BaldEagel

Pe

I have just got my MVVS 45 Mag out of moth balls, as the nice weather is supposed to be comming and put another gallon through it, and I can't blieve the results, on a CHP Pro series 22x8 I am getting 8300rpm far too noisy for anyone but impressive never the less, I have a UC clearance problem on the Comp Edge but will try again with a 22x10 Mejzlik, maybe a 22x12 would be better, I will report back the results.

Incidently the revs where confirmed on three different Taho's, what a wonderfull little engine this is.

Mike

DarZeelon

Mike,


WOW, I'd say!

What exhaust do you have installed on it?

pe reivers

Hi Mike,
Very good results I say! This little engine also handles a 24x10 at 6000!
for better ground clearance, put on a 20x10x3 prop

BaldEagel

Dar

I have an MTW 75 on a purpose built manifold by Mr Pe Reivers, it has a tight bend from the exhaust outlet to miss a cowl fixing and then a double bend to bring it back into the center of the fus, I have obviously just hit on the right lengths ect.

Pe

Obviously I will have to calm this down a bit with a bigger prop, but it has a big cowl, so the 20x10x3 would not work as well, I think the only alternative is to change clubs and see if I can find one with a smooth patch so that I can use a 23x12, will let you know how I get on.

Mike

DarZeelon

Quote:

ORIGINAL: BaldEagel

Obviously I will have to calm this down a bit with a bigger prop, but it has a big cowl, so the 20x10x3 would not work as well...

Mike,


Some fully cowled radial engine planes such as the '30s GeeBees, can often fly very well with a prop that is smaller in diameter than the outer cowl.
With most glow planes spinning props that are much smaller than scale, this is hardly an irregularity.

Most cowl are somewhat tapered-in at the front and if the prop blades protrude about 1" from that smaller diameter, it will fly!


I am quite sure that cowl is not 20" in diameter...


I did think Pé surely had something to do with the performance of this engine...

BaldEagel

Dar

Yes I know the Gee Bee's work with a prop that is only just bigger than the cowl, but they look so dam stupid, On the Edge the cowl is at its widest at the front, what I do have is a 22x10x3 which I may put on just to see what the engine pulls with it, could be interesting.

Notwithstanding Pe's involvement I like to think that I had something to do with it as well, I did twiddle the knobs and tighten the bolts myself.

Mike

pe reivers

I never touched the needles!

DarZeelon

Quote:

ORIGINAL: pe reivers

I never touched the needles!

No, you didn't, Pé...

...But you did make that 'purpose built manifold' for the MTW 75 exhaust on that engine...

BaldEagel

A couple of more runs today:

Using a Mejzlik 22x10 I had 7,500 rpm
Using a JXF 23x10 I was getting 6900 rpm

Just goes to prove that what most engine manufacturers do by giving HP ratings with very small props can give a missleading impresion, nevertheless these figures are very impressive for a 45cc engine. The JXP prop is a cheepy so I may well fly that to see how it goes, perhaps get some bigger wheels and see if I can get a 24x10 on, I just happen to have one undrilled sitting on the bench.

Mike

pe reivers

ballpark for most 45cc gassers and 22x8 is 7000+ rpm, so you seem to be doing rather well.
What is said about prop vs cowl size is correct. As long as the prop tips are of larger diameter than the cowl, thust does not seem to suffer, due to the very favorable aerodynamics of the prop wash around a round cowl.

BaldEagel

Pe

The only thing I have done thoughout is follow your advice on tuning and manifold lengths ect, I think the running in aspect is quite important as well as using the right oil (Mobil 2T synthetic motorcycle oil)

Small props and big cowls just don't look right to me, I just can't bring myself to do it to one of my planes, asthetics count in my book.

Thanks for all your help in the past Pe and hopefully in the future as well, I am going to try a 24x10 on this engine to see what results I get.

Mike

pe reivers

I hope you keep us posted?

BaldEagel

I certainly will.

Mike

EDIT: unfortunatly its been horrid weather here so have not had the plane out to try again, I will ASAP.

BaldEagel

Short break in the weather so I put the 24x10 on and found the engine was bogging down at WOT, so a little needle twidling and got it up to 6250rpm, but the engine did not sound happy, richened it up a bit and it settled down to a happy 6175 rpm, the only problem was the pick up was a lot slower, so not very usable except perhaps in a large scale warbird or some such.

To verify my previous results I put the 22x8 back on without touching the needles again and got a reliable 7800rpm still rich, the transition from mid range and low was very good, so I have left it at that and will try it in the air, in reality its to noisy, so this will not be my normal set up.

Mike

pe reivers

Mike,
The larger the prop load on the engine, the smaller the power to spare for accelerating the now heavier prop. So throttle response will be sluggish. Your engine is very powerful. With a 24x10 mejzlik, 6100 is the ballpark. Try the 23x10 first. It seems like the prop to use and if light, will accelerate well.

k_jitsu

Dear colleages:
Sorry for braking in your post, but I'm impressed with the numbers your giving. I have two MVVS45 that run perfectly, but I can't even dream with such rpm. I'm using Mobil 1 from the beginning and MTW75. Both engines are the softer and smoothest I have ever seen, progressive and reliable, but the top end is fine, but not as bright as I would like. My readings are 6.200 rpm on a Mezjlik 23x8.

You wrote about "right lengths" ... Please, could you tell me which is that length? Probably there is something I can change there ...

Thank you in advance.
Javier

BaldEagel

From the manilfold flange too the cannister face measured on the c/l of the manifold mine is 270mm.

Hope that helps
Mike

k_jitsu

Thank you, Mike.

Last weekend I did some test. The engine I have on the Com Arf Extra 2.12 is performing very well. I got 6,600 rpm on 23x8. The problem is in the one I have in the QQ yak 54. I will verify the lenght today, but I'm sure it is shorter than yours. Probably, the problem is there. I'll report my results.

Thanks again.
Regards,
Javier

k_jitsu

Hi again:

Well, the lenght was 25 cm. I modified it to 27 and test again. No change. Same rpm. What I have seen is that the compresion in this engine is quite lower than in the other one. Do you think that a ring replacement could help?

Thaks

BaldEagel

Any compresion loss would effect the performance of the engine, investigate the compresion loss to find the reason why, it may not be the ring, loose spark plug perhaps, if you have the engine out or can see inside the exhaust outlet have a look at the inside of the cylinder and the piston for any obvious marks, which could be caused by a broken ring. Let us know what you find.

Mike

octanehuffer

Just an update on my 45 GX2. I got my plane out for the first start of the year for an upcomming IMAC meet. Has not been started or touched since last fall, early November. It fired on the second flip. Ran it through a couple of sequences without touching needles. Ran 1 gallon through it tonight. After I flip until it pops, it will fire and stay running on the next flip. I only choke it for the first start of the day. Every start tonight, I bump the prop back and forth between the compression, and set the piston to BDC. So the ignition wont cause a backfire in the chamber(thank you for the tip Pe') Flip the ignition switch on(again without fear of an embarrasing pop), and give the prop a flip. Starts on the first flip every time. I really like this engine! My pipe is 10mm longer than baldeagles but I swing a carbon 22x10 to 6900. Allowing the plane to hover at 1/2 throttle. Last year after break in I ran 100:1 Amsoil with good results and this year I am running a different Amsoil to 50:1. Just for added insurance. Amsoil reccommends the 50:1 for my application.
Adam

k_jitsu

My new piston ring have just arrived. I'll keep you informed.

k_jitsu

Problem solved. Once the new priston ring was installed and the engine running-in, the compression was the same as in the other engine. Fliying performance are now similar in both engines, Rpm's are 6.500 on Mezjlik 23x8 The engine has about 3 h working with the new ring, still on the rich side and using 4% of oil. I think it's quite good and it will improve in the next days.

BaldEagel

Its nice when what you thought was wrong turns out to be correct, brings back your faith in yourself, especially if you have just dumb thumbed your favorite plane.

Mike

pe reivers

Sorry to hear that Mike. I hope the ship is repairable?
PS your ignition should arrive any moment now. Will send you mail.