BMW 7 series uses direct injection

[WinkOsmosis]

Wow.. I thought all lawnmowers were 2-stroke. I also used to think most bikes were 2-stroke. Hmmmm.

 

[ElFenix]

Originally posted by: Eli

Originally posted by: ElFenix
bah, 8000 rpm is nothing. this one does 35,000

That's a 2-stroke engine.

8000RPM actually is something for a stock 4-stroke engine. That's one of the reasons I chose the Honda GXH50, there are very few 4-strokes that rev that high without extensive modifications. Gotta love Honda.

not only is it a 2 stroke but its an RC car engine and i swear those things must have tiny strokes because they spin tons more RPM and make much more power than a similar sized aircraft engine. the RC 4 strokes do about 10,000 rpm

 

[Eli]

Originally posted by: WinkOsmosis
Wow.. I thought all lawnmowers were 2-stroke. I also used to think most bikes were 2-stroke. Hmmmm.

It seems that most dirt bikes are 2-stroke.. simply due to their high power/weight ratio.

I'm sure there's someone that still makes 2-stroke mower engines(Is Lawnboy still around?), but they're virtually extinct.. like I said, mostly convienence factors(mixing oil sucks), but also due to longevity factors.. It's pretty expensive to make a 2-stroke that lasts a long time(at least comparitivly), as it requires roller bearings throughout the engine.. while your resident cheapy 4-stroke lawnmower engine will run for 10 years on plain sleeve bearings with an oil change once a year.

The big-end rod bearings are just aluminum against the steel crankpin, not even any bearing inserts. The mains, again, are just the steel crankshaft against the aluminum engine casing.

The more expensive engines(All Hondas, and the Vanguard and I/C line of Briggs) will have ball bearing mains.

For mad indian, and anybody else interested.. here's a very simple animated gif showing how a two-stroke engine works.

2-stroke cycle

Here's another one, this one shows how an expansion chamber works.

2-stroke expansion chamber

Not sure how to get IE to play them over and over instead of just once. Heh. Can just use F5 I guess.

 

[Eli]

Bump for interesting discussion.

 

[mAdD INDIAN]

hmm..how about we take a different angle, and look at the Stirling Cycle engine. It's an external combustion engine, which pretty much adjusts the pressure and temperature of the gasses/liquids to create combustion. The idea is to use a set amount of gas to produce infinite amount of power.

Info on the Stirling Cycle

 

[mAdD INDIAN]

bump!

 

[Eli]

Originally posted by: mAdD INDIAN
hmm..how about we take a different angle, and look at the Stirling Cycle engine. It's an external combustion engine, which pretty much adjusts the pressure and temperature of the gasses/liquids to create combustion. The idea is to use a set amount of gas to produce infinite amount of power.

Info on the Stirling Cycle

The problem with the Stirling cycle engine is that it develops realitivly little power.... Especially compared to the ammount of potential power in the fuel used for external combustion.

Almost no torque at all. You just can't compare the force that a fuel makes expanding while burning to the force a gas creates while cooling and shrinking.

Do you still have the power problem with your lawnmower dying in tall grass?

 

[JYDog]

I read sometime back that by 2004 there will be a large number of buses and commerical trucks(that employs this diesel engine) that will have electromagnetic valves. Apparently, diesels presents less problems for EMV because of its short rev ranges and thus are easier to introduce to the masses.

 

[Eli]

Originally posted by: JYDog
I read sometime back that by 2004 there will be a large number of buses and commerical trucks(that employs this diesel engine) that will have electromagnetic valves. Apparently, diesels presents less problems for EMV because of its short rev ranges and thus are easier to introduce to the masses.

Yeah, that makes sense.

It will probably be a while after that before we see an S2000 with electromagnetic valves.