davewallace

My Feedback: (29)

Hello everyone,
I am uploading a port timing chart that I compiled over the last few weeks. The accurracy is of course only as good as a manual degree wheel and human eyesight can provide. I hope that you find it useful. It also will give some insight into the reason some stock engines perform better then others. Enjoy.

Dave

PS I added two chain saw engines

Antique

My Feedback: (4)

Great chart! Covers all of the engines I'm interested in ,,,,,,,,,,, now if we only had a primer on how to use it. Thanks!

OLD_SLOW and in the WAY

these timings are of course very conservative for the industrial purpose they were mfg'd for.for instance a race engine like the Sikk 27 or zenoah 260 will have exhaust timings from 178deg to 184 and the intake can have up to 160deg with 155 closer to the norm. with hi exh timings you lose effective compression and a smaller duration of the stroke to make the power before the port opens.. Imildly modded my G62 wich is almost a copy of the G26 4 transfers etc. and with out changing the exhuast timing ( to keep the torque for a big prop) it went from a so so engine to ... hey watch me hover!!

a caveat should be applied here, some of these engine dont have enuff material around the ports to get these type of timing numbers.

great info on the charts


you fet all those numbers by using a degree wheel and making a chart like this

blueberry

Fastrat,
Do you have any suggestions on porting an Echo 23.6 I want it to have enough power to 3D a Funtana 90. Is it possible?
Thanks,
Pete

av8tor1977

My Feedback: (6)

Wow, that chart was a lot of work. Thanks for sharing it with us.

AV8TOR

OLD_SLOW and in the WAY

Blueberry... Pm me and i can give you a call

Rupurt

fastrat: while you are giving away trade secrets, I would appreciate some advice on a homelite 25.

OLD_SLOW and in the WAY

reams and volumes have been posted on homelite mods and basically id have to write a book to explain them.... do a search here and on google then come back with questions...

noworknguy

My Feedback: (197)

Great help.

propellantchem

So where is everyone pulling all of the vintage threads from?

The exhaust ports on my 31cc Ryobi were closer to 130 degrees stock in the three that I did, but still a nice chart. (I found running in an end mill cut down the porting time considerably)

Thanks to whoever dug the chart out.

Twin Star

I really hate to be a spoiler but... There are varying specifications within the engine makes and displacements on you list as I have found. This is a great starting point though to begin a catalog of those differences. It would also be a good subject for open source contributions.