Hey All. I would like to qoute Donny Petersen, from his Techline article "Twin-Cam Performance part III - EFI", AIM, March '06, p. 48:

"....let's look at one way to make the engine run a little cooler:relocating the air temperature sensor away from the fuel injection throttle body.....Confidentially, an H-D mechanic explained that, due to EPA restrictions, the air temperature sensor located in the throttle body would lean out the mixture as air temperature increased. More heat equals the ability to burn a leaner mixture of gas, which has a higher fuel-to-air ratio. Sounds good, except that the condition will start to feed on itself: The mixture is leaned out by the computer as a result of the signals recieved from the air temperature sensor. Now the engine will run hotter, causing the computer to lean out the mixture further because of, again, signals sent by the sensor.
The factory mechanic recommended, and I heartily agree, installing a second air temperature sensor in the back of the air cleaner mounting assembly. Locate it so that the temperature-sending probe is inside the confines of the air cleaner element. Unplug the lead from the stock location air temperature sensor and plug it into the newly installed sensor inside the air cleaner element. Leave the stock sensor in place, as its new function is to plug a hole. The new sensor will now send back cooler signals to the computer, which, in turn, will dictate permission for the fuel mixture to be richer....."

Now, you opinions please.
Any experiance with this mod? is it effective as a (very) cheap alternative to a SERT, Fueler ect..?

 

I don't think that relocating your air temperature sensor is intended to replace an ECU management tool. If you have made mods to your engine, you still need to manage the a/f mixture somehow. What is described merely eliminates one factor that will increase your a/f mixture and create a lean condition that will make you run hotter. This relocation would only help minimize a lean condition due to heat. It will not manage your fuel injection. If you are completely stock and only want your bike to run cooler on a hot day, it will probably work.

 

Sounds like a good idea. Let us know how that turns out. Seriously!
I suspect (I don't KNOW, so this qualifies as an opinion. You asked for opinions, not knowledge that as long as the difference in temps at normal operating temperature between those two locations wouldn't be so great that it would run way rich and require a new dyno tune, that'd be a pretty "cool" mod.
But I've noticed that the breather gets pretty durned hot too (don't ask how I know this), so it may not be a problem.

Your HD mechanic friend doesn't think the HD engineers didn't see that coming and compensated in some other component of the ECM/fuel mixture formula? Not argueing, just asking. I know how the corporate hive mind works (any corporation) and can see them letting it slide to save a few bucks per unit. I see it every day...

 

Oops, sorry dude. I forgot you were quoting Peterson and it's his HD guy that doesn't have faith in the engineers.

 

It makes sense to me too. I'd thought about that because when I had my '96 CE Corvette it was a mod I did to increase performance, and worked well.

I don't know why it wouldn't apply to an FI H-D. You going to try it?

 

Donny Peterson prints many things that are innacurate at times. That aside, the maps are written with the sensor in the intake. When you hang it as he describes, it reads cooler and adds more fuel GLOBALLY. also, when it is cold out it will run VERY rich because ice cold air is on the sensor. There will also be a desparity between what the ecm is seeing on the Engine Temp and the Intake Temp sensors. I would leave it intact and tune properly for your combination.

 

My dad and I also saw this article. He has had a problem with his pinging from when he got it. It is a '99 Ultra, so it has the old fuel managment system which sucks. He took it in to few dealers with no luck. It seemed to be a problem that increased with heat. So we tried moving the sensor about a month ago and it seems to be better, so far no more pinging.

 

This is a common trick with EFI vehicles. Works on some, not on others. I think a lot of it depends on where you ride. Seems to work better on vehicles that get driven in warmer climates.

Like he said, it adds fuel globally. Maybe good, maybe not. It's cheap, give it a try.