justburnit

03 fortwo cabrio

8 posts in this topic

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i bought the 03 cabrio here in australia with burned valves for 1000 bucks.

 

the car has black paint and heated leather seats and the 6 speed paddle shift sequential by getrag.

 

as i said the motor suffered a catastrophic failure due to the general motors piston rings. i didnt know this until later... read on. the motor was fully rebuilt and the exhaust manifod had cracks in it so it was replaced also. the car ran fine on its new turbo until one day smoke started pouring out the back, the turbo was immediately blamed as it appeared to be leaking past the journal of the turbine housing.

 

as i mentioned the rings... the piston rings have a tendancy to collapse under boost, a characteristic of racing and drag cars that can leave people scratching their oil soaked head. the motor was pulled out and a custom made turbo was installed, hand made by two different companies one to hand make it and one to balance it (the latter being the balancing guru) turns out that the garrett gt12 is the worlds fastest spinning turbo at an insane 260,000rpm with no ball bearing in the world capable of 160,000+

 

this created a serious problem because the rings would collapse and push the oil out of the turbo, the dipstick hole etc, basically one huge mess

 

next rebuild was new pistons and rings, shaved head to raise compression slightly, full port and polish, conventional "m14" platinum spark plugs (tired of m12 thread) new journal for the turbo, and drag racing flexible teflon silicone oil pipes to allow the turbo to swing in and out when rebuilt.

 

boom blew oil out everywhere on new pistons... why... woops forgot to put gapless drag racing piston rings from the usa and have the new italian pistons modified to suit... my bad.

 

having done that and putting big beefy injectors in it, car wouldnt run without dripping at idle. completely unnaceptable for a smart car driver.

 

we all make mistakes, installed the wrong map on the ecu... game over for almost 3 years

Edited by justburnit

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as a side note on the turbo, i have a box full of them. i suggest a ceramic bearing of your choice of size to go behind the impeller or compressor (thats the fan, clean intake fun bit of the turbo. the other side being the filthy turbine)

 

you should grind the housing out and put a bearing within a bearing behind the compressor wheel on the shaft. you can keep the journal.

 

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Could you kindly advise why the turbo’s piston seal rings collapse. Note that these are not oil seals but their mission in life is to seal exhaust pressure and boost pressure from entering turbo bearing housing. 

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Posting a photo of the turbo piston ring seal inside the KKK KP31 turbo of my 2002 Smart Cabrio Cdi. I machined a second groove on compressor wheel side seal and made that seal a double piston ring seal. 

9CF0B030-1FAD-43D5-9671-205A024A5A73.jpeg

 

These piston rings are tiny and do easily break. I therefore made a special Spanish piston ring fitting and removal tool. Took only 5 minutes to make with a sharp file.

31E399DD-A8F8-4544-9A59-1DFA6DE75501.jpeg

 

The piston seal fits on turbo shaft each side. Piston spins with turbo whilst piston ring remains stationary. Oil level in turbo bearing housing must be below these piston seals. Therefore important to ensure there is adequate oil drainage from turbo bearing housing. 

 

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Both are called piston rings. If he means engine piston rings I still cannot see why they collapse. Combustion pressure go behind ring and push it hard up against cylinder.  Too tight clearance perhaps?

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allz i know is that there is no need for blow by these days, and this motor sure has none... not enough to irritate me anyhow. 

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nice work on the groove. i have a big stack of triangles on my vediamo. i should put the .ori in the vediamo finders file and change its extension to .cff or

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