I just got lower fairings on my Road King Classic (thread here) and it seems the motor is running cooler.

There is actually more heat on my legs but I think that is because the air behind the lowers is somewhat stagnant, and it may be that more heat is being moved off of the motor than before the lowers were in place.

The real evidence for me though is the EITMS isn't kicking on nearly as much. I live in SoCal and it would kick in at a red light even when the temps were in the 70's. Last week we had a few days where it was in the 90's and it didn't kick in at all.

One of two things is going on. Either the lowers are directing more air directly to the motor and causing the heads to run cooler, or the EITMS coincidentally broke the same day I put the lowers on, which seems highly unlikely.

Has anyone done before and after temperature checks after installing lowers on their bike?

 

I run the vented lowers on my 04 flhtc in cooler weather only,I run the Hd oil cooler that mounts in front of regulator,also run the Hd in fairing oil temp gauge. I would not run the lowers with temps in 80s, I noticed a 30 degree increase in temps at 85 degrees with vents fully open.

 

Its going to restrict the needed air flow, and it will be detrimental in hot weather. I had them with vents and in 95* weather pulling a grade I lost 12 psi in the oil and I have a cooler too. pulled over the oil was like water. changed the oil took them off and never had another issue. Thats been 2 years now. I then sold them, but my advice is dont wse them over about 60*.

 

This is an older thread, but seems to back my theory - vented lowers appear do nothing to increase heat. http://www.*****************/forums/ha...ngine-not.html

If you divide the lower in half, the outside half does nothing good or bad for the motor - air that far away wasn't cooling it anyway.

The inner half is between 2-4 inches from the edge of the cooling fins. That air was doing a lot to cool your legs, but little to nothing for the motor itself. Now all of that air is being forced directly on that first cylinder, and if it runs across the fins, the back cyl gets a benefit as well, which is explaining why my EITMS isn't cutting on. Since you have more air in the same space, you get higher flow as well - just like a jet engine.

Air coming between the forks and right next to the wheel is unaffected - it still runs over the motor.

Logically, I am unable to understand how it could harm airflow and increase heat. But...I could be wrong. I've been wrong before, many many times.

 

I thought there was some data from the MoCo that says vented lowers actually decrease temps. by directing air flow to the engine?? But then again, I could be mistaken!?!

 

that's what I had heard. I read it on the internet. I run mine all the time. Been in 110 deg heat, no problems.

 

If you look closely at the design of a set of factory HD lowers, you can see they have an inside front angled surface. With the bike in forward motion, the design of the lowers actually directs and forces more air into the engine than normally would be because of the front wheel and fender.

I was told by a long time exerience Harley owner/rider that if you were able to measure the wind velocity across the front jug with and without lowers, you would notice a difference.

ehans,
The hotter air blowing on your legs is because there is more air being directed into and across the front jug by the lowers.

 

That, and the fact that where my legs are - right behind the lowers - there is less air flow is exactly what I am thinking.

 

OK, I'm not an engineer but I am a retired aviator and I see the adjustable lowers as an airfoil.

Air is a fluid just like water is. When you move the adjustable vent, it compresses the air that is moving between the lower and the engine heads which, in fact, speeds up the air flowing over those surfaces.

More molecules of air though the compression effect plus the increased air speed running over those heads means more conductive cooling.

Anyway, that's the way I see it.

 

I believe this "lower temp data" was actually developed using lowers without vents but I can't seem to find the actual data. The vented lowers could actually be less effective lowering the engine temps than the non vented ones.

The only thing I'm 100% sure of is taking off your lowers creates an increased air noise that totally covers up the 5th gear noise on the '07-'09 Ultras.

Indisputable experience.