Lowering your car in order to increase fuel economy

[tomauto]

I have read that stiffer springs aid FE by reducing energy loss from the suspension working. It makes sense to me; just as mechanical brakes convert energy into heat, so do springs and shocks, so a stiffer suspension is not absorbing so much energy and converting it into heat, and ultimately that energy comes from the forward motion the engine supplies. Along those lines I tried a stiffer front sway bar and stiffer bushings- that proved to be a bit much. It "overpowered" the wheels and tires, by that I mean I could take corners at 80 mph with the tires squealing and that car wasn't leaning at all. It responded harshly to bumps too. Stock bar back in, but with the stiff bushings, restored much of the ride quality and the cornering capability hasn't suffered one bit.

There is no way that the suspension's energy loss can ever effect the cars mpg. First of all the suspension components move in a vertical or near vertical fashion. It could never aid in the vehicles' horizontal motion. Also, the suspension and the engine are totally different systems, and they don't another ones's assistance (i.e. taking or giving power) unless of course you are talking about the Bose suspension which was just spoken about in another thread recently.

[tomauto]

Although cutting your springs to make the car lower does help the overall aerodynamic efficiency (which is a step in the right direction) of your vehicle it isn't helping your ride or cornering ability, it is only bringing you closer to the ground and ruining the tuned factory settings which ford engineers worked hard on to give you the most comfort possible.

[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 ...

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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).

[MetroMPG]

Originally Posted by theclencher

In the future I will refrain from posting such things unless the source is at my fingertips or I properly disclaim it as mere postulate

No worries. It's an interesting idea, even just to chew on.

[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.

[SVOboy]

I have just seen too many pictures of springs that've sagged from being cut, or shocks that've blown out from being lowered on. So that's where my bias comes from. I rode my car 2" lower on 20$ lowering springs and it rode like crap, so I went and spent some money on shocks that were tougher to stiffen up the suspensionso I wouldn't bounce around like I had pogosticks in there.

Anyway, these are just my experiences is all.

[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