There's a very nice gentleman named Ron Hatton who sells a vehicle modification called the Gadgetman Groove. The modification consists of utilizing a Dremel tool to cut a groove in the throttle body of a fuel injected car (though the site indicates that it's possible to modify multi and tuned port injectors and carbureted sysems as well) just past the throttle plate. Hatton states that by doing so, it causes "amplification of the pressure wave" thus providing "more fuel blended with the air at the point of ignition" and "more complete combustion."
There is a
collection of youtube video testimonials from satisfied customers
who've had the modification done to their vehicle, with some very
dramatic claims for fuel economy increases. Here
is the most extreme claim I saw, where Kyle claims an increase from 12
m.p.g. to 27 m.p.g. while going 5 to 10 m.p.h. faster.
There was an internet dustup (in which I participated) regarding the
Groove at an Ecomodder
blog post about the Groove back in July of 2010. It was very clear
to me that Ron is no crook and really believes in this "technology."
However, his web site at the time (since changed) discussed having a
car tested on a dynamometer at Automotive Testing Laboratories in Mesa,
AZ. The results were posted at Ron's site (they're not there now) and
showed a decrease in fuel economy and an increase in emissions in both
(Federal Test Procedure) and the HFET (Highway Fuel Economy Test)
protocols. Ron attributed this to an inappropriate choice of vehicle
and its poor mechanical condition. To the best of my knowledge, Ron was
responsible for the choice of vehicle and the test protocol.
In any event, I'd more or less forgotten about the Groove, but received
an email that someone had posted a comment to the thread. This turned
out to be "Dave," an ex-policeman who has had the Groove installed, is
quite satisfied, and posted to defend Ron against a "hatchet job." I
replied that I believe that both he and Ron believe, but that none of
this constitutes evidence.
But let's take a look. Kyle's 1993 GMC truck was claimed to exhibit a
125% increase in miles per gallon. So, call the initial m.p.g. "x."
Then, after the modification, the m.p.g., with a 125% increase, he would
be getting 2.25x miles per gallon. Inverting this fraction, that means he's
using 1/2.25 or 4/9 as many gallons per mile. The conclusion is that
the other 5/9 of the gallons were not burned or were burned in such a
way as to not move the car. To emphasize, this is NOT the 75% of the heat from burned fuel that's wasted due to thermodynamic limitations, friction, etc., this is fuel that is supposedly NOT BURNED! How about a tangible example? Suppose that
Kyle has an 18 gallon tank. Every time he filled up pre-Groove, 10 of
those gallons were not burned. This is Kyle and Ron's claim!
This is about as good an example as could be hoped for of the futility
of reliance on anecdotal testimonial evidence. I am reasonably sure
that not only Kyle and Dave and the other youtube stars on the Groove
web site, but that Ron Hatton as well are truly convinced of the efficacy of
this simple modification.
And yet I am not claiming that the Groove produces no benefits, only that there's no valid evidence that it does produce them. If Ron stated that the result of multiple runs of blind testing of
otherwise identical vehicles under controlled conditions showed an
improvement of 5% in m.p.g. with a standard deviation of 1.5% and a
confidence level greater than 95% I'd believe it and consider the
modifcation for my vehicle. But I wouldn't consider spending $500 based
on a series of enthusiastic youtube testimonials.