Oh oh - more power again

[Jassi_Hayre]

Folks

Sorry for another "I want more power" thread especially if you've seen it on a couple of other forums. I'm just trying to gather as much info as possible for a project I'm hoping to start soon. The objective of said project is a relatively fast car for road and track use. I'm not looking to create a dragster or stripped out racer but a daily driver which happens to be a fast Smart roadster. This is going to have to be achieved by reducing weight but also increasing power (and torque) which ideally results with a 170 - 200 bhp per ton power to weight setup.

I have to confess to not owning a roadster yet as I'm debating whether to go standard or Brabus. The brabus has more power but also has more weight and costs more to begin with.

If you had approx. £2k to spend on a standard roadster and £1k on a brabus for pure power gains what can you achieve and how?

Would really like to hear from those of you that have done any tuning and what's worked and not worked i.e. no point in dump valves but panel filter, Tik, various hoses and remap have worked. Lets call that stage 1 and a full engine rebuild with stronger components stage 3 which is £000's. What can we classify as stage 2 and what can it realistically achieve on a standard roadster and Brabus?


Thanks
Jas

[Kapt. Q]

Personal experience leads me to believe that around 120hp is a realistic goal for 'stage 2', anymore requires different pistons, rods and turbo, I have the blown engines to prove it .

If I was in your shoes, I would try to buy a brabus because it has a charge cooler and a slightly better turbo then I'd strip the heavier bling including the alloys and sell it to further fund performance mods. A remap alone of this car will give you close to 120hp (£200ish). I would add a Corsa throttle body (£30ish) and SW hoses to suit that (£70ish). I'd probably sell the overpriced brabus exhaust and buy something better or at least drill out the baffles visible in the outlets (holesaw fits great).

If I went the standard roadster route I'd buy a used charge cooler set up (£500ish) Corsa throttle (£30ish) SW hoses for it (£70ish) a better exhaust (£350ish but only £150ish if a home made decat) and a dyno remap (£200ish). Better silicone or Brabus TIK (£50ish). Expect around 110-115hp

Cheers!

Ps. Run the airbox without the lid and change the stock filter more often, nothing more fancy is really required and an X-guage confirms under hood temps have no impact while moving.

[Jassi_Hayre]

Thanks Kapt Q. and sorry for the stupid question but what are the SW hoses?

[Evilution]

170bhp to 200bhp per tonne in a standard Roadster equates to 134bhp to 158bhp.
If you are entering smart Roadster ownership with the idea of buying a cheap Roadster and getting anywhere near 134bhp you are going to be disappointed and severely out of pocket when it breaks.

They just aren't reliable enough to rinse that sort of power out of an old one.
I'd recommend an old Japanese car.

[Kapt. Q]

Sorry, SW Exclusive hoses are made to suit the larger Corsa throttle body and are available through Fudgesmart.

Cheers!

Ps, A Subaru WRX has trouble doing 200hp per liter for long as the block flexes too much, hence why the most successful engines tend to be inline with more main bearings and straight sixes in particular.

[Thrumbleux]

anymore requires different pistons,

Been following this here and on Smartz. Kapt.Q, do you have any failed pistons you can post photo(s) of? Specifically the failed pin bosses on the thrust side. There may be an explanation for these failures - and a simple remedy.

[Kapt. Q]

Yes, at my workshop, will take some tomorrow. Basically the whole skirt comes away right through the wrist pin, the break is quite clean and the bearing surface for the wrist pin appears in good shape. Cheers!

[Kapt. Q]

Here's a fortwo piston that failed, it has been hammered a bit by the flailing rod, but you can clearly see the initial grainy looking break:



This engine showed no signs of detonation.

Here is a roadster piston:



You can see a couple of it's interesting features, the top ring groove is anodised to harden its surface and make it more wear resistant. There is a scuff coating on the sides of the skirts that plays a part during break in. Like the rods in the smart a nice bit of engineering and perfectly serviceable within it's limits. Other than the increased pin diameter the two pistons are almost identical in relation to the to area where the fortwo one has broken.



Notice the 'cracked' caps

Cheers!