RPM Rotax 582 limited to 4000?

[Koos Gasman]

I obtained a used Rotax 582 engine ( has run 300 hrs) to replace my old engine that had a seizure.
After rebuilding the engine on the frame of my cosmos trike, it started well and runs smoothly.
The only problem is that it does not get more than about 4000 Rpm.
The engine comes from a zeppelin in germany, where it was only used for propulsion of the airship. They replace these engines when the have run 300 hrs.
I was thinking that there might be a built in limitation in this engine that prevents it from running more than 4000 rpm, because it is not necessary( they don't have to make a lot of speed like we do at take off)
Does any one know if this might be the cause of the low rpm? Could it be in the gearbox in combination with the prop?

Koos

[KFA]

Hi Koos, thats a difficult one to answer if you do not have all the specs. What gearbox do you have on there and the prop size and pitch?

[Koos Gasman]

I do not exactly know yet. From your question I understand that it could be the reason for the low rpm. I will check out which gearbox is on the engine.
If it is an other type than on the old engine, the problem might be solved if i change the gearboxes. To day i am going back to the airfield and find out. I'll let you know.

[Boet]

Eeeee, Mike, met watter soort kar ry jy? .............. n Bloue..............

[Dobbs]

Hi Koos, you don't mention whether you are using the same prop that the engine used on the Zepplin - at wide open throttle, at 4 000 rpm, the engine is producing around 31 HP!

As KFA said, look at the gearbox / prop specs

[Koos Gasman]

Well, I found out that the new gearbox has an other ratio than the original ( 3,47:1 instead of 4,0 :1) which is a difference of about 12.5%.
Could this explain the lower Rpm?
And if so, what would be a wiser thing to do: Change the gearboxes or adjust the propellor angle. I have got a 3 blade prop which is probably an other kind than the one that was used on the zeppelin( I dont know , it is a guess). And if I adjust the angle, I could get more Rpm, but also less trust. Is it just a matter of trial and error to find the right balanced settings?

Update:
I heard from some other experienced pilot that adjusting the prop blades would only make a difference of 200 rpm at the max.
So I think I am going to switch the gearboxes in order to get the same configuration as with the old engine ( unless someones comes up with a very good reason not to.. )

[Dobbs]

Hi Koos, here you need the clever okes

A couple of things to consider - the prop diameter, pitch and tip speed (amongst other things) The bigger the diamater (within reason) the better, but for that you will need a higher ratio gearbox - so you have a number of options
- Contact Rotax for their opinion on what the optimum prop is for the gearbox you have
- Contact the supplier of the prop which you have for your options
- Contact SA's Mr. Propellor Pieter de Necker - always happy to assist with advice and he makes execellent props

Hope this helps

[Koos Gasman]

Hi guys,
Thanks for all the help. Tomorrow we will change the gearboxes, because that makes the most sense now.
i'll let you know the outcome. keep my fingers crossed
Koos

[KFA]

Hi Koos, do not take this personally.
I might be wrong but from your questions and answers I get the feeling that you might not be qualified to do this whole process by yourself. I do not think you need to change the gearbox, rather look at a prop to fit the gearbox you have. This process could cost you a lot of money or even your life.

Find out what type of gearbox is on there. B, C or a E box. That will give us an idea of what prop you need without the need for you to experiment. If I remember correct then the 3.47 is a c or e box.

[Tailspin]

Hi Koos

Ok Here we go.
1.) What gear Box you got on ?
2.) What prop do you have on ?
3.) You need to have the correct prop with the correct Gearbox.
4.) Start to get a AP or an instructor to help you, or get the unit infront of you and then phone PProp.
5.) Do not start making all sorts of changes as it could be one small thing and at the end of the day you are going to have nothing that works as you would have confused the whole line up.

You can call me on 0 8 2 8 9 8 2 1 4 5 Gavin.

[Koos Gasman]

Hi Koos, do not take this personally.
I might be wrong but from your questions and answers I get the feeling that you might not be qualified to do this whole process by yourself. I do not think you need to change the gearbox, rather look at a prop to fit the gearbox you have. This process could cost you a lot of money or even your life.

Find out what type of gearbox is on there. B, C or a E box. That will give us an idea of what prop you need without the need for you to experiment. If I remember correct then the 3.47 is a c or e box.

Not at all, KFA. I am glad with all the reactions. To take your worries away: I am not doiing this al by my self but have the help of qualified guys who will check everything we do.
A new prop is also very costly and the prop we have is a 3 blade Neuform prop in good condition that fits the box we had on the seized engine.
That's why we would rather change the gearboxes than messing with the prop, so the whole configuration is exactly the same as it was before on the old engine. So, as a matter of fact, in the end, we only replace a "short block" and leave evrything else unchanged.
Btw: We checked some other trikes on our airfield with rotax engines and although the gearboxes all look the same from the outside, the have different numbers ( the reduction) like 4.00, 3.47 etc. and of course all different props.

To Gavin: I think we do not confuse the whole lineup in this way, as we only replace the old engine by a working one, that is exactly the same as we had..right?

Koos

[Koos Gasman]

Today we tested the engine with the original gearbox and prop and, like was to be expected, the rpm is much higher now. But now the engine seems to get not enough fuel to reach the 6000 rpm. It runs well untill 4000 rpm. but when excelerating it does not get quick enough in the higher rpm area.It only gets 6000 rpm when we use the choke to add extra fuel.
We cleaned and checked the carburettors and they seem to be OK. Now there is only two different things left on the "new" engine.
1. There is an extra generator built in between the gearbox and the engine, which we don't use.
2. There is an extra "part" between the engine and the carburettors, that was not fit on the old engine. it contains a connection between the 2 inletports( via a little fuelhose, apparently to equal pressure differences between the two inlets?
I don't know if this could effect the lack of rpm when accelerating?

[Duck Rogers]

There is an extra "part" between the engine and the carburettors, that was not fit on the old engine. it contains a connection between the 2 inletports( via a little fuelhose, apparently to equal pressure differences between the two inlets?
I don't know if this could effect the lack of rpm when accelerating?

Nothing to do with equalising pressure. Those fittings on the inlet ports are for the 2 stroke oilpump line connections which you apparently don't use. You can cut that pipe off and block off those 2 inlets if you are using pre-mix. Also has nothing to do with lack of rpm.

Next, if anyone has removed the carburettor intake cover and not replaced the rotary valve plate EXACTLY in the correct position then you have the problem you describe.

And finally, here is a troubleshooting guide for you to look at because there are too many things to mention.

[Koos Gasman]

Thanks again for all the usefull information.
We sadly had to come to the conclusion that the lack of rpm is due to worn pistons and rings.
We now are going to take the engine apart and see if we are right..
Koos

[Koos Gasman]

yes, it was only two stuck pistonrings. Probably because the engine had not been running for over a year. Two new pistongrings and cleaning gave us a well running engine .
Again thanks evrybody foor the advices!
Koos