I have an Evolution 60NX that I decided to do some work on this weekend since I had it apart to replace the bearings. I ported the intake port a bit, staying away from the edges to keep from dorking up the liner. I also did some work on the crank and a bit on the case. The crank and case, I just put a radius on the edges to try and smooth the flow out. I didn't get into enlarging anything.

What do you porters and tinkerers recommend as far as light port work or have I done enough already?

A web search turned up this page that looked interesting as well. So I may do some portin' on the boost and transfer ports as well. I'll post pics as I go if anyone is interested. I have a new close up lens for my Nikon that I want to play with as well!

If you need more power, get a bigger engine, or if it's not, put it on a tuned pipe.
2-stroke glow engines require back-pressure to run correctly.
Polishing ports will cause more fuel to collect into larger droplets, reducing efficiency.
You might in the long run get more top-end but at the sacrifice of mid-range performance.

Just my thoughts.

This one is about as big as they get in a 40 sized case. I don't need the power. I just want to tinker and see if I can get more any way.

Setting the correct compression ratio for your fuel and using the correct plug, is likely to give you more improvements than any DIY car engine tune-ups from a teenager will ever give you...

Let us know what you think when you get the engine running again.

Check out [link=http://www.jettengineering.com/engines/bse40.html]JettEngineering.com[/link].
He has all this perfected.
Dub has a .76 in a .40 size case and it's lighter than any other commercially available engine in this size class.
Notice the RPM's he gets with the props listed and also notice how small the ports are, including the exhaust.

Mr. Cox makes a very good point as well.

Over the years I've found out with a typical "sport" aircraft engines that less-is-more when it comes to modifications. At the r.p.m. the airplane engines turn, compared to the car engines, you don't want to remove too much material. (it can slow down the flow velocity, and that is not good for low to mid range operation )

I typically put a radius on the sharp edges that are in the fuel/air flow path.
A radius on the lower edges of the F. and R. transfer port openings (on the outside of the sleeve ) and at the very bottom of the sleeve.

A bit of a bell mouth or radius at the crank opening into the case...maybe a "turbo cut" or two if you want to get ambitious. (look at the internals some r/c car engines if you want some ideas there ) Use a short piece of brass tubing over the crank pin to keep from accidently nicking it.

If the rod is a simple rectangular X section, then a radius on the edges...(the current TT .40 and .46 rod is a nice example of what you could imitate )

Sometimes I will work the piston skirt, it depends on if it masks the transfer channels too much while at or nearing BDC...removal of material under the wrist pin....but this is getting a bit into the "tricky" areas of modifications. If you have new wrist pin retainers, and want to experiment...

Magic Marker (blue or black ) work great for machinist "bluing" if you need it.

Oh, I cruise Jett's site often and drool. This 60NX is running one of his mufflers.

Ido it all the time. Moderation is the key. I have found lots of power lurking inside my engines. Look under ported and polished in the RCU videos

Cool! That's what I wanted to hear!

I'm digging the passionate responses from both sides of the fence.

A polished surface is great for airflow but causes fuel to bead into larger droplets. True for gas or glow.
Good luck.

Ihave been doing port work on my engines both glow and automotive for 20 years or more. Just think to yourself that flow doesnt like sharp edges or sharp corners and rough surfaces. Mirror polished is a waste of time , just smooth. And dont remove a bunch of material thus increasing the volume inside the case.
Not all engines are going to give up a bunch of power but if it wasnt optimum from the factory you can find quite a bit.
A Jett engine may not respond like my Thunder Tiger to the same mods because the Jett is already a Hot Rod. But we are not talking about that , we are going to find some cheap horsepower from an inexpensive engine without spending any cash.

Nickle plated cylinders do not take kindly to porting as it will start to peel from the point where you did the porting

As I stated in my original post, I'm not getting any where near the lining - at least not on purpose. I'm going to put a radius on the sharp edges and smooth out the ports on the outside of the liner a bit and call it a day. If I get 300-400 out of, I'll be ecstatic - not losing my virginity ecstatic, but close!

Yep...you have to be very careful to stay away from the inside edges if you're doing an O.S.

The Evolution series however are true ABC so we don't have to worry about that though...

As a matter of fact, I'm working on an O.S. .46AX and a Magnum .52 XLS (they both need new rear bearings ) did some work on both last night...will do some more this evening.
The Magnum .52 XLS is virtually identical internally to the Evolution .52 and except for the bore and stroke dimensions, the same as the .60

Porting and Polishing to glow engines is really a misnomer. The "Polishing" is done in automtive 4 stroke engines in the combustion chamber to eliminate sharp edges which will cause preignition and prevents carbon buildup. All moot in a 2 stroke with its nice smooth surface containing no valves .

Hi!
The above recommendations will not do much!

If you want more power ...use a pipe! A pipe will gain about 15-20% power.

Well, I have one on a pipe and one on a Jett muffler. So port it and put it on a pipe!

the easiest thing to do is as you have done, a simple cleanup, but you could raise exhaust timing to 168-172 degrees and gains some added performance as well, the old adage about polishing is just that , as it was truth for low rpm car engines IE 0-5000 rpm , which has no bearing on our rpm range for these engines. the carb as it is is a major bottle neck, so enlarging the carb throat to around 10-1.5 MM will make a large difference. OS engines heli engines 50 size and up use 10-11 mm throat diameters without the use of pumps, but use muffler pressure, heli engines usually run in the 16-20k rpm range with standard gearing.. which is right where most guys here are trying to achieve

Cool, sounds like I'm on the right track. I've ported a few cylinder heads for turbocharged race cars in my day as well. Can't use any of my bits on these engines though!

I'll just radius the areas that air/fuel will be flowing around and leave it at that. The bigger carb is probably out of my range of skill (don't everyone laugh at once!) but sounds interesting.

The polishing is not going to do much, if you really want a power gain you will need to put some effort into it, if it was easy then all engines would have it right from the box...

Hi!
Raising the exhaust is one thing you can do...But! Problem is that when using a Dremel with a diamond cutter might crack the nickel plating.
Reducing friktion is a good thing to do. Changing to Swiss made WIB C 4, racing bearings is making the crankshaft turn easier (These bearings are used in JETT and Nelson pylon racing engines).
It's also a good idea to lighten the piston and conneting rod (all things that reciproce).

Hi Spinnerrow, check out POWERHOUSE PERFORMANCE, he does some real nice port work, if you look closely at the photos of the work he has done you should be able to get a rough idea of what to do, other than that a good exhaust set up is the quickest way to gain power without screwing up a good engine.
Just a silly thought, have you ever tried using car fuel +/- 20° nitro just to see if that'll make your plane go faster???
I thing the fly boys use 5°-10° but aint to sure on that.[8D]

Thanks! I checked out the PowerHouse site. I got no where near as aggressive on the boost and transfer ports on mine. I might try that on a ringed Super Tigre G-51 I have since I won't have to worry about dorking up the plating on the liner!




The crank work he does is sick!