2Litre

According to ford spec's @ 8.1 cr (as per manual) conpression tests read as nornmal @8.5 bar @8:1Comp ratio
The following are my results-

1-130.5 psi
2-130.5psi
3-130.5psi
4-130.5ps



I believe my Cr is 7.6:1 but the head has been skimed, is there a linear progression? ie -

7.2:1(ratio) =110PSI (Compression)
7.4:1=120Psi(compression)
7.6:1=130Psi(compression)
7.8:1=140PSI(COMP)

And so on and so forth..............

Thanks for you time.y



My Best , Tim.



it makes sense that

the_frozen_one

iTrader: (1)

They're closer to 9:1

1 bar is 14.7 psi, call it 15 cos it's simple.

130 divide by 15 is 8.6, plus a little for the missing 0.3 and it's between 8.7 and 8.9

Rs1

iTrader: (1)

Compression and compression ratio are two different aspects.

There will be a trend/correlation providing you only ever changed the ratio aspect. get a bit more complicated when you bring in valve timming.....which has massive affect on compression.

the_frozen_one

iTrader: (1)

As does boost and charge temp in cylinder increase. But these are statics. As quoted in manuals and as tested with a spark plug replacement pressure gauge. 99% of passionford won't know their dynamic cr, 25% probably won't know what one is

gingerturbo

iTrader: (2)

Did you measure the bore/stroke volume and the volume of the combustion chamber at tdc as that's the best way to get a true compression ratio

gingerturbo

iTrader: (2)

^^^ true this, main reason why a lot have issues

the_frozen_one

iTrader: (1)

I'm willing to bet he doesn't have a 12 inch pin mag block, or a calibrated burette, any cc fluid or a cc plate.

gingerturbo

iTrader: (2)

To a lot of people you just spoke foreign, when you test measure yours do you use a dti gauge to get true tdc as the piston floats over or just go with the notch marks

the_frozen_one

iTrader: (1)

Glad someone understands :-D

True TDC with the dti. Rechecked for each piston ( don't assume firing pairs are equal) grease around the top inch of the cylinder to seal the rings on the way up, scrape excess grease from the piston/bore clearance with a scrap feeler blade and away you go

gingerturbo

iTrader: (2)

Snap. My dti is probily the most used engineering tool I own I think, other than feelers and a vernier