Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - 94 Accord EX, 5 speed

brucepick · 10-09-2011, 11:13 AM

Well - - - -

I commute 50-55 miles (depending on the route) each way. So I've worked through a few things re. frequent long trips.

I think there's potential in "faking" a higher gear ratio by going to a slightly larger tire size. My wife drives a '96 Accord DX with 5-speed. Owner's manual says 195/60-15 but it has 195/65-15's mounted. If you're running 14's the numbers are different but the idea is the same. We haven't had any issues with tire rubbing with those 15's.

If you're going to change tires you DEFINITELY should change to LRR tires: Low Rolling Resistance. And plan to run them at the sidewall imprinted pressure ("max sidewall" as we say here), and that's measured cold in the morning before driving. The softer the tire, the larger the "flat spot" on the road, and the more flexing the rubber has with each rotation. That's more work for your engine. I run my tires at pressures that I won't want to post here but I can say they roll very well and handle superbly on our twisty New England roads.

To find LRR tires, go to tirerack.com, and once you get to the page for your size tire, use the filtering on the left side panel to get the LRR tires. It's all the way at the bottom of the filter-options column.

For winter, I got Michelin X-Ice 2's. They are the only LRR snow tire I found available and they only cost me 1 or maybe 2 mpg compared with my regular LRR summer tires. I found them to be good on snow, and superb on any kind of ice or hard packed snow. Yeah studs are better on ice but forget about fuel economy with studs.

Don't worry too much about super low weight wheels but avoid any that are truly on the heavy side. Wheel weight is more of an issue for drivers with lots of acceleration, aka city driving.

I did some cursory reading on regearing Honda trannies and I'm pretty sure that their final drive is kinda buried down in there, and not easy to change. But, you should research here: Honda Accord (1990 - 2002) - Honda-Tech for better information.

The other thing that's hurting your mpg is the aerodynamic losses that increase dramatically at higher speeds. This is probably costing you more than what you lose by not having somewhat taller gearing. The power needed to overcome drag goes up with the either the square or the CUBE of the speed increase, depending on which way you interpret the formula. So doubling your speed multiplies the power needed by 4 or 8. You pay for that at the pump.

The easy way to reduce aero losses is to slow down but that's not so practical with long road trips, if you care what time you arrive. The other way is to reduce the drag. Start hanging out at the Aerodynamics subforum: Aerodynamics - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com to learn what you can do. You'll find several threads on different approaches to my suggestions below:

Flat wheel covers
Rear wheel skirts (I recommend extending down only part way so you don't have to bulge it out sideways to clear the tire)
Belly pan, especially from the front bumper lip to the firewall (that's where I got the most benefit)

Rear aero spoiler. I and California98Civic have both worked to build something that reduces drag at the rear. We don't have this solved yet but there's potential for gain there. My own project is currently in progress: http://ecomodder.com/forum/showthrea...upe-18906.html This not complete by any means but I do hope to gain from some version of this project.

10-09-2011, 11:13 AM	#2 (permalink)
brucepick OCD Master EcoModder Join Date: Dec 2007 Location: Eastern CT, USA Posts: 1,936 Outasight - '00 Honda Insight Team Honda Gen-1 Insights 90 day: 54.18 mpg (US) Thanks: 431 Thanked 396 Times in 264 Posts	Well - - - - I commute 50-55 miles (depending on the route) each way. So I've worked through a few things re. frequent long trips. I think there's potential in "faking" a higher gear ratio by going to a slightly larger tire size. My wife drives a '96 Accord DX with 5-speed. Owner's manual says 195/60-15 but it has 195/65-15's mounted. If you're running 14's the numbers are different but the idea is the same. We haven't had any issues with tire rubbing with those 15's. If you're going to change tires you DEFINITELY should change to LRR tires: Low Rolling Resistance. And plan to run them at the sidewall imprinted pressure ("max sidewall" as we say here), and that's measured cold in the morning before driving. The softer the tire, the larger the "flat spot" on the road, and the more flexing the rubber has with each rotation. That's more work for your engine. I run my tires at pressures that I won't want to post here but I can say they roll very well and handle superbly on our twisty New England roads. To find LRR tires, go to tirerack.com, and once you get to the page for your size tire, use the filtering on the left side panel to get the LRR tires. It's all the way at the bottom of the filter-options column. For winter, I got Michelin X-Ice 2's. They are the only LRR snow tire I found available and they only cost me 1 or maybe 2 mpg compared with my regular LRR summer tires. I found them to be good on snow, and superb on any kind of ice or hard packed snow. Yeah studs are better on ice but forget about fuel economy with studs. Don't worry too much about super low weight wheels but avoid any that are truly on the heavy side. Wheel weight is more of an issue for drivers with lots of acceleration, aka city driving. I did some cursory reading on regearing Honda trannies and I'm pretty sure that their final drive is kinda buried down in there, and not easy to change. But, you should research here: Honda Accord (1990 - 2002) - Honda-Tech for better information. The other thing that's hurting your mpg is the aerodynamic losses that increase dramatically at higher speeds. This is probably costing you more than what you lose by not having somewhat taller gearing. The power needed to overcome drag goes up with the either the square or the CUBE of the speed increase, depending on which way you interpret the formula. So doubling your speed multiplies the power needed by 4 or 8. You pay for that at the pump. The easy way to reduce aero losses is to slow down but that's not so practical with long road trips, if you care what time you arrive. The other way is to reduce the drag. Start hanging out at the Aerodynamics subforum: Aerodynamics - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com to learn what you can do. You'll find several threads on different approaches to my suggestions below: Flat wheel covers Rear wheel skirts (I recommend extending down only part way so you don't have to bulge it out sideways to clear the tire) Belly pan, especially from the front bumper lip to the firewall (that's where I got the most benefit) Rear aero spoiler. I and California98Civic have both worked to build something that reduces drag at the rear. We don't have this solved yet but there's potential for gain there. My own project is currently in progress: http://ecomodder.com/forum/showthrea...upe-18906.html This not complete by any means but I do hope to gain from some version of this project. __________________ Coast long and prosper. Driving '00 Honda Insight, acquired Feb 2016. Last edited by brucepick; 10-09-2011 at 09:41 PM..