[Slidewayz]

I've been pondering on how to make it from the Bay area to LA on a single tank of gas whilst also at a normal I-5 cruising speed (e.g. 80mph).

I wonder what the upper bound of possibility is on a 335i 6MT for fuel economy if a tune was 100% focused on fuel economy versus power...ideally, we could switch been 'economy mode' & 'power mode'.

It is cool that Shiv has built a bit of this into the PROcede tune, but at the moment it is a compromise between fuel efficiency and power, not something that can be manually switched betwixst one and t'other.

[NYCGarbagePrince]

I heard the prius was pretty good at going long distances without fill ups... That or any other hybrid..

All jokes aside, I am sure he could. But from the looks of what people have been saying it raises operating temps a bit and that would become worrisome for me if I was trading engine longevity for a 2 gallons of gas at $3 per gallon..

[vladster]

Can you please explain how could less power, generate more heat ?

[satakal]

I've averaged 29 mpg from bay area heading south on multiple ocassions. 30mpg * 15 gallon tank = 450 miles.

Be gentle with the throttle and you'll get there on a budget. With or without a tune

[khaye1]

i just did the trip from san diego to san francisco and took the scenic route with few stops in between(monterey and san simeon)...my average was bout 27.9 mpg and total spent on gas was less than $175 round trip...that also includes gas for running around town and such.

[Slidewayz]

The question I'm posing is 'what is the upper bound of fuel economy to which we can tune', not 'let's have a survey where we gather anecdotal mpg stats'.

[HankE92]

Originally Posted by vladster

Can you please explain how could less power, generate more heat ?

The general rule is that running lean results in higher exhaust gas temperatures (EGT). By leaning out the AF mixture too much you run the risk of damaging something expensive - pistons, cats, etc. Best to use a EGT gauge to keep an eye on EGT temps if you're fine tuning a/f.

[roadkillrob]

VW TDI - you didn't buy your car to get good mileage!

[EZ_TUR90]

If your driving out alone might as well fly, when I drive out to San Fran I usually go with a couple of buddies and we split the gas. I dont know about you but Im a bit of a fast driver and gas could be a bitch.

[Kroy]

Originally Posted by satakal

I've averaged 29 mpg from bay area heading south on multiple ocassions. 30mpg * 15 gallon tank = 450 miles.

Be gentle with the throttle and you'll get there on a budget. With or without a tune

+1 Cruise control is my best friend when I'm trying to be MPG conscious.

[Slidewayz]

Originally Posted by EZ_TUR90

If your driving out alone might as well fly, when I drive out to San Fran I usually go with a couple of buddies and we split the gas. I dont know about you but Im a bit of a fast driver and gas could be a bitch.

Yeah, I couldn't imagine driving 60-65 all the way down the 5.

I think a switchable optimized cruise mode would be useful.

[midlife]

if you are an AT, use D mode instead of DS mode and you should save a decent amount of gas.

Hey- when I was young and not so smart - we would pile into my FI Z28 - lite a bunch of doobies and head out to where ever but going REALLY fast !!!

But like I said - not too smart LOL.

[satakal]

Originally Posted by Slidewayz

Yeah, I couldn't imagine driving 60-65 all the way down the 5.

I think a switchable optimized cruise mode would be useful.

If you're gonna ask someone to do some development work, then do it. Why hide behind your little internet couch icon?

[Slidewayz]

Originally Posted by satakal

If you're gonna ask someone to do some development work, then do it. Why hide behind your little internet couch icon?

I'm not hiding behind anything...I have a full head of hair.

I'm not asking anyone to do development work. What I'm asking is what might be the upper bound of fuel economy for this car and how we might attain it.

[Audibabba]

Originally Posted by HankE92

The general rule is that running lean results in higher exhaust gas temperatures (EGT). By leaning out the AF mixture too much you run the risk of damaging something expensive - pistons, cats, etc. Best to use a EGT gauge to keep an eye on EGT temps if you're fine tuning a/f.

No! Strictly speaking, running lean results in lower exhaust gas temperature. You can't hurt anything running there because there is less pressure and temperature. If you are going for fuel economy, you need to run there. Just enough fuel to consistently ignite off the plug.

There is a point in the fuel-air curve that has the highest temperatures and cylinder pressures. If you were mistakenly on the rich side of that "peak" and lean the mixture, you could end up right on the peak, which would damage something.

Of course, there are other variables in the engine tuning bag that can be used, too.

[wvcajun]

Lean vs rich.
Too lean an a/f ratio could in fact result in higher compression chamber temps and thus increased EGTs. This is because the gasoline sprayed by the injectors has a cooling effect in and of itself. Too rich a mixture results in insufficient combustion and a loss of heat as well as a resultant buildup of unburnt residues, namely carbon. That is internal combustion engines 101.

wvcajun

[dlbrooks18]

wasn't Shiv working on this at one point or at least put a feeler thread out there?

[twinturbopg]

Originally Posted by dlbrooks18

wasn't Shiv working on this at one point or at least put a feeler thread out there?

don't know but I would love to get that feature....my car is my daily driver take anywhere everywhere...

[Slidewayz]

Originally Posted by twinturbopg

don't know but I would love to get that feature....my car is my daily driver take anywhere everywhere...

He has an algorithm built into his software that will lean it out based upon certain conditions. This is not the same as a toggle to keep the car in economy mode.

[JayKay335i]

As everybody said, you'll get your best mileage with cruise control.

Otherwise, buy a prius, hippie.

[cstavaru]

I think that the mileage could be improved further by using a methanol injection system which costs about $300. A special fuel economy map for methanol could really improve things, but even stock I think that upping the effective octane from pump's 91 to a high value will make the car consume significantly less fuel.

[e.n335]

My milage is around 27 using cruise control on the highway with my heavy e93. Not bad at all for a 360whp car. The power has to come from somewhere - the gas. I really think in case you want to drive more cheap you need a different car.

Eugen