I've gotten conflicting advice as to whether you can increase air flow by replacing a stock air cleaner with a larger SE air cleaner when you have stock mufflers on a 2012 touring bike (Road King FLHR). One mechanic told me that replacing the stock air cleaner with an SE cleaner would increase air flow and keep the engine running cooler, even with stock mufflers still on the bike. Another told me that the back pressure from stock mufflers would not allow any extra air to pass through the engine simply by replacing the stock cleaner with a SE cleaner. In other words, the air that gets limited going out, limits what's going in. Who's right? Thanks.

 

They're both right, a little.

The air flowing thru will increase slightly with a free flowing air cleaner, but no where near what it could with free flowing exhaust and a free flowing air cleaner.

If anyone tells you differently, you can show them this chart.

The blue lines are a bone stock 2012, the red lines are of a true free flowing Outlaw Air Cleaner (not a SE cleaner which feeds hot oily air into the intake).

You can see with just changing the air cleaner it unclogged it a bit.




Here is a chart of the same bike, now with a true free flowing air cleaner, free flowing exhaust and a tune.

You can see it is fully unclogged, with a large increase in Power.

 

@DKcustom........thanks for the charts. I would have loved to have seen just the AC with a tune so the comparison would have been apples to apples.

 

Don't have that, but have the next best thing. Here is the same bike. Stock A/C and stock tune, with just the free flowing pipes.

You can take the two charts and extrapolate the difference the tune made...of course, this will not be 100% accurate because of the synergistic relationship between free flow a/c, exhaust and tune, but it will be close.

Very roughly, the tune was good for about 3 HP and 4 ft. lbs of Torque

 

Judging by the charts you posted it looks to me like just a high flow AC actually adds more than just an exhaust system. Thanks.

 

IIRC the cat is in the collector, so if that was removed, or an aftermarket one installed, with stock mufflers, I suspect the gains will be worthwhile. Retain stock look, a little more noise and a decent amount of extra go! Just a though for an additional option.

 

If you're looking just at the peak numbers-

The Outlaw HiFlow Intake increased

HP by 5.75 HP
Torque by a bit less the 1 ft. lb

The True Dual Exhaust (which is not the best power making exhaust) with the Thunder Torque Inserts increased

HP by 6.5 HP
Torque by 1.4 ft, lbs

A Couple of important disclaimers-

1. This comparison is without a tune, which it really should have
2. More importantly, we don't spend much time riding at the top number...what is more important is the curve between 2000 and 4500 where most riding is done.

Torque is what we feel when twisting the throttle...not HP, so to me it looks like the exhaust with the TTI's gives a better curve and more peak also.

Yes, on the 2012 Touring models the cat is in the header. This can be cut out, or the header replaced. Cutting it out will give a very slight increase in sound volume, and a surprisingly small increase in air flow. But if you replace the headers with a good 2-1-2 header like the Fuel Moto, then there will be a noticeable uptick in power and a bit more sound volume.

 

Thanks Kevin, interesting stuff.