How to measure crank and port timing

[Anthoop]

Firstly, this thread will not be for everyone, some will not see any point to it and others should leave it alone if their toolbox consists of a hammer.

Hopefully I can impart some knowledge about this and that...but please do not assume I think I know, or, do know everything...I do not.

 

I will edit this post if there are obvious confusions or vital information I have left out...but I will be starting out with an assumption of a reasonable level of intelligence....I am not anticipating having to explain how to get the head off.

The method I am laying out here is one way to find when the various ports open/close pertaining to piston position. 

 

So...let us get stuck in..

 

Tools/items needed-

 

Listing clockwise from top left (ish):-

Engine on mounts...(backplate/carb./head removed).

Piston stopper (will explain further with the next picture).

Screws/washers/spacers (a screw to fit the crank and a head bolt).

Torch (Maglite fits nicely into the backplate hole)

360 degree wheel with a hole drilled in the centre (you could also print a wheel off the internet and stick it to a CD)

Wire (this will be our pointer for the wheel).

 

 

 

That is my Heath Robinson piston stopper...it is just a washer with a hole drilled and a nut/bolt.

Note that nothing has to be super tight...this is fingertip type work.

 

 

 

So everything mounted....I put the wheel and pointer on first...and set it roughly so that the pointer is reading 0 degrees at TDC...then wind the piston back down and fit the stopper.

 

Fitting the stopper will tell us exactly where TDC is and that is important because all of our measurements will be taken with this point in mind...so if we rotate the crank in a clockwise direction and take a reading...and then turn it anti-clockwise and take a reading, with a bit of maffs we can work out exactly where our wheel/pointer will need to be to indicate TDC.

Confusing?...mmmm

My piston stopper was stopping the crank from rotating 80 degrees...so if I set the wheel to read 40/320 then it is zeroed and after I remove the stopper and turn the crank to read 0 degrees then the piston is at TDC.

I will include a link at the end that may explain it in a different manner.

 

 

So if you got this far the rest is easy...

Torch in the backplate hole....in this picture telling me when the crank port closes....engine runs anti-clockwise veiwed from the front.

So rotating the crank gently anti-clockwise and looking at the crank port, a crack of light appears ...stop....note the reading on the wheel and write it down...continue turning the crank anti-clockwise until the port closes (as in the picture)...stop...note reading and write it down.

Now we know when the crank port opens/closes and also the duration.

 

 

 

We use a similar process to measure when the exhaust port opens. In the picture I am pointing the torch into the exhaust outlet.

We do not need to measure the closing point of the exhaust port because open/close are the same, just one is ATDC and the other BTDC.

 

 

 

 

Torch in backplate hole...to measure when transfer ports open.....write it down.

 

Finally measure and record the inlet port figures and we should have a set of figures telling us exactly when the crank port opens and closes and the duration of the exhaust/transfers/inlet ports.

 

Now we need to know what those figures can tell us......

 

 

 

 

Anyone wanting some extra reading on this and that...I will put some links on to this post....many are not specifically about RC engines but everything is applicable in one way or another...some are easy reading..some are not.

Have fun.

 

Alternative description for how to find TDC- http://www.macdizzy.com/cylinder_map4.htm

 

http://edj.net/2stroke/jennings/

http://www.palmarisracing.com/Timing_Calculator.htm

http://www.euronet.nl/users/tooms/timings/timings.htm

http://www.torqsoft.net/squish-velocity.html

http://rcboat.com/past.htm

Edited August 18, 2013 by Anthoop

[jordan_bench10]

looks rather confusing is this to change timing etc ?

im more into changine my phone rom on a daily as i can do it with my eyes closed but im intrigued to this now 

[Anthoop]

looks rather confusing is this to change timing etc ?

im more into changine my phone rom on a daily as i can do it with my eyes closed but im intrigued to this now 

Before you adjust the timing you must know what the timing is.

You are a different generation to me...I could tell you that I have to send my pictures from my old phone by bluetooth to a really old phone with a card in it so that i can get the pictures onto the PC...but hey...we all know different things eh?