1998 Seat Arosa - Project EcoModder - 77/100MPG

Vp37 is I think what Andy's Audi runs

**PICTURES TO FOLLOW**

So after working out the speedo error through a not terribly precise method of holding the car at an indicated 60 and then comparing it to a GPS speedo app on my phone, I calculated that with the stock tyre size - 175/65R13 - the speedo was 5.6% under-reading. So my initial calculations of 72MPG for the first tank were, in realistic terms, actually 68MPG. Still not bad at all.

The first thing on the list was to give it a good service. It had spent most of its life pootling around the North of England under the command of some old guy doing his daily routine. Of course, the first thing I actually did was to lower it. A lot. I bought some brand new budget coilies from Alramone, which were listed for a Mk2 Golf, but doing some research the front struts alos fir the Lupo/Arosa, so I bolted them on along with some new top mount bushes and bearings. The spring rates are actually pretty good, and due to the bottom bracket being separate to the coilover body, on its own threaded mount, I wound it down as far as it would go, without compromising any shock travel. Now the drive shafts knock on the chassis rails on bigger bumps. I may have to 'adjust' this at some point. I also bought a cheap de-badged grille, which will do nothing for fuel economy, but it looks good.

The rears are currently cut down stock springs and stock shocks. I ran out of travel on the shocks, and I've reserved a set of s/h shorter Lupo shocks from Dez, but more research showed that Corsa B shocks have the same eyelet/pin mountings as the Arosa, but are MUCH shorter, so I've bought a brand new pair of those to fit.

At the same time, I fitted a pair of 6.5x16 Megane Scenic steels to the front of the car, with Nankang 165/45R16 tyres inflated to 45PSI. I would have fitted the rears too, but the only one pair of tyres showed up by the weekend.

Luckily lowering the car also helped to correct the horrendous amount of toe out on the front suspension. It was so bad originally, every little bump and hole sent the car skittering to one side. This was bound to be causing drag and scrubbing off speed during coasting or engine brakes, and therefore adversely affecting MPGz. It rides much nicer now, still not perfect, but I need to wait until the rear wheels are on and the rear ride height set before getting the tracking done and set to zero degrees.

Finally, the engine oil was dropped out for some fresh Fully Synth 5W40 and the coolant - read: plain water - drained and replaced with the correct pink coolant. Oil filter was changed, and the air pipe removed from the air filter behind the front bumper, and replaced with a cone filter directly onto the inlet chamber. I'm not sure how reactive diesels are to warm air intakes, but we'll see. I'm also waiting to replace the fuel filter until after I've done my first tank of diesel/veg mix, as I'm told veg cleans a lot of the curse word out of the fuel pipes and tank and starts clogging the filter.

Next tank full yielded me an indicated MPG of 79.6MPG. The new tyres are slightly taller than the stock 13s, so another rolling calculation worked out that the speedo error is now down to 3.3%, so in real terms the tank gave me 77MPG, almost 10MPG improvement just through servicing, lowering, slightly narrower tyres at 45PSI on the front and the associated suspension geometry 'correction' through lowering.

This coming weekend, I'll be setting the rear ride height and fitting the 16s to the rear wheels, plus performing a diesel injector purge to clear any curse word out and hopefully improve engine performance. I've got a set of 16" wheels trims, and some 17" wheel discs - read: pizza pans, an ecomodder staple - on the way, so I'll also be fitting them if they arrive in time. I've also gone some black plasticard to start making mirror blanks from.

Just bought my first 20litres of SVO too, which will be mixed 50:50 with diesel and a splash of acetone added, which apparently helps break down the fat molecules in the SVO and reduces surface tension for a cleaner, more efficient burn (although it might be complete curse word).

The listed comparison between a 'normal' 1.2TDi Polo and a Bluemotion version is 72.4MPG vs 80.7MPG, so not far off.

I vary between 55 and 60 mph, usually drafting behind HGV, and freewheeling down slopes. Freewheel efficiency will increase once the toe has been set to zero degrees.

I'm already using Fuelly to track the increase in MPG, its a great little tool.

Once the wheel discs are fitted, the will be less aero drag than the 13s, as its only the cross section of the tyre presenting itself to the oncoming air that provides drag, and this is also reduced by lowering the car. There will also be a lower air dam fitted in the future to further reduce the air getting under the car, therefore the flatness of the floor will come into it much less. There will also be some semi-spats fitted to the leading edge of the front wheel arches to prevent air from pulling into the wheel arch ahead of the wheels, as well as full rear spats.

Pitchers!

Nothing particularly overwhelming to see at the moment.

It's interesting when looking at the car (looks good on those fronts) how many potential areas could and probably do affect airflow. Suddenly the act of de-seaming has a practical function. I think I remember reading further up your thread that all the modifications you make must be reversible. Would something like adhesive vinyl strips over the panel gaps make sense?

Brand new - but tacky looking - ones on eBay for £12/set and free shipping. You could barely post a s/h set to me for much less, so it made sense just to push the button.

I really wish they were glued on, but a quick peek told me they are probably clipped on so I'd have to deal with holes in the door. Not a major catastrophe, I have some yellow and black hazard tape which can cover the holes if need be, or even just recreate the strips visually with black vinyl.