Prop advice needed urgently

[Hot Stuff]

Well done Henni, good for you

[Cloud Warrior]

Hi Henni

Sounds as if you have a new aerie there. I have to admit that the freedom to tinker on my plane is one of the aspects of microlighting that attracted me to the sport.

Please tell me more about the tuned exhaust? I saw an American advert for something similar on a Rotax 583/583 giving a similar power increase and then raised the issue on the forum but was shot down by numerous people who advised me not to tinker with the standard Rotax design.

Apparently your engine life is severely compromised if you fit a tuned exhaust which is fine if you are racing go carts but not good for flying....

Thanks

Sebastian

[Henni]

Hi Cloud Warrior,

All I have for now is:

http://www.paraflite.net/muffler.htm

I'll get the South African tel no. for something similar and will post here. In my opinion, adding a tuned exhaust system would be similar to adding a turbo charger or nitro system, both of the last two being used sucessfully on aircraft applications for a long time already.

Please note that a turbocharged unit cannot be run at full throttle for extended periods without damaging the engine. Exactly the same with a nitro system - exactly the same with tuned exhaust pipes on a 582. If used with the same care, I see no more or less engine danger than a turbo or nitro system.

I do not want to use the extra power continuously, but for take-offs, emergency climbs etc. For all the rest I'll be happy to stick to 60mph at 5800rpm.

These are just my thoughts on such a mod & I'm going to go for it shortly, so we'll see. For extra speed, nothing will work better than reducing some drag, I'm well aware of this fact.

As for props: Someone with actual experience phoned me and warned me to stay away from the Powerfin series. He's had three already with disappointing performance. What does increase performance is the Kiev series or the curled trailing edge versions that Geo Kelly used to make in South Africa. Now, if I can get hold of something like this, I'll definitely go for it.

Keep well,
Henni

[Henni]

Hi everyone,

Just another update on increased Mizer performance for those interested.

I flew alongside Rudi today, all the way at 68mph indicated (on both aircraft) at 6400-6500 rpm, just 7mph short of where I want to cruise at.

After our trip and some discussions with Rudi, I decided to pitch my Ivo prop even more. Set it then for max static 6000rpm on the ground & proceeded to test actual flying performance.

Take-off (one up) suffered only very slightly. Overall climb suffered a bit, but not more than I can live with. However, she now cruises 75mph at 6200rpm, just where I want it. All out speed stayed the same at 85mph indicated, but now at 6500rpm (max I can now get out of her) For those wondering, there is at least 15% throttle travel setting difference between 6200rpm at 75mph and full throttle yielding 6400-6500rpm at 83-85mph.

Time only now will tell what my new fuel consumption will be as the engine now works much harder but at lower rpm settings. However, I can now cruise all day one up at 75mph indicated and should no longer prove to be a drag when flying with any group. (It goes without saying that I will now form part of the April 2008 South Coast outing as Rudi can live with such a slow cruising speed )

Keep well,
Henni

[Duck Rogers]

Please note that a turbocharged unit cannot be run at full throttle for extended periods without damaging the engine. Exactly the same with a nitro system - exactly the same with tuned exhaust pipes on a 582. If used with the same care, I see no more or less engine danger than a turbo or nitro system.

I don't think that statement's right..........what will happen?
In any event, you need to be in the powerband of the pipe to get the extra woema you want. Once you're out of the powerband, you'll have less power than you would have had with the standard Rotax pipe, so....you'll just get back into the powerband and then get back out again for fear of damaging the engine and so on and so on and so on .............. :D
Talk to Aerosan about tuned pipes. He used to race bikes with them on. Even had one on his plane.
For what it's worth....I don't like them and I don't think they're suitable for aircraft use

[Henni]

I don't think that statement's right..........what will happen?

Hi Duck,

I'm no expert on these things bar that I played with and souped up all my car engines (4 stroke only of course) when I was much younger. However, unless I'm overlooking something, both a turbo and tuned pipes put more loads on an engine than what it was designed for. Therefor, in my opinion at least, a tuned pipe will not cause more damage than a turbo to any engine - all it does is make it work harder. (Turbo improving the intake system, tuned pipes improving the outlet system)

But, you are spot on with the power band thing and one will most definitely only be be able to operate within a narrow rpm range effectively for most of the time. Question is, will this drastically shorten the life of the engine - I honestly don't know. If so, then a turbo would have the same effect on an engine. (Yes, I know that if used with care - and this is what I meant previously - it will do nothing more than sustain sea level performance up to a certain altitude) Come to think of it, won't a tuned exhaust system do exactly the same - that is, restoring the power as it should be at sea level? I.o.w, it might be safer and less harmful to an engine at the reef than at the coast. And the higher I fly, the less damaging the effect on the engine would be! I think I've just convinced myself here

I seriously considered exchanging my Rotax 582 for the more powerful Hirth F30 engine. Only thing maybe holding me back is that this 582 is the most reliable microlight engine I've ever owned and & honestly, I am not sure what to expect from the Hirth. But then on the other hand, I'm also unsure what would happen to the 582 should I install tuned pipes.

Alas, with only a few logical & simple changes, I've manage to increase my Mizer's climb & cruise performance from what it used to be when I fetched her to what it is now. I hope that a few other (not so expensive) modifications would improve her even more. If I can fly with the Cheetas, Ran's, Bush Babies etc, I'll be satisfied. I already have much more aeroplane than I ought to have for the money paid, but what's wrong with even more! I think that by giving more attention to the prop and exhaust system, I might just be able to achieve this.

Regards,
Henni

[ZU-CDW - Shark]

Hi Hennie,

I would just like to comment on the modified performance exhausts- yes they do improve the performance and profides a couple of extra horses, but that is a sure way of shortening the life span of the motor.
Chat to Niren from Aviationengines who can give you more info,as per him it is also a no no.
Fly safe
Regards
Jacques

[Henni]

Hi Jacques,

Thank you for your advice - I'll keep it in mind.

Regards,
Henni