1.6 e16se compression question

[stevei]

maby a long shot but the compression ratio i want to obtain is with ref the Build Manual, 11.4:1 - just wondered if anyone has done the same thing in the past and basically how much was skimmed of the head?

i.e 20 25 30thow ...... ish

ste

[Stuart]

you need to measure the volume of the combustion chamber in the head, then calclate what you want to take off.... better than guess work ;)

Its between £20-£50 to get a skim usually.

[stevei]

block is messured at standard:

bore: 79.0mm
stroke: 81.5mm

cc per cylinder = 399.54cc
x 4 cylinders = 1598.16cc

combustion head is standard at i think about 22cc

whats the formula of how much needs to be skimmed of the head, the heads at the engine builders at the mo' and they think it should be about 25thow

ste

[mowgli]

for group A spec, hi-compression pistons can be used. I think they were cosworth ones originally, but they used to use german 4star leaded (100+ octane) in those days.

[stevei]

thats the one, the cossie pistons stuck out the head a tiny bit so the compression ratio was achieved, so the head did'nt have to have a skim.

ste

[craig green]

Use a 16XE bottom end??

[Stuart]

yes "as std" its X but what if the head has been off before and is skimmed to somethign else, or even it wasnt X at manufacture due to tollerances...

get them to CC the head, then they can work out how much to take off to get to the CR you want.
its simplified by the volume of a cylinder formula using the diameter of the combustion chamber and the volume you want to remove to calculate the thickness to remove

[stevei]

my heads a bit mashed with the formula, can you give me example. might make me twig better

many thanks

ste

[Stuart]

a cylinders volume is pi*r^2*h

r = radius
h = height
pi = 3.141blah

you need to measure the volume of the combustion chamber to start with (DONT use the book numbers). Work out the current CR and also work out what the new CR needs the combustion chamber volume to be (sig link has reverse calculators)

measure the diameter of the combustion chamber, halve it
then have the ammount of CC you want to remove from the combustion chamber handy.

V = cc to remove
V / (pi*r^2) should give you the number of CM to take off the head (multiply by 10 to get mm)


that should all be right :D

[Stuart]

as a rough example you need to have 38cc available at TDC for the CR to be 11.5:1 (that includes the head gasket, the piston bowl/valve cutouts and the head)

so 22cc cant be close for a std head lol that gave a CR of 19:1

[Philsutton]

wow you run that on diesel then lol

[stevei]

lol

stuart your like a male caral vorderman:D

if i get the messurements, can you figgure it out for me?

if so, what do i need to messure on the head, i'll have to ring up the engine builders now

Cheers

ste

[stevei]

sorted it peeps, 20thow needs to come off

[mowgli]

sorted it peeps, 20thow needs to come off

if you don't mind me asking, how did they work it out? because 20thou is 0.50mm & it will remove about 2.5cc per pot...

[stevei]

it seems the head is standard at 40cc per combustion chamber, i'm not sure the engine builders sorted it for me. how did you come across your findings?

also the head i have has a egr hole on the inlet side through to the exhaust port - apparantly this is the later head and it runs slightley lower compression

i'm all a bit confused now:confused:

ste

[mowgli]

the bore is diameter is approx 80mm, so to get area in cc the sum is radius x radius x 3.1415926 (radius is 1/2 diameter so = 4cm)
4 x 4 x 3.1415926 =50.26 cm2 now multiply that by .05cm (the 20thou cut)
= 2.51 cm3 or 2.51cc per bore.

I can't remember if its been previously mentioned, has the head gasket thickness been factored in??

[mowgli]

all 16i engines have the egr & come at 10:1 cr