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Old 10-16-2010, 01:34 PM   #151
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Originally Posted by lil-bump View Post
Well I'm no engine modeler. I can only speak from experience. I have one of those engines with a turbo crank done by the mention person. The engine is a Novarossi 3sct tuned. The engine did not turn out the way I wanted it. It had decent midrange and top end; but the bottom end was non-existant. I tried every type of clutch adjustment known to man and the engine would not get out of it's own way. I'm not sure if it was the mods he done to the sleeve or the crank. I just replaced the piston and sleeve back to stock but I'm not sure If I will have to replace the crank. The engine was pretty much new so I'm slowly piecing it back to normal. I'm not here to bash his work but his mods did not work for me at all. If anybody wants to donate a 3sct crankshaft it would be greatly appreciated

Pass you soon.... with a different engine
well,what exhaust did you used with that engine?
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Old 10-16-2010, 03:38 PM   #152
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well,what exhaust did you used with that engine?
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Old 10-27-2010, 04:53 PM   #153
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Default I remember....

Back in the late 80's I was reading all sorts of things about how people made their engines run faster. I cut a lot of stuff with my Dremel to see if I could improve my own engines.

Most of the time, the mods that I did didn't do anything except ruin my good stock engine.

Since I run boats, the effect was obvious. Wouldn't launch or pull any sort of fast prop.

I decide that I needed to do things in a more refined manner. One of my Engineer buddies helped me with a tool to make it easy.

That changed everything..... Now all mods are done knowing exactly what I am doing and how much to change.

I would invite you to look at the Past Tech Notes that I have written over the past 25+ years. There will be a huge amount of information that will clear up a lot of questions.

Also, I would appreciate it if you would look at the tool that we developed to help with engine mods.

The tech notes that I referred to are located at: rcboat.com Many are specifically for RC Boats, but a ton will be helpful to any RC Racer.

MartyDavis
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Old 10-27-2010, 07:15 PM   #154
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I love talking to the good boat guys. They know their stuff.
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Old 10-28-2010, 03:35 PM   #155
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They sure do...

rcboat.com has always been one of my favorite web pages...
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Old 10-31-2010, 07:45 AM   #156
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Does anyone in here currently own marty's software???
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Old 10-31-2010, 09:51 AM   #157
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Originally Posted by MugenDrew View Post
What about rod ratio and it effects?
What about change to primary compression?
Is it better to change port timing or increase/decrease area to obtain your goals for the torque curve?
There's an interesting read if you can find it regarding stroke/rod length ratios and crankshaft/bore offset authored by Desaxe. In simple English, it discusses manipulation of the rod length to maximize the torque effect. It's a pretty complicated subject, but it's at least interesting to know what's going through the minds of the engineers when they choose certain rod lengths. Desaxe also experimented with offsetting the centerline of the crank as it relates to the bore, also attempting to get the most effect from the power stroke.

The theory goes something like this: After the piston passes TDC, the rod applies the pressure from above the piston to the crankshaft via the conrod. You're converting linear motion to rotational, so there are few things going on that can be optimized. Understanding that the highest level of engine torque is when the conrod is 90 degrees to the rotational axis of the crank, the rod length can be manipulated to slightly extend that period of optimal torque. It's not without its drawbacks because a rod that's too short will cause unnecessary side loading of the piston on the combustion stroke, and especially during the compression stroke. So, there's a trade off in changing the length of the conrod, and the Desaxe theory helps to arrive at what would be the ideal rod length. Offsetting the axis of the crankshaft isn't typically done because it increases the complexity of engine manufacturing to far to great an extent when weighed against the minimal gains, but this is an extension of the Desaxe stroke/rod length ratio discussion. Dave Gierke (a well-known engine guru who spends most of his time on the airplane side) explains the Desaxe theory in more detail. Although the book focuses on model airplane engines, all the same theories apply.

http://www.airagestore.com/planes/bo...rcraft-v1.html
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Old 10-31-2010, 10:46 AM   #158
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Hey Roelof, any suggestions on a degree wheel? I made one years ago but not being a machinist it was rather crude and not very accurate. I really need something a little more professional if you know what I mean.
Hey Sean, this is the degree wheel that I use. It's originally set-up to time the camshafts on Ducati V-twins, but it's almost perfect for use with RC engines. The center hole is 6mm, and it needles to be drilled (reamed) out to 7mm to fit over the big section of the crank in our engines. I use a combination of a flywheel collet and a prop washer to bolt it to the engine, and I've also had a jig made to hold the engine, and telltale solidly for accurate timing measurement. I have a picture somewhere of the jig and equipment I use to measure port and induction timing. I'll post it when I find it.

http://www.motionpro.com/motorcycle/partno/08-0092/

Last edited by SteveP; 10-31-2010 at 04:00 PM.
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Old 10-31-2010, 10:55 AM   #159
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No degree wheel for me, I am switched over to digital meters, it is fast and very precise:




My homemade setup can be found here:
http://www.modelbouwforum.nl/forums/...-en-tunen.html
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Old 11-06-2010, 02:12 AM   #160
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Originally Posted by German Muscle View Post
Cutting the crankshaft counterweight like that will induce several negative effects.
-Promoting of turbulence
-Unbalancing the rotating assembly
-Increase in crank case volume
-Interruption of airflow

Those things decrease performance individually and do the same when paired together.

The more air and fuel you can move through the engine without blowby the more power it will make. Velocity is a key thing these engines use to make power. Efficient airflow is also something that will make power. While it is not possible to fully balance a single cylinder 2 stroke engine there is a tolerance to get it close and within specs. Cutting the counter balance like that removes all of that and throws it out the window. This will result in alot of physical and sonic vibration in the engine quickly prematurely wearing out the engine bearings, crank pin, rod bushings, wristpin and eventually the piston and sleeve. Crankcase Volume is usually close to optimum is most engines out there. When you increase that volume you decrease flow and velocity which will take away power.
So, in saying that, then is putting a "Fang" in the crank cheek the same thing....as its basically useless even if balanced once done....? Basically just leave the hole as a hole...?

Also wondering,

If you have the sleeve port timing and the induction valve port timing, Im guessing the sleeve ports will determine the power band and the induction valve port determines the response of the engine and the amount of charge into the crank case...????

Thanks
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Old 11-14-2010, 05:29 AM   #161
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Default Engine Break In

I have a stock engine that Im breaking in, another MGT 8.0. I have the fuel mixture screws set at what the manufacturer states, but as soon as it gets warm is doesnt want to idle well. The idle flutters around fast as if the engine's running rich then lean then rich then lean, at a fast rate....etc. Ive tried tweaking the HSN and the LSN to see if I can get it stable. But it just stalls. Also, it wants the glow igniter left on, when I take it off, it stalls as well, once the oscillating idle happens. Like I said, I have the FMS's set at factory settings and have also tried to adjust. It starts up well at cold.... everything is stock including pipe. Is this normal in a break in....? Ive never had this kind of trouble before, not even on an engine that I have modified, and this is stock....?

If anyone has any idea's, be mucly appreciated.

Respect...!!!!!!!!!!
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Old 11-14-2010, 05:40 AM   #162
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Compleetly wrong topic but it seems your glowplug is not OK or you are running not the right fuel.
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Old 11-14-2010, 12:18 PM   #163
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Originally Posted by ausrcnut View Post
I have a stock engine that Im breaking in, another MGT 8.0. I have the fuel mixture screws set at what the manufacturer states, but as soon as it gets warm is doesnt want to idle well. The idle flutters around fast as if the engine's running rich then lean then rich then lean, at a fast rate....etc. Ive tried tweaking the HSN and the LSN to see if I can get it stable. But it just stalls. Also, it wants the glow igniter left on, when I take it off, it stalls as well, once the oscillating idle happens. Like I said, I have the FMS's set at factory settings and have also tried to adjust. It starts up well at cold.... everything is stock including pipe. Is this normal in a break in....? Ive never had this kind of trouble before, not even on an engine that I have modified, and this is stock....?

If anyone has any idea's, be mucly appreciated.

Respect...!!!!!!!!!!
Glow plug or air leak problems is the cause of this. First try a new glow plug. If that doesn't work: plug exhaust and carburettor intake with Plasticine, and blow into the fuel hose with the engine in a bucket of water (hold Plasticine in place with your fingers whilst blowing). The bubbles will tell you where the leaks are.

Kindest regards,
Lars.
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Old 11-14-2010, 05:09 PM   #164
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Does anyone in here currently own marty's software???
I purchased the software a year ago and I tell ya, for the money there isn't a better program out there. This guy know his shizzil and I use it to set up my engines and will from now on. Boat guys I say are the best .21 engine tuners out there cause they have already tried every combo known to man and know what doesn't work. Just my two cents.
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Old 11-14-2010, 10:08 PM   #165
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Cheers guys. Will give all that a go.
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