LT-4 GDI Two Stroke Engine Design
Thread Starter
FormerVendor
iTrader: (1)
Joined: Nov 2008
Posts: 2,155
Likes: 18
From: Santa Ana, CA. USA
Professional Motorsports = Gallons per Mile ! 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
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
TECH Senior Member
Joined: Jun 2016
Posts: 22,291
Likes: 3,616
From: Central Cal.
Thread Starter
FormerVendor
iTrader: (1)
Joined: Nov 2008
Posts: 2,155
Likes: 18
From: Santa Ana, CA. USA
Charge Timing : Piston Port vs Poppet Valve 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
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
TECH Senior Member
Joined: Jun 2016
Posts: 22,291
Likes: 3,616
From: Central Cal.
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?
TECH Addict
Joined: Oct 2016
Posts: 2,513
Likes: 480
From: PDX-OR-USA
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..
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..
TECH Apprentice
Joined: Sep 2006
Posts: 328
Likes: 3
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
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 ??
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
Last edited by Krom; Jul 30, 2018 at 07:37 PM.
TECH Senior Member
Joined: Jun 2016
Posts: 22,291
Likes: 3,616
From: Central Cal.
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.
Last edited by G Atsma; Jul 30, 2018 at 08:21 PM.
TECH Apprentice
Joined: Sep 2006
Posts: 328
Likes: 3
Krom, you sure don't read well. My point is that 2-stroke engines have HISTORICALLY been relatively far less efficient furl 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.
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
Originally Posted by G Atsma
SUCK fuel for power output
Last edited by Krom; Jul 30, 2018 at 08:20 PM.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo TECH Senior Member
Joined: Jun 2016
Posts: 22,291
Likes: 3,616
From: Central Cal.
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.
TECH Apprentice
Joined: Sep 2006
Posts: 328
Likes: 3
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
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
Originally Posted by G Atsma
SUCK fuel for power output
TECH Senior Member
Joined: Jun 2016
Posts: 22,291
Likes: 3,616
From: Central Cal.
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.
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.
TECH Apprentice
Joined: Sep 2006
Posts: 328
Likes: 3
epa data is here if you dont like or trust the nice color graphs:
https://www.epa.gov/compliance-and-f...-and-equipment
https://www.epa.gov/compliance-and-f...-and-equipment
TECH Apprentice
Joined: Sep 2006
Posts: 328
Likes: 3
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.
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.
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.