa, as the ECM down-adjusts for the 'proper' amount of fuel injected for a given amount of air. Some tuners express theories about improved spray patterns, or not.

I felt silly installing (more $$) an AFPR, then setting it to stock setting, as my tuner advised.

 

[Superc63]

I May Try It

I may try it just because I don't want to take apart my intake to install a new sensor.

I'm considering making my own extension wires and just buying the sensor from Autozone for 20 bucks though. I figure if I tuck the sensor someplace down by the battery it will get an accurate enough reading.

 

[mseven]

The purpose of the mat sensor in the 90-91 cars is to monitor cylinder temp/pressure. The idea was that through the use of the sensor, fuelings changes can be made based on airflow and temp. (using add-on tables in the prom). Relocating the sensor does not have the effect some would think in closed loop operation, unless you re-do the tables to compensate for the lower temps that the mat will now be "seeing".

 

[aklim]

I may try it just because I don't want to take apart my intake to install a new sensor.

I'm considering making my own extension wires and just buying the sensor from Autozone for 20 bucks though. I figure if I tuck the sensor someplace down by the battery it will get an accurate enough reading.

Accurate reading of what? The air temp around the battery?

 

[aklim]

The purpose of the mat sensor in the 90-91 cars is to monitor cylinder temp/pressure. The idea was that through the use of the sensor, fuelings changes can be made based on airflow and temp. (using add-on tables in the prom). Relocating the sensor does not have the effect some would think in closed loop operation, unless you re-do the tables to compensate for the lower temps that the mat will now be "seeing".

I thought it is to monitor the temp of the air coming into the cylinders? The pressure in the manifold should be done by the MAP sensor, shouldn't it? With that, and the TPS, the ECM will compute how much air is coming in, right?

If you want the ECM to "see" cold air, why not stick it all the way into an Strawberry Daiquiri or the AC box? What is the point of feeding the ECM false data? Why not feed it the right data and have it fixed in the ECM program to enrich the fuel curves?

 

[mseven]

I thought it is to monitor the temp of the air coming into the cylinders? The pressure in the manifold should be done by the MAP sensor, shouldn't it? With that, and the TPS, the ECM will compute how much air is coming in, right?

yes it monitors air temp, and airflow, to supposedly aid in the product ofcombustion. The look-up tables include: inverse airflow (grs. per sec) and temp.
The system is complex and if we rule out the other 50 or so add-on tables, ultimately fueling air calculations begin with the input of the 02 and ends with a correction to the final calculated PW.
Aside from the map being key, the cylinder volume input aids in the effective volume used in sd calculation. Ve tables then actually become scalers (used as look-up tables). Since there is no such thing as "ve sensor" and cylinder filling is of a function of load, which becomes inferred through a map sensor.
When using look-up tables, the cylinder volume, TPS % vs. map/load (through vac.)vs ve. tables vs. coolant vs. temp. vs IAC vs timing etc.etc. work together to achieve fuel air calculations. Aside from the map being the source used (vac.) for all load related functions it is also used for a baro input.

If you want the ECM to "see" cold air, why not stick it all the way into an Strawberry Daiquiri or the AC box? What is the point of feeding the ECM false data? Why not feed it the right data and have it fixed in the ECM program to enrich the fuel curves?

lol....
that is exactly what I meant by "not seeing the effects that some think". Actually if one has to relocate it due to aftermarket intake, those tables will need to be re-done. Based then on ambient temps, the fueling will not be accurate for normal driving wot etc.
If one wants to get the max out of their current configuration, tuning is the answer not tricking sensors.

 

[mseven]

Accurate reading of what? The air temp around the battery?

lol..

I think that many would like to find an easier way to gain some extra ponies....unfortunately it takes real parts to make power.