Engine Port Timing

[Chris Davis]

I interested in accurately measuring port timing in my nitro engines. I have used degree wheels for years in automotive fields. Are there any good articles anyone can suggest? I imagine i will use a piston stop to find true TDC and set the wheel. Exhaust timing seems like it would be simple to locate since the port is visible. Intake timing more complicated. Any and all thoughts or ideas greatly appreciated.

I guess My next question would be optimum port timing for the Picco 45 EXR. I have been collecting parts just for a fun project. going to see what I can squeeze out of one of these engines.

Thanks Chris

 

[TUNLBOTR]

Chris,

One trick we use is to use a small led flashlight to shine up through the case to see the true point that the port(s) close. Use Marten Davis' program, or as they call the wheel, a drink coaster. Also follow the formula for reading blowdown by calculating....

total exhaust open duration, minus total transfer open duration, divided by 2.

above 30 degrees low end starts going away, quickly..

hope this helps.

RP

Marty's technical papers can be located at RCBOAT.com methinks... been a long time

 

[dwilfong]

Marty's software is the best way to go.

But if you want to use the wheel here is a pic that you can size any way you want.

Print it out and put on a pice of thin wood to make a wheel.

 

[Chris Davis]

Wow! Incredible site with so much useful information. Even with the engine analysis software don't you still need the wheel and mechanical measurements for the software to work. I guess I am old school, its funny the coaster template is the exactly the same as my 12" wheel used on my Big Block Chevrolet's. I can tell already this will be fun. What do you guys think.... an EXR 45 with optimum port timing, drum mods and a great carb. Will this combo keep up with newer engines?

 

[dwilfong]

No wheel needed with the program.

Just measure from the top of the sleeve to the top of the piston at TDC and the distance to the top of the ports.

Input the bore ,stroke and rod length and these measurements it is all calculated for you.

Just use the eng you have and get the feel for it.

It will give you many hours of fun.

Learn to walk first it will have a life of its own from there.