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Old 04-26-2012, 03:02 AM   #3 (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)
Thanks: 1
Thanked 3 Times in 3 Posts
Originally Posted by ecomodded View Post
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 View Post
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 View Post
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. 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.
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