New Bike for 2021

[WOODY@DDLLC]

A few eons ago I got to work on a Sportster and the previous owner had none of large HD sockets so all those hexes had been savaged by a (calibrated?) cold chisel - including the the crank pin nuts. 

[mc2032]

Finally got around to unpacking the top end.  Custom turbo pistons, ceramic tops, moly sides.  Cases and crank headed off to get balanced.

[Stainless1]

Good looking squish on those... Nice work from Hammer Performance...

[Speed Limit 1000]

Racing porn

[ggl205]

Those are beauties, Ross. Now you can turn up the boost and flow some alky.

John

[Dakin Engineering]

State of the Art
Oooolala

Sam

[Sporty Dan]

Wow, those pistons are works of art! Very nice! What compression ratio are you going to be at?

[mc2032]

I think these are set for 9.5:1 but will verify.  Online effective compression calculators say at speed/15-16 psi boost,  I should plan for apprx. 20:1.  Bike no. 1 lived with those numbers on Sunoco 110 and 112 so this new set up should hopefully tolerate it as well.  Also, plan is to run E85 or methanol so that needs to be addressed as well.  Bike no. 1 post race inspection showed static compression still in the 180 psi range with minimal leak down.  Every other nut or bolt was loose and the header was cracked from either years of heat stress or the turbo hanging off of it unsupported.

[Stainless1]

Looks like Hammer Performance did a nice job custom matching the head and piston. 

[thefrenchowl]

Hi.

Since heat likes to collect on sharp edges anywhere in an engine, then promote unwanted red hot points/pinking/self ignition/destruction, what's the idea for these cavities surrounded by lengthy sharp edges on your pistons?

I've seen loads of these in 20+ to 1 C.R. slow revving auto ignition diesel engines, but fail to see the attraction in a controlled ignition engine.

A flatter but higher dome to get the same C.R./better squish should be a lot healthier?

Thanks for some justifications.

Patrick

[mc2032]

French, my understanding is the pistons are "matched" to the combustion chambers then "relieved" to the appropriate static compression ratio.  As to the effective compression ratio, that is a calculated number based off of static compression then adjusted for relative boost.  The Hammer pistons are designed for turbo  applications with lowered ring heights, ceramic crown coatings, Teflon skirts, etc.  If the basically stock pistons lived for as long as they did under boost/Bonneville conditions, I feel fairly certain these new one should too.  YMMV.

[thefrenchowl]

OK, thanks...

Patrick

[mc2032]

Squint really really hard and you can kinda sorta see the beginnings of a race bike.  December 13th and warm enough to roll the bike out onto the drive way and degrease the crap offa it.  Now to strip it down and start rewiring for minimal electrical and EFI.