Lowering your car in order to increase fuel economy

[Matt Timion]

Recently a few members of this forum have lowered their cars and have found an increase of fuel economy. krousdb noticed a 3 mpg impovement instantly.

Lowering your car will theoretically improve your gas mileage as it reduces frontal area of the car, lets less air under the car, and as a result increases the aerodynamic "flow" of your entire ride.

This thread will be a place to log results of this particular modification. Please give Fuel economy before and after. Please log as many tanks as possible for both the before and after condition.

[MetroMPG]

I'd have to see a bit more info on the debate of energy savings from firming the suspension, but one of my first reactions is that while the suspension may be generating less heat, the vehicle still has to react to the contours of the road.

Where previously the unsprung mass of the (soft) suspension did most of the movement in response to road contours, a firm suspension transmits more of those contours to the sprung mass of the car body (thus the jiggly, harder ride). Since the body is much more massive, from an energy perspective what does that say?

EDIT: Hmm... then again, even the soft suspension "pushes" with the same force as the firm one, doesn't it? The difference being the inertia of the softer sprung mass (the car body) causes it to be steadier while the spring momentarily loads & unloads. I should just excuse myself from this debate now ...

--

On the topic of ride height & Cd, the 2006 Lexus LS430 with air suspension - which lowers the car about an inch at higher speeds - has a published Cd which is .01 less than the same car without the air suspension option. The comparison is quoted often (equating the Cd change solely to the active suspension).

[SVOboy]

hmm, i can't see ever cutting springs, especially not heating them. cut springs have a tendency to sag and heating changes the spring constant of the spring, not my cup of tea. also, i wouldn't lower 2" on stock struts, they're just not made for it, not enough damping ability, do you bottom out at all?

hopefully you have nice roads and won't lose your struts to them, , i'm only lowered 1.5" on tokico illuminas and i fear every bump might blow my shocks out, but i'm paranoid.

anyway, the spring rate argument is something i've read a lot but have no idea about. hopefully you guys will turn up something good in search.

[kickflipjr]

I have also thought about the loss of engery in the suspension and engine mounts. If bother were firmer would there be a change in overal mpg? (probally not). The energy is probally tansfered to the body of the car.

About motor mounts. Dosen't make sense if you put race(solid) mounts in a car it would improve mpg because less energy is wasted in the engine going back and forth? or is that energy just sent to the rest of the car body and shows no advantege at all?


I noticed road bikes (bicycle) never have shocks and are intentially made to be stiff. This is because energy is lost in the shocks. But bicycles and cars are very different, but the efficiency is simillar. Thin tires/ High PSI/ Aerodynamic shape/

[SVOboy]

I'm not looking at the car, I'm looking at the posts people make like "oh snap, I cut my springs and it was fine for a few months now one side is sagging" or "I lowered my car and blew my struts out, what should I do?"


Shocks blow from bottoming out internally because there is less shock travel on a lowered car. Plus the stiffer springs make greater change or something like that which puts more stress on them, I'm not sure on that second pard.

What you need to keep in mind is that I have no idea how ford stuff works, this is all honda knowledge. I have driven a nissan once that broke a coil off a spring and that shock was extremely trashed, but that could be the unevenness.

[SVOboy]

I think hondas might have less suspension travel. We also have some of the best stock struts I've know that are made, on our nice suspension that we have (screw you, mcpherson).

I'm not sure about how people cut, just know that when I first heard about it years ago it was my cousin complaining about how his friend cut and screwed something up, Iono, it was so long ago, and the was a DSM.

[GasSavers_Ryland]

I've been asking around at the auto parts stores about lowering, and they said that if you want to lower a Honda 1" that you can get lowering springs, and have to use stock struts, to go lower then that it sounds like you can use stock springs, and get adjustable struts to lower, it looks like the adjustable limitations are around 1.3" to 2.5".
the rear of my car has new stock hight springs and struts, and sits a little over 1" lower then the front because of how I use my car (hauling tools, food, cloths, camping gear), so I really want to lower the front to match the rear, but I need to figure out where to measure hight, is it the jack point? the floor pan? the fender lip? the bumper lip?
I can only imagine how much drag it causes haveing the nose of my car sitting over an inch higher.

--Ryland

[ZugyNA]

Originally Posted by Ryland

I've been asking around at the auto parts stores about lowering, and they said that if you want to lower a Honda 1" that you can get lowering springs, --Ryland

Or...you can install a pair of these on each spring for less than $40. They aren't that easy to get in there...but they both lower each spring by one coil and stiffen it even more by acting as stops for the coils above and below.

Need to watch for interference with sheet metal and so forth...and snug them down good so they stay on opposite sides of the spring.

I had these on a sports car with crapped out struts and it still handled real well.

[MetroMPG]

Originally Posted by ZugyNA

Or...you can install a pair of these on each spring for less than $40

A pair of what? (Maybe you posted a link that didn't come through?)

[GasSavers_Ryland]

the reason you don't want a bicycle with soft shocks is that when you are "standing" on the bike to pedle harder, like going up a hill, the shocks are compressing every time you pedle and are absorbing the energy you are trying to put to work, this is why quality suspention parts for bicycles come with a lock out, to "turn off" the shock and make it extreamly stiff.
with cars, you do want, to a point, soft suspention so that the tires will role over bumps and dips smoother without making the whole car move up or down that fraction of an inch, hitting a bump is like going up a tiny hill, and if your whole car has to go up that half inch, or whatever it's going to take more energy, from what I've read, stock honda's come with suspention that is tuned for traction, not for comfert, their struts are designed to let the wheels recoil back to the pavment faster then they lift, thus the ride feels "rough" because you feel more of the tiny bumps.