We all have heard about the fuel line magnets, turbonators, throttle body spacers, hydrogen generators and miracle additives designed to make our cars more fuel efficient. They all come with claims of success and explanations of how and why they do what they do. Sometimes they even come with the test data. So here is another one:
Looking at the stock xB intake duct always made me wonder if having two 90 degree bends can somehow have a negative effect on the engine's efficiency:
Without going too deep into the science of things let me just say this: I wanted to straighten the airflow into the manifold:
The throttle body insert is made out of thin aluminum plate. I tried to make sure its edges cause as little resistance as possible:
Was it wrong for me to even try? After driving through two tanks of gas with it installed I saw the best gas mileage that my 2006 xB with automatic transmission and 80K miles on the odometer has ever shown: above 35 miles per gallon. That's about 2 MPG gain. I must say that I really wanted to see some gains so I did slow down on the freeway and didn't go above 70 MPH. But half of the driving I do is in the city anyway. And isn't sticking a piece of metal into the air duct supposed to make things worse?
So it was time to do some testing. I did few runs on a dynamometer:
And shots of my Scangauge without the fin installed:
And with it. Only a minute apart:
I did about 8 runs under different loads. Sometimes there was no difference for the better and sometimes there was. It never registered drop in MPG and under lighter loads almost always showed 1–3 MPG increase.
Is this a miracle?