Alternative 1098 Piston for 16psi+
Turbo Mini Forums

Hi maniacs,
I was searching the web for 10H pistons, who are up to some revs and boost.
I will not consider this option for me, but it might be interesting for curious folks:

Smart Roadster pistons from the 698cc engine.
They come in 66.5mm bore as standard, and it goes two steps up to 67mm.
There are two versions of the pin: A slipper one with 16mm diameter and a circlip version with an 18mm pin. Considering that the 10H standard is 15.8mm its pretty close.

Now the drawback: compression height is 25.5mm, not the 30.33mm.
So if the 10H Pistons was on TDC same level with the block, you now end up with 4.8mm of space.
Plus the dish of 5.5cc. If you do a 12G940 conversion you will look at a cr about 7.28:1

The 82hp 0.7l Smart engine runs about 16psi of boost, making a BMEP around 290psi.
With this BMEP the 10H should put out 136lbft. In other words the piston in the 10H should easy make 150hp/5800Umin at 16psi. Considering that this is what the pistons gets in the Smart every day and the low cr I would raise the boost to 19psi and rev it to 6k, it should be around 170hp - but then the torque will crush your gearbox :)

Prices are about 44GBP/piece (problem: You can not buy sets, you would get only 3)

During the drive home another issue came into my mind: If the Piston is in the BDC it must still be safe in the bore and not able to slip out. Have to look on my 10H how much lenght is left at BDC

There are forged pistons available that have happily run over 20psi. also, the hypertecs haverun this with no ill effects.

I run the Aus Mini Sport pistons at 15psi on a daily with no issues too.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

Yes, but forged and fortune are not only phonetically close together. The Hypertecs are only excellent in 998s spec IMHO. The 10H pistons can not keep up (three ring design, sloted).
CalverST has some Graham Russel Pistons for 175GBP exc VAT, but they are flat tops. Don't know how much you can dig in there.
The Smart ones are 176GBP but with VAT and they are designed for the 16psi.

Edited by 1252er on 19th Feb, 2013.

I would agree the three ring slotted design is not great, but they take a hammering in my engine, and looked perfect after over 10k

Calvers are hypertecs, easy run 20psi, but yes, no dish. 3cc max really.

176 for 3 though? so you're getting close to forged money for 6.

You have a good point though. the choice of decent turbo suitable pistons for small bore engines is poor, and if a decent alternative was avaialble then I'd be more than happy.

Sadly, because of the pin height, I'm not sure these are.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

If you are going to run 16psi+ and are asking for decent pistons and turn down the forged version because of price, I think you are missing the point.
Buy them, fit them, don't be cheap.

http://www.swiftune.com/Product/459/omega-...a-flat-top.aspx

Don't cheap out. It will cost you more in the long run

Buy Cheap Buy Twice