2-stroke vs 4-stroke - power/efficiency differences???

[Jacked]

2 bangas for sure. Why you think under the LAMS motorcycle laws they banned all 250cc 2 stroke bikes but allowed some bikes upto 600cc!

[Zeyphly]

Alot of old GM 2 stroke diesels were blown not supercharged. The difference is that the intake and exhaust were open at the same time to allow the cylinder to be totally free of exhaust fumes.

[tweak'e]

Alot of old GM 2 stroke diesels were blown not supercharged. The difference is that the intake and exhaust were open at the same time to allow the cylinder to be totally free of exhaust fumes.

quite correct. the supercharger was to feed air in rather than to provide boost. the later ones add turbo as well which provided the boost.

[GU-ish]

2 stoke = powerband.

[300WinMag]

This topic needs to be either Petrol or Diesel, as they are so different the way they work.
And 2 stroke Diesel's are Blown Not Super charged, some do have turbos fitted over the blower. It looks the same, works the same but technically is called a blower!

[uninformed]

there is some new (well old now) tecnologys coming into chainsaw 2 strokes, that use fresh air to help exhaust gases. by 2010 chiansaws will have changed becasue of epa, they will still be 2 stroke, but not as they are now.

this is how far some can take a simple 2 stroke engine:

http://www.youtube.com/watch?v=dk74GNiHp8U

Serg

[WRXZook]

This topic needs to be either Petrol or Diesel, as they are so different the way they work.
And 2 stroke Diesel's are Blown Not Super charged, some do have turbos fitted over the blower. It looks the same, works the same but technically is called a blower!

Blower/supercharger, both terms are used. GM call it a supercharger in the service and parts manuals I have used. It is there for scavenging, and there is a low pressure boost.

[KiwiBacon]

2 stoke = powerband.

And either side of the powerband. Not much.

[rockcrawler31]

mmmmmm. my old UDR rig had a 6V53 that used to sound farking horn on full noise. That bastard would rev it's tits off 23 hours a day and couldn't care less.

The last full size rig i was on had 2 600HP CAT's running the pumps and i still stalled them out

The offshore rig Wilcraft had 4 HUGE V12's running the pumps and another 4 for the hydraulics. At full song you had to wear earplugs under muffs and still couldn't stay down there for longer than a few minutes without permanent hearing damage.

Edit: sorry just realised it wasn't the wilcraft, but i'm buggered if i can remember the name of which one it was. Getting old sucks

[bogged]

2 stoke = powerband.

[Tomo_89]

just to make it clear.. detroit/GM 2 strokes have blowers not superchargers. They do not force in air or build up boost in the way that a supercharger does. Some people use GM blowers on big petrol applications but they rquire the rotors to be teflon coated etc.. to create enough pressure. Diesel 2 strokes use a blower to push out burnt gas on the overlap as there is no such exhaust stroke. As the piston goes down the exhaust valve opens and the exhaust starts to flow out of the port. when the piston gets low enough to expose the intake port the air from the blower pushes out the burnt exhaust gas and allows the cylinder to be filled with fresh air. A petrol 2 stroke has the fuel air mix delivired into the crankcase and is forced through a transfer tube into the cylinder by crakcase pressure. this is why petrol 2 strokes run oil in the fuel to lubricate the crank where as diesel run oil in a sump like a 4 stroke. turbo 2 strokes have a bypass valve on the supercharger which allows the air to bypass the super charger once it comes on boost.
GM stopped making them though due to emmissions and ecconomy. They sound nice at full noise though and rev alot harder than any other engine. i believe some are still produced for military applications where they need fast accleration and throttle response. Oh and alot of buses still use them.

[-Nemesis-]

2 strokes sound shit




At 7am sunday mornings on Stockton - why do they get up so friggen early!

[foolsp33d]

2 strokes sound shit




At 7am sunday mornings on Stockton - why do they get up so friggen early!

LOL.

ahhhh V12 anyone!?
http://www.youtube.com/watch?v=mutb7KgA9NM

[want33s]

just to make it clear.. detroit/GM 2 strokes have blowers not superchargers.

I don't think so Tim...

GM call it a supercharger in the service and parts manuals I have used. It is there for scavenging, and there is a low pressure boost.

Any belt or gear driven pump that pushes air into an internal combustion engine above atmospheric pressure is called a SUPERCHARGER. (not a blower)

[want33s]

I believe cutoff dates have been set for motogp (125's and 250's) and Trials.

Trials are dominated by 4 strokes now... Sherco, Montessa, Gas Gas to name a few are all 4 stroke.
No more stinky ring a dings.

[WRXZook]

Pretty much a moot point whether it is called a supercharger or blower as often both terms are used in the industry to describe the same thing. However.... it is more than 40 years since I began my apprenticeship, and will accept that training courses and my memory may have changed a little . Been looking for my old Detroit training manuals to provide some figures. Regardless most people who work on them have a great fondness for the engine. Very simple and with its own unique characteristics. I have seen glaring mistakes made when reassembling the inline engines because heads, cams, balance shafts, cranks etc can be reversed in the blocks. Always liked sitting in the dyno room while running in a rebuilt engine, turn the lights off and see the exhaust glowing red hot under load and with almost no exhaust noise because it is ducted outside, listen to all the mechanical noises.

I notice there seem to be a few who have ridden trials. I used to ride trials in the 70's and 80's and whenever I get the opportunity like to see any rounds that are close by. Can't believe the stuff they are riding now. Would love to have a ride on one of the modern 4 strokes.

[dumbdunce]

just to make it clear.. detroit/GM 2 strokes have blowers not superchargers.

I don't think so Tim...

GM call it a supercharger in the service and parts manuals I have used. It is there for scavenging, and there is a low pressure boost.

Any belt or gear driven pump that pushes air into an internal combustion engine above atmospheric pressure is called a SUPERCHARGER. (not a blower)

SUPERcharging refers to increasing the charge pressure above atmospheric. (turbos are SUPERchargers - TURBOCHARGER is a contraction of TURBine driven superCHARGER). Although it is possible to supercharge two stroke diesels, the correct term is "scavenge blower" when the BLOWER acts only to provide positive direction to the inlet airflow and exhaust. It really is called a blower on a two stroke diesel, and it is NOT a supercharger.

a two stroke diesel will not run without being scavenge blown.

[WRXZook]

Dumbdunce your training and experience is a lot more up to date than mine, I'll have to fall back on old age as an excuse. Did my automotive engineering in 67, diesel in 80 and automotive electrical in 85 so it has been a while now. I keep thinking I was taught that there was a pressure boost of 3psi above ambient in the GM 2 stroke non turbo engine but accept my recollection may be wrong. Still can't find my old text books and service manuals to prove how wrong I am.