Fuel consumption

[scillyisles]

The fuel consumption average seems to stay around 22/23mpg - most of my driving is around town etc but generally not in rush hour traffic. Longer motorway runs can push the average up to 28mpg or so.

Is that from the trip or actual calculation ? Mine seems to overestimate fuel consumption. At present displaying 18mpg with correction nearer 20mpg on Optimax.

Guess the only question is what else can cause poor consumption apart from a heavy right foot.

These figures are from the readout but agree with my calculations when I work out the figures. On a long motorway run I get about 280 miles before needing to refill. Fuel consumption around town tends to dip down - lowest I've ever seen was about 18mpg. My VIN number is in the 1200s March 95 registration.

[alastairg]

Just to complete this story. Despite my stated desire not to re map I did ! Excellent result as documented elsewhere. I have now improved mpg as well which a good remap should achieve.

[AAH!]

I have been watching my fuel consumption quite closely since my remap (which I am still very pleased with) and my initial impression was that it had gotten worse. So as of last week and with my last capacity fill up with opti, i have started keeping notes and although this "highly technical study" is barely underway I have found that with 74 miles of stop, start, slow, short journey, central London driving I got 12.2mpg from the TC (trip computer), which is down from my pre-map TC average of a very approximate 14.5mpg.

I filled up today to capacity and did the maths (for the first time ever) and it came to 15.3mpg, which is a little shameful in these days of political correctness but at least it is better than 12.2mpg. I have a 100 mile motorway run this weekend and will see what that turns up.

I am wondering if the new bosch motorsport fuel pump is confusing the TC a little. There is a thread on the S2 Forum about the whole TC calibration thing, but it doesn't seem come to any definitive conclusions, or maybe I am just not taking in what is being said. I'll reread it now. http://www.s2forum.com/forum/showthread.php?t=8050

In the meantime any ideas ?

Angus

[alastairg]

IMHO best ignore the TC. Just do the maths brim to brim miles covered. Or just miles on trip to low warning.
I think the conclusion was different injectors i.e RS2 ones in S2 will mess up TC. Not the pump which has no direct influence on fuel delivered unless broke !

[AAH!]

Yesterday wasn't a good day for my brian. I just relooked at how I calculated my fuel consumption and I got it totally wrong!

Doing the calcs properly it now looks like I am getting 11.2mpg around town (30litres for 74miles), even worse than the TC. Almost more shamefull than my maths.

Angus

[alastairg]

'Brain' or 'Brian' as of 'the life of' You need more rest than I or more beer ( or less ). That mpg just shows how silly London is.

[AAH!]

oh god, it just getting worse!

can't do maths, can't spell, can't do polls! I think i'll take the doctors advice and get some rest or beer or both

[GlynRS2]

My overall fuel consumption is about the same to slightly better since my remap. Get 275 - 300 miles from a tank between refills - usually get about 55 litres in at the pump. Driving is quite a lot of around town short stuff with the occasional 10-20 mile trip. The tank when coming back from the rolling road got 325miles - after some fairly enthusiastic motorway / A road driving.
I did replace the lambda probe just before the remap as it was still the original one at 80,000 miles.
Are you sure you don't just have a very heavy right foot?

[AAH!]

I think I am probably guilty of a heavy right foot, it just seems to be the right thing to do.

Just did an 85 mile enthusiastic motorway drive with a little bit of town thrown in for good and got 21mpg (TC said 20.2mpg). I do this trip every weekend so next time I will try and be positively unenthusiatic just to see how much it helps, then I'll ignore the results and go back to how I like to drive.

[DavidB]

Hello Alastair
my RS used to do 320miles on a full tank and the display used to average 23.9 ish untill i had the cambet done , the cam belt was fitted to the correct marks on the top an bottom pulleys as i have found out these are wrong , the camshaft timing is appox 2 teeth out from what it should be , the car runs and perfoms well but he fuel cosumption is higher . it is worth getting it checked out properly as it is not a diy job

[super-g]

I hope you are all coming to the same conclusion with an average mpg of 23-24 that’s if you are able to keep moving. Long motorway trips @ 92-100mph should see 280 – 320 miles that’s say to Cornwall before the 30 mile warning light comes on with a refill requiring 56 litre approx.

Flat motorway driving down to the south of France will increase to about 350 miles before 30 miles in tank warning. (Not always set correctly but easily calibrated with a spare can of fuel just in case)

These figure are only achievable with fairly conservative driving and gently applying the throttle to the cruising position. At 70mph 25-27mpg is achievable but don’t bother you’ll lose the will to live.

All this mpg might sound as if were all driving slowly but when I compare my speeds with others around me I’m still going faster and with less fuel stops getting there quicker.

Use the RS2 acceleration when on a mission will reduce the tank mileage to about 150–180 miles; with 4750bhp reduce to 80 miles per 60 litres.

The mpg I achieve when cruising is between 92 -100 is 23.7 this is with a rebuilt short engine having covered 56,000 total 156,000 with all other mechanical engine and electrical parts been original apart from impulse sensor on the crank, which just failed while on holiday.

If you are not achieving these figures first look at the brakes for sticking pads. Mechanical vibration will also increase mpg as well as tyre pressure. I run Pirelli P Zero 225 x 45 17 @ 38psi. I get 48,000 from rears, suspension set to zero tow in or straight ahead so the rear tyre is nice and shinny with polished glow all over indicating perfect tracking. Front tyres return 28,000 – 32,000 zero tow (only achievable with powerflex) for even wears but you will not achieve polished rubber on the front from this suspension design. The car should feel kart like on turn in with only the weight of the car noticeable at high speed cornering which takes the edge of things.

Improving the suspension geometry (powerflex etc) making the suspension softer, will also help to improve mpg? The higher the mileage of the springs and dampers the softer the car this will also increase mpg.
Any vibration or twitchy suspension will actually slow the car down, the one thing all Audi 80 S models suffer from which is mainly down to poor spring settings and not dampers. That noticeable nervousness in the straight-ahead position on poor a roads is caused mainly by the springs and suspension geometry.

When set up correctly and with high mileage spring it is possible to tune the dampers to the softer springs to get a better a road set up. You will not be able to get close by just changing the dampers and using new springs. The Koni top adjustable are the best for this as you can take apart and reset the foot valve to match the softer spring,

Note you can only set the foot valve correctly to match the spring rate but with top adjustable dampers you can cheat a little and go back a bit further.

You then use the top adjuster for harder or softer damping. It’s a shame that Koni or KW don’t offer the same damping adjustments you can buy for the likes of Subaru etc.

Please note you are not going to get close to a road rally setup with new or up rated springs, the ultimate would be to have some made but I never seem to get round to it, as the mileage increases the springs get a little better.

Hope this helps and when I get time will post more info on suspension set up.

best

[AAH!]

the cam belt was fitted to the correct marks on the top an bottom pulleys as i have found out these are wrong , the camshaft timing is appox 2 teeth out from what it should be , the car runs and perfoms well but he fuel cosumption is higher

Off topic but:

The RS2 specific cam pulley (with the smaller sensor window) doesn't not seem to be able to line up exactly with the V mark, in my case (and it seems a number of others) it is either half a tooth beyond or before the mark. The correct position is half a tooth before/anticlock of the V mark. In my case it had been set at half a tooth beyond the V mark and threw the ecu in to limp home mode i.e no boost, when the engine went above 2500rpm and gave a faulty cam sensor short to positive fault code, which is somewhat misleading.

My cam pulley was refitted incorrectly (not in exactly the same position as it came off) after having the cam sensor replaced. It took six months and a lot of experienced and knowledgeable people scratching their heads to get to the bottom of why I had no boost. Including the so called specialist who replaced the cam sensor!

The trick is to put the cam pulley back on the way it cam off, unless of course you want to get better mpg which you will as you will have no boost to suck that petrol up.

Angus

[alastairg]

I hope you are all coming to the same conclusion with an average mpg of 23-24 that’s if you are able to keep moving. Long motorway trips @ 92-100mph should see 280 – 320 miles that’s say to Cornwall before the 30 mile warning light comes on with a refill requiring 56 litre approx.

Flat motorway driving down to the south of France will increase to about 350 miles before 30 miles in tank warning. (Not always set correctly but easily calibrated with a spare can of fuel just in case)

These figure are only achievable with fairly conservative driving and gently applying the throttle to the cruising position. At 70mph 25-27mpg is achievable but don’t bother you’ll lose the will to live.

All this mpg might sound as if were all driving slowly but when I compare my speeds with others around me I’m still going faster and with less fuel stops getting there quicker.

Use the RS2 acceleration when on a mission will reduce the tank mileage to about 150–180 miles; with 4750bhp reduce to 80 miles per 60 litres.

The mpg I achieve when cruising is between 92 -100 is 23.7 this is with a rebuilt short engine having covered 56,000 total 156,000 with all other mechanical engine and electrical parts been original apart from impulse sensor on the crank, which just failed while on holiday.

If you are not achieving these figures first look at the brakes for sticking pads. Mechanical vibration will also increase mpg as well as tyre pressure. I run Pirelli P Zero 225 x 45 17 @ 38psi. I get 48,000 from rears, suspension set to zero tow in or straight ahead so the rear tyre is nice and shinny with polished glow all over indicating perfect tracking. Front tyres return 28,000 – 32,000 zero tow (only achievable with powerflex) for even wears but you will not achieve polished rubber on the front from this suspension design. The car should feel kart like on turn in with only the weight of the car noticeable at high speed cornering which takes the edge of things.

Improving the suspension geometry (powerflex etc) making the suspension softer, will also help to improve mpg? The higher the mileage of the springs and dampers the softer the car this will also increase mpg.
Any vibration or twitchy suspension will actually slow the car down, the one thing all Audi 80 S models suffer from which is mainly down to poor spring settings and not dampers. That noticeable nervousness in the straight-ahead position on poor a roads is caused mainly by the springs and suspension geometry.

When set up correctly and with high mileage spring it is possible to tune the dampers to the softer springs to get a better a road set up. You will not be able to get close by just changing the dampers and using new springs. The Koni top adjustable are the best for this as you can take apart and reset the foot valve to match the softer spring,

Note you can only set the foot valve correctly to match the spring rate but with top adjustable dampers you can cheat a little and go back a bit further.

You then use the top adjuster for harder or softer damping. It’s a shame that Koni or KW don’t offer the same damping adjustments you can buy for the likes of Subaru etc.

Please note you are not going to get close to a road rally setup with new or up rated springs, the ultimate would be to have some made but I never seem to get round to it, as the mileage increases the springs get a little better.

Hope this helps and when I get time will post more info on suspension set up.

best

Thanks, an interesting post. At what age/mileage should you consider spring changes ?
And I have heard several answers to this. Did the RS2 use different springs. AMD and QST say so or were they simply the standard with Air con front springs ( you can get air con non air con weight rating I guess )

[super-g]

Alistair,

No need to ever change springs they just get better, unless you are having special ones made. Why not meet to compare setup and see what you think?

I had a Laser Red S2 Avant before the RS2 it’s on the web somewhere reg number A5 AUX, I don’t think there’s any difference in springs just dampers and camber settings.

fittest...