COnfused S13

[MyFirst240SX]

What is this guy talking about with a low or high compression engine?  Nice runs on the dyno tho.
http://wac.addr.com/auto/240sx/240sxdyno.html

[S13Grl]

He's got an 8.6:1 compression on a naturally aspirated car. You understand how that works, right?

[MyFirst240SX]

Not exaclty i just know that is a lower than adverage compression.  IS that a stock compression?

[S13Grl]

Stock compression, I believe, is 10.something to 1. That's really low for a naturally aspirated car.

[MyFirst240SX]

was that engine is that? did he do that? is that an nissan factory option?

[LanceS13]

I think comprssion ratios for the 240 range from 8.6:1 to 9.5:1 depending on the year...never did they go above 10.0:1.

[S13Grl]

I dont' know what he means by &quot;earlier motor&quot;. The site is really old and there is no link to ask him. That's definitely not stock compression. Maybe he was on crack when he was &nbsp;typing that. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'>

[White240sx]

According to Nissan brochures the SOHC motor has an 8.6:1 compression ratio. I believe that the train of thought is that the early SOHC motors came with a 9.1:1 compression ratio, but I know not of the substantiality of this rumor.

[S13Grl]

I gotta go bang my head against a wall or something of such sort. I'm becoming really stupid. Be right back...

[geeaj]

The rumor is correct. Early 89' s13s (built from 11/88 to 2/89) had the higher compression pistons. The compression was raised by virtue of dished piston tops, similiar to the 9.5:1 pistons offered in the Nissan motorsports catalog.

[MyFirst240SX]

SO how would i know which one i have and which is better?

[geeaj]

Look at the manufacturer plate on the door jam. There is a build date which denotes the month and year in which your car was built.

If you are really clever, you can decipher your VIN and figure it out.

[LanceS13]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from geeaj on 3:44 pm on Jan. 28, 2002
The rumor is correct. Early 89' s13s (built from 11/88 to 2/89) had the higher compression pistons. The compression was raised by virtue of dished piston tops, similiar to the 9.5:1 pistons offered in the Nissan motorsports catalog.
</td></tr></table><span id='postcolor'>
Do you mean &quot;by virtue of domed piston tops&quot;? &nbsp;Dished pistons would lower compression.

[geeaj]

duh. My bad, I meant dished. I need Mavis Beacon!

[AJ]

u need it again... DOMED PISTONS! (right? or am i just confused)

[Cheater240SX]

All I know (by virtue of the Motor Vehicle Manufacturers Specs) is that my '91 KA24DE has 9.5:1 CR. &nbsp;I remember reading that earlier cars had lower CR due to lack of a knock sensor. &nbsp;So, to avoid detonation, Nissan had to lower the CR. &nbsp;Once a knock sensor was implemented, they were able to raise the CR.

[thewholefnshow]

You nead hemi cylinder heads! That is what they stuck in the trueno that is what powered dodge through the 60's and 70's (running 13:1 +) Those are high compression pistons.