Occasionally bemused at only getting 30 MPG @ 75 mph on long trips, and having a Dawes equivalent fitted to my MY99 turbo, if I fit an EBC and turn the boost right down for a long motorway journey:

1. Will I get more miles per gallon?
2. Would this hurt my engine?

Anyone tried it?

Cheers
Steve

 

im amazed your getting 30 mpg i only got 170mile from my last tank of fuel

 

I did say on long trips ;-)

If you are getting 17 to the gallon I'd try releasing the handbrake :-o

 

that was on a long trip all motorway miles

 

I have a HKS EVC5 fitted and got 27mpg on my trip to NBO (cruising 90++).

Will it hurt your engine - no!

Personally, I'd rejoice at 30mpg but if you bought a Scoob expecting any semblance of economy (in most circumstances) then you bought the wrong car.

 

I was never under any illusions about Impreza MPG, but as I age, and my mortgage goes up! I think about an Impreza with a 2 wheel drive, zero boost button, so I can cruise up to Scotland from the Midlands at 40MPG before blatting round the Highlands at 15MPG.

Is that too much to ask?

 

put an avcr on it has 2 maps one can be normal boost and the other can be set high boost , got an avcr on mine but ive only got the 1 map on it

 

drumsterphil

27 at 90+ sounds like heaven, what boost are you running?

 

Hello Steve

Long time no speak.

30 mpg is indeed very good for a classic impreza turbo. On a 75mph cruise i getting much less than that.

Lowering the boost, will not IMHO do any harm at all, but with the MBC you control the boost by your right foot to a large extent. i.e. if you are cruising and not going much over '0' boost then lowering the boost etc will make no difference on cruising.

Kind regards


Iain

 

If you're not hammering it up to 75mph, turning the boost down isn't going to make much difference. Once you've got up to 75mph, you won't be using boost to sustain that speed, and will be using closed loop fuelling, controlled by feedback from your lambda sensor.

There are only 2 ways I can think of that might help. The first, and dearest, is an ECU remap. If you had a Tek3 you could specify you were more interested in economy than performance, and the mapper would happily map that way for you. The second is to use some sort of AFR controller (HKS AFR Type L for instance) to make your closed loop fuelling leaner. But I don't know whether that would have any implications when it switches over to open loop, for instance if you had to accelerate hard for some reason temporarily. Lean open loop fuelling in 5th gear at 75mph WOT doesn't bear thinking about...

As already mentioned above, 30mpg is a pretty healthy return.

Never gonna happen mate, not in a Scoob. Get yourself a diesel...

Yes it is! How many petrol fuelled 2 litre turbocharged cars do you know of that return more than 30mpg...?

 

I run (depending on air temp) 1.15bar low and 1.25bar hi. My car is far from std however (not least a GT2835 turbo that doesn't really spool up till 3.7k which helps majorly with motorway economy...........)