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Old 05-25-2010, 11:20 AM   #1 (permalink)
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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.

[...]

Stock real-world: 23.34 mpg average.
Springs installed: 26.4 mpg.
EPA Highway rating: 25 mpg
Don't know about you, but while I'd expect to see some improvement, a 13% result seems gleefully optimistic.

Cue the analysis of Eibach's testing methodology (and credit to the company for posting the details on their site):
  • Same 2010 Chevrolet Camaro 2SS 6 Speed Automatic, tested: 8/15/09 & 9/26/09.
  • contracted an independent company, Test Pilots Independent Testing Services, to do all the driving
  • Identical highway route of 167.7 miles (HWY 15N & 10E to Palm Desert and back)
  • Cruise control set at 70 MPH the entire way (takes away any human bias)
  • Each start time 5:00 AM Saturday morning
  • August 15th: temp. start 61°F, finish 74°F
  • September 26th: temp. start 62°F, finish 76°F
  • Very little wind both times.
  • Start and finish same gas station, same pump and pumped full with 10 clicks.
from: http://performance-suspension.eibach...ws_test_eibach

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Old 05-25-2010, 11:39 AM   #2 (permalink)
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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!
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Old 05-25-2010, 11:39 AM   #3 (permalink)
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MetroMPG -

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.

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Old 05-25-2010, 11:57 AM   #4 (permalink)
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Quote:
Originally Posted by MetroMPG View Post
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.
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Old 05-25-2010, 12:05 PM   #5 (permalink)
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Nice summary, Mr Smalls.

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!!
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Old 05-25-2010, 03:03 PM   #6 (permalink)
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Cd from 0.37 to 0.31 ...

if it where that easy gm would have dropped it a bit themselves i should think...
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Old 05-25-2010, 03:38 PM   #7 (permalink)
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Unfortunately it is legal to get away with marketing "fluff"

Their testing sux and they know it. They also know millions of pseudo-gearheads will bow at the mantle of lowering springs now.
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Old 05-25-2010, 04:50 PM   #8 (permalink)
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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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Old 05-25-2010, 06:50 PM   #9 (permalink)
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^True. Somewhat better than nothing...
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Old 05-25-2010, 07:44 PM   #10 (permalink)
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It would help but I doubt 13%.

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