PDA

View Full Version : Calculating Compresson Ratio

jreiley
08-09-2009, 07:32 AM
I know the bore and stroke of the engine, but not the compression ratio. This is a running engine, i.e. heads on it. How can I figure out the ratio.
OneBadGMC
08-09-2009, 08:39 AM
Pretty much impossible. If you know the cranking compression, you can get an idea of final dynamic compression.
jreiley
08-09-2009, 09:03 AM
I know the cranking compression.
Tod74
08-09-2009, 11:21 AM
OH NO......

http://forums.racingjunk.com/viewtopic.php?t=9864&highlight=compression+test
OneBadGMC
08-09-2009, 12:07 PM
That was a comical read...

There are, however, enough astute engine builders over on www.yellowbullet.com that can give you a basic idea what the dynamic compression is based on cylinder pressure.

Specifically, the guys that do the 'pump gas drag' motors. Trying to squeak every last pony out of a given combination by maximizing dynamic compression without detonation.
bbchevy
08-09-2009, 12:23 PM
Whats New WJ?
The MAIN QUESTION Here is................................................ ..............?
Did the Fellow Ever get His ARM out of the HEADER?
Later
G 8)
Tod74
08-09-2009, 01:04 PM
That was a comical read...

There are, however, enough astute engine builders over on www.yellowbullet.com that can give you a basic idea what the dynamic compression is based on cylinder pressure.

Specifically, the guys that do the 'pump gas drag' motors. Trying to squeak every last pony out of a given combination by maximizing dynamic compression without detonation.

I agree with this. Lots of smart dudes over there...Just make sure you go to the newbie thread and introduce yourself first. Trust me on that one. :lol:
ashbros
08-09-2009, 03:11 PM
What a read.... LOL

That writing craftsmanship was suttle but to the point.....

I am still trying to figure out who road the best pony on that one... LMAO

By the way, all of you forgot to factor in the 3/4 duration on that stroke and compression calculation..

When you get it figured out let me know what you come up with....
ashbros
08-09-2009, 03:12 PM
Guys, I can't help it I am still rolling over that one. My ribs hurt sooo Bad............ :lol: :cry: :lol: :cry: :lol: :cry: :P
OneBadGMC
08-09-2009, 03:39 PM
Was a hard lesson learned for the kid repeating bad information like a parrot and then defending it. I bet his buddy caught hell over it.
Tod74
08-09-2009, 04:04 PM
The part that made me laugh was him being stuck in the header for 4 hours....my comment about him knowing Rudy was in reference to Rudy getting his finger stuck in a NOVA Door trying to open it with the handle removed...he sat there all day until someone found him...rofl :lol:

http://forums.racingjunk.com/viewtopic.php?t=9662&highlight=finger+stuck
OneBadGMC
08-09-2009, 05:50 PM
On a wild drunken night, I got my pinky finger stuck in a 69 Camaro door.

The stereo was blasting, and the exhaust was loud (naturally), so he never heard me yelling to stop and wait...

He drove off, and it was either me running along side and running into the brick mailbox next to the driveway, or ripping my finger out.

So..........I ripped my finger out and lost the nail in the door. He found it laying in the door sill the next day and brought it back, like that'd do any f'n good.

But yeah, trapping yourself with a header is classic.
jreiley
08-10-2009, 05:40 AM
After reading the CarCraft article, I see no way of calculating compression ratios without a lot of data that you can only get when the engine is being assembled. Thanks for all the comments.
ashbros
08-11-2009, 03:35 PM
Was a hard lesson learned for the kid repeating bad information like a parrot and then defending it. I bet his buddy caught hell over it.

Like a parrot??? Help, my eyes are watering, I am Loosing my breath

I can't take it.......LMAO!!!!!!!!!!!!!!!!!!!!!