Go Back   EcoModder Forum > EcoModding > EcoModding Central
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 08-11-2014, 12:23 PM   #1 (permalink)
Cyborg ECU
 
California98Civic's Avatar
 
Join Date: Mar 2011
Location: Coastal Southern California
Posts: 6,299

Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 66.42 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
90 day: 3671.43 mpg (US)
Thanks: 2,373
Thanked 2,172 Times in 1,469 Posts
Fuel economy & valve lash (1998 Honda Civic)

I am wondering how valve lash affects fuel economy and emissions. It seems like loosening (within reason) should benefit both.

In essence loosening the valve lash to max spec should slightly reduce the overlap time between intake and exhaust, resulting in at least three things: less fuel escaping unburnt into the CAT, therefore more complete burn in chamber, and more low-end torque.

As ecomodders who drive the low end rpm band all the time this seems like a good thing. Heck my car almost never crosses 2500 rpms (~65-70 mph) even on the freeway.

So on my 1998 Civic the service manual's recommended spec is 0.009-0.011 for exhaust valves and 0.007-0.009 for intake valves. I set them to max spec of 0.011 and 0.009 on advice I trust and after some corroborating reading online.

I'd be interested in a technical discussion, because much of it would still be over my head a bit and therefore give me a chance to learn something!

Thanks.

__________________
See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.



  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 08-29-2014, 03:05 PM   #2 (permalink)
Administrator
 
Daox's Avatar
 
Join Date: Dec 2007
Location: Germantown, WI
Posts: 11,203

CM400E - '81 Honda CM400E
90 day: 51.49 mpg (US)

Daox's Grey Prius - '04 Toyota Prius
Team Toyota
90 day: 49.53 mpg (US)

Daox's Insight - '00 Honda Insight
90 day: 64.33 mpg (US)

Swarthy - '14 Mitsubishi Mirage DE
Mitsubishi
90 day: 56.69 mpg (US)

Daox's Volt - '13 Chevrolet Volt
Thanks: 2,501
Thanked 2,585 Times in 1,553 Posts
A test would be a great way to show if there is any benefit...
__________________
Current project: A better alternator delete
  Reply With Quote
Old 08-29-2014, 03:12 PM   #3 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,513

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.71 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car - '14 Mitsubishi Mirage ES (base)
90 day: 60.16 mpg (US)
Thanks: 4,058
Thanked 6,957 Times in 3,602 Posts
The economy cam in the Metro XFi was ground for lower lift and duration, shifting the torque peak down.

You'd be effectively doing something similar by going to maximum adjustment, no?
__________________
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
Old 08-29-2014, 04:08 PM   #4 (permalink)
Master EcoModder
 
Join Date: Sep 2009
Posts: 5,927
Thanks: 877
Thanked 2,024 Times in 1,304 Posts
Max gives you less lift and duration as well as max distance to the next adjustment.

regrards
Mech
  Reply With Quote
Old 08-29-2014, 11:41 PM   #5 (permalink)
Cyborg ECU
 
California98Civic's Avatar
 
Join Date: Mar 2011
Location: Coastal Southern California
Posts: 6,299

Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 66.42 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
90 day: 3671.43 mpg (US)
Thanks: 2,373
Thanked 2,172 Times in 1,469 Posts
Well, I wouldn't know how to ABA test such a thing, because it would take most of a day in between runs, allowing too many conditions to change. But the engine sounds differently (I think a little louder). And my FE has not suffered, though I can't tell if the valve setting has anything to do it. My primary goal was emissions test prep. And my smog test went smoothly. A side effect seems to be that it *might* help fuel economy at the same time.
__________________
See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.



  Reply With Quote
Old 08-30-2014, 12:48 AM   #6 (permalink)
Too many cars
 
Gasoline Fumes's Avatar
 
Join Date: Oct 2009
Location: New York State
Posts: 1,568

CRXFi - '88 Honda CRX XFi

Insight 256 - '00 Honda Insight
Team Honda
Gen-1 Insights

Insight 5342 (no IMA) - '00 Honda Insight
Team Honda
Gen-1 Insights
90 day: 66.3 mpg (US)
Thanks: 1,316
Thanked 781 Times in 465 Posts
I set my intake and exhaust valves to the thickest of my feeler gauges. I don't remember the size. It rattles more and it might cause excess cam wear, but I felt a slight torque increase.
__________________
2000 Honda Insight
2000 Honda Insight
2000 Honda Insight
2006 Honda Insight (parts car)
1988 Honda CRXFi
1994 Geo Metro

  Reply With Quote
Old 05-27-2015, 03:36 AM   #7 (permalink)
EcoModding Lurker
 
Join Date: May 2015
Location: U.S.
Posts: 9

Betsy - '97 Honda Civic HX
Thanks: 0
Thanked 0 Times in 0 Posts
I realize that it has been months since the last post on this thread but I am curious if any results came of this experiment?
  Reply With Quote
Old 05-27-2015, 09:34 AM   #8 (permalink)
Cyborg ECU
 
California98Civic's Avatar
 
Join Date: Mar 2011
Location: Coastal Southern California
Posts: 6,299

Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 66.42 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
90 day: 3671.43 mpg (US)
Thanks: 2,373
Thanked 2,172 Times in 1,469 Posts
Quote:
Originally Posted by Egriffy View Post
I realize that it has been months since the last post on this thread but I am curious if any results came of this experiment?
I can't tell. If there was a benefit as there might have been jn theory, it would have been very minor. No way to see such a small change through thr background data noise. Sorry.
__________________
See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.



  Reply With Quote
Old 05-27-2015, 09:46 AM   #9 (permalink)
Experienced UAW Mechanic
 
Join Date: Sep 2014
Location: Bear Lake
Posts: 363
Thanks: 7
Thanked 73 Times in 63 Posts
0.020" shouldn't hurt, but I'm not sure it'll help. And you really can't go any tighter than factory spec. More lash will cause the intakes to close earlier, trapping more fresh charge in at lower RPM, wwhich should help if your cruise RPM is too low. Likewise on the exhaust, the extra lash will help low RPM torque there again.
But if your cruise RPM is too high, then the tight end of factory spec would be better.
As you improve the aero of the car, it'll like less cruise RPM, or less lash.
  Reply With Quote
Old 05-27-2015, 10:41 AM   #10 (permalink)
5 pin sensor
 
Join Date: Sep 2014
Location: Dallas
Posts: 350

Zippy - '96 Honda Civic Hx
Team Honda
90 day: 40.77 mpg (US)

Boring - '11 Ford Fusion Sel
90 day: 21.88 mpg (US)
Thanks: 38
Thanked 73 Times in 56 Posts
I have not performed a valve adjustment in my civic, most likely has not been done in 150k miles.

__________________
Current: 1997 civic lx
Past: 1998hx/1996hx/1997lx/1997hx Cali/1997hx
OG lean burn member

My civic thread
  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com