Mazdaspeed6 Econo-performance car!?

[Vansquish]

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!!!

Now...here'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!

[ecomodded]

Welcome to the site and congratulations on your mileage improvement. You will find many mpg improvement by slowing down yet even further, to say 60 mph ( If the roads are favorable i try for 55 mph) you could save 5 more mpg, pump up your tires to max sidewall pressure and you will see that 5 mpg gain for sure.
If you were to start coasting on hills and changing gears earlier, keep your rpm lower before changing gears(shift 500 rpm's lower then you are shifting at now) And you will improve on it yet again(to be determined by your real life gains).
Your car has a mess of torque to propel you with, I suspect your tunes changed the fuel map to give your car more torque down low in the rpm's where it is more beneficial to the economy. About any tuning software can offer that if that's what a person wants.

[Vansquish]

Originally Posted by ecomodded

Welcome to the site and congratulations on your mileage improvement. You will find many mpg improvement by slowing down yet even further, to say 60 mph ( If the roads are favorable i try for 55 mph) you could save 5 more mpg, pump up your tires to max sidewall pressure and you will see that 5 mpg gain for sure.

Thanks for the welcome!

I'm aware that the best mileage I could probably hope to achieve is circa 45mph, but that's not generally feasible, nor safe, nor timely for the highway trips that I take. Even 55mph is pushing it a bit too far for me under most circumstances.

The stock inflation requirements for my tires are 38psi on all four corners, and I generally keep them inflated to 40-42psi, as I'm generally pretty gentle on them, and it doesn't seem to impact the treadwear pattern at that level. I accidentally ran at 48psi at one point and began to see some undesirable wear in the center blocks of tread, as well as at the inner edge of the tire (relatively aggressive camber).

Originally Posted by ecomodded

If you were to start coasting on hills and changing gears earlier, keep your rpm lower before changing gears(shift 500 rpm's lower then you are shifting at now) And you will improve on it yet again(to be determined by your real life gains).

I try to coast when possible, but I'm not a big fan of "pulse-cruising" or whatever the appropriate term is. If at all possible, I try and maintain a relatively constant rate of travel and stay in vacuum as much of the time as possible.

Originally Posted by ecomodded

Your car has a mess of torque to propel you with, I suspect your tunes changed the fuel map to give your car more torque down low in the rpm's where it is more beneficial to the economy. About any tuning software can offer that if that's what a person wants.

True...my engine does produce a lot of torque, but that's only when the turbo is spun up and providing boost. Considering the car made 280lb-ft at 2800rpm *stock* and that I'm now over that by nearly 40lb-ft, making torque has never been a problem. The issue is that if I let it produce those kinds of numbers low in the rev range, there's a good chance that I could end up "venting the block" with one of my con-rods. It's a relatively long-stroke, high-compression engine for being a turbo. (9.5:1 and 2.3L with a 94mm stroke).

It grumbles quite a lot about being driven at low revs, so with my 6-speed, I end up shifting a lot around town to stay in the small band of revs between about 1200rpm and 2000rpm and not be "lugging."

The map revisions that I've been running have focussed primarily on highway fuel economy, as around town, it's much more of a crapshoot for me.

I've targeted the 2000-3500rpm range as the area that is most important for fuel economy, and have made what I hope are some appropriate changes for Closed-Loop, low load applications:

0 boost
Ignition timing advanced by between 5* and 15* (depending on where logs have shown that I'm getting detonation)
AFR targeted at ~17.0:1 instead of stock 14.7:1 (or lower)

I also intend to play with the VVT tables a bit, as I suspect there's both power and fuel economy to be gained there as well.

I'm also running synthetic oil, but have had to go with a higher viscosity than recommended by the manufacturer (5w-40 instead of 5w-30) in order to increase surface tension and stop my turbo's seals from leaking.

At any rate, my goal for the summer is to have my car relatively consistently breaking 40mpg on the highway at ~70mph. I think it's an achievable goal, based on the successes that I've had thus far without any aerodynamic modifications whatsoever.

[larrybuck]

Welcome! This is a classic example of having your cake, and eating it too!

Not many of us have a car that does EVERYTHING well! Congrats!!!!

Keep us informed of further mods.

[rollercoaster]

You forgot to mention your car requires premium/super unleaded...

[Vansquish]

Originally Posted by rollercoaster

You forgot to mention your car requires premium/super unleaded...

You are correct (generally). I can actually run 91 Octane and still hit all the targets I've hit in the past. However if I tune to run 87, there's a significant drop in the amount of ignition advance and boost levels that I can run before I start to have detonation, and of course, that effects both fuel economy and performance.

[cf_dallas]

I blew up a 2009 Mazda3 at the track yesterday... the engine blew, then caught fire. If it's game-over for that car a Mazdaspeed6 sounds really interesting. This thread makes it even more interesting... high-30s MPG and 300+ hp, what a combo!

Keep us all posted on what you do! Aero mods are always fun, and equally useful for both the Clark Kent and the Superman sides of the coin.

[UltArc]

Subscribed. I wish a tune wouldn't havoc my warranty, so I could do cool/fun things

Look forward to following.

[Vansquish]

Update:

I've installed a new turbo, a new intercooler, a new intake, a new fuel pump, and have cleaned my intake valves (DI engines are terrible in this respect).

Since the turbo went in, I've managed slightly better fuel economy than before. I'm now averaging about 31mpg with 2 people in the car (I'd see closer to 29 before), and in excess of 35mpg on a more regular basis than ever before. I've also seen my combined fuel economy average increase to around 27mpg (which is 2mpg higher than the OE highway fuel economy estimate).

The car is also making ~352awhp/360awtq, up from 289/335 just before the turbo swap.

[UltArc]

Have you done any aero mods?

What does your dyno place say about all this FE business? Lol