Rotax 582 Exhaust Issues and oil burn

[Johnny Be Good]

Hi all

Yesterday I started my Blue top 582 on my bushbaby for the very first time which was quite a milestone after years of building.

The motor started fine but ran rough with more than what I believe is a normal amount of vibration but it did get better above 2000 rpm. When I shut it down after a couple of minutes I noticed that it was blowing a lot of burnt oil/fuel mixture back past the ball joint on the Y junction where the exhaust manifold joins the elbow. This was then deposited against the side of the motor around the water pump and blown back over the firewall. A lessor amount also "leaked" out at the joint with the silencer. I tried tying some asbestos tape around the ball joint on the manifold and that did reduce the blow back. This leaking past the ball joint must be affecting the performance of the exhaust in terms of it's function to create back pressure which will in turn affect engine performance.

Can anybody give me some advice on the following questions:

I mixed oil into the fuel at 100:1 as per the rotax manual for initial start up as well as setting the auto lube alignment marks correctly. Would this result in excessive oil use to the extent that the exhaust would leak liquid fuel/oil mix or is it a sign of over-priming the engine?

Would the blow back be caused by the exhaust moving excessively because of the vibration of the engine.

What can I do to seal the ball joint more effectively - I believe the springs are installed correctly. I haven't put anti-seize on them at this stage.

Should I continue to run the engine following the normal break-in procedure and see if the vibration sorts itself out after a bit and being run at higher RPM's?

Any advice will be appreciated.

Thanks

Johnny

[Duck Rogers]

Off the top of my head, without consulting any documentation...........the mix is too much at 100:1. Yes I know what Rotax says
The carbs also sound to be out of "sync".
Idling under 2000 rpm is not advisable. Correct rpm for idling is over 2000. In the region of 2200 - 2400 is right.
Those carbs need tuning.
Get those things right and we'll talk again

[Johnny Be Good]

Thanks Duck - I'll have a look at it this weekend and report back.

[Morph]

what oil, typically we use a 50:1 mix, i.e. one 500ml oil per 25 liters of fuel, so you are running very rich

next, post pics of the exhaust/engine installation. have a look at this pic, is it mounted the same?

there should be minimal flexing between the engine and the exhaust. Copper Slip is used on the ball joint.

[Johnny Be Good]

Hi Morph

I have attached a pic below. I can't remember what oil it is offhand (I'm at work) but I bought it from Aviation Engines in Jhb.

The premix as per the Rotax manual for the first tank is at 100 : 1, ie: half (not twice) as much as normal plus whatever the autolube puts out. I'm thinking that I over primed the engine using the primer pump and that probably contributed to the fuel only partially burning and being pumped into the exhaust. Being the first time it had started I was loath to give it a burn above 3000 rpm either.

Have a look at the left side installation. What is your feeling on the fuel pump and hoses sitting above the exhaust outlet and should I fit some sort of protective plate in between? This set up was copied from other BB installations.

[Morph]

Boet is the expert on this particular installation. Let's see if he responds

[Johnny Be Good]

It's a bit like fishing - throw out the bait and see what happens...........

I know that Boet has a lot of experience, particularly with 582's and I value his advice. If he was here in Zim I would have finished the plane a long time ago!

[Boet]

Jip. Here I am!! Sorry, I went walkabout for a while.... Your installation seems ok. You can pull the front part of the baffle plate up though. Just make very sure that all the air coming in the front MUST exit thru the radiator. IE: must cool something down. I will give some of my pics to help clarify. Not the the "venturi-like" lip on the bottom of the cowl. That is very important, as this creates a low pressure area below the engine, helping to get rid of the hot air. Enjoy the pics, and fly safe!!
Boet

[Boet]

Also note that I pulled the silencer up higher, and thus further away from the radiator, lessening the effect of radiated heat towards the water radiator. You must remove the WHOLE rope-starter system. You will not have any use for it in this installation. Ever. Save weight too.

[Johnny Be Good]

Thanks Boet - nice pictures.

I am happy that my cowling seals properly and air will be forced out through the radiator.

Please give us your thoughts on whether I need to put some sort of insulation between the fuel pump assembly and the exhaust to protect it from heat and also in the event of a fuel leak. Secondly, what do you think about the "blow back" of oil / fuel from the join of the elbow to the exhaust manifold (see first post above).

Thanks

Johnny

[Morph]

I would be nervous about that. Additionally once you switch off, the radiated heat from the exhaust will cause the petrol in the pipes to boil and this could cause vapour locks.

I would definately route the fuel away from the exhaust, or add protection to the pipes

[Johnny Be Good]

Ja, I've got a fuel injected Cessna that gives endless sh*t to start once it is hot and has been on the ground after landing. I just copied the installation from other BB's that I have seen pictures of but in retrospect I don't think it is ideal. I need to either move the fuel pump up or put in a plate of some sort.

[Morph]

The 912's have a little bowl that is placed below each carb to catch any overflow. There is then a drain pipe running down from the bottom of the bowl to the firewall and out the bottom to direct the leaking fuel. You don't want any fuel dripping on a hot exhaust. Either do that or move the pump/Fuel filter. It is these joints that are the highest probability of leaks, although I have seen that translucent blue pipe split for no reason whatsoever. Happened to me on a long cross country. Only noticed it when I had landed and parked it in the hangar amonst 4 other very expensive aeries. Saw fuel dripping out underneath the plane. Opened the cowling and it was dripping straight onto the exhaust It was the fastest I have ever emptied a hangar of planes.

I only use the high pressure black fuel injected piping available from most car spares places

[Johnny Be Good]

I also have only used proper fuel hose but the piping for the primer pump doesn't look like it will last too long in a high heat environment. The carbs are not near the exhaust but the fuel pump sits above it. I am going to have to do something about that. Thanks for the input.

[Boet]

I have done a large number of these installations on the 582, and it is a trouble-free system. Never had any petrol related problems, but have completely stopped using that blue pipes. You get it in 2 grades. VERY good, and lasts a long time. Shit grade that starts cracking and breaking off after a while. As the two products are identical, and COST THE SAME PRICE, you never know what you are getting. I have changed to proper black rubber petrol hose. One gets spoiled however, beiing able to SEE the petrol flowing, so all the pipes from the tank, and in the cockpit area is 8mm od semi translucent nylon tubing. When you heat up the end of the nylon tube with a lighter*, it pushes a nice "hose barb" ring. I use short lengths of rubber tube to join the nylon at the petrol taps etc.


* To be done with NO petrol present though.........