F7P cylinder head volume

Level 7 User Joined: 27 Feb 2004 Posts: 243

can any1 out there with a spare cylinder head measure the cc of the combustion chamber plz. need to work out how i want skimmed off wen i take it off in next cupla weeks. cheers

jimbo

Retroholic Joined: 12 Feb 2004 Posts: 5685

Dunno how or why but 23cc is stuck in me head(real head, not F7P Razz

)

Level 7 User Joined: 27 Feb 2004 Posts: 243

bloody hell, thats not much

jimbo

Forum Moderator Joined: 16 Feb 2004 Posts: 1356

Yes, take off a mm or two and you lose 1cc or so... well something along those lines. I think it was jonnyboy who had quite a hefty skim... that will have effected the cc by a fair amount.

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

i had a 12 thou (roughly 0.3mm) skim off mine, a fairly large amount.

Jimbo, IIRC the first couple of mm into the combustion chamer in the head, it still has 'walls', so you can use the cross sectional area to easily work out the exact volume for a given skim depth (or vice versa if thats what youre doing).

Even just using a fudge factor its still got to be more accurate than measuring water into the head or other bodge methods i would have thought?

Is that custom inlet manifold yours, and for the F7P?
My housemate says it looks like its made from honda B16 bits...

Level 7 User Joined: 27 Feb 2004 Posts: 243

yeah its a honda jobbie. wen ive fabricated a mnaifold for the f7 itl look somthing like that.

from wat ive read, the only proper way of measuring the cc is to use liquid.

im after a CR of 10.5:1 or 11:1. ive got it mapped for 98ron fuel anyways, so pinking shudnt be a problem. neither will valve clearnces. got all that taken care of.

jimbo

Level 1 User Joined: 14 Apr 2004 Posts: 29

what about if you want to use a wilder cams? with somewhere 2mm lift at TDC... would this be ok?

Level 7 User Joined: 27 Feb 2004 Posts: 243

im running wilder cams as it is. the willims lump runs deeper valve pockets on the pistons. il make sure theres plenty of clearence before skimming.

jimbo

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

its about 40 cc if I remember rightly.

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

well i got a head but havent got a burette (thingy?) for measuring the liquid???

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

Really, lets grow a brain here.

What is compresion ratio? Its a result of the differing volume of the combustion chamber from BTDC to TDC.

Lest say for simplicities sake the engine is 2000cc, itsd a 4 cylinder beast running a 10:1 compresion ratio.

1 cylinder is 500cc's (thats capacity divided by number of cylinders).

Bear in mind capacity is the swept volume.

500cc squashed up to be 10 times smaller makes 50cc.

So the combustion chamber volume is 50cc.

At 10:1 CR.

So if the chamber on a 16V was 23cc it would be 20:1 or something, diesel territory.

This is not the volume of the head, this is the total combustion chamber volume, that includes gasket, vale cut outs etc etc.

Most standard engines are way off by 1/2 point due to crap tolerences.

Tomorrow, the times table.

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

Actually i think youre wrong there

compression ratio is (swept volume + combustion chamber volume) / combustion chamber volume

so for your example a 500cc swept volume and 50cc combustion chamber would be an 11:1 CR, would it not?

Try to rearrange the formula with CC volume as the unknown and you will hopefully be able to see that if you only have swept volume and compression ratio, you cant easily work out the combustion chamber volume mathematically in this way.

Really Chris, grow some manners.

Tomorrow: Heat transfer in high bypass ratio turbofan engines

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

"Tomorrow: Heat transfer in high bypass ratio turbofan engines"

is it gonna be polytropic or adiabatic???

just so i can go over my notes!

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

Neal my boy you are indeed correct, that is the correct formula, my brain ios on holiday and I have a valid reason for that.

Anyway I had talked about this before on RSC and written about it months back and the total cc volume is indeed 49cc's.

I don't need manners, I am surrounded by stupid peopel everywhere, when I meet others with an equal intelect I will be polite.

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

yeah 49 rings a bell...worked it out once..will take some will power to remember how i did tho. but ill back up 49

Level 7 User Joined: 27 Feb 2004 Posts: 243

yeah i plugged those numbers into my special excel calcutlor, 49cc with standard 1.3mm gasket makes 9.9:1 CR wich is about right. remove 1mm fron the head face, and that brings CR upto 11:1.

jimbo

Forum Moderator Joined: 16 Feb 2004 Posts: 1356

Would that affect performance much?

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

well if the thing would run without pulling back lots of timing then yes 11:1 would make a good increase.

Level 7 User Joined: 27 Feb 2004 Posts: 243

it wud be running vernier pulleys, so the timing can be advanced. as well as modified valve pockets on pistons if needed. do the plasticine trick.

jimbo

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

Chris is on about ignition timing.
if u increase CR TOO much, u'll get detonation----knock sensor then retards ingnition timing to stop onset of detonation.

dont think 11:1 would be a problem tho??

Level 7 User Joined: 27 Feb 2004 Posts: 243

yeah i no hes on about ignition timing, but i run super unleaded, and its mapped for it anyways. the cam timing will also be retarded becuase of the skim to the head, so that wud be corrected with vernier pulleys and a setup on rr.

jimbo