bakomack

im confused on my compression. ive been told im gonna be 10:1 to 12:1 i dont understand how to calculate it out.

i have a b16a stock crank and stock rods. CTR pistons. the head hasnt been milled I dont think.

what compression can you safely run on 91 pump gas?

will aftermarket cams bump up the compression? im running blox type b cams, brian crower ss flat face valves.

thanks

delphicwhisky

Look up an online compression calculator. Search Google for "B series compression calculator".

I wouldn't run more than 11:1 on 91 but that's just me. Someone with more expertise may answer better.

bakomack

ok I need help im using this calculator

http://www.zealautowerks.com/bseries.html

b16a block, b16a crank, b16 head, PCT piston standard bore, b16a rods, oem 3 layer head gasket, the guy who ported my head told me to mill the head 20 thousandths ( havnt done it yet, is 20 thousandths labled .020"? )

max rotating rpm 8500

elevation 300 feet

if I calculate those and leave the milled section at 0 heres the results and the screen turns yellow.

static comp ratio. 11.91:1
effective comp ratio. 11.85:1

if I put .020 for milled the screen turns red
static comp ratio. 12.76:1
effective comp ratio. 12.70:1

ontariorider

I hope the chipped ecu is just for initial startup..this kind of setup you will want a proper dyno tune.

very curious how the gsc n2 cams do. I wasn't even aware of them until last week when my engine builder suggested those over skunk pro series...

JRCivic1

There is a flaw in the "Zealworks" slaw my friend...
The Factory rates the B16B engine at 10.8:1 compression. By simply clicking boxes with the appropriate choices in the Zealworks calculator, I believe you arrive at the numbers that you have quoted. However, closer examination suggests a compression height of 30.73mm... placing the piston top sitting above the block deck .007"... this is an error. Changing that value to 30mm, like most "B" series pistons are, comes up with a compression ratio of 10.9:1. This is very close to the factory rating. If for a moment we assume that the CTR (PCT) piston has the same install height as the ITR (P73) piston of 30.23mm... your compression only increases to 11.19:1 on the calculator. Next, reducing the chamber size by adding flat faced valves will increase the compression... a close approximation of the reduction (without actually measuring your chamber with stock valves installed and then doing it again with the flat faced valves installed) would be 1.2cc (.3cc per valve average)... so if you change your chamber size in the calculator from 42.70cc to 41.50cc, the calculator now says your compression ratio will be 11.52:1.

DO NOT mill .020" off of the surface of the cylinder head !!! Just because this works on V8 Chevy engines doesn't mean it works well on DOHC engines. This causes increased timing belt slack, a necessity for adjustable cam gears because your cam and crank timing events are no longer proper... not to mention you have lost a significant amount of quench area for making power. If the head is already milled, I suggest you buy a Cometic head gasket that is a custom thickness of the stock size PLUS the amount of material removed from the head surface. For example, the stock head gasket thickness (depending on who you ask) is between .026" and .030". If you milled .020" off the head, you would add that value to the original thickness... so .026" + .020" = .046", or .030" + .020" = .050".

If you use a well qualified tuner, tuning a 11.5:1 compression "B" engine on Premium Unleaded pump gas should be no problem... and it can have a very long, reliable life.