compression ratios

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marty40
Posts: 64
Joined: Tue Dec 29, 2009 11:54 pm

compression ratios

Post by marty40 »

well all.

i currently have 1.3mm skimmed off my head which i think gives me around 10.3:1 compression ratio. Torque down low has very noticably increased.

I was wondering what compression you all think the standard bottom end will take. I know i cant skim more than about 1.6mm or else it will start cuting into the bowl area.

just curious as i was thinking about building another head.

thanks :D

hondaNickx
Posts: 713
Joined: Wed Aug 05, 2009 1:06 am
Location: Belgium

Re: compression ratios

Post by hondaNickx »

I would worry about your piston to valve clearance ,and the fact that your valve seats are closer to the head.Besides that i think stock pistons can handle a lot of compression.You see a lot of guys running 12 :1 compression on p29 pistons and such.It just all depends on what condition your piston rings and pistons are.

If you want more compression then 10,3 :1 you would be better of getting high compression pistons.Milling your head to 1.6mm gives you 10,7 :1 compression which isn't really worth the trouble.

Btw the bowl area is inside the intake/exhaust ports.And the D14a4 's quench area is about 2.5mm deep .
Quote from Endyn:"The combustion chamber is a better shape than the DOHC.So don't chunk those 1.6 SOHC engines, they can make really good power. For a pure performance application, regardless of application, I'd choose the SOHC. No bull!"

marty40
Posts: 64
Joined: Tue Dec 29, 2009 11:54 pm

Re: compression ratios

Post by marty40 »

sorry i forgot what it was called :?

yea thats y i can only skim around 1.6mm off the head because of the piston to valve clearance. dont think i could go anymore or else i wuld start to run into trouble.

high compression pistons could be an idea altho i dnt fancy spending too much money on them.

cheers for the reply!

Law_
Posts: 1154
Joined: Wed Aug 05, 2009 3:37 pm
Location: Portugal

Re: compression ratios

Post by Law_ »

Can i ask you guys, what is a good value for skim a D16Y8 head with stock pistons? remember, D16Y8 head is lot more "closed", with smaller chambers. cheers

hondaNickx
Posts: 713
Joined: Wed Aug 05, 2009 1:06 am
Location: Belgium

Re: compression ratios

Post by hondaNickx »

Law_ wrote:Can i ask you guys, what is a good value for skim a D16Y8 head with stock pistons? remember, D16Y8 head is lot more "closed", with smaller chambers. cheers

D16y8 head has the quench pads closed up which gives you a bigger quench area which is better in high compression ratio like 12 :1.Less prone to pre detonation.
If you mill the head 0.025" or 0.64mm you'll get a compression ratio of 10:1 on a D14a4/a3 bottem end. 0.025" milled is not too much imo.
Quote from Endyn:"The combustion chamber is a better shape than the DOHC.So don't chunk those 1.6 SOHC engines, they can make really good power. For a pure performance application, regardless of application, I'd choose the SOHC. No bull!"

Law_
Posts: 1154
Joined: Wed Aug 05, 2009 3:37 pm
Location: Portugal

Re: compression ratios

Post by Law_ »

Seems nice. will mill that 0.64mm and remove a layer from head gasket then ! Should be fine :D Thanks !

Jocky2k85
Posts: 11
Joined: Wed Feb 06, 2013 8:16 pm

compression question

Post by Jocky2k85 »

I was just wondering if anyone knows what the comp ratio is of a d14 wit pm2 piston's (at least I think that's what's in my a2) and a z6 head.

or even if anyone knows the any info on the pistons.

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