I've heard that one reason UK scoobie turbos have poor mpg is because running the engine rich helps cool it, ie it is a safety measure. If this is true, how exactly does it "cool the engine"?

Also, on another note, how many miles do you need to clock up before the engine is loosened up (not run in) to the point at which fuel consumption is at the best it will ever be?

Any comments appreciated

 

Hi Ernie, i actually got the best consumption out of my my00 when i was running it in!! seems to have dropped a bit now that its got a few thousand miles on the clock!!

 

Had the exact opposite - when the car was running in - fuel comsumption was very poor (around 21mpg), now it varies between 24 and 28 depending on how heavy my right foot is. Impreza owning colleague reckons he never gets better than 18 mpg!

One of the reasons for the poor fuel consumption is the compression ratio. As I understand these things, turbo engines run lower compression rates than 'normal'engines and because of this, they use more fuel.. and they're more fun than most cars, so you put your foot down more.

I've also heard that the engines on the UK cars run a little rich. This would seem to be true judging by the number of comments about very black exhaust pipes. I'm sure one the more technically minded members of the board will give you better explanation.

Chris

 

I thought the reason Scooby's run rich is so that when you get rid of the cats you can have flames

DaveW

 

well i must confess that i have been using super unleaded since 7miles on the clock so i think that helped!!! the rest is down to keeping it out of the turbo alot, now its run in, its now running!!!!

 

I've averaged about 23mpg in my MY00 and it's not varied much since new but the trend appears to be slightly upwards. Now at 2800 miles. The most significant factor seems to be who drives it, me or the wife. She seems to consistently get 4mpg more.

I fitted Broquet from new. I've also noticed that the exhaust is very black. Can this be changed by retuning? Is this worth doing or is it just a feature of the car?

Spreadsheet of usage at:

 

Hi,

My MY94UK usually does around 17~20MPG (depending on right foot) Always run on SUL, and the exhaust is black. Much more so than a friends STiv Type R.

Another annoying thing is the size of the tank. I can NEVER fit on more than 42 litres... Thats not far at 19MPG

Mark.

 

I got about 28 when the car (UK MYOO)was new. Now it has increased to about 31 , six months and 17,000 miles later.

However it depends a lot on how you drive it. With a roof box and family of four and a holiday in the Pyrenees, roaring up and down mountain passes etc, Oh dear, about 15 mpg.

And before anybody says I am a total Granny, the front tyres needed replacement at 15,000 service.

JD

 

My TypeR will give me 30mpg on a run, which is most of the time, as it sits on the motorway at a steady 80-90mph. The car currently has 18K miles on the clock and just keeps getiing better.
The worst I've had was about 8.5mpg! I used almost (52litres) a whole tankful of SUL in just over 80miles. It was a lot of fun though.

Matt

 

I didn't used to believe that SUL made any difference until recently.

I reset the ECU after a few tanks of SUL (I also added a bottle of Millers Octane Plus to temporarily raise the RON to 99 just prior to the ECU reset). After this the difference in economy was quite significant. I now get around 280 miles per tank (around 26 mpg) and thats with a heavy right foot.

D.

 

Hi all

24-28mpg bloody hell i dont see over 20 as for reason they run rich if they do im only a cook, i say a rich mix would not completly burn so therefore would run cooler same as a lean mix would be hotter.

Simon
Ps please remember ive not got a clue what im talking about:d

 

I have a four week old MY00, and it seems pretty good on the gas. Best so far is about 330 miles on a full tank, but that was driving it back from Holland on motorways below 4000 RPM, so it's probably not a good indication.

You can hear the tank emptying when it's thrashed though. Oh well, I didn't buy it for its fuel consumption!

Geezer

 

How many miles per tank ???

I do well if it does over 170 miles per tank

I can see the fuel gauge move when I use boost

Mark.

 

I get between 200 and 225 miles out of a full tank - but then there is nothing like 6000rpm!

 

I once had 6mpg - on the road! - And that was for a whole tank.

They really shouldn't let children get access to the ECU

The reason why Scoobies have pathetic mpg is that they are simply a HOOT to drive

R

PS My other car did 37mpg last week, over 1000 miles of motorway (80-90mph), urban crawl, M25 traffic jam, rural spurt - with the air-con on. And it's not a econobox, but a 1500kg barge!!!! Fantasy Land

[This message has been edited by Rannoch (edited 01 September 2000).]

 

Poor MPG,
ruining the environment, depletion of the worlds resources....

What am I saying ?
The lower MPG the bigger the

Mark

 

Hi All,

My LINKed MY98 UK cruises on vacuum at 95-100, running with a air/fuel ratio of pretty close to stoich (c14/1).

This gives approx 26mpg at those speeds with A/C on - not too bad methinks

I use closed loop operation (lambda mode) when cruising, and this gives a worthwhile improvement in economy over the base map. Of course it doesn't help at all when I'm wearing my lead boots...

For those with a standard ECU who are getting very poor economy, it might be worth having the lambda sensor checked. This is especially true if you've had your downpipe changed as they are mechanically fragile and may have been damaged in the process.

Cheers,

Alex

 

i only seem to get 190 miles a tank,(before the light comes on )

bloody expensive

:{

 

Hmmmmm....I've been using SUL for the past year, some 40,000 miles or so.
Initially, the car seemed to pick-up better and fuel economy increased. It gradually went back down again though.
However, last week I changed back to NUL from a cost point of view more than anything. I was also keen to see what difference it would make to the performance, if any.
I can in fact say that after 1 week of using it, the performance is no worse, if anything it's slightly better and the economy has increased yet again.
I was getting approx 240 miles to a tank but I've got up to 280 in the last few fill-ups!
Anyone care to offer an explanation? I am driving the same as always!
Needless to say I will be sticking with NUL from Esso wherever possible, unless the car suddenly starts to dislike it.

Stef.

 

More fuel vapour in the combustion chamber cools the engine the same way adding cold water cools a boiling kettle. The cooler temps reduce the risk of knocking (premature ignition of petrol in the combustion chamber) which destroys the piston heads.

Lower octane petrol (95 or 97 RON in the UK) is more susceptible to knocking than higher RON (100+ in Japan), so Subaru adjust the European ECUs to run rich as a way of compensating. Jap import owners often have to add octane booster to their cars as the ECU doesn't always compensate properly for the lower octane fuel.

Johnfelstead posted something recently about checking the state of your exhaust pipe after a track session. Black & sooty is good, light grey/brown indicates a lean mixture which is bad. On Subarus anyway.

 

And by "Jap import owners" I mean "owners of cars imported from Japan", not "Japanese owners of imports"!

 

Hurray...no more worrying about my black exhaust

 

Adam,

I wish I understood half of what you posted . I take it the LINK can be selectively programmed to make it more economical on long runs yet also give better performance?

Cor. My warranty runs out in November. Hmm.

Nick.

 

Stef,

I found that I had equal or better performance when going back to normal unleaded aswell!! Turned out to be a honeymoon period though as by the third tank I couldn't cope with the 'rough running' and went back to SUL. Now averaged 26.4 over the last 6 weeks, and that's on an MY00 with an engine which is probably shafted!

Otis.

 

Chiark,

Yes - on cruise (off boost, low load) the car is mapped to run pretty lean. The Lambda sensor (which the standard ECU also uses) lets the ECU adjust the base map dynamically towards a predetermined, target air/fuel ratio.

As soon as you use more throttle (on boost), the ECU switches to different rows in the map which puts more fuel in for safety.

Best of both worlds in other words, although the standard ECU also works this way.

Cheers,

Alex

 

AlexM,

my 6mpg for nearly a whole tank came about as I had Lambda on...

...I was hooning around the lanes, on the way to the motorway and then, not much time passed and I noticed the tank was empty. When the lambda gets really hot, it makes the Link think the car is running lean and it keeps richening up the zones. Leaning to crap economy and washing out the bores, diluting the oil etc.

That was the last time I used closed loop.

By the way, apparently (Mike Nunan posted this originally) optimum economy comes at 1.05 of lambda. So tune it to that for Rows 2 and 3.

Rannoch

 

Who cares......put your foot down.

If you want econ buy a diesel!!!

Doll firmly thrown out of pram....

The best I get is about 22 MPG, thats mostly driving through town with a good blast at any and every opertunity.

SS

 

If you are doing lots of motorway miles( a steady 80-90,(to many unmarked *******s to go any quicker) expect about 320 out of a tank. I normally manage about 280 using normal UL.
I only use SUL on track days or fun weekends. On track days I'm convinced that there is a hole in my tank, as the gauge sinks faster than the Titanic. I do well to get 170 out of a tank.
The heavier the right foot the less mpg, but normally the bigger the smile.

Jon

 

**** me - 280-320 Do you have two tanks on your car?

I would dream of 280-320 per tankful on any kind of fuel!

R

 

Ern
The rich mixture has two largely independent effects - for a given specific output:-
1. More fuel evaporating in the cylinder cools the overall charge due to the energy required to evaporate the fuel (like boiling a kettle).
2. Combustion in the cylinder happens more rapidly this means that the combustion is more or less restricted to the time when the piston is at top dead centre and the surface area is minimal. This means that temperature of the engine is minimised and efficiency is optimised. (efficiency is largely a function of exhaust temperature).

The issue as to SUL fuel giving rise to better fuel consumption is more likely to relate to the effect generated by the knock sensor which retards the ignition when knock is sensed.
UL fuel is more likely to knock than SUL, thus ignition is more likely to be retarded with ordinary fuel. Optimum fuel consumption coincides with optimum ignition timing so SUL is better.