Chipped for fuel economy?

[urS6Tom]

This may seem a weird question, but has anyone tried to chip a 20V engine in order to increase fuel consumption (I'm thinking low boost limits, very lean burn etc.)?

The reason I ask is that I currently get around 25mpg from my S6 (when driving conservatively). That's fine, because I don't use it for work etc. But, if my circumstances changed and I started doing lots of miles then I would have to get rid of it (which I don't want to do!).

So, I'm wondering whether it would be possible to have a dual ECU setup, one for performance, one for fuel economy and switch between the two as necessary?

Tom

[Jamo]

Yes the homefry will give you better MPG and if you read the thread on the forum this is already covered http://www.s2forum.com/forum/showthread.php?t=34018

[Rusty]

Twin maps has been discussed and is in the Homefries pipeline.

DOn't forget, zero depreciation can offset the FE of a car that's supposedly cheaper to run. A mate was looking at swapping his B5 S4 for a 123d BM to save money and it worked out £200 a month more due to the monsterous depreication on new cars.

[GazzaG60]

my vems returns a better consumption than the standard ecu chip did.

i trun 650cc's and its still pretty good. managed 135miles from the last 1/2 tank.

all 4x4 turbo motors are crap on locomotion-lotion.

[Jamo]

yeah stock chip runs rich, homefry gives better mpg than stock chip as well as performance gains

[UrS4boy]

If you are worried about fuel economy in an UrS car, it's time for a new car, e.g. used Yaris. Otherwise, why don't you just disconnect the N75 waste gate frequency valve (WGFV). With the WGFV disconnected, all you will get is about 6 psi (0.4 bar) boost based on the mechanical boost of the WG spring. The car will be a dog (like a 7A) and you will just have to accelerate very slowly. BUT it might return an extra 1 or 2 mpg.

[S2central.net]

Actually my multimap chips do this 'valet' mode rather more cleverly - and the car is nice enough to tootle around with 0.4bar mechanical boost - curtails big fuel consumption from use of high boost... Its worth more than 1 or 2 mpg but I've never had the patience to test it on a proper economy run. I have never tried to create a chipset purely for economy but the boost limit is a quick win for that.

ABY, AAN and ADU multimap chipsets available now...
3B multimap with a few Beta users - should be widely available in June.

[johne]

I can confirm that I'm getting over a 2mpg improvement using a standard Homefries.

That's based on comparing consumption on over 20,000 miles before Homefries and doing the same over 15,000 miles on Homefries where I'm getting 28.6mpg.

This is real mpg based on brimfull to brimfull, not using the on board display. Also all on 95 RON unleaded

John

[A80Avant]

who said that by taking the N75 you are actually altering any fuel map?? none at all,the car will still run on same fuel consumption and also run richer when the foot goes down. So taking the N75 off will not get you any better fuel consumption.

Ideally you would want a car mapped on cruising speeds of 1.05lamda or even more if EGTs allow it.But to be honest, if you do a 2hour drive with EGTs holding on 850C, you may get your fuel economy,but you will also get strain and fatigue on the turbo and exhaust manifold at least.

[S2central.net]

This doesn't alter the fuel map - its just a boost limit - less fuel is consumed at 0.4bar boost than say 1.4bar.

The best way to get better cruise mileage is with a wideband lambda that can fake a narrowband signal into the ECU and make it run leaner than target stohic mixture - care to be taken of course so as not to run so lean that plugs, valves or turbo suffer damage. Latter isn't going to be stressed on cruise condition though.

[A80Avant]

Paul,
do you think then that running on/off on a mean EGT on the turbo of 800C is ok for a 2-4 hour drive? I thought that although turbos/ EM can take up to 1000+degrees,that doesnt mean that they dont stress under less C but longer duration.
Also what would the acceptable lean limit would be provided that EGTs are acceptable as well. 1.05 lamda for example is ok?
What is your opinion?

As for the N75, i believe the initial question was not when driving the car on boost,but basically casual/everyday driving.

[UrS4boy]

who said that by taking the N75 you are actually altering any fuel map?? none at all,the car will still run on same fuel consumption and also run richer when the foot goes down. So taking the N75 off will not get you any better fuel consumption.

Disagree. With the N75 disconnected, the engine will only make a maximum of 0.4 bar boost. The ECU will see this limited boost signal (via the internal MAP sensor) and provide the appropriate fuel and timing signals from the existing maps in the chips. There won't be any rich running unless there are existing problems with the O2 sensor or post MAF boost tract leaks.

BTW, there won't be any fun either. My solution: Buy a used Yaris for those days when fuel economy is important and fun isn't.

[A80Avant]

really?
i wasnt aware that motronic can switch to a different fuel map to compensate for the 0.4bar of boost(mechanical).It may be so on original chips,but when it comes to remapped cars, at least from my car,when i take the N75 off the line and give it some WOTs i can see the EGTs dropping like mad, which implies that there is more fuel there than needed,as the map would be expecting higher boost there

[GazzaG60]

there is a technique called hyper-milers. the yank tank owners use it and volvo teach wagon drivers it too.

A80avant - setting the vems to 1.05 helps a little. at around 1.1 my engine starts to not like it too much. i never see egt over 730 at 1.05. around the 680 mark is normal on the motorway. 850 i think is a little high. cruising at lean burn wont hurt it will help. you may see 30 mpg too.

like paul says a narrowband feedback can help for stoich. wideband are not asa good at accuratelyt targeting stoich as narrowband. not as fast to adjust either. you will be fine with the vems. set the lambda target to 1.05 run it log it and adjust to suit.

[dest]

ABY, AAN and ADU multimap chipsets available now

Where do I sign up?!