ausrcnut

They say you can gain rpm by widening the exhaust port. How would you go about widening an exhaust port that is not square or round, but irregular polygon or irregular hexagon...? Would you widen the port by making the port a rectangle with square edges all at 90degrees via width only or so....?

Regards

afm

Just enlarge the top corners of the exhaust port .

AFM

ausrcnut

Hi Roelof

The way that I modifiy the crank, I do as instructed by other editorials. The closing edge of the inlet valve is knife edged, but so is the opening end = increasing the over-all opening. Because I only go as far as to the edge of the port, and not over the edge...ie, not extending the original parameters of the outer casing, is this still increasing the duration...? The port is opened up more, but it is in the original outer limit.....? Also I ground the crank cheeks extra centrifuge's to create more turbulance and crank case pressure. I have really noticed a huge difference and the exhaust exits very strong and fast stream of smoke. The response is very crisp and snappy. Im still running the engine in, but after one tank on low rpms, the cooling head didnt even get above 60 degrees temp. I was amazed. I also match-ported the inlet port to the carburettor and ported the sleeve as well. In addition to this, I ground out the transfer channels in the crank case to match the ports on the sleeve, as I find that most engines are not properly done. This engine is a SH CXP.28-P6. Im now experimenting with an Associated Pro 8.0 .50, seeing if I can get some more RPM's out of the torque monster. If I cant, then at least it will be more responsive and have more power. I widened the exhaust port just as you said, but this time Im trying something different with the crank cheeks, not so cut up. But I know that I wont get the same crank case pressure as the previous engine I did. I actually cant believe how well that little engine absolutely pumps the gases out....!! Thanks for all your advice, I have learned to much and this is heaps of fun on my rainy days....!!!

German Muscle

iTrader: (8)

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.

Roelof

There is a well known modifier making these kinds of mods:
http://www.powerhousercperformance.com/
And he has explained several times on this forum the why of this mod, personally I think it is more a signature.

wingracer

iTrader: (24)

Yeah I don't buy it either but he swears it works. Sure does look cool either way

Might have to try it sometime just for the hell of it.

maxflo777

Wingman, here's an answer for and really old question! before Novarossi did the long stroke offroad engines they were square 16.45 x 16.45 like the first couple genereations of RB s7 & ws7 those rods were 30mm. those fit directly on the engines if you raise the sleeve .5mm, but you can also do it with an OS or sirio rod.

Kind of late maybe

xe

German Muscle

iTrader: (8)

Im aware of that. There are also several other modders that claim other stuff that does nothing or that negatively impacts these engines.
I wouldnt waste your time.

Racecrafter

iTrader: (25)

"Turbo-ing" a crank shafts counter weights does absolutely NOTHING but hurt performance of an engine two stroke or four.

If this actually worked not only would the top R/C manufacturers do it to their engines, the builders of 500cc GP bikes would have done it and most certainly the F1 boat engine builders would have done it.

As it was explained to me in the mid '80's by a very well respected factory Honda and now Yamaha engine builder/tuner:

"It gives the engine builder something to show the client of which neither party knows what it really does."

wingracer

iTrader: (24)

Hahaha, I love that.

Roelof

Yes, that it!

As mentioned before:
Just show 2 kind of engines to someone who is in to buy a modded engine:
1st engine: Only changed timings, no visual stuff
2nd engine: no change of timings but a lot of visual cuts and polishing

I bet that almost 90% will go for the visual modded engine while some of us know the timed engine is the better choice.

romeo32982

i need to know where to get the body doe a dm1 that u posted a while back plz email me asap





11-26-2009, 01:23 AM #2589
Jspeed
Tech Elite



Join Date: Oct 2006
Posts: 2,124
Trader Rating: 0

+1 guys.

Here's a prime example of what none of us want to see screw up our growing GT1 or GT2 class.



Kudos to it’s designer, for the aggressive aero-design and sneaky bubble over the engine’s cooling head fins in an attempt to conceal it’s true nature. We don’t think any of us will ever see a car like this driven legal on a street; much less in any fast-food drive through. lol.

I'd also love to see what kind of visability you'd have on the street over the front fenders too, lol

While this style body may fall within the rules followed in some “Rally Game” type R/C racing classes, this style body pictured above unfortunately doesn’t fit into the spirit & rules of our GT1 Open or GT2 Spec class rules.

This type of body is not a legal for the Ipanema Sports 2010 GT World Championships.

Hope ya'll have a happy Thanksgiving!

wingracer

iTrader: (24)

No idea what you are talking about. This is an engine thread, not a body thread.

wingracer

iTrader: (24)

Just bumping this ahead of all the moved threads. Got to keep the best engine thread around on the first page.

lil-bump

iTrader: (89)

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