# Geo Metro 3 Cyl - A Good Engine??

### Help Support HomeBuiltAirplanes.com:

#### Vigilant1

##### Well-Known Member
The difference between the 3 cylinder and the 4 cylinder for vibration and smoothness is night and day, and the ChangAn is now sitting in my factory.
Thanks for the report. Did you get a chance to compare 'em at the RPM in which we'd expect to run them in an aircraft (about 4500 to 6000 RPM)? Same thing? I'd expected the 3 cyl to be more shaky than the 4, just due to the fewer torque pulses and the inherent rocking couple of an inline triple that an inline 4 doesn't have.

The "pros" of the AM10 for many folks will be the very good HP/lb, the very good HP/$(especially since the elevated thrust line of the AM10 PSRU will allow users to avoid the higher costs of the laid-down inline versions). Good BSFC too, compared to an air cooled alternative. More vibe is maybe the price for that. I suppose Mark K has looked at using a similar offset PSRU to raise the thrust line on the AM13 and AM15 rather than lay the engine down (which increases the price by$2000). The offset PSRU of the AM10 is rated for 120 HP, so big enough to handle the baseline output of the AM13 (100 hp) or the AM15 (117 hp).

#### Vigilant1

##### Well-Known Member
Nope.

An aircraft-unrelated project.

The guy who designed the engine bay used to work in a sardine tinning factory ...

View attachment 97798
Ridiculous. It makes my back hurt just to look at it.
Seems that mechanics could all pitch in and hire some rough blokes to pay a visit to the designers of such things. Nothing violent, of course...

#### cheapracer

##### Well-Known Member
Log Member
Thanks for the report. Did you get a chance to compare 'em at the RPM in which we'd expect to run them in an aircraft (about 4500 to 6000 RPM)? Same thing?
Same thing. The 3 is course all the way, it's like hopping into a limo with the 4 cylinder.

It wasn't the only 3 cyl I drove the other day, I tested a QQ 1.0 6 valve and a 1.0 12 valve as well. I have driven a number of older Suzuki Altos also (0.8 3 cyl) previously.

I know Aeromomentum blueprints and balances their engines, that can make a decent difference, but they blueprint and balance their 4 cylinders as well, so a step up, but status quo.

Shame the older Daihatsu 1.0 3 cyl is so heavy, as it has balance shafts. The short motor alone is 50 kgs.

#### don january

##### Well-Known Member
Log Member
I've been following along and the question still comes up in my mind on what air frame this engine will be pulling or pushing around the air? OP wonders if this engine is any good? I have to say it depends if you take it upstairs and you get it back on the ground with your own input's. One thing that comes to my mind is how will an all wood aircraft hold up against high vibrations from the power plant? Real hard to make a guess without knowing just what mission it is up against. IMO

#### rv7charlie

##### Well-Known Member
No idea on whether you can get replacement parts for the Raven drive, but they seem to be quality parts. I knew a guy years ago in FL that had a 2 seat trike, used to tow hang gliders. He replaced a Rotax 582 with the 3 cyl Raven (I don't think it even had the turbo option), and said that it outperformed the 582 by quite a bit. Both my wife and myself got back-seat rides at SNF, and it had no problem getting 2 people off the ground and up to pattern altitude quickly. He was very happy with his Raven engine package back then.

None of that may apply to your particular project; the turbo, manifolding, etc cautions are valid and we don't know the airframe, so no idea on whether the engine HP/drive ratio/etc are appropriate for the airframe.

Charlie

#### robertl

##### Well-Known Member
I have seen the 4 cyl Geo on a Zenith CH-701 and the guy liked it a lot. I think there is a Trike builder in Canada that is still in business and he builds Geo engines. His name starts with a V, and I think he's Russian. That's all I know.
Bob

#### Vigilant1

##### Well-Known Member
I have seen the 4 cyl Geo on a Zenith CH-701 and the guy liked it a lot. I think there is a Trike builder in Canada that is still in business and he builds Geo engines. His name starts with a V, and I think he's Russian. That's all I know.
Bob
Yes, that's Vasilli of Air Trikes. He visits this forum sometimes. His conversions have a good reputation from all I've ever heard. He has worked with many types of engines (Suzuki, BMW motorcycles, many others), fitting them with the SPG PSRUs.

#### billyvray

##### Well-Known Member
He is watching this thread. AirTrikes, post #16...

#### Air Trikes

##### Well-Known Member
Here's something related:

I was driving around in a 1.0 Daihatsu/Toyota/BYD KR1 just 3 days ago, then jumped into a 1.3 ChangAn Suzuki G13BB, both sold by Aeromomentum in their various improved forms.

The difference between the 3 cylinder and the 4 cylinder for vibration and smoothness is night and day, and the ChangAn is now sitting in my factory.
Yes, I agree/ The difference between 3-cyl and 4-cyl is also night and day, that is why I build and sell 4-lyl engines G13BB now

#### Air Trikes

##### Well-Known Member
Yes, that's Vasilli of Air Trikes. He visits this forum sometimes. His conversions have a good reputation from all I've ever heard. He has worked with many types of engines (Suzuki, BMW motorcycles, many others), fitting them with the SPG PSRUs.
Yes guys, it is me. I work with Suzuki G series from 20 century. My experience is enough to build an aircraft with Suzuki G13BB which becomes FAI World champion for 4 last years, and I know at least 2 companies (one from China, another from US using China made engines and gearbox components) "reengineered" our gearbox design. I'm working with G13BB installation on Air Creation Tanarg trike at the moment.

#### mullacharjak

##### Well-Known Member
From all the discussion it seems the G10 is a good engine and the Raven redrive is also ok.Only that it vibrates a little which if you have no other option can be lived with.Now to the airframe if its the size of a Taylorcraft I think this engine will fly it.

#### PagoBay

##### Well-Known Member
Very aware of the requests for air frame details. Please standby.

The comments from Mssrs. Matheny and Simpson at Posts #10 and #11 gave me good reason for pause and reflection. Reliability issues were raised on solid grounds.

The builder has a strong engineering background so I am sure there was ample thought into the engine choice. BUT...I don't yet know the HP of this engine, its history, or its year of manufacture. So I have a number of good questions to ask just about the engine. Generally, I am getting weak on this particular implementation. Otherwise, it is clear that the Suzuki is a very good engine choice.

The air frame is suited for the Rotax 503 and bigger engines up to Rotax 912S/ULS. Does this trigger any additional thoughts or cautions?

#### DanH

##### Member
That's a Metro, not the earlier Sprint, the primary difference being the cylinder head. Suzuki, sold by Chevy dealers with a Geo badge.

Re vibration, as a 120 degree three with no balance shaft, the vibratory block motion can be demonstrated by holding a pencil at the center of the shaft, and wobbling it so the ends describe circles. There are obvious ramifications for the propeller disk.

The core engine is reasonably reliable. IIRC, there were no available undersize rod beaings, so scored journals make the crank a throwaway. I would not want the turbo.

Jeron Smith (Raven) created an interesting system for the redrive, a friction damped soft element enclosed in the upper hub, i..e. a nylon (or similar) slip clutch in parallel with rubber inserts. Never had an opportunity to measure torsional vibration amplitude, but the principle is correct, observation said it worked, and users reported that they were reliable.

Jeron retired three or four years ago. I would not worry about parts for the redrive. It's simple; should be able to source or fabricate any of it.

The funky welded intake manifold does not look like Jeron's work.

#### aeromomentum

##### Well-Known Member
The older gearbox that was being sold by Airtrikes that was made in Poland was great and if I could still have gotten them I would never have engineered my own original design gearbox. The later Russian made gearbox currently being sold by Airtrikes is also good. When we made our all new design CNC billet case gearbox we of course looked at a bunch of other gearbox designs including those made in Russia, Poland, New Zealand, USA, etc and those made by Rotax. Research is the first part of designing. Most of the 2 spur gear gearboxes are very similar in basic concept. Most have a cast cases. The devil is in the details and the engineering. Our gearbox was engineered to both be lighter and stronger than the others that we researched. We build the gearbox here in Stuart, FL and the gears are made in a factory that makes gears for some top automotive companies. Some customers have succesfully used our gearbox on engines over 225hp but the weight is only 16 lbs.

#### Air Trikes

##### Well-Known Member
I have never sold anything made in Poland I know, AirTrikes 160 (AT-160) can be successfully used with more powerful than 160 HP engines. The questions are duration and reliability. Marketing numbers and strategy is your choice. I prefer to be conservative in everything related with aviation. I build and test my aircraft by myself. If you were flying your creations, you probably would change your vision a little.

Another point, HP is not always the most critical thing for the gearbox reliability and choice. For example 2-cylinder 115 HP BMW boxer is able to kill the gearbox easier than 180 HP Subaru. I estimate many things (for example ratio, prop and flywheel moments of inertia etc.) before advising one or another gearbox. I hope you know this as well as me.

#### jedi

##### Well-Known Member
I note in the OP "Located in SW USA desert country ". I have some knowledge of the area and will comment that who you purchase from can be as important as what you purchase. Buyer beware.

If the equipment is operable and not too remote from Tucson, I may be able to have a look at it.

#### PagoBay

##### Well-Known Member
I asked Topaz to move this entire thread over to the Geo Suzuki Sub Forum. He is probably engaged and has not seen my message. If Mr. Simpson could do that, please? I did not see that sub-forum until a couple of days ago. My apologies. I will start a new thread on the air frame here in Hangar Flying sub forum in next few days. Thanks. This project is located in Phoenix, AZ. As mentioned a bit ago, I am inclined to pass on the purchase. But others may be interested. Please stand by for details.

#### jedi

##### Well-Known Member
I asked Topaz to move this entire thread over to the Geo Suzuki Sub Forum. He is probably engaged and has not seen my message. If Mr. Simpson could do that, please? I did not see that sub-forum until a couple of days ago. My apologies. I will start a new thread on the air frame here in Hangar Flying sub forum in next few days. Thanks. This project is located in Phoenix, AZ. As mentioned a bit ago, I am inclined to pass on the purchase. But others may be interested. Please stand by for details.
Red flag #2.

I agree on the move but would not be following this thread if it were on the Geo Suzuki Sub Forum..
PM me so we can talk about potential bad apples. This is not the place to publicly air my concerns.

#### aeromomentum

##### Well-Known Member
I have never sold anything made in Poland I know, AirTrikes 160 (AT-160) can be successfully used with more powerful than 160 HP engines. The questions are duration and reliability. Marketing numbers and strategy is your choice. I prefer to be conservative in everything related with aviation. I build and test my aircraft by myself. If you were flying your creations, you probably would change your vision a little.

Another point, HP is not always the most critical thing for the gearbox reliability and choice. For example 2-cylinder 115 HP BMW boxer is able to kill the gearbox easier than 180 HP Subaru. I estimate many things (for example ratio, prop and flywheel moments of inertia etc.) before advising one or another gearbox. I hope you know this as well as me.
My mistake. I had been told that the first style gearbox that we were buying from you at one time was made in Poland and even found a website in Poland claiming that they were making them. Maybe they were also just buying them like you but then claiming it was their design. In any case the quality was very good.

I am sure the AT-160 can be used on some engines higher than 160hp. We engineered our gearbox to be 40% stronger than the AT-160. But the real engineering criteria is peak impulse torque as you know. Our gearbox is engineered for 800 ft-lb peak torque impulse with an additional 2:1 factor of safety. We tested it to over 1500 ft-lbs but our test rig broke before we could break the gearbox.

The peak impulse torque on a 2 cylinder engine is about 10 times the rated torque so yes a 2 cylinder engine is harder on a gearbox. The peak impulse torque on a 4 cylinder engine is about 3.7 times the rated torque. The peak impulse torque on an 8 cylinder engine is only about 2 times the rated torque. Plus the moment of inertia of the engine and flywheel has effect on the peak impulse torque the gearbox sees. Our gearbox could be used on an 8 cylinder engine of up to 400hp @5500rpm assuming reasonable moments of inertia, etc. But it is still light weight due to extensive engineering and the stronger, lighter CNC case.

I fly my engines on many aircraft and have one installed and flying on my own CH701. But as someone with a couple of master degrees in engineering this does not change my vision. I calculate the numbers with well established margins of safety and then do extensive testing (both on the ground and in the air) as per the engineering method. Both are needed and both work best together.

#### PagoBay

##### Well-Known Member
KOLB Mark III Project - Phoenix AZ \$8500
AIRFRAME / DETAILS ON MODIFICATIONS / COMPLETE PHOTOS at this link: