Compression ratio happiness

Reply Subscribe

Thread Tools

Search this Thread

Oct 7, 2003 | 09:13 PM

#21

PUSHINTHELIMIT

Pro Rider

Joined: Jan 2003

Posts: 2,141

Likes: 0

Compression ratio happiness

Quote:

Originally posted by: MisterHP
I checked a 12.5 piston today and it had 5cc of positive dome and pin heighth would set it at zero deck. After doing the math this comes to a grand total of 10.1:1 actual compression ratio with a stock unaltered cylinder head.

I think compression ratio should be given using the cc's of a stock unaltered head with stock valves at factory seat heighth. Anything other than that would be speculation.

MrHorsepower

With that being said, by all rights that 12.5:1 piston can be run on pump gas right?? with those circumstance I mean..

Oct 8, 2003 | 12:03 AM

#22

MrHorsepower

Pro Rider - Oldham Racing
BUILDS THE FASTEST DS's ON THE PLANET!
Want a hot DS, or maybe one of the fastest DS's on the planet? This is the man to contact!

Joined: Jun 2003

Posts: 553

Likes: 0

Compression ratio happiness

The 14:1 is just that, with two base gaskets and stock combustion chamber. I'll be running mine with one base gasket[img]i/expressions/face-icon-small-wink.gif[/img]

PUSHIN it would seem that way but I'm sure not going to tell someone to do it.

MrHorsepower

Oct 8, 2003 | 12:35 AM

#23

PUSHINTHELIMIT

Pro Rider

Joined: Jan 2003

Posts: 2,141

Likes: 0

Compression ratio happiness

So are you saying it wouldn't work on premium 92-93 octane? I would like to know since going by your previous information that the 12.5:1 piston is more like 10:1 it should obviously work, right?

Oct 8, 2003 | 12:47 AM

#24

SANDMAN430

Elite Pro Rider

Joined: Sep 2002

Posts: 6,641

Likes: 0

Compression ratio happiness

that must stock like 5-1 well maybe 6.

Oct 8, 2003 | 04:41 AM

#25

Slowride

Thread Starter

Pro Rider

Joined: Apr 2003

Posts: 275

Likes: 0

Compression ratio happiness

I thought the folks running a 13-14 comp ratio were running alky. Is anybody running 13-14 comp ratio on 100? Or is 110 minimum?

To me, running 100 or 110 is the same hassle. If I opt for one, than the other is just as viable. A guy I know says he has tested the 100 octane stuff at the pump and it seems to hover at 94-95 octane. He said as long as the fuel is in the barrel, it'll store fine. But one it hits the pumps, it'll rapidly deteriate as all of high octane fuels do. You guys had any experience with this?

From all the discussion on compression, I was wondering if any of you with 12-14 comp ratios has checked the compression results using a calculator like at www.smokemup.com/auto_math/pressure_ratio.php and verified the calcs with reality. Seems too simple to me and the fact it corrects for barametric pressure was cool.

Obviously, cc'n a head is the absolute answer......

jbt