pantera_efi

iTrader: (1)

Hi Krom, sure you ARE CORRECT.

THE application IS professional motorsports, Air Boat Racing !

I AM SURE that if you asked John Force the same question "what is your engine BSFC", I would NOT be able to POST his remarks, to your question, here on LS-1 Tech !

MY GUESS , for his report, is about 80 GALLONS per mile.

Lance

G Atsma

But what would that be in lbs/HP/hr, which is what BSFC is measured in?
My point above is that BSFC for a 2-stroke is greater than for a 4-stroke due to it's inherent comparative poor efficiency.

pantera_efi

iTrader: (1)

Hi G, the common two stroke Piston Port Valve timing is fixed AND symmetrical.
Thus the LOW efficiency causing a NEED for an Expansion Chamber exhaust style.

The Valve Timing I will chose will allow the exhaust poppet valve to open at 80*ATDC AND close at 45* ABDC.

The GDI will have matching timing, start of injection, at 45* ABDC.

My belief is that this valve timing will add efficiency AND LOWER the BSFC.

Lance

G Atsma

Agreed, Lance. But can a fully optimized 2-stroke ever meet the efficiency of a fully optimized 4-stroke? In other words, on a level playing field, can they be equally efficient?

pdxmotorhead

With the old Detroits, the torque was off the top,, you could not spin them fast, there is just too much intake to keep full, but you didn't care cause they hit full torque at about 1200 RPM.. The last of them used a 871 blower + 2 charge turbos to keep the blower full. There are still large diesels that use this method to get power,, Caterpillar V12 and V16 generators have a pair of blowers fed by a turbo each..

There are several traditional 2stoke applications that went 4 stroke for emissions and to keep oil in the engine.... But Yamaha and others are starting to do Injected 2 stokes that DONT need oil in the fuel ,, they use squirters on the piston bores from underneath and the exhaust ports are above BDC so far the jury is out on whether the port in block or port in head will win the day. The upside of in head valves is you could convert about any motor.

The Mazda Millenia motor I believe exploits a lot of pre-filled cylinder tech to get its efficiency and power.. Its not a standard cycle engine. Might be some tech to reference from it..

Krom

lb/hp/hr, as opposed to the si (metric) g/kw/hr

The thing is you havent made any point at all, just a un backed up empty claim

Not sure why you unable to, or un willing to answer such an easy question..
What BSFC to you consider efficient, and what is what you call ??

Any performance 2 stroke is far in excess of 100% VE, naturally aspirated
Evinrude's 2 stroke outboards have better fuel economy, and lower emissions than competitors 4 strokes.
Hell even the wiki for bsfc lists a 2 stroke as the 3 most efficient piston engines (beaten by a combined cycle turbine)

https://en.wikipedia.org/wiki/Brake_...el_consumption

G Atsma

Krom, you sure don't read well. My point is that 2-stroke engines have HISTORICALLY been relatively far less efficient fuel consumers than 4-stroke engines. I don't need to quote numbers. It is the relative efficiency between the two types that I am discussing. And my points are directed to Lance, not you.

Krom

nice try at backpedaling, you never said, mentioned, or implied, historically, you refused to answer a simple question, and "directing your points at lance" doesn't make you, or them any less wrong.
if you are going to make a bullshit claim like that, at least have the ***** to back it up...
You are the one that started the inefficient crap, BSFC is how its measured.
For an engine at WOT making peak power (the conditions that pertain to this thread, and lance is talking about) what is the bsfc that below you consider efficient, and above is

G Atsma

Cut the BS, Krom, I'm not going to argue historical facts with you or anyone else. 2-stroke engines are inherently less efficient than 4-stroke engines on a pounds of fuel per horsepower per hour basis. 2-strokers were never meant to be a fuel-economical design. They were designed as a cheap-to-build, cheap-to-buy simple design originally intended for cheap-to-build and -buy motorcycles and industrial engines. Specific fuel consumption was never intended to be their strong suit. All of this is historical fact.

Krom

The only bs is you and your claim

Krom

I'm not asking you to disprove Einstein here....

For an engine at WOT making peak power (the conditions that pertain to this thread, and lance is talking about) what is the bsfc that below you consider efficient, and above is and trying to call your opinion "historical fact"... good one lol

G Atsma

OK, disprove my "claim" I'm waiting....

Krom

Krom

That took a long time didn't it....

Would have been quicker, but you don't have the ***** to define your claim....

Krom

I forgot one..
This one would be important to the topic at hand, as with a prop, and no transmission, low rpm torque is important :

G Atsma

That's one example. And l'll give that to you. The reason most outboards went to 4-stroke from 2-stroke was fuel economy. Also starting ease, emissions... etc.
Evinrude is obviously doing something right. And/or there's been some amazing engineering breakthrough. But this is an exception to the general experience of 2-strokes.

Krom

epa data is here if you dont like or trust the nice color graphs:

https://www.epa.gov/compliance-and-f...-and-equipment

Krom

You're totally wrong about that too... LOL

outboards went 4 stroke for the simple reason that it was cheaper and easier to meet emissions standards with a carb 4 stroke...

2 strokes are very efficient at peak power, every 2 stroke with an expansion chamber (any and every performance application) has way over 100% VE at peak hp. Emissions get difficult at part throttle, technology makes that easier.

G Atsma

Your graphs are nice, and illustrative of what you have said. I believe all of it. Are there other examples of this besides Evinrude's?

Krom

Plenty.... 2 stroke DI has been in production since the late 90's
Etec, ficht, orbital, optimax, 90% of the sleds sold are 2 strokes