Project Midlife Crisis

[THEDON]

Let's have some Fun:

In January of 2018 I turned 45. I decided to pass on the purchase of a brand new white 911 convertible and bought a 2003 Smart 450 Pure.

The car is in good mechanical condition with only 45k on the clock.

I picked the Pure because it is the lightest weight of the Smarts and that's what I am after: No top heavy glass roof, no power steering, only the bare minimum.
The most fun I had in my automotive life was always with small lightweight underpowered cars.
1980 Mini 1000, 1989, Peugeot 106, 1995 Fiat Cinquecento Sporting.

So, let's create the most Fun you can have on 4 wheels..

Next steps will be:
-Bump the power to around 100BHP
-Save some weight

More to come soon...

[Thrumbleux]

Focus on the handling.
Lowering it sorts the steering (view rear suspension geometry re toe-in with roll as to why) and decent section (eg 195/50 alround on Roadster steel wheels) tyres give shed loads more grip and banish the crippling understeer (which will always be cutting what power there is via ESP). Finish with the 13mm rear anti roll bar for best effect.

[THEDON]

Well...
That is very close to what I did first. No lowering but rear rims on the front with 165/55, it gave me a lot more grip but... actually, it became less fun to drive.The car felt heavier and I realised that I was not looking for the best grip or handling but for just the right amount of it.
I guess this is what James May is talking about in this video:

[Thrumbleux]

450s are sensitive to front wheel offset. When I tried rear (Jetline 175/55) on the front of mine it wrecked the steering. Slaphappy aiming for an apex I had a better chance of a lottery win than hitting the apex.
Stick to what is known to work (we've been doing this for nearly 20 years) and the car is transformed. You will not believe the difference lowering makes to the steering.

[THEDON]

Thrumbleux What would you recommend to lower the car but keep it as soft as stock?

[Thrumbleux]

You mean no harder than stock. It aint soft to start with. See below.

[Thrumbleux]

I used Eibach IIRC (can check) but lowering springs will always be stiffer. Given it's so damn uncomfortable as standard, the slight deterioration in ride quality isn't so bad and definitely worth it to be rid of steering that needs two inputs for every corner taken.

[THEDON]

Next step is to improve engine breathing or what I call Brabusation.



That is for the intake and fuel.
and a new muffler:



I need to fabricate a specific down-pipe.

[mikerj]

Next step is to improve engine breathing or what I call Brabusation.

Note that the Brabus 450 and Roadster 82bhp/101bhp engines also use a different camshaft. You will need either a remap or a Brabus ECU (plus SAM and clocks) to actually get the extra power. You'll also need a cat to pass an MOT emissions test (and stop the ECU flagging a fault).

An oil cooler would be a wise investment, either an aftermarket oil/air or the standard oil/water cooler as fitted to the Brabus/Roadster engines.

Focus on the handling.
Lowering it sorts the steering (view rear suspension geometry re toe-in with roll as to why)

Agreed on lowering benefits, but a De-dion axle can not suffer from toe changes on roll, unless the entire axle is bending. "Roll steer" is the rear suspension problem with the Smart.

[Thrumbleux]

Agreed on lowering benefits, but a De-dion axle can not suffer from toe changes on roll, unless the entire axle is bending. "Roll steer" is the rear suspension problem with the Smart.

Roll steer traditionally refers to toe out on the outer rear wheel (from the days of live axles on leaf springs or trailing links) but the transverse arms on a standard height smart point downward from the car's centreline to the hub thus in roll they push the outer wheel into toe in - which steers the car back out of the turn requiring another input at the steering wheel. Lowering and flattening the angle of the transverse link remedies that.
So technically it is 'roll steer' but in the opposite sense of where the term originated.

[mikerj]

Toe represents the angle one wheel forms with respect to the other on a given axle. If this is changing on the Smart axle due to the action of rear links then they must be physically bending the axle. There is certainly some stress on the axle caused by the rear links, but I'd be surprised if it was bending the axle significantly, though if this is the case a simple brace across the axle would fix it (at the cost of more deflection in the rubber bushes).

IMO a bigger problem is the entire axle pivoting from the front bush, coupled with the static camber being considerably larger than the static toe setting. As the axle pivots down a component of the camber will get converted into toe and vice versa, e.g. if the axle was free to pivot all the way down to 90 degrees, you'd end up with 2 degrees toe out and almost no camber. As the axle moves up, the (negative) camber converts to toe in.

[Thrumbleux]

Toe represents the angle one wheel forms with respect to the other on a given axle. If this is changing on the Smart axle due to the action of rear links then they must be physically bending the axle. There is certainly some stress on the axle caused by the rear links, but I'd be surprised if it was bending the axle significantly, though if this is the case a simple brace across the axle would fix it (at the cost of more deflection in the rubber bushes).

Toe is with respect to car's longitudinal axis.
As the outer link 'flattens' in roll (pro toe in) the inner link droops and angles the axle toward the inside of the corner - so in plan view both wheels move together in the same direction and no fight. It is in bounce that there is conflict which I'm told (by those who have replaced the rubber bushes with Rose joints) is acomodated by axle flex.

IMO a bigger problem is the entire axle pivoting from the front bush, coupled with the static camber being considerably larger than the static toe setting. As the axle pivots down a component of the camber will get converted into toe and vice versa, e.g. if the axle was free to pivot all the way down to 90 degrees, you'd end up with 2 degrees toe out and almost no camber. As the axle moves up, the (negative) camber converts to toe in.

A point I made several years ago on Smartz - and was ignored!
In roll though, as the outer wheel rises (wrt to chassis) the toe change is toe in (as you say). So another source of toe in (on the outer wheel) during roll though less severe than that from a the transverse links on a standard height car. Smart at every move dialled understeer into that chassis - they had to with a 72'' wheelbase. Lowering and flattening the angle of the transverse links in their static position goes a long way to obviating the worst outcome of smart's (pro understeer plus some more) philosophy.

[THEDON]

Humm..🤔 ... so lowering is good? Should the transverse link be as parallel to the ground as possible? and move from slightly beneath parallel to above?

[Thrumbleux]

Lowering is the biggest single difference that can be made to a fortwo .Largely because the discussed effect on the rear geometry. Lowering the car sets the links at an acceptable angle where in roll they will be close to horizontal. It's in the steering the reward is. Predictable, fluid, consistent - all the things lacking with the standard set-up. When you drive it you'll know.
Give it proper grip (195/50 alround) and you have a front end you can lean on and a tail (with the 13mm AR bar) you can play with on the brakes if you are feeling brave.

[THEDON]

The down-pipe is welded and ready to be mounted.



Light weight free flowing setup:



Ready for a short test...

[tolsen]

Looks impressive but I bet no performance improvement only rather noisy and incredibly short life air filter very likely quickly ruining engine.

As for lowering only do that if you want a bone shaker Smart.