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damo 09-15-2009 06:47 PM

Hello from Ireland
Hi, I've been browsing the forum for a little while. Both my cars are reasonably fuel efficient. My first car is an Alfa 156 2.4 Turbo diesel. The govt mpg figure is 42 (UK), but I get around 48. I bought a Smart Roadster coupe at the start of summer, the govt mpg on that is 55 (UK), but I've struggled to average that since I've got the car. However, on my last tankful where I was trying very hard I managed 61 mpg (51 US).

Interested in improving the Smart Roadster's aero, as while the cdA would overall be quite good as its low slung, the body shape is fairly pants! Having said that, the Coupe model I have has a Kammtail which improves the topspeed against the ordinary Roadster by 3mph!

Also I'll be looking at the current crop of euro cars with eco aero detailing and comparing them against their normal trimmed models (VW bluemotion, Ford econetic, vauxhall ecoflex).

See you later,

damo 09-15-2009 07:09 PM

Example of a Smart Roadster:

Smart Roadster Coupe (identical to my car)

Smart Roadster v Roadster Coupe Kammtail:

Smart roadster coupe rear

andylaurence 09-22-2009 10:01 AM

I've also got a Smart Roadster, although mine's a notchback, rather than the Coupe. I've fitted Michelin Energy tyres (40psi) and removed the antenna so far. I've got a big list of stuff to do, just not got round to it yet. I've been planning a coupe conversion (without the big hinges) and a few small changes, like taping up the gulleys behind the doors and removing the mirrors.

robchalmers 09-22-2009 10:47 AM

I did a run from manchester to edinburgh and back in a friends coupe the other month and got 67average which included enjoying myself going over the 'beeftub' road. he runs standard size tyres @38psi but thats it. I was stunned how comfy and quiet it was, I was expecting it to be a lil buzz box.

Good luck Damo keep us informed !

andylaurence 09-22-2009 11:01 AM

I've never done that well on my economy but then, I do enjoy my driving! What amazes me is that I can do a track day and get 36mpg. I suppose that's why I've not been too bothered about doing mods. You must have had low expectations of comfort and noise if you thought the Roadster was good. It's the noisiest car I've ever had and it's hardly the height of comfort, although I did manage 3800 miles around Europe last month and my 170 mile trip to the office and back is fine.

vtec-e 09-22-2009 11:17 AM

Welcome Damien.

Thats a very nice machine you got there. Is your coupe a manual or auto/tiptronic?


andylaurence 09-22-2009 11:22 AM

There's never been a manual. It'll be a tiptronic, which is a manual three speed 'box with a two speed overdrive and all electrically operated. The driver just uses the gearstick in the centre console to select drive/neutral/reverse and tap forwards to change up, pull back to change down. Whilst there is a clutch, it's operated by the ECU and there's no pedal. There's an optional extra to have gear change paddles on the back of the steering wheel too.

robchalmers 09-22-2009 12:56 PM


Originally Posted by andylaurence (Post 129095)
You must have had low expectations of comfort and noise if you thought the Roadster was good. It's the noisiest car I've ever had and it's hardly the height of comfort.

Nah but I'm used to driving everything from competition spec minis, caterhams through to battered 300 scrappers on a commute and grew up around Midgets, B's and Healeys. ANYTHING seems comfy compared to them! I also get the complete opposite when I get to drive a car at work though!:thumbup:

the only big issue I had was that the tip stick was a push away to go 'up' and pull back to drop a cog, which just seemed wrong and un natural, there was a couple of times where I buzzed the engine when i pushed it the wrong way!:D

damo 09-22-2009 12:58 PM

When you look at them closely, the Roadster's aerodynamic aren’t great. They do have some things going their way.

Small frontal area
• Almost full undertray (apart from under the engine at the back)
• The Coupe has quite a nice Kammback.
• Front panel gaps are good.

However, there's loads of bad stuff too (in order of importance IMO):
• Huge bulbous front wheel arches (The single worst aero feature)
• Air intakes along the side of the body (2nd worst)
• Round recessed headlights
• The wipers are in an area of high pressure and almost unshielded
• The side mirrors are quite big for the size of the car.
• As standard the wheelarch gaps are quite big (7cm) for a small sporty car.
• The Tridion stands proud of the rest of the bodywork at the sides and top (esp noticeable on the Coupe).
• Large external hinges on the coupe.
• Wind deflectors for softtop. These are pretty much required to reduce the soft top wind noise and buffeting.
• The panel gaps round the doors are terrible (about 8 mm).

The main problem with the bulbous wheel arches, side air intakes and wheel arch gaps together is the unattached airflow along the side of the car.

I have made some mods:
• I put brown P profile weather striping along the side and bottom of the driver's door. Used "Back to Black" to 'paint' the strip black.
• Moved the front number plate up (to partially cover the front grille/ air intake)
• I made polystyrene blocks to fit into the sides of the front grille. Covered them with black insulating tape.
• I made a clear plastic deflector to deflect air past the driver's side-air intake.
• Changed the normal aerial to a shorter stubby.
• Pushed the side mirrors back a little
• Disconnected the Electric power steering
• Upped the tyre pressure to 31/30. Manufactures recommended pressure is 29psi (I have 16 inch spike lines with 205 section tyres), but that's the max I find bareable. I think because they are low profile there's not much gain anyway.

Going to change:
• I've got lowering springs to lower the car by 25mm.
• Maybe remove the passenger wiper.

• Modify the pass side air intake to channel more (pressurised) air into it.
• Try to get smaller or more aerodynamic door mirrors. The problem is that it's difficult to get mirror bases for the roadster and the standard mirrors have leakage problems anyway.
• Headlight covers from Big performance
• Brabus (or other) sideskirts
• Going to make small aero blocks to fit behind the coupe hinges

Can't do (not worth it )
• Steel roadster 15 inch wheels with 175/185 section eco tyres. Also try to fit aerodynamic hub caps.
• Lightweight seats. Standard seats are 20kg each. x 2 is 40kg.

I don’t think Smart ever published a cd figure for the Roadster. I’ve saw 0.41 mentioned for the ordinary roadster, but I don’t know how scientifically that was figured out. I suppose though even with that figure taking into account the frontal area, the cdA probably isn’t as bad as I think it is. I think what’s really interesting is the top speed difference between the Roadster and Coupe ~109 v 112 mph, eventhough the Coupe is 40kg heavier. The Kammback does have a significant effect there.

My car, with the 205 section tyres, probably affects the fuel economy as much as the aero deficiencies put together. But financially (and aesthetically) it doesn’t make enough sense to change them for Roadster steel wheels.

damo 09-22-2009 01:06 PM

Thanks everyone's replys. I prepared the above post at work!

Mine has the paddle shifters, they are very handy. The Stick shift is hard to get onto at first as I also consider it to be back-to-front. The gearbox can be slow, but if you hit the sweetspot (about 75% of the time), the gearchanges are about half a second.

My MPG has been about 52-55 IMP most of the time without trying too hard (I tend to drive economically minded anyways but stick to the speed limits). With my last tank I tried really hard (55mph - 65mph) and got 61 which is only 10% more, but still pretty impressive!

I think they are a pretty good little machine for what they are!

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