daem0n

Seeing the advantages to temperature-accuracy with the AIT being relocated, is this a safe modification on a stock ECU? At least with the PFC if you see it running lean because of the temp changes you can change the maps to run more rich. Any ideas?

Mahjik

iTrader: (1)

There was a huge thread on this a while back.

I'm not sure that relocating the AIT is a good thing. People say that it heatsoaks under the UIM, but what if the temps are really that high in that location? Then you definitely want the sensor there.

I would leave it alone until more information becomes available on this modification.

rynberg

My experience on the dyno last Saturday shows that the stock IAT location SUCKS! Because of heat-soaking, I started leaning out a bit because the PFC was reducing the fuel due to supposedly high intake air temps...not to mention the timing retardation.

I see no advantages to the stock location. If the air heats up a few degrees going through the UIM after the relocated sensor, who cares? The worst case would be that the mixture would be a little on the rich side, which is hardly a problem.....

Just my 2 cents after a frustrating day at the dyno....

Mahjik

iTrader: (1)

I guess my question is, how do you know that the AIT was not reflecting the actual temps of the air in that location?

I've yet to see anyone provide data that says those are not completely accurate in that location. Not that I'm saying the mod is bad, I would just like to see more data to back it up.

rynberg

Hey Mahjik, a couple of weeks ago I posted about getting stuck in a traffic jam. My intake temps went up to 95 C (200 F). I refuse to believe the air entering the engine was actually that temperature. Especially, when it took over 15 minutes for the IAT to drop to 65 C once I got out of the traffic.

If the UIM is not heat-soaked (highway driving), I can boost the hell out of the car and never go above 47 C.

I believe that the air temp will go up slightly as it goes through the UIM but not as much as the difference between a non- and heat-soaked UIM would indicate.

Mahjik

iTrader: (1)

I do agree that there is probably some heaksoak. However, without actually knowing the effect it really has on the air, you may be creating another dangerous condition of the computer thinking the air is cooler than it really is....

I'm just playing devil's advocate here so people can make an informed decision on some of these mods that don't have a lot of data to support them at the moment.

daem0n

hey Mahjik I'm glad you brought up these points because I keep thinking the same things. The only reason I'm in a rush to do this mod is because I'm replacing mine right now anyway. I guess I'll just save the old one in case I decide to do the mod. Has anyone made a UIM made out of something else that would get less heatsoaked? I think the stock location is the best place for the AIT, but the fact that it gets heatsoaked is the problem. I think the question we should try to answer is how do we modify the UIM and that area to be less heat-soaked?

ptrhahn

iTrader: (9)

double post

ptrhahn

iTrader: (9)

I can't see how it would do any damage... all you are doing is relocating it so that it gets a MORE ACCURATE reading of the actual air temp. The innacuracy is due to its direct contact with a large mass of metal that gets hot... the UIM.

Ever notice how it takes quite a while for the intake temps to come down after you've restarted hot when it been sitting a few minutes? Thats cuz it takes that long for the manifold to cool, not the air that was outside just a second ago... I've seen tests performed that show that, off the car, the sensor actually reacts very quickly to change, but you'd never know it to watch it working on the car.

Say you locate a second sensor to the plastic elbow for instance that won't transfer heat as much, theres no way the on rushing air will heat up as much as the difference in readings would likely show in the lousy 10 inches it would travel in a split second between the two... The stock one is more likely giving you a combo of air and UIM temps rather than just charge air temps.

Just my 2 cents.

daem0n

Do you think the stock ECU maps took this into account (the location of the AIT) because it doesn't seem to shorten engine life? I'm wondering if this might only be an advantage to a Power FC or aftermarket ECU. I know the sensor acts slow where it is, but maybe Mazda knew this?

ptrhahn

iTrader: (9)

I guess the answer is, you're relocating because the ACTUAL temps for which the maps are designed are not being read due to the heat soak, and you're car is not running optimally.

Since nobody seems to argue that the car DOESN"T run optimally once the sensor is soaked, i guess we can assume that Mazda DIDN"T allow for it... or it would run right, correct?

Rx-7$4$me

well, what if one took the sensor, and simply relocated it to somewhere else on the manifold via there own tapped area.

Even if the sensor is okay in the stock location, its still a PITA to wait for the ignition timing to revert back to a more normal setting if the damn thing gets soaked ( stock ecu people), and even then, with aftermarket ECUs, It still is heatsoaked, causing stupid annyoing problems, so whats the negatives of moving it?

The air might change a few degree's, however I doubt it will have any impact as people stated before the air is moving so quickly.....

daem0n

Your arguments are good and what I would say too, although aren't we moving the sensor for the benefit of the engine? And if this is the case, then why do stock motors usually last the longest?

Rx-7$4$me

because stock motors tend to not have mods done. More mods=more power= more friction= more wear and tear= less life.

Also depends on driver, area of living, maintinence. IE to many variables.

Why not retap a hole in the UIM outside of it, and get the reading from there. IT would still get the same reading as being on the underside of the manifold, but would be less prone to heat soak

Rx-7$4$me

Im sure most people dont want to do that, so the alternative is as close as possible to the intake ports. But We know that on the UIM a bit above the boost gauge nipple would probably be the best location.

daem0n

yeah good call

On another note, if you do want to relocate the sensor (which I was going to do originally but was worried)...the thread https://www.rx7club.com/forum/showth...ensor+relocate says M10x1.25 for the thread size to be tapped. Is this a pretty common tap and where did you guys find it? I went to home depot but I didn't see anything that matched it exactly. Also, what type of drill bit do you recommend...one good for metals? And one last question - what kind of wires did you use to extend the wiring connection for the sensor and how did you join the new wires to the old ones safely? Thanks, -Joe

Mahjik

iTrader: (1)

That's actually what I was referring to... Having data to see what are the temp differences of the sensor being located in a better position on the UIM verse the elbow.

To my knowledge, I haven't seen anyone do this to show any data (which is what my original post was about). It would be extremely helpful to see real data for a mod like this other than theorizing.

daem0n

yeah that's a good idea too, but the actual sensor is the part that's INSIDE the UIM, so I don't see how that would matter? I know that being on the bottom of the UIM it's a lot hotter, but would that really matter when it's really only the wiring that's there? Data would help a lot, but I don't have a spare UIM to screw around with. If someone did or was willing to give one up it would be some great info to know. Also, regardless I still need help with my original questions above one post...

ptrhahn

iTrader: (9)

The problem, as i understand it, is not the sensor's location under the UIM, but its location ON it. The UIM is a large hunk of metal that gets very hot, and as a large chunk, retains that heat for a long time. The UIM is physically touching the sensor (with a fair amount of surface area with the threads) so it will conduct alot of heat to it.

What you want, is:

A. To attach the sensor to something that will non conduct heat as well (effectively insulating the body of the sensor), i.e: plastic elbow

B. To attach it to something with less mass, that will store less heat, and shed any heat it does store more quickly... even if its still metal... like IC piping... theres alot less mass there.

As far as data, i'm sure there are folks out there with aftermarket air intake temp guages (there are most commonly mounted near the IC outlet) that could now compare those temps with the reading from the PFC.... I do remember a friend used to have one on his PFS IC, and he told me at the time (this was long before we had the PFC to reat the factory sensor) that he rarely saw temps more than 10-20 F degrees above ambient... even on hot days... i wouldn't say the same for mine... more like 1-20 decrees C... on the PFC.

daem0n

Trout2

iTrader: (5)

If you really want to keep it on the UIM a good idea would be to tap the manifold for some kind of plastic or nylon insert that could be then be drilled and tapped to hold the sensor. That way the sensor wouldn't be in contact with the hot metal.

Mine is relocated to the IC outlet pipe and still heat soaks in traffic or when the engine is shut off but quickly recovers once moving. If I did it over, I would use some kind of non-metallic connection point as described above to reduce the heat soaking affect but still relocate the sensor to the IC outlet.

I suspect that more than a few engines were blown after the sensor heat soaked and the driver went wide open throttle before it recovered and was sucking in much cooler air.

Jack

daem0n

Trout2 - that sounds like a good idea about the plastic insert, but wouldn't it melt? Maybe there's a good plastic out there that could stand the heat.

Also, does anyone know about my above questions?

Trout2

iTrader: (5)

I haven't researched it but they make plastic intake manifiolds so I'm sure I could find something to work.

Jack

Mahjik

iTrader: (1)

Are you going to use the stock elbow?

What I would do is remove the AIT from the UIM. Find a drill bit that is "just" small enough to go into the old mount in the UIM. Use that to start drilling into the elbow. Then you should be able to either get the elbow threaded with the AIT or just keep slightly enlarging it until you are there.

If you are using the GReddy elbow, you can use a Helicoil kit which would probably be a better idea there.

Mahjik

iTrader: (1)

BTW, for the wire, you could probably just use some 18-Gauge wire. You should solder the wires together instead of just twisting and using electrical tape.