67/80 pipe stinger

[David Ashcroft]

The stock cmb 67/80 large volume Pipe stinger id is about 3.93thou seem small.What id do you like stock or larger? Not much meat on stinger could probably drill Max . 420thou. Using in mono cmb80.

Thanks

 

[Terry Keeley]

I like 0.400" on my 67 motors and run about 0.430" on my 90's...

 

[Jim Allen]

These numbers are interesting, considering that the stinger on my 26 cc gas engine is .406" ID X 5.5" long. The gas engines exhaust gas temperature is very much higher than a nitro engine. What could be the reason for this difference in ID's?

JA

 

[FloridaScaleBoater]

David;

Jerry Crowther, years ago supplied me with a new pipe that was drilled with (4 1/8th inch holes) at 90* 12 oclock, 3 oclock 6 oclock and 9 right where the stinger starts to enlarge into the pipe (that would be at the leading end of the stinger)

Worked on my 67 Ducer

 

[David Ashcroft]

Rick four 1/8" holes interesting.

Jim I have read small stinger id can improve low end rpm,but too small can destroy piston (too hot).I did drill stinger to .420 to relief back pressure because I want to trial large spraybar on my carby .

 

[bermudadude]

i use .470 for .80 engines ,as a bench mark. 1/2” for anything larger,nitro or otherwise. idk how guys run these small stingers. maybe it explains all the overheating and destroyed engines i read about ..idk. diff people like diff stuff i suppose

 

[David Ashcroft]

Shawn you using a macs pipe or which?

 

[Jim Allen]

Rick four 1/8" holes interesting.

Jim I have read small stinger id can improve low end rpm,but too small can destroy piston (too hot).I did drill stinger to .420 to relief back pressure because I want to trial large spraybar on my carby .

David,

Stinger inside diameter & stinger length will be determined by the total displacement of the tuned pipe being used, when compared to the displacement of the engine. Tuned pipe volumes that are less than 18 times the engines displacement will require short, large diameter stingers, when used on high compression engines. Many racing two strokes use pipe volumes that are 30 times the engines displacement. Stinger inside diameter greatly effects the engines operating temperature, while stinger length has less of an effect. Actual measured pressure amounts of approximately 120 inches of water or 4.3 psi within tuned pipe systems can be greatly decreased by to large of a stinger inside diameter & to short of a stinger length. Low tuned pipe pressure amounts make the use of large, straight through bore, carburetors impossible. When tuned pipe volumes, compared to engine displacements, are optimized, it becomes easily possible to use stingers with a total length of 13.5 time the stingers inside diameter. There will be no engine overheating problems.

JA

 

[David Ashcroft]

Yes thanks Jim I understand I think comparing my 13.2cc engine to pipe size.,I reckon around 300 -330cc pipe volume would suit with a 5.6" stinger at. 420thou