Go Back   EcoModder Forum > EcoModding > Off-Topic Tech
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 04-16-2018, 12:42 PM   #31 (permalink)
(:
 
Frank Lee's Avatar
 
Join Date: Jan 2008
Location: up north
Posts: 12,272

Blue - '93 Ford Tempo
Last 3: 27.29 mpg (US)

F150 - '94 Ford F150 XLT 4x4
90 day: 18.5 mpg (US)

Sport Coupe - '92 Ford Tempo GL
Last 3: 69.62 mpg (US)

ShWing! - '82 honda gold wing Interstate
90 day: 33.65 mpg (US)

Moon Unit - '98 Mercury Sable LX Wagon
90 day: 21.24 mpg (US)
Thanks: 1,426
Thanked 3,088 Times in 1,964 Posts
The valves are held closed. Any flow takes hp.

__________________


  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 04-16-2018, 12:53 PM   #32 (permalink)
Master EcoModder
 
Join Date: Nov 2013
Location: Texas
Posts: 437
Thanks: 12
Thanked 97 Times in 89 Posts
Where is that data found. I'm willing to read it.
  Reply With Quote
Old 04-16-2018, 01:18 PM   #33 (permalink)
Master EcoModder
 
Ecky's Avatar
 
Join Date: Dec 2011
Location: Vermont
Posts: 2,815

Gaptooth - '00 Honda Insight
Team Honda
Gen-1 Insights
90 day: 66.06 mpg (US)

Such Fit - '07 Honda Fit Sport
90 day: 41.27 mpg (US)

Velomobile - '13 Sun Seeker EZ-TAD SX
Last 3: 2142.86 mpg (US)
Thanks: 969
Thanked 1,074 Times in 681 Posts
This was worth a read:

Honda Worldwide | Civic Hybrid | 1st Generation Civic Hybrid

Quote:
The New Honda IMA System employs the VTEC System to stop operation of valves in three of the four cylinders, reducing engine friction by 50%, and making possible highly efficient electrical regeneration.

VTEC Cylinder Idling System
When the throttle is open during acceleration or cruising, the valve liftmode rocker arm and the idle-mode rocker arm are engaged via a synchronizing piston. During deceleration, as soon as the throttle is closed and regeneration begins, the synchro piston is positioned inside the idle-mode rocker arm, disengaging the lift-mode rocker arm so that the valve remains at rest. Since the cylinder is sealed off, pumping losses (resistance caused by engine aspiration) that result in engine friction are reduced, and the wheels' rotational energy is effectively transmitted to the motor. Moreover, cylinder idling can be maintained at engine speeds as low as 1,000rpm, for even greater regenerative efficiency.
So, Honda chose to keep the valves closed, rather than open, the logic being that the air inside will act as a spring, and the energy used in compression would be mostly recovered during expansion. Leaving them open would force the engine to pump air in and out of the cylinder, resulting in lost energy.

So, it's better to deactivate cylinders by closing all valves, rather than leaving them open.

Honda's system is also extremely reliable. You basically never hear about failures with their variable cam system, which has been in most of their production cars since the early 90's.
  Reply With Quote
Old 04-16-2018, 01:28 PM   #34 (permalink)
Master EcoModder
 
Join Date: Nov 2013
Location: Texas
Posts: 437
Thanks: 12
Thanked 97 Times in 89 Posts
Thank you, but this refers to deceleration. I'm interested in using reduced cylinder numbers to maintain speed. I will look into the V6 non-hybrid system.
  Reply With Quote
Old 04-16-2018, 01:33 PM   #35 (permalink)
Master EcoModder
 
Join Date: Nov 2013
Location: Texas
Posts: 437
Thanks: 12
Thanked 97 Times in 89 Posts
This is more applicable, and yes, Honda closes deactivated valves. I may need to revise my thinking on leaving the valves open. I still prefer my rotating deactivation, giving each cylinder it's firing 1 out of 3 normal times.
Honda Worldwide | Technology Picture Book | VCM

Last edited by Angel And The Wolf; 04-16-2018 at 01:40 PM..
  Reply With Quote
Old 04-16-2018, 01:59 PM   #36 (permalink)
Master EcoModder
 
Join Date: Nov 2013
Location: Texas
Posts: 437
Thanks: 12
Thanked 97 Times in 89 Posts
Honda seems to be saying that compression and down stroke balance each other out in deactivated cylinders, but I believe each is a resistance, unless... the valves are deactivated at BDC with a full cylinder of air. In that case, spring back from the fully compressed cylinder might assist in powering compression in the fully expanded cylinder.
It may even help if the deactivated cylinders are closed halfway through the intake stroke.
only half the air to compress or expand.
  Reply With Quote
Old 04-16-2018, 02:02 PM   #37 (permalink)
Master EcoModder
 
Ecky's Avatar
 
Join Date: Dec 2011
Location: Vermont
Posts: 2,815

Gaptooth - '00 Honda Insight
Team Honda
Gen-1 Insights
90 day: 66.06 mpg (US)

Such Fit - '07 Honda Fit Sport
90 day: 41.27 mpg (US)

Velomobile - '13 Sun Seeker EZ-TAD SX
Last 3: 2142.86 mpg (US)
Thanks: 969
Thanked 1,074 Times in 681 Posts
It should help either way. If the valves are closed at TDC, there will be a vacuum to overcome on the downstroke, but that same vacuum will pull the piston back up with equal force on the upstroke. Conversely, if they're closed at BDC, air pressure will create resistance on the upstroke, but it will push the piston back down on the downstroke. My bet is on vacuum being slightly better, because you'll have less heat lost through the cylinder walls if there's less air, but that might be negligible in the grand scheme.
  Reply With Quote
Old 04-16-2018, 02:03 PM   #38 (permalink)
Master EcoModder
 
Join Date: Nov 2013
Location: Texas
Posts: 437
Thanks: 12
Thanked 97 Times in 89 Posts
Quote:
Originally Posted by Ecky View Post
So, Honda chose to keep the valves closed, rather than open, the logic being that the air inside will act as a spring, and the energy used in compression would be mostly recovered during expansion. Leaving them open would force the engine to pump air in and out of the cylinder, resulting in lost energy.
Is it possible that Honda didn't want the deactivated cylinders draw and blow to interfere with the other cylinders' intake and exhaust? Something that might be avoided by separate intakes for each cylinder?
  Reply With Quote
Old 04-17-2018, 03:01 AM   #39 (permalink)
Master EcoModder
 
Join Date: Nov 2013
Location: Texas
Posts: 437
Thanks: 12
Thanked 97 Times in 89 Posts
OK, I want to thank Ecky*, Frank Lee, Piotrsko, cRiPpLe_rOoStEr, mannydantyla, and Grinder74, for helping to guide me through this exercise, and showing me how various parts of it won't work, Synchronizing the two engines without much cutting into the engine cases, and the staggered firing pattern I came up with because of the unbalanced deactivated cylinder pairs (two trying to pull vacuum at the same time). Seems the only promising idea is the combined clutch/shift pedal, and I'm not sure there isn't a better layout for that. Anyway, I'm abandoning this thread. Thanks guys.

  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2018, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com