rvd

Just wondering what tricks some pylon racers do to their engines to sqeeze more power or rpm out of them..
I know that revealing secrets can educate your rivals but I'm just a hobbyist that enjoys tinkering.

rvd

i guess this is a touchy subject.. hehe no biggie though

Scorpionjack

Well! I don't do it now but years ago to get about 2-500K more from an engine I use to polish the complete fuel Tranfer ports.
IE. Using a pencil eraser on a dremel extention polish the Carb of any flashings all the way through to the crankshaft. Crankshaft same thing all the way through to a High sheen. Engine transfer ports/side of case High sheen again.
Rossi's I use to match the exhaust port of the exhaust to match the exhaust port of the engine. But this required cutting and I soon quit as this was a modification not polishing!

Bill Vargas

My Feedback: (5)

I like using a 30,000 RPM Die grinder on the crankshaft to make it lighter

BV

Ed Smith

Polishing transfer passages is a myth. Have you ever noticed how moisture 'beads' on a highly polished surface. This is exactly what happens to fuel traveling along the transfer passage. We want a consistant fine mist going into the combustion chamber, not globs of fuel. It is called a spray bar remember. Anybody who takes a grinder to the inside of an engine obviously thinks he has more knowledge than the original designers who must have got it all wrong!

Hours can be spent 'improving' an engine with at best a remote chance of actualy realising any real power increase. This is not free however. Any modifications made will be paid for in terms of reliability and longevity.

The best thing one can do to get the maximum power from an engine is to follow a correct break in procedure.

To answer your original question, very few of us do anything to the insides of our engines. We are not arrogant enough to think we have more engine knowledge than Henry Nelson, Dubb Jett or any other Engine Manufacturer


Ed S

MaxQ

I've just recieved two new TT Pro 40's to get me started in 424 racing and I'm interested in how you experieced guys break these engines in to achieve max RPM. Any and all feedback appreciated.

MaxQ

Scorpionjack

Ed; Say what you like I'm not getting into a ***-a-tat on something as trivial.

Fact: Some engine manufacturers have piss poor QA!

Fact: Some engines run better with a cleaner air/fuel mixture!

Fact: I said polish not grind (grinding your DQ'd), look in the crankshaft you'll see channeling ridges. If these were ground off I'd agree with you.

Fact: Atomized fuel burns better than raw fuel. No one made any comment ref: the spray bar.

Fact: I said I did it years ago! Manufacturers were sloppy and yes we set our own timing on Motors for F1 and in U-Control B/C/D Proto Speed engines, as well Rat Race engines.

As you said you don't open your motors. Today's technology is so much better in some ways. But you still have sloppy QA's in every manufacturing/production line.

Bill Vargas

My Feedback: (5)

MAX, Start by running th engine rich for 3 tanks while on the ground,,, then go fly it,,, keeping it rich for at least another 20 flights,,, after that lean it out for the MAX RPM and back it off by about 5-600 rpms,,, that should be really close to "ball park" Racing RPMS.

If you are unsure about this proceedure,,, checkout the Racer II pic at www.pylonworld.com Its under Q500 Planes

BV

rvd

ok well i'm not going to be racing in a league because in my area there is no such thing unless i drive for about 4 hours and i can't see myself doing that anytime soon.

So tell me about grinding the crankshaft... what would that do to the performance? The opening on the crankshaft that you can see under the carb? do you port that out?

I would appreciate if you could explain this to me.. I'm an engine fanatic and love to experiment..

Thank You

Ed Smith

rvd

After my last post where I advised against grinding the inside of an engine I was accused of being somewhat trivial. Now, here we have somebody who actually wants to attack the inside of his engine with a grinder. The original suggestion to grind the crankshaft was to make it lighter. Where to grind was rather vague, whether any balance or strength was affected was such a trivial matter that was not worth mentioning I suppose.

Most crankshafts are made from tensile steel that has been case hardened. Case hardening results in a hard outer skin (Case) for wear restistance and bearing surfaces. The inner core is softer and tough, to prevent the end from snapping off every time you hit the ground. If you start grinding away somewhere you will remove some of the hard skin. It is quite likely you will have localy weakened areas. By removing material You will also have affected whatever balance the crankshaft may have had. You are attempting to increase the RPM remember which will emphasise this condition

The inlet and exhaust openings on a two stroke can be compared to the valves on a four stroke. They are never open at the same time. If you grind the leading edge of the window in the shaft the intake is now opening sooner. Grinding the trailing edge will keep the intake open longer. It follows that if too much is ground off the window will still be open when the piston is on it's down stroke. This will result in fuel being blown out of the venturi rather then sucked in. Hardly a performance booster. The window creates a weak point in the shaft (One of the drawbacks of F.I. engines) opening it up does not improve this situation.

If you are new to engine rework I would suggest the following

If you have a good medium performance engine, leave it alone.

If you want a high performance engine then buy one of the many available similar to the one you alredy have and compare the differences.

If you realy must experiment, and who does not, collect a whole pile of junkers and go to it.

I realise this post was rather long winded and, no doubt, I will be accused of spending too much time on a trivial matter, but you did ask for help.

Ed S

Bill Vargas

My Feedback: (5)

Another simple engine trick would that you could try is to add a .005 shim under the piston sleeve

BTW, Valves in a 4 cycle engine are open at the same time. This normally occures between the exhaust and the intake stroke for about 10 - 15 degrees of rotation. This is called valve overlap.

BV

raskco

Well the only thing I could say is I love porting motors also... I just wanna play with my new grinder... The only thing is I don't stop grinding til there's only the glow plug left then I realize that I went to far...... In other words, If people want a motor to "rev" out more... Why don't we contact the manufacturer to improve their motors.. (again) It's a none stop thing.. poeple are never satisfied I guess.. Speed does funny things to us guys...
RVD has ported my motor (magnum 46pro) and my other buddy's 40la that was a bag.. They both woke right up. I have no ideal how much rpm we gained but mine climbs to the sky now... Might not last long but it will do for now.. (til I get the nelson)My buddy has the 40la in a pt 20 and beleive me, It probably goes about 20 miles an hour faster.. As for the balancing part of it. well I have no ideal if it's out of balance or not but they seem to run really good. I wouldn't recomend doing something like this on your favorite motor or anything, But like ed said, If you have the junkers, your go to go...
Oh yea one more thing, rvd has a 47, 60 gms and 60 os and 46 skyward and ?? He ported all of them... When he starts something he can't stop... He even ported he 47 for his trainer. And he wonders why he has flutter when it's pulling 30,000 (it seems) rpm.... the guy is a maniac.. He sleeps on metal shaving cuz his basement is full of shavings.. HEHE.. L8ER

rvd

Raskco that's funny

Sleeping on shavings no, but porting everything YES.

That SuperTigre GS40 that I did for Shawn's plane really flies good now! Lot more speed and vertical.