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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 12-04-2012, 12:51 PM   #1 (permalink)
Adventurist!
 
Join Date: Sep 2012
Location: Nashville, TN
Posts: 144

CLaero - '97 Acura CL Premium
90 day: 34.59 mpg (US)

CR-v - '03 Honda CR-V EX
Team Honda
90 day: 26.52 mpg (US)
Thanks: 9
Thanked 21 Times in 21 Posts
Terminal F/E; What's yours?!

After playing around with my VAFC for a little bit (fine tuning Vtec engagement) I decided to find out what my terminal fuel economy would be using a very simple method... Given that my car runs at 2700 Rpms during cruising speed, I tested the unloaded engine (vehicle stopped, trans in neutral) for fuel consumption in gph and netted approx 45mpg terminal F/E

70mph / 1.55gph = 45mpg

This would be the resultant mpg my Acura would make at a constant 70mpg, flat road, with no rolling resistance, air resistance, or drivetrain losses. Obviously this on its own does relatively no good, but it does allow for a realization of expectations, and will help guide you with the use of EOC, DWL, P&G, DFCO, aero mods, etc. in order to help achieve your goals

So my question is, what's yours?

__________________
'97 Acura CL 2.2L 5spd
'03 Honda CR-V 2.4L EX 4wd Auto
  Reply With Quote
The Following User Says Thank You to nbleak21 For This Useful Post:
brucepick (12-04-2012)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 12-04-2012, 01:20 PM   #2 (permalink)
OCD Master EcoModder
 
brucepick's Avatar
 
Join Date: Dec 2007
Location: Eastern CT, USA
Posts: 1,933

Outasight - '00 Honda Insight
Team Honda
Gen-1 Insights
90 day: 54.18 mpg (US)
Thanks: 429
Thanked 391 Times in 261 Posts
Does this men your car used 1.55 gph at 2700 rpm, not moving, warmed up, with all accessories switched off? I think that's what you're saying.

If so, try this calculation. Turn the math around and divide gallons by miles. That will tell you how much fuel is being consumed per distance, JUST to keep the engine turning. That is, not considering any useful output from it.

Now compare that number to your actual usual gallons per mile at that cruising speed. For my car, I found a surprisingly high percentage of fuel was used just to spin the mechanicals.

Now, if only you could cover distance without rotating your engine quite so many times. You'd save all that fuel.

Voila. The reason why many of us are big fans of coasting, with the engine idling in neutral or off as appropriate. Every revolution of the engine eliminated is fuel saved. You're better off at 2/3 or 3/4 throttle part time and engine "on vacation" the rest of the time, than you would be driving in a reasonable gear at whatever throttle position would work at that speed.

Using that technique, your terminal mpg isn't terminal at all because you can cover distance on highly reduced fuel use or none at all.
__________________
Coast long and prosper.
Driving '00 Honda Insight, acquired Feb 2016.



Last edited by brucepick; 12-04-2012 at 03:04 PM..
  Reply With Quote
Old 12-04-2012, 02:46 PM   #3 (permalink)
Master EcoModder
 
RobertISaar's Avatar
 
Join Date: Jul 2012
Location: camden, MI
Posts: 324

MC SBX - '95 Chevrolet Monte Carlo LS
Last 3: 29.75 mpg (US)
Thanks: 7
Thanked 55 Times in 46 Posts
Quote:
Originally Posted by nbleak21 View Post
I tested the unloaded engine (vehicle stopped, trans in neutral) for fuel consumption in gph
unrealistic of real-world driving conditions.

2700 RPM while not moving is a significantly different situation compared to 2700 RPM while accelerating in any gear, 2700 RPM while holding a speed in any gear and 2700 RPM while engine braking in any gear.

the load placed upon the engine is different in all of those situations.
__________________
  Reply With Quote
Old 12-04-2012, 06:18 PM   #4 (permalink)
Adventurist!
 
Join Date: Sep 2012
Location: Nashville, TN
Posts: 144

CLaero - '97 Acura CL Premium
90 day: 34.59 mpg (US)

CR-v - '03 Honda CR-V EX
Team Honda
90 day: 26.52 mpg (US)
Thanks: 9
Thanked 21 Times in 21 Posts
Quote:
Originally Posted by brucepick View Post
Does this men your car used 1.55 gph at 2700 rpm, not moving, warmed up, with all accessories switched off? I think that's what you're saying.

If so, try this calculation. Turn the math around and divide gallons by miles. That will tell you how much fuel is being consumed per distance, JUST to keep the engine turning. That is, not considering any useful output from it.
Yes, that is exactly what I did, netting a Terminal F/E of approx 45mpg at 70mph.


Quote:
Originally Posted by RobertISaar
unrealistic of real-world driving conditions.

2700 RPM while not moving is a significantly different situation compared to 2700 RPM while accelerating in any gear, 2700 RPM while holding a speed in any gear and 2700 RPM while engine braking in any gear.

the load placed upon the engine is different in all of those situations.
Yes, I understand all this, hence "Terminal."

My point in this thread is that by calculating your completely unloaded engine F/E at a given RPM, is that you CAN NOT exceed (nor by any chance meet) said MPG without the addition of other methods for extending fuel economy.


Was my original post really that hard to understand?
__________________
'97 Acura CL 2.2L 5spd
'03 Honda CR-V 2.4L EX 4wd Auto
  Reply With Quote
Old 12-04-2012, 06:35 PM   #5 (permalink)
Master EcoModder
 
Join Date: Oct 2012
Location: Carson City, Nevada
Posts: 612

Jimmy - '00 GMC Jimmy SLT
90 day: 21.18 mpg (US)

The White Gnat - '99 Suzuki Swift
Team Suzuki
90 day: 51.87 mpg (US)
Thanks: 240
Thanked 114 Times in 90 Posts
Interesting idea.

I think for me, a more usable figure would be to run it in gear, drive wheels off the ground, at "cruising speed", & see what THAT figure is. (we can actually get "miles covered" that way, too). I know that adds in the drivetrain drag, but how do we realistically reduce that? If you're going to say thin or synthetic oil, etc, etc, ok good. But (to me, again), maybe THAT's the way to test the synthetic oil, etc, etc. - wheels jacked up, running at cruising speed in gear. To me, that removes the aerodynamic and "real life" road variables (wind, grade, traffic, etc), but still leaves in the "real world" drivetrain & wheels turning.

What do you all think of that?

Or am I out in "left field"?
  Reply With Quote
Old 12-04-2012, 07:34 PM   #6 (permalink)
Adventurist!
 
Join Date: Sep 2012
Location: Nashville, TN
Posts: 144

CLaero - '97 Acura CL Premium
90 day: 34.59 mpg (US)

CR-v - '03 Honda CR-V EX
Team Honda
90 day: 26.52 mpg (US)
Thanks: 9
Thanked 21 Times in 21 Posts
Quote:
Originally Posted by wmjinman View Post
Interesting idea.

I think... wheels jacked up, running at cruising speed in gear. To me, that removes the aerodynamic and "real life" road variables (wind, grade, traffic, etc), but still leaves in the "real world" drivetrain & wheels turning.

What do you all think of that?

Or am I out in "left field"?
Not at all in left field!... That would be a great way to include the drivetrain losses in the calculation. Unfortunately though, running with the wheels off the ground creates a whole mess on its own... No matter how balanced your tires may be, they will not rotate at such a high rate of speed without excessive hop, as every forgiving tolerance becomes less loaded (bearings, CV's, etc.) If you've ever seen a HMMWV walk itself off of jack stands, you'll know how dangerous this can be!!! O.o

Utilizing a dyno would mitigate these dynamics, but unfortunately we don't all have one in our garage!
__________________
'97 Acura CL 2.2L 5spd
'03 Honda CR-V 2.4L EX 4wd Auto
  Reply With Quote
Old 12-04-2012, 07:47 PM   #7 (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
Quote:
Originally Posted by nbleak21 View Post
Yes, that is exactly what I did, netting a Terminal F/E of approx 45mpg at 70
So you're cruising at 70? You could save quite a bit if you slowed that down.
__________________
"Judge a person by their questions rather than their answers."

  Reply With Quote
Old 12-04-2012, 10:36 PM   #8 (permalink)
OCD Master EcoModder
 
brucepick's Avatar
 
Join Date: Dec 2007
Location: Eastern CT, USA
Posts: 1,933

Outasight - '00 Honda Insight
Team Honda
Gen-1 Insights
90 day: 54.18 mpg (US)
Thanks: 429
Thanked 391 Times in 261 Posts
nbleak21's original post here shares an interesting idea. I and others have gone off on various (interesting?) tangents. That said, nbleak21 deserves credit for the idea.
__________________
Coast long and prosper.
Driving '00 Honda Insight, acquired Feb 2016.


  Reply With Quote
The Following User Says Thank You to brucepick For This Useful Post:
nbleak21 (12-05-2012)
Old 12-05-2012, 01:00 AM   #9 (permalink)
Master EcoModder
 
Join Date: Oct 2012
Location: Carson City, Nevada
Posts: 612

Jimmy - '00 GMC Jimmy SLT
90 day: 21.18 mpg (US)

The White Gnat - '99 Suzuki Swift
Team Suzuki
90 day: 51.87 mpg (US)
Thanks: 240
Thanked 114 Times in 90 Posts
Whoa! Yeah, "walking off the jackstands" certainly wouldn't be good - especially if you weren't prepared for it.

Hmmm... before I go out & do it, I guess I'd better come up with some "safetys"!!

Thanks!
  Reply With Quote
Old 12-05-2012, 08:50 AM   #10 (permalink)
Adventurist!
 
Join Date: Sep 2012
Location: Nashville, TN
Posts: 144

CLaero - '97 Acura CL Premium
90 day: 34.59 mpg (US)

CR-v - '03 Honda CR-V EX
Team Honda
90 day: 26.52 mpg (US)
Thanks: 9
Thanked 21 Times in 21 Posts
Quote:
Originally Posted by Lazarus View Post
So you're cruising at 70? You could save quite a bit if you slowed that down.
Yessir! Ideally I would gain a few MPG dropping my speed, but most of my commute is interstate, and slow lane speeds avg 65-70mph travelling with the flow of traffic, so generally I find a semi to get some limited draft off of (I don't do the tailgate drafting!)

__________________
'97 Acura CL 2.2L 5spd
'03 Honda CR-V 2.4L EX 4wd Auto
  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