NRG 140cc twin engine in progress.

just a thought, how are you going to set them to fire at opposing times? somekind of cdi thats been faffed with by a 15 year old computer genius?

 

I'm going to use 2 ignition pick-ups, 180 deg's apart, 2 cdi's. The cdi's wiring is piggy backed, it's only the pick up wire that's different.

 

A 2 into 1 pipe would be quite cool. A nightmare to work out, get right and setup properly..but still pretty cool

 

dont hold me on this as iam not a 2smoke genius,,,but a 2 stroke engine produce's pulses through the exhaust which turns around in the expansion chamber giving different power at different revs

some exhausts are good for torque and some give the power at the top of the rev range,,,,,,,putting one exhaust on two cylinders would be like double penetration,,,,someones gona get hurt!!!

have you seen the italjet formula 125cc??,,,twin exhaust


but saying all that,,i could be wrong

 

Which is why youd have to join them after the expansion chamber, itd have to be some masterful work of art to make 2 cylinders go into one pipe

 

but then you would have the same setup as marsh has done but with one end can,,,,abit pointless

 

The only point i could see, is it might look cleaner. Just having one end can could look less cluttered than two

 

nahhh,,,,it would look like a fat guy with a little willy

marsh has got it right,,,,would look better gp style,,stacked

but its gona be a beast whatever the weather

 

Hahahaha liking the comparison

 

I'd think the hardest thing with a 2-1 would be finding a pipe that matches the engine and can handle double the volume of exhaust gas going through it. Doubt anything off the shelf will do it

 

have you seen the moving diagrams of a 2 stroke engine?,,,,,,,,watch what the exhaust gasses do when they enter the expansion chamber,,,,,,now imagine two cylinders putting gasses in one pipe

 

It would just fill up twice as fast. No problem

 

then why have we not seen one?,,,,,,every twin cylinder 2 stroke i can think of has two pipes

 

Fair point. Cheap and easy are the only real reasons why most things are how they are though tbh. The V4 2T NSR race bikes had some kind of double 2-1 if i remember and alot of early 2t cars had 2-1/4-1s for what its worth. Probably not totally impossible if you care enough. This thread goes to show theres a first time for lots of things

Marsh is one of those 2smoke genuises you talk about though so I'm sure the idea is in good hands either way lol

 

the v4 2 stroke nsr race bike has 4 expansion chambers and 4 end cans

 

here you go, thats for a gt380 or 550 triple. i think it was allspeed that made them i could be wrong tho. ive seen them for twins too

 

first off,,,,sorry marsh for the long convo in your thread because its a cracking project

scubabiker,,,both bikes you mention have 3 exhausts for each cylinder,,,,,,i think the exhaust in your picture must of been abit of an experiment,,not sure how it could work because the expansion chamber is way to small,its the same size as one of the standard chambers

interesting to see though,,,would be good to see it fitted to a bike and running,,still cant imagine how all three cylinders could pump into one exhaust


i mentioned the italjet formula 125 a few posts back,,,,,this twin cylinder scooter has two exhausts as standard,,,,,you can also buy a performance endy exhaust for it,,again this is a twin exhaust

 

thats an aftermarket exhaust, micron to be exact, they made them for the twins and tripples, maybe gibson/allspeed made them too. i believe gibson are still making pipes

 

right chaps this is what ive found,,,,,a 3-1 2stroke exhaust will never outperform an expansion chamber for each cylinder because of the pulses hitting eachother inside the pipe

a 2-1 2stroke exhaust will give good results when setup to the crank but still wont perform better than a chamber for each cylinder

setup right these pipes are good for saving weight and producing a noise like no other,,,,but again there experiments that dont fit well with the 2 stroke design

these words have come from someone who builds exhausts just like the ones posted above

just watched a few vids of these,,,,,they sound like screaming banshees,,,very nice

and supposedly there used on snowmobiles all the time,,,something to do with the crank degree,,not sure

peace out

 

I'm all for hearing and taking good advise, I'm no 2t expert or 2t tuning wizard, I like two pipes and the way they sound just like my old rg 250's of years ago, so that's what I'm using. Once the twin's up and running I could re-make the pipes "stacked". I'm doing the twin as a project like the Italjet 125 but this should be more reliable! I'm only doing the twin as something to do.