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,
Damien

Example of a Smart Roadster:
http://obchod.spstyling.sk/images/ca...oadster_xx.jpg

Smart Roadster Coupe (identical to my car)
http://www.carandclassic.com/uploads/new/47590.jpg

Smart Roadster v Roadster Coupe Kammtail:
http://www.pozitifpc.com/editorblog/...ster_coupe.jpg

Smart roadster coupe rear
http://motortorque.askaprice.com/ima...uilt-20716.jpg

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.

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 !

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.

Welcome Damien.

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

ollie

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.

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

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.

Possibilities.
• 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.

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!

One other thing. What would you consider the US EPA for the roadster. I used the 55.4 UK combined figure and simply converted in to US gallons (~46mpg). However, the EPA for Smart cars in the US seems a lot lower?

The front wings are bolt-on, so I've thought about taking a vacuum-formed mould of the current wings and laminating the inside of the mould to reduce the size of the bulge before making a vacuum-formed wing from the reduced size mould. Time is my main barrier to doing this!

Are they that bad? They could easily be covered with some vacuum-formed plastic as they're nearly all decorative.

Big Performance do some Perspex headlight covers that should help with the lighting aero, as you've discovered.

I've fitted some Bosch aero wipers, which helps a little. I've thought of fitting a cover to the bonnet that send the air over the top but that'd stop the bonnet opening!

I've bought a rear-view camera, which I'm going to fit to remove the need for the wing mirrors. You can't realistically fit mirrors inside the car, simply because the shape of the car would prevent you seeing anything with them!

You're right, they're huge! Making new front wings would help here, I think. Alternatively, some plastic sheeting could cover the rear arches entirely and most of the front arches to make the gap smaller.

Really? I've never noticed that. I'll take a peek later.

Have you tried removing them? It's on my todo list, once I work out how they're attached. You can hear the wind noise they make, so it must be pretty bad!

All the panel gaps are huge. The bonnet and the boot are also pretty bad.

I've noticed (in the rain) that it reattaches at several places, the windows for example. The constant separation and attachment is really bad for the Cd.

I don't quite understand that. Do you have photos?

Cunning! I've noticed that temperatures are never high on the Roadster, even at 35 degrees or more. In fact, it's only heat soak that makes the temperature go up when you stop. I've seen 100 degrees on the gauge!

Do you not find the steering a little heavy?

I've been looking at the wheels from a ForTwo. They're the same diameter as mine (15") but not so wide. They fit 145 section tyres, so there's gains to be had there. The front arches can then be correspondingly smaller.

I've also been thinking about a rear diffuser. That should minimise the wake of the car. In addition, adding creases to the trailing edges of bodywork should help separation. The round shape of all the panels can't be helping at the moment.

Good list! Some to add to mine there.

I saw a noticable difference by going to Michelin Energy E3A @ 40psi. From memory, it was about 5%. Flat hub caps are on my list too. I was thinking about a sheet of plastic cable-tied to the wheel spokes.

I had the idea of using polyurethane expanding foam and a plastic bag to make a lightweight seat. It's only needed for padding. However, you'll need to fabricate some seat belt mounts as they mount to the seats as standard. Also, you'll lose the ability to move the seat, which is fine for me, as the only driver and at 6'3", I have the seat far back anyway!

Certainly. Although, take the top speed with a pinch of salt. Last month, I did 197kph (according to GPS) on a German autobahn in my notchback.

You're getting better mileage than me!

What are you going to do to cover your mirrors? Be good to get broken mirrors from somewhere, then you could use the base plates.

I haven't tried to remove them, I'm too scared! But it's bound to be worth removing them during winter when the roof won't be open anyway.

I used P profile weather strip you get from B&Q and stuck it along the leading edge of the door. It's about 5mm wide, so almost covers the gap round the door.

Yes, it's doable in winter time. Maybe want to move it again in midsummer

Yes, but it lightens up fine > 10mph.

The sportline alloys look an excellent candidate. However, they would require 20 - 30 mm spacers at the rear.
http://s3.agedstock.com/vehicles/photos/3405/496655.jpg

This may work but there's not much space for a diffuser behind the exhaust back box.

Wow, that's an impressive top speed. Not many 80bhp cars can to that (if any?). Overall the cdA can't be too bad!

I've not exactly worked that out yet!

Ditto!

I think I see what you mean now. Good solution.

You can buy them for just over £100 new from WellSmart. I've been pondering what tyres to go for. 135/80 is about 2% bigger rolling circumference, so I'll drop ~100rpm on the motorway. I can only find budget tyres but they're cheap at £27.10! 155/80 gives a 10% larger rolling circumference and about ~300rpm drop on the motorway. I can get branded tyres for £38.50. I think they'll be a good compromise, although I don't know how stiff the sidewalls are and what effect that'll have on the handling. I moved from the standard Bridgestones to Michelin Energy E3A, which meant a lower sidewall stiffness and slightly more nervous handling.

They're available in Germany but they're not cheap. They're more for styling than effectiveness though.

I don't think that was VMax power-wise. It was very noisy, so I couldn't be certain but I'm pretty sure it was bouncing off the rev-limiter, rather than running out of power. It certainly got there quite easily and wouldn't go faster, even downhill (I tried once on the flat and once on a downhill section).

Tonight, I removed the wind deflectors on the top of the windscreen. They're just stuck on with hot glue! I just levered them up with a flat-headed screwdriver and scratched the glue away with my fingernail. I've also removed the passenger side wing mirror, although I've not worked out a way to make it neat yet. I may end up using a piece of 4mm Perspex and hoping for the best!

Good work on the deflectors. Have you noticed any difference in wind noise? I think mine will be coming off tomorrow!

This week I've removed my passengers side wiper and put rain repellant on that side. The rain stays off it ok when you go over 50mph, but beads a lot otherwise.

I think my next mod will be mold inserts for the side vents. I'm going to use foil and wrap it closely against the body. Then use packing tape to make the outside part the mold (tape from the door sill to the outer part of the vent). Then use expanding foam in the crevace, building it up slowly to minimise any air bubbles. Hopefully then the outer layer will be hard enough to spray silver (to match tridion), don't know if I'll need any filler on top.

Have you any experience with doing this sort of thing?

This is the area I'll be filling up, except leaving no vent (actually I will have to do something like this for the passenger's side)

http://shop.michalak.eu/images/produ...ages/153_0.JPG

Have you any pics? I was thinking of unscrewing the mirror from the base and leaving the base attached to the car (obviously this would be sticking out externally). Don't want to risk any leaks when I have a dry car!

Also how did you remove it? My mirror base doesn't seem to have any screws. It seems to clip together. I know there were loads of revisions of the mirror bases.

Evilution - Smart Car Encyclopaedia

I didn't read Evilution before removing the mirror but I worked it out just how it's written; two torx screws to split it apart and two more that hold the main mirror part on. I've not split the mirror from the base, just left it open (it's not raining today). It's definitely not waterproof at the moment! One thing I've noticed from driving to work today is that I use my passenger side wing mirror a lot. I'll need to replace it with something. I'll have a fiddle in the garage later and take some photos.

The wind deflectors and wing mirror have resulted in a massive decrease in wind noise. It's very noticable, especially at high speed. I've not had the roof down to check the difference in buffeting yet.

I may remove my passenger wiper in a minute - it's pretty useless anyway!

I also checked the prices of steel wheels and wheel trims for the ForTwo. 3.5"x15" wheels are ~£31+VAT and 4"x15" are ~£35+VAT. I can get some clip-in wheel trims for £25 and a few minutes with a hacksaw, a sheet of ABS, a craft knife and some epoxy should get me some aero wheels.

I was looking at the side of the car last night and there's certainly room for manouvre by covering the vents up. Given that the body panels are all bolt-on, there's scope for building a more aerodynamic bodykit. I was thinking of using my current panels to mock up some rear arches that incorporate creased ttrailing edges and wheel covers. Then, I can get them off and use a vacuum former to make lightweight copies for peanuts and in seconds. I'm going to try out the vacuum forming idea with a panel at some point soon to see how it works in practice (weight/flexibility/price/finish).

I've separated the base from the mirror this afternoon. I did cut a sheet of 4mm Perspex to size and put it in the oven on a baking tray at Gas Mark 6 until it went floppy. By the time I ran it out to the garage, it'd cooled, so I gave up with that and used the base. Best bet is probably to butcher the base for an improvement. I stuck a piece of gaffer tape on the hole that the cable passes through, being carful not to block the drain hole in the bottom. It should be as good as standard now, just with a little less frontal area.

I also tried to remove the passenger wiper arm but I couldn't pull it off when the nut was removed. I suspect the aluminium and iron have welded themselves together over the last 5 years. I'm not willing to put more welly behind it and I don't have any pullers.

Anyway, here's some photos:

http://roadster.endurancelay.co.uk/i...ngMirror/1.jpg
http://roadster.endurancelay.co.uk/i...ngMirror/2.jpg
http://roadster.endurancelay.co.uk/i...ngMirror/3.jpg
http://roadster.endurancelay.co.uk/i...ngMirror/4.jpg
http://roadster.endurancelay.co.uk/i...ngMirror/5.jpg

I was looking at the offset differences in switching wheels.

Using the fq101 wheel info FQ101 : Taking Modification to the Next Level

and then an offset calculator Wheel Offset Calculator

It looks like if you changes to 4 inch rims on the front, the rims would be recessed by 16mm against your spinlines. Rears would be in by 25mm. I think the smart wheel trims look good (and aerodynamic) but are expensive at £25 each.

http://i.ebayimg.com/03/!BZzvKUw!2k~...n25T!~~_12.JPG

The wiper arms were difficult to take off, I had to get a wiper arm puller from e-bay. Don't think it will ever be worth £10!

Must get some pics of my grill block for you.

Also I was thinking about the diffuser you mentioned. I think it would make the aero worse. The vacuum it creates would only add more drag. The Chevy Volt aero video convinced me of this. On the other hand, i'm not sure if i'm prepared to add straight edges to the back of the car to help the airflow detach from the back of the car cleanly.

At least they're recessed, not further out. That can be fixed with some appropriate spacers. I'll get some wheels for the next set of tyres I fit. I'm getting close to needing a new set anyway. I checked my tyre pressures earlier and Mercedes had helpfully dropped them to 30psi at the last service and I'd not checked them in the intervening 6 weeks! I'm back up to 40psi now.

Coincidentally, my wife has just walked in the door with a nice new round steel tray from Ikea. £7. Some measuring will be going on later.

A puller will be useful, so I'll get one anyway. I bought some cheap wipers on Ebay and the passenger one is rubbish. The only thing it does is stop the arm scratching the screen - I won't miss it!

As far as the diffuser goes, my theory was that it'd minimise the size of the wake by reducing the vertical surface area of the rear. It's all guesswork at the moment. If nothing else, it'll finish off the undertray that stops before the engine. I have a spare carbon boot floor that's going on the Mini at some point and it almost got fitted to the underside of the Roadster this afternoon! I think a few sharp creases on the car may help its looks, especially if I can combine them with smaller wheel arch bulges. One thing I learned today was how simple it is to mould Perspex with a little heat from the oven.

Pics of my grillblock:
http://img39.imageshack.us/img39/2641/image053dy.jpg http://img39.imageshack.us/img39/ima...jpg/1/w640.png

You can't see it very well, but that's the point! Also I moved the number plate up a bit. On a roadster I don't think it makes much difference anyway.

I wasn't able to get the deflectors above the windscreen off, they are very stubborn. I'll try to heat it up with a hairdryer at the weekend and try again.

You really can't see the grille block from the photos - good job! I may follow your lead with the number plate - it's a good solution, I think. I found the best way to get the deflectors off was to push them with my thumb so I could get a flat bladed screwdriver underneath, then gently lever up until they're off. It took less than a minute but then I had to spend 15 minutes scratching off the adhesive with my fingernail.

I've done a frontal area comparison in GIMP of the Roadster with and without wing mirrors. The difference with a double wing mirror deletion is ~2.3%, which should gain me ~1mpg. We'll see the real world results when I have done a few tanks of fuel.

It's funny I just found out the frontal area today from here:
http://www.cartoday.com/content/maga...20Roadster.pdf

They came up with 1.93m sq or 20.77 sq feet (x10.76). How does that compare to your figures?

That thread on TRn is what reminded me to do it! I don't have a figure in square metres or feet. My figures are in pixels!

Got it! Pixels is fine since you're able to get an accurate % difference.

I'm going to remove the passengers side first; not sure if I want to remove the driver's side (eventhough I think I use the passengers more when changing lanes).

Also as well as decreasing the frontal area, I'm pretty sure it will improve the cd as well, since the mirrors are aerodynamicaly very dirty and they are in an area of high pressure.

Is there anything else we can remove? :-)

I must work out the frontal area reduction in lowering my car 25mm. Got new springs partially for looks, partially since they all seem to break and also for a slight aerodynamic improvement!

There's too many inaccuracies to take this as gospel but it looks to be ~3%, although I don't know if you're supposed to use the area under the car when calculating the benefits of lowering. I did this time, although I didn't when calculating the benefit of removing the mirrors.

I'm very seriously considering putting my passenger mirror back on. I don't feel comfortable with my reduced vision. I keep noticing cars moving into my blind spot, which is now much larger!

I don’t think you count the area under the car, just the tyres frontal.

Area of 2 205 width tyres lowered by 25mm.
205 x 25 = 5125 mm sq x2 = 10250 mm sq
20.5 x 2.5 = 51.25 cm sq x 2 = 102.5 cm sq
0.205 x 0.025 = 0.005125 m sq x 2 = 0.01025 m sq

Total frontal area is 1.93m sq

% of original frontal area being removed:
0.01025m sq / 1.93m sq = 0.00531 * 100 = 0.531%

I’m not sure if that’s correct, but I suppose there are other advantages to lowering (less air under the car, smaller wheel arch gaps).

If you feel not having the pass mirror is a safety issue then put it back on, it's just not worth the risk of an accident.

That'd make sense, really. Of course, the narrower your tyres, the lesser the effect. I'm on 185 width tyres and considering a move to 135! As for the mirror, I'm going to fit one inside the car and see if that's good enough, if not, I have a reversing camera to fit and my last resort is to reinstate the mirror.

Andy, What about aftermarket mirrors? Auto style do mirror bases for the roadster.

http://www.euraxltd.co.uk/documents/...le_mirrors.pdf

The KT16B look v aerodynamic (DTM style), while the KT37 look nice.

Unless I'm missing something, the compatibility matrix doesn't show a Roadster. I like the F1-style ones though - tiny frontal area.

Look for MCC Roadster! KT 1100

D'oh! I still plan to try internal mirrors but this could be a good fall-back option.

Just had a read through this thread! I must say Damo I'm quite jealous - a Smart Roadster and a 2.4 JTD Alfa 156? Two cars with great fuel efficiency yet loads of fun and sound great too!

I'd just like to make a few queries/comments on things that have been mentioned so far.

Interesting. Is that all that has to be done to remove power assistance from the Roadie? I know with hydraulic power steering it's a big faff involving removing the unit, changing belts and so on if you don't want to push the power steering motor around every time you steer. With an electrical system is it as simple as removing a fuse or something?

Do you have an image of what these look like? I've always assumed the recessed lights wouldn't be too hot aerodynamically (though they're something I'd personally be prepared to put up with as the Roadie is fairly economical anyway)

Does it cost that much for some original Smart steel wheels? Surely many owners are getting rid of these and replacing them with alloys. I actually really like the look of the steel wheels - they suit the car more than any of the alloys - though you do have the Coupe version and I think the steel wheels may look a little small for the car - they suit the non-Coupe Roadster very well though. They were standard equipment on the Roadster Light, which if I were ever to get a Roadie would be the model I'd want:

http://i19.photobucket.com/albums/b1..._582916654.jpg

Best I've seen was on one of the Smart forums a while ago - an owner had fitted some of those sculpted carbon-fibre seats in, which weighed something ridiculous like 5kg each (or less)! Probably a bit pricey though...

Wow, 205 section tyres? Can't even imagine how much grip that thing has, it must weigh a hundred kilos less than my mk1 MX-5 on 195 section tyres and the Mazda has ridiculous levels of grip. I'd certainly be looking for some of the 15" wheels on narrower tyres - it'll improve your non-assisted steering, give you lower rolling resistance and you'll still have an abundance of grip.

Just a thought, but would it really be wise blocking up the air vents on a mid-engined car? The engine on the Roadster looks pretty tightly packed-in so it might benefit from getting better airflow.

As I said, they're decorative. They are not actually vents, so blocking them causes no issues. There's one section of one of the vents that is used, which would have to be left open.

Yes I think i've chosen well. They were both fairly cheap to buy, since everyone's afraid of them! I haven't had any real problems yet, luckily.

Simply disconnect the torque sensor from the steering rack. It doesn't save as much energy as a hydraulic system, since it only gives full assistance at low speeds.

http://imcdb.org/images/103/769.jpg
http://www.bigperformance.co.uk/imag...hc-clear-2.jpg
http://www.bigperformance.co.uk/imag...hc-clear-1.jpg

Think the steel rims are £120 + vat. I've seen some come up on e-bay, but it's quite expensive to get them over to N.Ireland from england!

Yes, front end grip is unreal. Also since there's no engine in the front, the direction change is very quick!

I unplugged the fuse to my electric power steering and all i got was a pulled muscle in my shoulder! No mpg gains at all.

ollie

I bought a suction-mount mirror from the local motor factors and stuck it to the inside of the passenger window. My blind spot is now completely eliminated. When I turn my head to look at the mirror (which is in the same place as before), I can either see a car in the next lane over through the window (peripheral vision) or using the mirror. However, my fuel economy has not improved with the mirror delete. I put that down to driving faster at the moment than I normally would.

That's interesting, thanks. I can't believe it needs much assistance at low speeds anyway with that little weight over the front. If a manual rack is good enough for an Elise, it's good enough for a Roadie!

Thanks for the pics. It's funny actually, even before I saw the Merc badge in that shot I thought "hmm, looks a lot more Mercedes-like"... I think I still prefer the styling as it is, but I can certainly see how light covers would offer aerodynamic benefits.

Yeah, that's not a bad price but I can imagine it going up a bit to ship them.

It seems then that you wouldn't lose too much by going to thinner tyres. It'd probably make the steering even sweeter.