is it possible to work it out from the rod length, bore and piston height?

its all going into a 2.0l zetec with std throw crank

reason im asking is cos the piston has a flat top, i assumed it would be dished as i wanted a CR of 7.8:1

Rods are Carrillo, pistons Wiseco

Rods:
centre to centre 5.362
P.E bore 0.8132 (little end?)
B.E bore 1.9645 (big end?)

pistons:
comp height 1.181 (from centre of pin to top of piston??)
bore size 3.3660

Stroke:
88.0mm

compressed head gasket thickness is 0.5mm

only thing i dont know is the cc of the combustion chambers in the head

cheers anyone lol

 

Dan,

If you have the original zetec rod length and comp height i should be able to work back from the original CR and give you a figure.

PE will stand for (wrist) pin end or piston end which is yank speak for little end.

 

the pistons are flat top?

I dont see how they can lower the CR then without causing horrible issues with having no squish bands on them

what is the deck height of the piston in the bore?

there isnt enough information above to work out the CR

head volume is an important one for a start, although if you know what hte standard quoted head volume is you could use that to get a guess at approx cr

 

http://www.newagemotorsport.f9.co.uk...ion_ratios.xls

put your figures into that spreadsheet

 

ok mate cheers.

i cant find the std stuff tho lol, exccept the original bore is 84.8mm and the CR is 10.0:1

i think the rods tho were made to the same length, but cant be 100% sure on that

 

chip, i cant find the cc for the head mate, and i aint got the block machined yet to find the piston deck height (whatever that is )

matt, cheers, ill ave a look

 

If you dont know the clearance volume there is little you can do without measuring it.

 

matt, that comes out at 7.56:1

but not sure how accurate it is lol

it says the head cc is 45.5 (think thats what that bit is lol)

 

Chip,

Because of its under square bore stroke ratio, i fear that a really low comp zetec (<8:1) will be very hard with out loosing the squish band on the piston or shortening the rod length to enable thicker crowns/deeper dishes on the pistons.

 

whats that stu?

it says on the spec sheet: suggested clearance 0.0030 if thats it?

 

Dan, numbers or STFU

 

that will be the piston to bore clearance needs setting at 3 thou

 

ill scan the spec sheets in and post up when maytee gets back off lunch as i aint got a scanner

 

Dan, are you building this yourself, or are you going to get someone who has at least a vague idea about engines to lend a hand

Cause if its DIY, i reckon you should start ordering some spare bits

 

pmsl chip - no, philm/machine shop he uses are building it lol

 

well drop all the bits off and ask them to tell you the CR then mate rather than ask a load of people on the internet to guess without being able to take measurements!

 

ah fair enough lol

i also emailed the guy at wiseco, as the pistons were done ages ago but turned out to be for e a n/a zetec, he got these back on xmas eve and date on info sheet with em is from 08/12/05 then shipped from the US so i guess they are the right ones lol

 

Sounds like the shape of them is dicated by the internal geometry of the stnadard engine as Doug mentions above.

I guess to get really decent power from a zetec then you will need to shorten the crank throw slightly in order to allow you to maintain rod length whilst also moving the centre of the piston down so it can be dished with raised sides.

Obviously not the sort of thing you are trying to do, but thats probably the way to go for BIG power.

 

well its gonna be running 350-400bhp mate

 

thats not really what i meant by big power, i was thinking more martin/rod

hopefully 350 shouldnt be an issue even on that design of pistons

 

its big for a ZT unless your sunny and get a WRC lump lol

 

try this speadsheet


www.afracing.com/cr.xls


Alex