Wings Forum

Wes · Posted: Fri Mar 14, 2008 4:12 pm Post subject: Rotax Air Filter

ALL,
Just looking for experience on Air Filters for the Rotax.
Since it looks like I won't be using the Rotax intake box, cause it won't fit!
The filters I see on most installations are the cone shaped K&N (don't know the P/N) and the clearance between the fire wall is pretty tight, at least on the left side.
When I ordered the firewall foreward package form Just, they sent the K&N filters (P/N SP-2706) shown in the photo that are a whole lot shorter than the cone shaped ones. It would seem these flatter filters would be better (more firewall clearance). They called and said they sent me the wrong filters, but right now I don't see the problem with them.
Anybody have any objections?

Wes
Kit #95

082 · Joined: 16 Feb 2008 Posts: 7 Location: wisconsin

Wes,
No objections but I can share some insight on sizing K&N's (and other filters).
On all carbureted normally aspirated engines, there is a "stand off" of fuel mixed air that occurs just outside air intake to the carb. This stand off is approximately the same distance away from the carb as the diameter of the carb opening. If you interrupt this stand off it disrupts the air flow thru the carb, reduces flow, and bottom line eats HP. Due to this event the filter should stand off the carb at least the diameter of the carb intake. On many installations clearance makes this impossible. One of the many compromises we make building these machines.
FWIW,
Dan 082

DaveU · Joined: 16 Aug 2006 Posts: 165

The one in the photo probably won't clear the oil tank if you mount it on the firewall behind the engine.

Dave

scubarider2 · Joined: 28 Jan 2008 Posts: 227 Location: Cleveland, GA

Dave is right. The oil tank will not fit where "most" install it which is in the middle on the firewall. I would suggest getting the two cone shaped filters. I am sure Just will send them to you. Worth the wait.
Dennis

Wes · Posted: Sun Mar 16, 2008 1:36 pm Post subject: Filters

OK,
I did some more mockup stuff and as shown in the pics, the clearances from filters looks OK.
I did Dave's measure of 7 1/8 from the left carb lip to an imaginary firewall and it looks tight, but do-able.
I also checked the carb inlet diameter(~ 1 3/4 in) and there is about 2 in of open area inside these flat filters.
So right now I don't see a problem.

How do you like my Tupperware tank mount?

Did everybody build their own tanks mount brackets, or are they available some place?

Thanks,

Wes

Kit #95

DaveU · Joined: 16 Aug 2006 Posts: 165

looking at the overhead view, I do not think it will fit that way. I had to remove the black plastic stator cover and the oil tank then sits just off the bolt under the cover, much closer to the pilot side carb.

If you have a shimmed out mount, or altered the brackets it may work. There was not that much room on my application.

DAve

DaveU · Joined: 16 Aug 2006 Posts: 165

Wes,
I found an overhead shot of the installed parts on my bird. Here it is, and as you can see it is tight.

DAve

Wes · Posted: Sun Mar 16, 2008 5:28 pm Post subject: Oil Tank vs Air Filter Fit

Dave,
Thanks for the photo, that explains a lot.
I new it was going to be a tight fit to get that oil tank back there where I want it.
I need to go ahead and get some of these pieces bolted up on the front of the airplane and
quit agonizing!
Got to get some painting finished first.

Thanks again,

Wes

Gerald V9 · Posted: Sun Mar 16, 2008 5:56 pm Post subject:

Wes,
Something for those going through the rotax installation process. There are old and new oil tanks out there. So when you go to order nipples for your oil tanks make sure to verify wether you need old style (male) or new style (female) AN fittings. It only eats up a few more days when you make the wrong order. The catalogs may not list/indicate the new part numbers.
Good Luck, Gerald V9

Wes · Posted: Sun Mar 16, 2008 8:17 pm Post subject: Oil Tank fitting

Gerald - many Thanks for the tip,
Do you know the Rotax service letter or instruction that spells that out?

Thanks,

Wes

scubarider2 · Joined: 28 Jan 2008 Posts: 227 Location: Cleveland, GA

I did the same thing. I ordered the firewall forward kit and received the WRONG fittings. Luckily, I got the right fittings with the engine. Used them and all is right with the world. 8)

Gerald V9 · Posted: Mon Mar 17, 2008 11:38 pm Post subject:

Wes,
Sorry, but no idea of any service letter or instruction from Rotax. To throw something else out there, my engine doesn't quite look like yours either. My engine was ordered through the boys at Cornell Aeroworks from LEAF and it arrived with fully firesleeved fuel lines to the fuel pump and then to the carbs. The manifold pressure equalizer was detailed somewhat differently. Oil sump and oil pump fittings were the AN style. And the oil resevoir came with no fittings, which lead me down the road to finding out about the "new" oil can.
Good Luck, Gerald V9

Wes · Posted: Sun May 04, 2008 3:20 pm Post subject: Oil Line Fittings

Well, after finally checking into the oil line fittings, I find I have the wrong type! (see pic)
I did some research into Rotax doc's and found the info in SI-912-003, "Oil Line Conections with UNF Threads".
Apparently back in May of 2000, Rotax bowed to the American market and introduced a 3/4-16 UNF flared fitting as an alternate to the standard metric fitting which has the opposite flare (male vs female).
My oil tank was supplied with metric fittings and the oil drain and pump output fittings are both hose barbs. The firewall foreward kit supplied the UNF flare fittings shown.
So, what I think I will do is order the metric elbow fittings that will mate with the oil tank and swap out the hose barbs on the engine for UNF flare fittings that will mate with the FF package supplied fittings. I prefer the flare connections over the hose barb, just because I know I will be taking these things apart and I have fond memories (and the knuckle scars) of removing old hoses from barbed fittings on the boat!
Hope this helps.

Wes
Kit #95 - still spraying