aerotow1

I am looking for a 20 size engine with rear exhaust, I want to run a pipe and have the engine able to turn some high rpm. Anyone have a suggestion?


Thanks,
Dan

piper_chuck

My Feedback: (12)

K&B made a 3.5cc rear exhaust. It's no longer made, but is frequently available on that "other" auction site.

ZAGNUT

My Feedback: (1)

MVVS might have one? or any of the buggy engines with a long shaft could have a prop hub added and the heat sink chopped off the head.



dave

Rudeboy

Yeah, the MVVS .21 can be assembled as a rear exhaust... Don't know if I could call it HI-PO though, since I haven't tried mine yet.

Rossi used to make a real .21 power house... an absolute racing engine that was capable of extreme rpm and power output... but I don't know if they still make 'em.
You could try these guys: http://www.modellmotorentechnik.de/ They still have it on their site, so I suppose they still have some.
These gems don't come cheap though.

crrcboatz

My Feedback: (34)

Check Nova Rossi. They have several 21 marine motors that you could order an aero head button and finned head for. Hang on though cause you are talking about 2-3hp and over 34000rpms.
They also make an aero side port motor that is right at 2hp and 30000 rpms. I have one I converted to marine and will tell you it is a real strong motor. I believe it will serve your purpose better and there is no need to convert it. Has a nice muffler and sells for about $125 I think. Look at the NOva Rossi site for it.

Regards Curt

bob27s

My Feedback: (19)

.20 size has sorta become a vauge term these days It use to really mean something!

Anyway.... I will assume for a moment you are looking for an aircraft engine.

If you are looking for a rear exhaust engine in the .20-.30 crankcase size (ie, OS25, OS32 size)

Take a look at the [link=http://www.jettengineering.com]JETT BSE-30 or BSE-35 FIRE [/link] varient.

Very difficult to beat for easy of operation, and will produce high RPM as you desire.

Pipe can be provided and tuned to your requirements.

The engine is the same size and appx weight of an OS 32. Same mounting dimensions.

I hope this is helpful.

Bob

ZAGNUT

My Feedback: (1)

and right after your post we get a JETT banner....

bob27s

My Feedback: (19)

really.....? Maybe thats why I never see them!!

Ive gone a day on here without ever seeing one.

Per original post....
BTW....... if you can get a hold of one of the Rossi .21 aero engines....... those were mighty potent, fairly compact in size

aerotow1

Thanks for all the info. Can anyone give me any more info on the Rossi .21 My German is not so good and I would really like to get a hold of a couple of these engines.

thanks,
Dan

huey-pilot

My Feedback: (17)

I have two of the Nova Rossi .21 engines, one is the rear exhaust turbo model that is rated at 2.2 hp at 34,400 rpm. I am very satisfied with these engines. You can purchase these engines from PlanetHobby, http://www.planethobby.com

bob27s

My Feedback: (19)

Yeah, that is actually the one I was thinking about.

The NovaR RX21FR 7 port. Nice engine. Runs well. The RF is the older design, runs quite well too.

The marine version might see 34K rpm, and maybe set up for c/l combat or speed, but you will not likely run it much over 20-22K on an r/c aircraft application, and then only with the correct pipe/carbon prop/aircraft.

Huey, what prop/pipe set up are you running on yours ? What rpm ?

jaka

Hi!
We used these engines in Quarter Midget pylonracing over here in Sweden 15-20years ago running full lenght tuned pipes and 80/20 fuel (no nitro) and the best props were 7x5 carbon fiber or APC props turning around 22000-25000 rpm.
Regards!
Jan K
Sweden

apaloosa

Hi, the itaian made PICCO is a very steardy engine - i have one in hand - it can turn 36000 rpm i advise you to give it a thought .regards

huey-pilot

My Feedback: (17)

My Nova Rossi .21 Turbo turns 26500 static rpm with an APC 7x5 propeller on 15% CoolPower fuel. The engine is on a Diamond Dust that has been checked with radar at 130 mph. The engine unloads in the air and the rpm seems to get a big jump when the airplane picks up speed. I probably need to cut the header a little shorter but the engine runs well with this set-up and I don't think my nerves could handle any more speed.

Rudeboy

I think you need a bigger prop instead of cutting the header....
If you already need speed to get on the pipe, then cutting it is only going to make things worse!

I've flown the DD on an APC 8x8 sport prop... it was good, but borderline... for more speed I needed either more prop or more RPM (read more engine)... but certainly not LESS prop...

The bigger engine is coming

rfenster

My Feedback: (49)

I have experience with both the K&b 3.5 and the Novarossi (side exhaust) 09/20c. The Novarossi is a stronger engine but also heavier. I could not get a 10 sized shrike to balance (even with a AA battery pack all the way in the back) with the NR. The K&B is lighter and I can get 16.2K on a MA 8x6 on a tuned pipe and 10% Omega fuel. Considering my lack of patience with tuning a tuned pipe you could probably get more RPM. Using the stock muffler I get 14.7K on the MA 8X6 and 19.3K on a MA 8x3.
I vaguely remember the NR bettering the K&b by about a 1000 rpm. I had one in a HOB Mustang and it seemed to like a 7x6W prop. It was a good engine (heavy) but I didnt really have a use for it after I sold the Mustang.
FWIW I own 4 of the K&B 3.5's. One is on a Sig Wonder. One that is about worn out (where the rpm numbers listed earlier came from) is on a PBF, One is destined for a Shrike (Hopefully one that will not fold its wings again) and I will find a use for the other one. The 21 sized speed planes Hobby Barn is selling looks promising.
Its a shame K&B doesnt make the 3.5 in an aero version any more. I really do like this engine. Maybe you can get some useful info from this post

Rudeboy

Now that you mention it... the 20c in 09/20c stands for Club 20... that's a racing class we fly over here... and the good engines are turning the 7x6W way up there... but you really need the horsepower to turn that prop up to where it works. (that's 20+K rpm)
I've seen a couple of guys messing with the 09/20c and it wasn't too impressive. Perhaps on a full tuned pipe it would do better, but on the Irvine "Magic Muffler", it doesn't. I think this thing is geared to much towards high RPM-small props to be useful on a standard .21 size plane.

The high end Nova engine is probably much more suited for HI/PO stuff...

rfenster

My Feedback: (49)

If I remember right I was getting close to 20K on the pipe with a 7x6. However that number could be a little higher if tuned by someone who had more patience than me. I liked the NR engine but considering weight and performance the K&b is a much better fit for what I fly. The NR liked high RPM's but to get it up to the 25K range you would have to put such a small prop on it that the thrust would almost be non existent.

piper_chuck

My Feedback: (12)

I've just started getting my K&B ready for a shrike 10. I'm using 15% Omega fuel. On the bench it's turning an 8x7 MAS at 15,600 with just a header. When I added the pipe the RPMs went up to 16,350. I've still got more tuning to do, but it seems to be a decent start.
Yes, it is a shame that K&B doesn't make the aero version. I wonder if we could create enough interest to convince them to do a run? Should be easy since it's so similar to the engine on the outboard. I've only got 3 of these engines, but 2 of them are actually outboards. And yes, I got some useful info from your post. I'm hoping to finish my Shrike in the next few weeks. I'm trying to determine the best prop size.

rfenster

My Feedback: (49)

Chuck, here are some more numbers for you for the K&B:
APC 7-6W 17.2K
APC 6.5-6.5 21.5K

According to your numbers, I need to tune a little.

These were taken using 15% cool power at 15ft ASL and all with a pipe. I flew my Wonder with the 7-6W prop and it still had plenty of thrust to be tossed in the air. I was playing around with the 6.5-6.5 and this engine really turned up the RPM's with this prop. I have not tried to fly it yet with the 6.5-6.5. Hopefully the wind will be calm this Saturday and I can give it a shot.

I found some numbers that I recorded with the Novarossi. This was before the engine was fully broken in and using the stock muffler. All the props are APC
7-6W 17.5K
7-7 14.5 K
7-8 14K
8-6 14.14 K
8-5 16.2 K
8-10 (for kicks and giggles) 9K


I only flew my Shrike with an 8-6 MA on the K&B. It was plenty fast (although I think I have now been bitten by the speed bug and nothing seems fast enough) and I didn't experiment with any props. I do remember that when ever I hand launched the Shrike I could expect about a 75 to 90 degree left turn with it before it had enough airspeed for the vertical stabs to function. I assume it was engine torque pulling it left. I don't experience this with the Wonder.
Oh and by the way, I am using a K&B black carb instead of the Perry carb. I will put a Perry carb back on and see if the numbers are any better. With the K&B carb the word idle is non existent. It doesn't really matter because I fly it wide open from the time it leaves my hand until I dead stick it.
And I also have wondered why K&B stopped making the aero version of the 3.5. A quick trip over to the auction site shows that there is still a demand for these engines.
Rob