Aftermarket spring maker Eibach now advertising MPG savings of lowering kits
Discovered this tidbit via the DetNews:
Quote:
Eibach says springs give cars mpg bounce Tests by suspension company show springs push vehicles to 13 percent better gas mileage
Oliver Rathlein, Eibach's vice president for marketing, said fuel economy was gauged while rolling along at 70 miles per hour on California freeways and was affected only by the way the springs lowered the car and thus reduced aerodynamic drag.
I'd say gas pump error could be one factor.
They don't mention engine operating temps.
Since they tested two different days, there is no guarantee it was exactly 70mph both times.
No mention of air pressure in tires.
No mention of whether it was the same driver both times, heavier/lighter driver could affect numbers.
Its very cool that they tested this, and I am really surprised they went as far as to say how they tested it. Seems like a large increase though!
Yeah, definitely optimistic, but I bet they are trying to justify the cost. Lowering springs have a pretty high initial cost. I think a ScanGauge is cheaper and gets you more savings.
Even though the temperatures are the same, a month between tests doesn't make sense to me. I think they should have gotten two Camaros with A/B tests both ways where one is a control Camaro. You could use the first run to "calibrate" the differences between the Camaros. The control Camaro would remain stock while the modded Camaro would be stock for one round trip and lowered for the second.
Cue the analysis of Eibach's testing methodology (and credit to the company for posting the details on their site):
Sure, I'll bite.
At 70mph, such a draggy car spends 83% of its power overcoming drag, so highway FE is a pretty good drop-in for Cd. Essentially, they're reporting having reduced the Cd from 0.37 to 0.31 by dropping the suspension an inch. Not likely, but who knows without a valid test?
Their methodology isn't the worst I've ever seen. They did lots of things right: the test was long enough to burn 6.4gal on one run and 7.2gal on the other. That will eliminate transient effects like cold starting.
Unlike at our fuel economy runs, 0.1gal of fueling error wouldn't have changed the outcome much. Good of them to test at 05:00 on a Saturday when traffic wouldn't interfere, and good of them to make sure the temperature was the same.
Now for the bad: Why did they wait six weeks between the "before" and "after" runs? What else happened to the car, the road, etc, in the mean time? When you wait six weeks between runs, you need to do A-B-A for sure.
Their sample size, n=1, is terrible science. If they don't try to do a few identical runs, they won't know how good their methodology is.
Just because an independent company helped in the testing, does not make it double-blind.
The article itself is awful. This advertorial is just a usual piece of sponsored "reasearch", unfit to be published without the disclaimer "Advertisement". Note the article ends with information about price, applications, and how to order Eibach lowering kits.
Article: worthless
Testing: looks clean, but without independent verification and higher sample size, it's worse than worthless.
Sadly, because people read it in the Detroit News, and know a "test" was done by Eibach, 13% fuel savings from a 1 inch drop is now the "truth".
Carlos: that's exactly what they're doing - promoting the springs as a cost savings device. They even do the math for you on their site.
None of this deters me from wanting to lower the Firefly, but I'm not fool enough to expect a 13% (or even a measurable, for that matter) improvement in fuel economy.
Edit: HA - I just noticed the Google ad on the bottom of the page now is for Eibach springs. Don't click!!
On the bright side, maybe it's better that the masses spend money on what are likely marginal MPG benefits of lowering kits ... than completely waste it on fuel line magnets or __ (insert 100% scam item here) __.
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