my custom exhaust build.

[a.graham52]

the time has come for me to throw away my gutted CG muffler and build myself my own creation. i downloaded the 2stroke exhaust wizard and will base my exhaust of their calculations. i wll be updating this as i go.

measurments (that i would like to have you guys critique as nessasary):

skyhawk gt5 66cc.

bore 47mm
stroke 36mm
exhaust port degrees: 183
transer port degrees: 122
exhaust port + gasket lenth 19mm

 

[a.graham52]

i removed the head to measure my bore and stroke. used my head bolts and some sockets as spacers to clamp down the cylinder.


i mesured my bore (diameter of the cylinder) and stoke (distance from bottom dead center to top dead center) with basic caliper. my measurments are in the OP.

after that i pulled the cylinder off the engine for measurments of the port sizes.

next i took cooking foil


and lined the cylinder with it


followed by installing a rubber glove inside the bore and blowing it up with compressed air, this formed the tinfoil to the cylinder wall nicely. i still had to take my finger and imprint the ports a bit more to get a good shape. im only worried about the size of the ports, not their locations in the bore and therefore dont care it things move around a bit.

now iv got this: Transfer, Exhaust, Transfer, Intake



the reason i needed do all this is because i needed to know the shape (not hard to tell anyways) of the exhaust port as well as its height and width. all this info is needed for the exhaust wizard.

next step is needing to measure the port opening degrees, (i strongly recommend doing this first before dissasembling the cylinder. i happend to do all this in the order of the wizard). i found a degree wheel offline and printed it off. cut it out and tapped it to the crank of the engine.

 

[a.graham52]

reserve post 1

 

[2door]

Looking forward to what you come up with. Are you going for performace or looks?

By the way, what is a 'reserve post'?

Tom

 

[a.graham52]

the reserve post is so i can seperate things like design, building, tuning etc and not have tons of conversation in between. i know i can edit the op but imo this is nicer looking.

so far the exhaust iv come up with is very long and very skinny.

 

[AssembleThis]

Hi a.graham52!

I would love to see your exhaust build. Pictures, many pictures, in stages if you can manage that. It would help me a lot in building my own. Welding I can do easily, it's the ideas I'm mostly looking for to mix with my own. I personally visualize things in 3D and go over them in my mind many times, having your ideas would help.

Dave
AssembleThis

 

[a.graham52]

is there any way to get the image ban lifted?

 

[2door]

is there any way to get the image ban lifted?

Image ban? Not sure what you mean.
If you want to repost a photo simply change the file name. You can just ad a number to it or whatever you want to change the photo file name.

Tom

 

[a.graham52]

I can only post 5 pics per post. Any way to change that?

 

[a.graham52]

my exhaust is on hold until i get a response back from buildandclick. im not liking the design tool. no matter how i make changes to the settings, the exhaust outcome is practically the same.

now they have a wicked anti piracy policy and if you fail to conform to it, the program will give you an exhaust that will "burn up" your engine. maybe i installed the program wrong, maybe its a dud, but either way until somone gets back to me im on hold.

 

[AssembleThis]

Hi a.graham52!

Bummer about the software glitches, hope it all works. I would really like to see your success in this project.

Dave
AssembleThis

 

[a.graham52]

yeah it produced this really long and skinny exhaust set up, i wanted to see if different adjustments would make it any bigger but it was a no go. still waiting on an email from the software guys.

 

[Theon]

That pipe does look a little thin, length is probably about right though, where were you after max power?
Normally I'd be wanting a 1" id header, with expansion chamber of around 3x header Dia.

 

[a.graham52]

my target rpm is 5500. puts me at about 26-27 mph. its a daily commuter so speed is not necessary.

 

[maniac57]

I'd guess there's a problem in the software. That pipe is far too thin to have much tuning effect on your engine.
Recheck your inputs. Something is wrong here.

 

[a.graham52]

I would agree. Hence why I did not proceed. Now here is my 2stroke ignorance... Does a stock CG have a boost port?

 

[Theon]

Target RPM of 5500 may be what's confusing the software? Probably too low?
For those revs I would be studying JAG's torque pipe.
This is fairly loosely what I have based my home made pipe on and it was lifting the front wheel at around 4500 to 5000 with a 44t and 26" wheel ( also boost ports, reeds, high comp, ect.)
I have it on a different motor now and a 39t but is still giving excellent power up to 8500 RPM, at which point it seems to put a rev limiter to the engine, likely the baffle needs to be a little longer for more revs, but the low to mid is a huge improvement and I'd like to build another similar , experimenting a little and getting the chamber to clear the cranks better.

 

[Theon]

Will need reeds to run a boost port, so no boost port on a stock CG.