RE: Increasing 2 stroke performance - how?
 

Explanation:


Since air resistance to the movement of the prop blades rises, with the square of the actual speed the blades are moving; and since the force is applied over a proportionately longer distance, per time unit, HP is greater by 1 + the percentile speed rise, to the third power.

If, for example, RPM is doubled, resistance is multiplied by 4, over twice the distance per time unit, so HP is 8 times larger. Twice the RPM; eight times the HP output!

So think well before flashing that .40 of yours that spins a 10x6 prop at 25,500 RPM...

RE: Increasing 2 stroke performance - how?
 

loughbd. you are so negative about this modding,you have to understand that I do these mods because I find it interesting and have fun doing it. Thats the whole idea to have a hobby right? It is not hacking or chopping away randomly, there is a lot of time invested in research before I bring out my dremel tool. And just imagine the power if I now add a tuned pipe, he, he :D actually it is funny that you mention the crank as that is the next part I want to mod. I want it to be similar to the crank in highend buggy engines(turbo cut ) to just add a bigger engine isn`t all that fun, even you could do that:eek:. I know all about expensive engines as I run both os, ys and rossi engines;)

RE: Increasing 2 stroke performance - how?
 

You just don't read -- intact tract tuning has been specifically mentioned, as have crankshaft induction-passage mods.

Why do you assume that "we" don't know what we are doing? Many of us have been playing this game for a long time (over 50 yrs in my specific case). It used to be quite necessary to modify engines years ago. The Oliver Tiger was the rat-race king at one time & the very first thing that you had to do to have even a ghost of a chance of winning was to drill the crank passage as large as it could stand, chamfer the crank outlet, square the ports & chamfer the inner lips of the ports -- or you were a loser. Further refinements included chamfering & polishing the rotary-valve inlet opening, pollishing the inlet passage --- etc, etc. Guys who left their engines stock were just spectators. If you know that, what is your problem?

Manufacturers produce engines for a market price point & carefully planned profit margin. They will market it with enough power & reliability to be acceptable in the market place at their offered price -- but not to extract every bit of power available & certainly not to be the most reliable out there. OS is an excellent case in offering acceptable, but not outstanding power, combined with minimum acceptable reliability & the maximum price that the market will bear.

RE: Increasing 2 stroke performance - how?
 

people who are so afraid of ruining an engine should not be flying at all, eventually it will wear out or they could ruin it in a crash, oh dear, oh dear, the world will go under:D I`m really exited for myself and can`t wait to improve the crankshaft too. I have already gotten some tips from a guy who has altered the crank on mvvs 49`s. the search for more power will go on wether some people like it or not[sm=lol.gif]

RE: Increasing 2 stroke performance - how?
 

I look at modifying an engine as just annother aspect of our hobby...and there are (as we know ) many aspects of it.

I have been a 1:1 aircraft mechanic since 1980, and have several years of machine shop experience...

I'm not on the defensive, just making a statement, that there is a certain ammount of planning and forethought going into this process. I'm no engine designer, but like britbrat said, there's room for improvment, and what's wrong with that?

I want to get a little more specific output per cu.in. it's that simple really.
Years of porting cylinder heads for automotive engines helps give me the background and self confidence to take a Dremel to a brand new model engine, and know that it will be more powerful after I get done with it.

Doing the ports in a Saito...now THAT'S a little tricky! You have to have a real steady hand for that.



Besides...I've always been one of these guys who can't leave anything alone!:D (my folks were fond of asking me that "can't you leave ANYTHING alone?!" :))

RE: Increasing 2 stroke performance - how?
 

he he, I could not have said it any better myself Proptop. I even have a maglite(the recargeable one) that I have tuned. drilled out the hole in the reflector and added a bigger more powerful bulb:) Oh boy does it light up, but the battery now lasts only 45 mins as opposed to 90 mins before[sm=lol.gif]

RE: Increasing 2 stroke performance - how?
 

Come on, the engine doesn't cost much and its a great way to learn somthing. Lighten up! Its just a hobby!

RE: Increasing 2 stroke performance - how?
 

Please keep this On Topic and civil or we will have to assume that it has outlived its usefulness and lock it up, Thanks.

RE: Increasing 2 stroke performance - how?
 

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Most R/C folks, not all, are not familiar with control line competition folks. I always look to the control line boys for the latest engine mods.

If one is a "typical R/Cer", one is more familiar with the buy-n-fly mindset of model engines. Engine modding is not something one does in American R/C, unless you are a competition nut and are deeply immersed in a specialized field. I think that the person trying to discourage modding is merely concerned that someone will throw their money away and wishes to prevent that from happening.

Some countries have model clubs that are all inclusive. They are not strictly R/C airplanes, or boats or cars, as are many clubs in the US. The advantage to having many facets of R/C modeling in one club is the spill over of skills and technology from one discipline to another.

I agree that engine modding is a hobby in itself - and an enjoyable one at that.

RE: Increasing 2 stroke performance - how?
 

Why would you lock up a topic that is of intense interest? Discussions are not always exercises in agreement, & technical examples from other disciplines are usefull & applicable.

RE: Increasing 2 stroke performance - how?
 

I CAN read and I have been doing it for more than 50 years. I was even HShacks engine repair tech. I was also an Avid C/L fliers in the 50's and 60's and modified many engines. In those days they could gain a little something from tinkering. Today's R/C engines are pretty well set up for max performance.

OS has minimum reliability?? Well, there went your credibility.

One other little item. Hacking on an ABC cylinder is a good way to get the chrome to flake off.

OS is cheap?? Obviously you don't own a 5 cylinder radial.

RE: Increasing 2 stroke performance - how?
 

i just want to know how to raise the exhaust timing 25 degrees on my k&b 6.5 what tools to use .rotory files ect.. but mostly de-buring don't want to mess up chrome

RE: Increasing 2 stroke performance - how?
 

John,


The chromium on ABC engines will hold up to some playing around.

It is the nickel coating in ABN engines, that is in grave consequences, if its continuity is broken, as it does not bond as well as chromium to the brass sleeve's surface.

...As owners of some ring-less OS engines, mostly FP, SF and FX found, a slight scratch could cause peeling this non-electroplated coating. Hence the copper flash-coat in some newer ABL engines.

RE: Increasing 2 stroke performance - how?
 

Then why did Fox recall ALL their first 40 ABC's? They were CHROME and the plating peeled off.

Some content removed by moderator....

RE: Increasing 2 stroke performance - how?
 

jbel...I personally have not had the nerve (not yet anyway ) to try changing the timing of a plated sleeve. I have done it to steel sleeves w/ ringed pistons, but that's obviously another story.

You might be able to get away with it if you don't break the mechanical bond of the chrome. (don't chip it at the edge )
I would try and "hone" the edge just slightly afterward with a small stone just to "break the edge" so the piston won't want to catch on it.

There are re-chroming services available too if you want to have a go that route.

RE: Increasing 2 stroke performance - how?
 

While I don't have first-hand experience with altering port heights on nickel-plated sleeves, I have squared-out ports on nickel sleeves without trouble (so far -- fingers crossed)). I was carefull to file inward from the nickel surface only & to rub down the edges of the cuts. The nickel sleeves seem to be more forgiving than chrome (nickel is more ductile than chrome & less likely to chip & flake). OS' problems with nickel seem to be exclusively OS' problems & aren't necessarily reflected in any other brand. I guess that eventually I will find out.

RE: Increasing 2 stroke performance - how?
 

Patrick,


It was mentioned in another thread that this happens, since OS are the only ones that use a thin-wall brass sleeve; thinner than TT, or Webra use.

This could be the reason the other ABN manufacturers don't make 'frequent peelers'.

RE: Increasing 2 stroke performance - how?
 

Seems to be that way

RE: Increasing 2 stroke performance - how?
 

I have also wondered if it has to do with the alloy used? Correct me if I'm wrong, but are some O.S. sleeves made from brass tube?
We have Revere copper, brass and aluminum here in Rome, and one of my flying buddies worked in the tube mill for many years. He would tell me of the experimentation with different alloys to get the tube to "handle" through the machinery better.

Perhaps the thicker sleeves are machined from bar stock, and a different alloy that accepts plating better?

That thought has been going through my mind for some time...
I could be way out in left field... (wouldn't be the first time )

RE: Increasing 2 stroke performance - how?
 

I would think that extrusions are used, with finish machining -- but I really don't know.

RE: Increasing 2 stroke performance - how?
 

keith your a genious

RE: Increasing 2 stroke performance - how?
 

did you brush your teeth

RE: Increasing 2 stroke performance - how?
 

25 degrees is an awful lot even if that's total opening time. Unless I miss my guess, the K&B 6.5 (as opposed to a K&B 40) is already a high performance engine so it's likely to have quite a high timed exhaust already.

RE: Increasing 2 stroke performance - how?
 

John,


Brian is very right.

A typical sport engine would have 145-150º of exhaust timing and a high performance engine would have about 160º.

Only engines designed for very high RPM competition have more.


This K&B engine was tested by Peter Chinn, in 1970s MAN magazine and exhibited outstanding performance... On par with Rossi, OPS and other racing engines. It was then considered a candidate for Q-500...

Its production quality was not as good, however.

Chinn noticed the rear bearing's outer race, was quite loose in the crankcase and was actually turning as the engine ran...

RE: Increasing 2 stroke performance - how?
 

I DID do engine mods back when I flew C/L speed, combat, and Rat Race. Didn't care about idle because top end was all that mattered. That and easy starting BY HAND. Now that I fly R/C and have been since I used my first Babcock single channel radio, reliability and idle outweigh any power gain that one might get from hacking on an engine. I like to flip the prop once by hand (that's how I still do it) and take off knowing that it isn't going to stop until I want it to 15 minutes later. I just hate having to go dig an airplane out of the woods because the engine quit at some inopportune moment. I believe in the one flip of the prop, one flight philosophy.