Stage I vs. Stage II intake ?? - Harley Forum

Scruffy Pup · #1 03-26-2009, 10:32 AM

Guys,
Got a question for you - what is the difference in a HD Stage I air cleaner backplate as compared to the Stage II backplate? Seems like I read somewhere that the Stage I is recommended for up to 95" and the Stage II is for 96" and above due to increased air flow volume. Are the filters of a different diameter to get this increased volume? If not, will the Stage II filter fit a Stage I backplate? I'm running a stock '07 FLHX Big Twin but am getting ready to install hi-flow muffs, a Cobra fuel management system and of course the new intake. A buddy gave me a Stage I backplate and I'd like to use that to save every nickel I can right now. I know I have to order the bolts and o-rings.

I appreciate your feedback.

tommyglide · #2 03-28-2009, 11:26 AM

Hey Scruffy, what's the part no. for that back plate? I have the Stage 1 plate and filter which increased filter surface area by 30%. Zipper's has a Stage 2 filter that is bigger yet that also fits, which I am going to get, I think it is 2.75 inches deep compared to the Stage 1 at 2.5" and stock at 2". The stock air cleaner cover will still fit if you wanted to re use it.
What mufflers were you thinking of getting?

Scruffy Pup · #3 03-29-2009, 09:21 PM

TG,
Thanks for the response. The backplate p/n is 29478-05A. I was curious if the increase in air flow is due to filter diameter but I see it is due to filter height. I was thinking of going with a round custom cover of some type and I didn't want to run into problems with fit. I based my original question on kits & covers I saw in after-market catalogs (J&P, Custom Chrome, etc.) listing Stage I separate from Stage II.

As far as the muffs, I'm most likely going with Rush w/2 inch baffles (I can change baffles later for a different sound if need be). If not Rush, most likely Rinehart or Cobra.

Are you going to get any riding weather this year? We've had just a couple of decent days here in Kentucky and here it is almost the first of April. Bummer.

Thanks,

03fxst · #4 04-02-2009, 07:20 PM

Hey Tommy
Thanks for those measurements. I'll have to check my SE filter for size and maybe consider that Zippers unit to hide under the stock cover and keep the sleeper look I like. Here's a question though. At what point is intake about the size of the Carb and manifold combo and not the volume of the filter?

03FXST

tommyglide · #5 04-02-2009, 10:34 PM

That is a good question, 03. I made a bit of a boo boo, the SE filter is 2.25 ". As far as when the carb and mani over powers the filter capacity, a Wise Man once said "who knows? Better to increase your odds with as good a flowing filter as possible" or something to that effect. BUT, even if I imagine removing a high flow filter and running the engine at wot, I can imagine it getting a way more air than with the filter in place. Not very scientific I know, but such are the air flow measurement tools I have.

evoKENevo · #6 04-03-2009, 09:17 AM

Scruffy...check out Woods Performance. They offer a variety of K&N filters made to their specifications that should fit the backing plate you've got.

Scruffy Pup · #7 04-03-2009, 11:54 AM

tommyglide and Ken,
Thanks for the enlightenment. I guess I've been looking at too many aftermarket catalogs and trying to compare apples to oranges.