Go Back   EcoModder Forum > EcoModding > General Efficiency Discussion
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 04-10-2008, 10:08 AM   #1 (permalink)
Dartmouth 2010
 
SVOboy's Avatar
 
Join Date: Nov 2007
Location: Hanover, NH
Posts: 6,427

Vegan Powa! - '91 Honda CRX DX
Team Honda
90 day: 66.52 mpg (US)
Thanks: 92
Thanked 114 Times in 82 Posts
Send a message via AIM to SVOboy Send a message via MSN to SVOboy Send a message via Yahoo to SVOboy
Variable compression engine reduces fuel use 30%?

From ABG: http://www.autobloggreen.com/2008/04...-ratio-engine/

Quote:
Meet the MCE-5 VCR engine, coming at you from France. VCR stands for Variable Compression Rate, and its creators claim it will replace conventional Fixed Compression Rate engines. According to the press release (found after the jump), what is special about this engine is that it's based on a combination of rod-crank mechanism and long-life gears, integrating both power transmission and compression ratio control for each cylinder.

MCE claims that this allows ratios from 7:1 to 20:1, which adapts the engine for most usage requirements. Oh, and this reduces fuel consumption by 30 percent, as two other prototypes of VCR engines showed by Saab and Audi in 2000. MCE also claims the design is more durable and robust, and will have lower maintenance costs.

This engine has no impact on the rest of the components of a vehicle, so it's potentially installable in every sort of vehicle. MCE's current prototype offers 160 kW (218 HP) with a 1.5-liter engine.
Sounds interesting, at least.

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 04-10-2008, 10:24 AM   #2 (permalink)
Master EcoModder
 
tasdrouille's Avatar
 
Join Date: Jan 2008
Location: Mirabel, QC
Posts: 1,672

The Guzzler - '08 Hyundai Elantra GL
90 day: 33.12 mpg (US)

Got Soul? - '11 Kia Soul 2U
Thanks: 35
Thanked 85 Times in 56 Posts
Here's additional information at autospeed:

The technologies and control of variable compression ratio engines.
__________________



www.HyperKilometreur.com - Quand chaque goutte compte...
  Reply With Quote
Old 04-10-2008, 12:24 PM   #3 (permalink)
ECO-Evolution
 
Lazarus's Avatar
 
Join Date: Nov 2007
Location: Central Texas
Posts: 1,482

Iron Horse (retired) - '97 Iron horse Intrepid

Ninja - '08 Kawasaki 250R
90 day: 76.23 mpg (US)
Thanks: 17
Thanked 44 Times in 33 Posts
Very interesting. I wonder how it will stack up with emissions testing though?
__________________
"Judge a person by their questions rather than their answers."

  Reply With Quote
Old 04-10-2008, 08:17 PM   #4 (permalink)
Liberti
 
LostCause's Avatar
 
Join Date: Feb 2008
Location: California
Posts: 504

Thunderbird - '96 Ford Thunderbird
90 day: 27.75 mpg (US)
Thanks: 0
Thanked 7 Times in 7 Posts
Great articles SVOboy and tasdrouille.

What I don't understand is how the heightened compression ration will be used. If knock isn't going to be eliminated by direct injection or some other technique, is there something I'm missing? I suppose an engine may not knock under low load (cruising) and only under acceleration...

I also wonder why variable compression can't be achieved with variable valve timing. Toyota's "Atkinson" cycle engine uses late valve closure to reduce the compression ration, so why not apply variable valve timing to choose high, low, or gradations in between as technology becomes more advanced. Seems simpler than linkages, moveable heads, variable height pistons, etc.

- LostCause
  Reply With Quote
Old 01-02-2009, 05:31 PM   #5 (permalink)
amateur mech. engineer
 
Join Date: May 2008
Location: New York City
Posts: 112

Sporty Accord - '88 Honda Accord LX-i
90 day: 23.25 mpg (US)

Dad's Camry - '01 Toyota Camry CE
90 day: 22.81 mpg (US)

Artie's Camry - '98 Toyota Camry
90 day: 37.3 mpg (US)
Thanks: 0
Thanked 15 Times in 3 Posts
LostCause:

What you're missing is that the compression ratio will be high during low loads and low during high loads. The compression pressure will remain almost constant while the engine load changes. The higher compression ratio will give much better efficiency during low power operation. The peak pressures will be limited to avoid problems with knocking and preignition.

Variable valve timing will change the effective compression ratio but it can't give the engine high compression during light loads. A really efficient engine would have both variable compression ratio and variable valve timing. It could stay efficient over a wide range of power levels, unlike normal engines. The low combustion pressure and high pumping loss makes them less efficient at low load operation. Variable valve timing reduces pumping loss and variable compression ratio allows higher combustion pressure at low loads.

The disadvantage of the variable compression ratio is that it might be too expensive for some economy cars. I think that a reasonable compromise is to use a high fixed compression ratio such as 14:1 with variable valve timing, variable intake air temperature, and variable fuel mixture. The engine could use high octane fuel only for high power levels and low octane fuel most of the time. Some water injection may also be good for eliminating knock when making high power.

Last edited by Andyman; 01-02-2009 at 05:38 PM..
  Reply With Quote
Old 01-02-2009, 06:51 PM   #6 (permalink)
Master EcoModder
 
Join Date: Jan 2008
Location: Victoria , Australia.
Posts: 499
Thanks: 20
Thanked 46 Times in 33 Posts
An interesting idea but to get the same result for a lower cost and with already proven technology a turbo / supercharger combination would be a better alternative from the car makers point of view.
No licence fees to pay either.

Pete.
  Reply With Quote
Old 01-02-2009, 09:10 PM   #7 (permalink)
Master EcoModder
 
Join Date: Mar 2008
Location: Edmonton, AB, Canada
Posts: 531
Thanks: 11
Thanked 12 Times in 11 Posts
No not the same results Peter,
Forced Induction gives you variable compression but a fixed expansion ratio. This engine does both. Its the fact that the expansion ratio is larger than the compression ratio in the atkinson cycle that makes it more fuel efficient.

  Reply With Quote
Reply  Post New Thread


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Engine braking without using fuel idea Dane-ger EcoModding Central 38 02-04-2010 10:35 AM
How much fuel does it take to re-start a warm engine? MetroMPG Hypermiling / EcoDriver's Ed 9 08-15-2009 02:31 PM
Coasting experiment: engine on VS engine off on a fixed route = 12.9% gain MetroMPG Hypermiling / EcoDriver's Ed 6 02-22-2008 08:38 AM
DIY decel fuel cutoff; alternator regulation; auto start/stop MetroMPG EcoModding Central 0 11-29-2007 02:04 PM
Basic EcoDriving Techniques and Instrumentation SVOboy Instrumentation 2 11-17-2007 11:38 AM



Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com