Honda Spree and Elite 50 Forums

Which 2- stroke engine produces more power? vertical or horizontal head design? explain why!

horizontal becues my express has a horizantal and it has major power. also it does not have to pus the piston up, but sidewayss.... and maby how the pair and gas get into the engine...

wow what a great question.. i will take a shot at this one.. i think horizontal because it is geting more oil that way and makes the piston slide alot more ezer then it would haveing to go up and down. idk just a suggestion

Well, assuming the same displacement, and the same crank size... What's at work here?

Gravity... The fuel and the air it's suspended in have to fight directly against gravity, using air pressure to get into the top half of a vertical cylinder. However, the piston does get a very slight assist when on the downstroke from the same force...

In a horizontal, most of the motion is lateral, perpendicular to gravity... You don't have as much distance to travel vertically to get air/fuel moved... and if you're already in motion, the forward acceleration (if there is any) should help the piston kick back into position.

Truthfully, I can't see as any of these reasons would lead to a notable increase in HP... I mean, gravity? lateral acceleration? We're measuring newtons of force here... Please fill us in on the answer.

yeah this should be interesting

My 2 cents. Its a packaging/design issue. I'd say horizontal has more potential, at least on scooters.

All the vertical designs I've seen on scoots don't allow the carb to package onto the back of the cylinder, they have to port through the case. This increases the intake volume and lowers the compression on that side of the piston, since 2-strokes compress both ways. Also, the intake tract is longer, hindering efficient high RPM operation. On horizontal engines, the carb can port straight through the cylinder (like it is on most bike engines, ala RZ350). Short, semi-straight runs, good for flow and high RPM.

The disadvantage is that horizontal engines are longer (jug sticks out in front,) so the overall bike either grows in length (bad) or the frame has to be designed to envelop the engine (more expensive.) Spree frame is a good example of an inexpensive design.

The other major power boost, watercooling, seems to be indifferent to vertical or horizontal, so that's a non-issue IMHO.

BTW, gravity effects are negligible compared to mass inertia effects. Do the math.

yey i was right... some what?

From what i remember about the article it mentioned slosh at high revs floods the piston, thats why all 2-stroke dirt bikes have a vertical design?even the old rare 650cc triples were vertical, you can port case the channels to minimize slosh but thats getting radical.