How much gain can I expect from a hptuner setup. I'm looking at doing quite a bit of high way driving and am wondering how many mpg's I can gain from running a good tune for mpg vs. power.

 

In order to answer your question you need to tell us what you drive

 

Well, from what I have read (which isn't much) stock PCM is tuned for the least amount of emissions, not for performance or mileage. The point of maximum efficiency is pretty close to the point of maximum power (only a fractional difference in AFR), so I'd expect a 1-2 MPG increase from a stock tune. There are no set law, so it will vary depending on what engine you have. What car do you have, and what mods have been done to it already?

 

With all due respect to the above post, the point of maximum efficiency is nowhere near the point of maximum power. Tuning for max torque output (best torque/efficiency, or lean-best-torque, aka LBT), the AFR is between 12.9:1-13.4:1 depending on the engine build, fuel variables/quality, etc, whereas tuning for max fuel efficiency is tuning for lowest brake specific fuel consumption (bsfc) which requires an AFR from 15.7:1 and higher, again, depending on engine build, fuel variables/quality, etc, etc. This is as much as a 20% difference between the two extremes. The manufacturers do a great job of tuning for highway mileage at speeds of 55 mph and greater. Expecting fuel mileage increases of 2 mpg or more on any vehicle of model year 2000 and newer is rather ambitious. 1 mpg is readily acheivable on certain vehicles, but not without significant tuning effort and dear sacrifices in exhaust emissions output. There's a lot of snake oil sold by some aftermarket performance outfits claiming huge increases in fuel eceonomy and these claims/promises should be considered with caution. The best bet for good fuel economy is simple...MAINTAIN YOUR CAR. Change the oil regularly, keep the trans and diff in tip-top shape, always maintain ideal tire pressures for your vehicle and most importantly, drive the slowest steady-state cruise speed that you can get away with. If you can drive 60 mph and not **** traffic off, you'll save huge fuel compared to driving 75 mph and being one of the faster cars on the road. The 15 mph speed difference in steady-state cruise can save you 10% or more on fuel consumption. And the best part, driving habits are FREE!!

 

Well I learned something today lol

 

How much you gain depends mostly on how crappy the tune
is, presently. That's a big unknown.

But you would have the ability to put it to its best possible.
Whatever it is.

 

You should write a book about this stuff.


























Just kidding, of course. I have your latest and reference it quite often.

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what is hptuner ?

 

A laptop based tuner.

I've been thinking about making a custom pid to show what speed gives me the best MPG. I'd think it should look like a bell curve, with the peak somewhere around 60mph. I've got plenty of flat roads around here in Alabamistan, one is about 20 miles without a stoplight and 65mph limit on the way to school. I should be able to get a healthy dose of counts in each cell (while in 6th gear) from about 45 to 75 mph. If I found out that 58 mph (or whatever) was the best for economy then you can bet that It would be on my mind whenever I exceeded that speed. It would also be kinda cool to get the data for how fast my economy falls off with each MPH increase above the most efficient speed.

For the first time in my life I've got a situation where I drive roughly to the same places on each tank. I saw a 30 mile increase in how far my tank would take me just by putting the correct amount of air in my tires. That was about a 1 mpg increase. My driving has been so consistant that I know that each tank over the last 6 months has been within +/- 10 miles. As is starts to fall off I look for whatever is dragging it down, and back up it goes. Pretty cool, if I might add, to know your car that well. When I get around to welding up my true duals and finally having a leak-free exhaust then I should be able to bring my economy up a little more.

I'm hoping that I can see about 28 to 30 mpg highway after I get my exhaust sealed up, add a few MPG boosting bolton's (ewp, UDP, etc.).

On a side note, I once averaged 34 mpg on a roadtrip from Montgomery, AL to Charlotte, NC. I pushed it into neautral on all the downhills, kept it at 65 mph, and tailgated semi's at a mythbusters interval. I don't recommend that to anyone... but it makes for a cool story

To the OP: You won't get very far squeezing out that last MPG with HPTuners without a wideband and a big understanding of HPTuners and how EFI engines operate. I've read two of Greg Banishes books and have his CD from summit... and I'm still pretty lost, lol. You pretty much earn a labcoat if you can tune a modded EFI engine for max power, economy, and reliability.

 

So what truly kills MPG then. I mean there's guys here's getting 12mpg but they're cars aren't exactly street cars. What mod cam, stroker, boost.....where does it start really affect MPG.
If I'm running a porsche 944 (sits at about 2800lbs) with a ls1 block, 102mm intake and TB, 59cc patriot heads, a 224/224 114 cam, modified hooker headers, 3 inch magnaflow, and I'm debating stroking it up to 383. With a car that light, could I expect anything close to what you're getting?

 

A 6 speed will give you better economy than a stalled out A4, so unless the 12mpg car is an auto then they've probably got a really radical combo. I'd say a good portion of those cars could pick up some MPGs if they went to a dynotuner saying "I want the best MPG that I can get" instead of power. Most of the 12 MPG cars aren't daily drivers and probably have a tune to safeguard against detonation.

One of the sponsors has created a system that has two PCMs that can be switched back and forth with a switch. With something like that you could have a nasty tune and then another that doesn't particularly care for the taste of gasoline.

... sorry, that answer sounded like it came from a politician who did a decent job of answering the question without actually answering the question. I guess I can't really tell you what part would start killing MPG. It probably has something to do with compression ratio and how things like camshaft choice effect it and how different cylinder heads change it.

 

this is mistake!!! When tranny is in neutral, you NEED fuel to engine operate (idle speed). When tranny is in gear and car moving, drivetrain rotating mass maintains engine rpm and you have ZERO fuel consumption.

 

set up lean cruise mode

 

Then why does the MPG gauge fly past 100mpg when you pull it out of gear? The engine still consumes fuel when you're decelerating.