I've seen after-market air breather cost as much as $200 to $300, ie; Doherty Twin Cam Power Pacc.

I don't know much about air breathers except that they filter the air that gets sucks into the engine. I'm not talking about the filter element itself, I understand how the filter works. It's the base mounting system that I'm wondering about. Other than being like most of the other accessories that are expensive, is there a high tech un-seen knowledge base that explains why one after-market air breather does a better job that another?

How is a Doherty Twin Cam Power Pacc better or different than the Stage 1 setup I have on my '09 Ultra?

 

Funny, I was going to ask the same question. I'd be interested in an answer too. It shows a big gain in HP but so does fuelmoto at half price.

 

I had the Doherty on my '99 Fat Boy and now on my '10 Ultra and I love it. The backing plate is billet aluminum (that's why it costs so much) and has a radiused venturi that increases the velocity of the air entering the intake manifold. I noticed 'Seat of the Pants' HP increase (no dyno yet). I would do it again and would recommend it to a friend. The breather vents (on the pre TBW) worked great also, but the TBW assembly is in the way so the new models don't have the vents.

 

What are you call the vents? Is that the vents with tubing connect that vent the crankcase to the intake system?

 

Your question is actually about the crankcase venting?
The stock setup uses 2 large bolts (mount bolts at the cylinders) with nipples and hoses that run near the intake opening to "draft" the crankcase pressure from engine.
I had an Arlen Ness Big Sucker setup which used hollow bolts which matched up with the backplate ports which did the same "job" as stock , just a different way.
As long as the venting works properly , that's all that really matters.
All the brands do the same venting , just a different style is all.
The really expensive ones just look nicer , or have a better finish than others.
I just run a K&N stock replacement filter , so all the Harley breather hardware stays stock and it flows and filters a bit better than the stock setup.
The bigger "larger filter" assemblies can flow a bit more air at high rpm's , but that's not where I do my riding at.
The larger setups are a bit noisier because of the back being open so much more.
Hope this clears up the breather end of it a little.
Mick

 

http://dohertymachine.com/product_in...4853545249ae1a

These are the vents I was talking about, because of the TBW they went back to the plastic tube set up (as described above) because these don't fit anymore.

 

I run an S&S tuned induction system & Doherty MystFree - eliminates blowby

 

Check out Wimmer Intakes.