Anthoop

Jim,you could just buy a manual micro mill that will do a proficient job and you could always upgrade by attaching stepper motors and the electronics.The manual mill will do the same job as the cnc difference being time and effort.
Personally(i have a mill) so far i've only modded my engines by hand as i'm pretty comfortable with a Dremel and setting up the sleeve/crank on the mill would take a fair ammount of time,by no means impossible but (say) setting up and calculating takes 1 hour,machining time a couple of minutes..do the whole job by hand... 15 minutes.
I,as you am only in this as a hobby but i love what i can do with my mill and the outlay is relatively small,maybe you should think about aquiring one yourself.
Pics of my stuff within this thread:
http://www.rcuniverse.com/forum/m_63...mpage_2/tm.htm

JB COMP

sorry to bring up an old thread, but SAVAGEJIM could you send me an email, I have a few questions for you and you don't seem to be answering any PMs at the moment.

my email is [email protected]

JB COMP

mods please do not delete my post, I need to get a hold of savagejim, but he don't see to answer my PM's

DMOne

Hey savagejim or downunder i know that these post are old but reading them over and over and trying to duplicate what your saying to do is tougher than i could have imagined. i am not a stupid person but im feeling that way trying to time my mill out, when im measuring for HTOT on my crank am i measuring from the top of the crank or the top of the whachamacallit i dont know the actual name for it so i took this picture, from this info i can figure out the rest of the measurments because they pretty much start at the same spot except H1 is that the middle of the whole on the crank?? thanks in advance for the help.

Anthoop

The induction port is the square shaped hole along the length of the shaft. Picture below.

You do not have to measure H1, you calculate it from the other measurements.

DMOne

Hey Downunder this trig thing has me all wound up and im trying to do this calculating in xls but i am getting lost, I can not see your files i tried saving those two docs like you said but windows seven is not allowing me to see either of them please help im getting very frustrated trying to figure this out. Ive gotten all of the measurments from SAVAGEJIMs' essays but when he gets into the trig stuff, xls is not helping me out much either..would there be a chance i could get you to send me a walk thru of the formulas you wrote to accomplish this horrible task??

DMOne

Hey thanks Anthoop i was on the wrong track but its good to you guys are out there sorry about all the stupid questions i will get this stuff sooner or later im thinking later though.

DMOne

so the induction port would be the W1 correct?

DMOne

Ok i get it thanks for that pic as i sat and thought about were you were measuring from the light bulb finally went on and the numbers are more acurate. Still not sure of the trig stuff and how to use excel but i might try the timming wheel instead any thoughts?

DMOne

i now know its HTOT not W1

Anthoop

It is only maths...who is excel?
The timing wheel can give you opening and closing point in relation to the piston, a simple calculation from that will tell you duration.

DMOne

Hey Anthoop, here are the numbers i get from my t-15 form hpi D=9.97mm, W1=6.08mm, H1=3.13mm, R=4.98mm, HTOT=8.11mm what formula should i be using in excel? i know it should be in degrees but what would the formulas look like.

Anthoop

I do not know how excel works.
If you print out the instructions (from step a onwards) and the picture attachments in Jims first post, it should be fairly simple to work through each step with a calculator.

downunder

This is about the best I can think of to walk you through the spreadsheet and the formulas used so you can make up your own spreadsheet but you have to make sure you put everything in the same cell numbers that I've used in the photos below. For cell D6 (which is highlighted in one screen shot) you need to copy the formula that shows at the top. For cell D10 in the other screen shot copy that formula exactly. In column B I've just entered some random figures for rod length, stroke and measured timing so put your own engine's figures in there instead.

What this spreadsheet is all about is to determine how far to raise an exhaust/transfer port by grinding/filing to alter to a desired timing. First you have to use a timing wheel to find the original timings and then strip the engine to measure the conrod length centre to centre of both holes.

In the screen shots you'll see I've shown the timing of an exhaust port as 70 degrees BBDC while it also shows 105 degrees ATDC. For the same engine it should really be 110 degrees because you can measure either from ATDC or BBDC but in this case I've used the ATDC cell to indicate an engine that's had its exhaust timing theoretically changed from 70 degrees BBDC to 75 degrees. Cell D7 shows the distance that the top edge of the exhaust port is from BDC for the standard 70 degree exhaust while cell D11 shows what the distance would be if the exhaust timing was raised to 75 degrees. The difference is the amount that needs to be machined/filed off the top of the exhaust. You can see in the screen shot how I've entered those two figures in the Modifying bit at the bottom. Cell D16 has the formula =D15-D14 to give the answer in mm and cell D17 has the formula =D16/25.4 to convert it to inches.

Just for interest's sake, another way to alter port timings is to machine/file the piston crown at around a 45 degree angle on the edge (matching the port width) by the same amount instead of the liner. This is probably best with engines that use a nickel plated liner instead of chrome (most OS engines) otherwise the nickel can start to peel off if it's not a continuous plating. It's easy to tell if a liner is nickel plated because it'll be plated both inside and out. Chromed liners are only chromed on the bore itself and slightly into the ports.

DMOne

Hey thanks for your help its really awesome that you take the time out to help understand your craft have you decided to start doing mods for other people yet? You have all the machinery and you know this stuff inside out it just makes sense that you would make some extra change. Me I just want to make the most out of my mills and don't have extra cash laying around I rather spend it on other parts, again thanks for the help can't wait until 2moro to put this to work.

Flippedover

I wish this thread could continue

1QwkSport2.5r

Yeah, I think a lot of people do. There are a ton of pre-determined values for port size and timing for many engines but engine modders (the "pros") won't share them. If you degree the engine to determine the duration, port size/shape, timing of the ports, and the compression ratio and take all of these values into account, anybody can peak a given engine to max power. It's very time consuming and requires a lot of testing. Having a number of good pipes is necessary as well. The exhaust system has a huge influence on performance.

nitroexpress

So let me get this straight.I can buy a Novarossi P5 built with all the expertise of Mr. Rossi.It would bebuilt using all the resources/money/experience thatMr. Rossihasto be as good as possible. Then I could get this gem modded by areputable enterprise and it willbe much better. It will have more power and more mileage and no downside. Doesthis really seem reasonable?

Changing port and crank timing and their interaction should be second nature to engine designers(Rossi, Roem, etc.). Any combination to timing that a modder produces can be duplicated in a factory. So why don't the factories match the specs of themodders?A port is a port. Easily cut on a CNCmachine.

downunder

Regardless of the info I've given long ago I totally agree with you. Any manufacturer worth his salt (like Rossi for instance) knows far more than any of us as to what's needed for high performance and has the equipment to make it. Other manufacturer's of lesser quality engines would also likely know the tricks used by Rossi etc. but most would be too time consuming or expensive for mass production. For those who like to fiddle then it's necessary to know some of the finer details about what they want to try and what affect it could have. I've read some fantastic claims in this forum for mods that are totally dreadful and will absolutely ruin an engine so it's wise for anyone thinking about doing mods to have a good understanding first as to how they work.

D3MON

I know its been awhile since this has been updated/posted on and ill probably have people talking about waking old threads, but i want to say thank you to all for creating this, it has been very informative and some great calculations compiled all in one spot. I know nitro isn't as big as it once was, but IMO nothing beats tinkering with them.
just wanted to throw my thanks out for all that had input and information added to this, and i can at least speak for myself your hard work is greatly appreciated and still being used!
-Mike

1QwkSport2.5r

D3MON

i understand what you mean about engine mods, and if you do not know what you are doing, is more harm than good.
i was looking at the informative side of what was posted, as in the calculations for timing, and stroke positions. i know that there is no single perfect mod. more or less like with 1:1 cars, a single mod wont do much, but most mods compliment each other to make both better than one single mod.
its a shame that nitro isnt as big as it used to be, i understand the want for some to run electric but imo it feels lazy running them, except for certain types that nitro is a hindrance (i.e. rock crawling).

1QwkSport2.5r

ChrisKnee

It is a common misconception is that the "top tuner" knows much more than you. I ran into that situation often in engineering. Also, no one likes to say that they don't know. Modifying an engine is actually designing a NEW engine. To design a new engine you have to have a good knowledge of the physics involved (thermodynamics and acoustics), the chemistry (stoichiometry), the geometry (visualizing 3D flows) and metallurgy (metal strengths, densities and tribology) of all the things that make up a two stroke engine. It will also help to know the history of the two-stroke as regards what things have been tried and what doesn't work.

To become more educated, you can read the following books: Design and Simulation of TWO-STROKE ENGINES__Gordon P. Blair.pdf, Graham-Bell-Two-Stroke-Performance-Tuning.pdf, Philip Edward Irving - Tuning for speed_ performance motorcycle racing (1967).pdf, Two-Stroke TUNER’S HANDBOOK__Gordon Jennings.pdf. These books are not perfect but are a good starting point even if they are mostly motorcycle oriented. This is not a bad thing. Riding a bike allows one to learn the power of a two-stroke engine in a direct way. Being able to sense detonation, rich running, over heating is all very important in knowing how to run and get the most out of a two stroke. Also, learn how to operate an engine well. Watch any person starting an engine. If he battles to get it running he probably doesn't know much.

Gordon P. Blair's older book contained computer programs that other people have used to write their own programs on two-stroke engine operation. Apps like EngMod2T ($400) and MOTO (252 AUD) supposedly can tell you what area of your engine is lacking.

You need a dynamometer to measure the change in performance of any change you do to an engine. You also need to know how to test with it. An informative paper on dynamometers is THE SCALING OF PERFORMANCE AND LOSSES IN MINIATURE INTERNAL COMBUSTION ENGINES by Shyam Menon.

Engines like Novarossi now are highly refined so that the space for improvement is small. Back in 1972, an OS Max .20 engine had 0.27 hp. Now in 2019, an OS VZ-B .21 engine has 2.89 hp which is more than 10 times the power from the same engine size!

Finally, your best friend is Microsoft Excel. This single app has all the facilities to support two-stroke engine development. Each cell in a spreadsheet is a calculator and the most complicated calculations can be easily simplified by using multiple cells and clear labels of what the variables are and their units. Output trends can easily be graphed or charted so you can see what is happening with the numbers.

Its database capability allows quickly finding gems of information out of tons of seemingly useless data. Excel can draw live diagrams from active data. Also, getting help is a simple as asking the question in Google.