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Old 04-26-2012, 01:51 AM   #1 (permalink)
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Vansquish's Avatar
Join Date: Apr 2012
Location: Ann Arbor, MI; Madison, WI; Bloomington, IN
Posts: 10

Vansquish - '06 Mazda Mazdaspeed6 Grand Touring
90 day: 32.63 mpg (US)
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Mazdaspeed6 Econo-performance car!?

Hi all,

Let me first say that I am, and always have been a huge gearhead. I have always had something of a penchant for performance vehicles. As a result of this, the fact that I live in the midwest, and that I commute to Wisconsin on a fairly regular basis I had a few criteria in mind when I bought my car.

1) Fun to drive. Stock, my car makes 274bhp, 280lb-ft, has a 6-speed manual, and a stiffened chassis over the normal Mazda6.

2) AWD - for driving in the winter in Michigan and Wisconsin, I knew that this was something that I wanted.

3) Decent fuel economy. Stock, my car is rated at 19city/25highway, BUT, being a 2.3L direct-injected turbocharged 4-cylinder, I suspected it could do significantly better.

The second thing you should know is that the 3rd criterion is very important to me, as I do a fair amount of long-distance driving, and when I'm not out playing with the car, I might as well be playing the eco-game instead. Each pursuit has its own type of gratification.

On my first long drive from Houston to Chicago after buying my car, I managed 27.5mpg, a not insignificant 10% improvement over stock. I cruised at around 72mph, and as I wanted to "get to know the car", I wasn't exactly light on the throttle when accelerating.

I figured it could do better with some tweaking though, and so I bought 2 items that I knew would have both performance and economy benefits.

1) I bought a Cobb Accessport - this is a device that allows you to fine-tune the engine and choose your Air-Fuel Ratio, Injector duty cycle, Ignition timing, boost levels, and a host of other settings.

2) I bought a Short-Ram Intake (affectionately known as a "hot air intake" here, but that very phrase is a derogatory term in the performance world)

After flashing my ECU with a relatively mild tune, I saw significant power gains (about 20 wheel-horsepower and 40 lb-ft at the wheels), but more impressively, I started getting 31-33mpg on the highway with relative ease. That's a 24%-32% gain over stock mileage!

After I bought the SRI, I began getting about 2mpg better than that even. 35mpg was relatively easily attainable at ~72mph. That's right...40% improvement over stock!

The best I've ever done was cruising at 67mph with those mods. I managed 37.5mpg, a 50% improvement over stock!!!'s the thing. I haven't made any aerodynamic mods to the car, and all of my experimentation thus far has simply been with off-the-shelf tunes from Cobb Tuning themselves. I have recently begun playing with leaner Air-Fuel Ratios at low-load, highways speeds. Rather than stock (14.7:1) I'm now attempting to run 16.5-17:1, to see how that goes. I know that certain VW DI engines run up to 22:1 AFRs stock with lean-burn cats, so we'll see how the experiment goes.

At any rate, I don't think this is too shabby for a car that's now putting down about 300bhp, and 320lb-ft of torque, has AWD, 18" wheels and 225-section width tires, and weighs 3600lbs without me or anything else in it.

Sorry for the long intro! I'm looking forward to seeing how you all do things and what nifty aero-mods I should try after I'm done experimenting with my car's tune!

I suppose I should mention that I've bought a bunch of choroplast and intend to make a flat-undertray (prototype at least) for my car at some point over the summer.

See you 'round!

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