Bun Freestyle's Offset dome's

A

astral

Location
knoxville,tn
Anyone have any info on these and the advantages to running an offset dome..Never seen it before.Says ==tranlated(kinda)

You offsetting chamber on exhaust port side when you want peak turn.

And a low level improves when it turns and sets a chamber 180 degrees.

use for Bun Freestyle cylinder head (Yamaha - all type).
Wonder what the compression is on these. :Eyecrazy:
 

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#ZERO

#ZERO

Beach Bum
Location
Florida - U.S.A.
It appears like the standard domes only come in the 23cc and 24.5cc sizes and they're most likely for flat top pistons using race gas.

Where did you find the offset domes, I don't see them on their web site? :scratchchin:
 
A

astral

Location
knoxville,tn
The inside of the dome looks like its smaller than 24 cc.. could just be the pic.Im running 26 cc dome's at 215 psi got to be alot of compression..
 
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R

restosud

old 2 smoke trick.a few outboards had that setup back in the day.i have a billet 550 head like that.
in theory it makes sense and does allow you to make up for flow discrepency within the cylinder in some cases.
worked well on 550's but they did not have boost ports either.
 

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DangerBoy

DangerBoy

Runs with scissors
Site Supporter
Location
Rincon Beach
they function to allow the intake charge, which is supposed to climb the intake side of the cylinder flow up thru the dome and down to the exhaust port and meet the charge coming up the exhaust port side, to aid in filling the cylinder with a fresh charge, they also change the way the Squish operates


they really only start to work at rpms that exceed those of our jet ski motors


Db
 
E

egbrig

The offset dome is designed for dealing with heat issues on the piston crown. The crown gets hotter the closer it is to the exhaust port so in effort to reduce the chance of detonation the combustion chamber is moved towards the cooler intake side of the crown. You can look it up in Turners.
 
SuperJETT

SuperJETT

So long and thanks for all the fish
Location
none
The way I read their description you put it on the exhaust side for peak rpms and on the intake side for bottom end?

I'm skeptical, show me a dyno!
 
E

egbrig

Another benefit along with decreased heat issues is the benefit of the burnt gases being cleared out of the combustion chamber more effectively or thats the theory. How it really works is something I'd like to know.
 
Flash-FX

Flash-FX

No Square..No Round..FX-1
Location
South Jersey Shore
restosud said:
old 2 smoke trick.a few outboards had that setup back in the day.i have a billet 550 head like that.
in theory it makes sense and does allow you to make up for flow discrepency within the cylinder in some cases.
worked well on 550's but they did not have boost ports either.
Click to expand...

The ad for that...The colors look cool.
 

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Dustin Mustangs

Dustin Mustangs

uʍop ǝpıs dn
Location
Holland, MI
egbrig said:
The offset dome is designed for dealing with heat issues on the piston crown. The crown gets hotter the closer it is to the exhaust port so in effort to reduce the chance of detonation the combustion chamber is moved towards the cooler intake side of the crown. You can look it up in Turners.
Click to expand...

What is 'Turners'?

Here is the section on this in a book I have, Two-stroke Performance Tuning by Bell.
 

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#ZERO

#ZERO

Beach Bum
Location
Florida - U.S.A.
Dustin Mustangs said:
What is 'Turners'?

Here is the section on this in a book I have, Two-stroke Performance Tuning by Bell.
Click to expand...
Turners Two-Stroke Racing & Turners Expansion Chambers he's well known for the TRS software and the squish velocity programs. http://www.tsrsoftware.com/

Good reading:

http://www.mediafire.com/file/trbmmunmyxh/Two-Stroke Tuner's Handbook by Gordon Jennings.pdf

http://www.mediafire.com/file/mmyzmwzjwz4/The Basic Design of Two Stroke Engines by Gordon P Blair.pdf

http://www.mediafire.com/file/wj4hemiyoym/Two-Stroke Performance Tuning by Graham-Bell.pdf

http://www.mediafire.com/file/imo2tzimfyo/Racing Handbook 1998.PDF
 
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