Play Guess Matt's Compression!!!

[Rennen]

[Game Show Host Voice]

Its time for everyone's favorite game: Guess Matt's Compression!!

*applause*

This week's engine is Nissan's KA24E.

*ooohs and ahhhs from the audience*

The KA was used in the 240SX because Nissan was too lazy to make the SR20DET pass California smog regulations. Its a 4 cylinder engine making around 140hp stock and 150 ftlbs. This particular model has 138,000 miles and burns oil like crazy.

Here it is on a 3k rpm launch at the last autocross: http://www.imagestation.com/picture/sraid146/p5c63e49a6c003cb12016712daa91a543/f63d7484.jpg

and again floored on a 2nd gear straightaway: http://www.imagestation.com/picture/sraid146/pcfea6bbe5e32ede46b84e497173253c3/f63d73ee.jpg

Now stock compression on this engine ranges from the standard 192 psi to a minimum of 142 psi per the Factory Service Manual with an allowable 14 psi variance between cylinders.

I have the answers here in a sealed envelope, courtesy of a friend's compression tester.

Who will start the guessing? the winner gets an all expenses paid trip to the bahamas.... or a cookie.

[/Game Show Host Voice]

[gsracer]

124.7


The message you have entered is too short. Please lengthen your message to at least 10 characters.

[SlowCoupe]

i'll give it a 110

[ghostuss]

97.9 Ok Hmm that's a lot SMOKE!!

[mrmephistopheles]

150 145 80 120

[RSP13-Sideways]

I'm going to have to say,

95, 110, 93, 108 - Blue smoke is bad mmmmmkay....

[orion::S14]

141, 143, 139, 129

[/mind reader]

[S14DB]

142,140,2,138

[ledzeppelin240]

Blue smoke doesn' mean much about compression...I'll go with about 140PSI.

The KA24E was used in the 240sx so it didn't take the 300zx out of the running. If we had SR that would mean Nissan would have 2 sports cars with very similar performance, but one of them much cheaper.....

[S14DB]

The KA24E was used in the 240sx so it didn't take the 300zx out of the running. If we had SR that would mean Nissan would have 2 sports cars with very similar performance, but one of them much cheaper.....
Ah, yes american logic. "The SR20 makes more power than the 2+2? can't happen" The Fairlady and the Silvia are on two different levels in Japan. Sort of like the Camero and the Corvette.

[Flybert]

Shouldn't it say,

"The KA was used in the 240SX because Nissan was too lazy to make the CA18DET ..."

We are of course talking about a pignose.

And my guess is 60 140 142 148

[Rennen]

um yeah, ignore the SR bit, that was copy and pasted from one of my posts on a non-240 forum, to make it sound a little more game-showy. It wasnt the intent to start a flame war. Oh, and you guys arent anywhere close ;)

-Matt

[theicecreamdan]

a million.

[sykikchimp]

Is it closest that doesn't go over?? If so:

1 1 1 1

(my "The Price is Right" answer)

[Ghettokracker71]

You guys aren't answering in the proper form!!!

*buzzer* Is your compression under 90psi ?

[TheSnail]

what is... 87, 110, 62, 93

[Rennen]

Blue smoke doesn' mean much about compression...


*ding ding ding*


We have a winner!!!


I would have guessed 140s with one cylinder real bad, but...

Strangely enough, When I tested it, I got 170psi across the board :confused: This is within the OK range, and quite good considering how hard I flog this motor, and its sketchy past.


This brings up the reason this is in tech talk. Where is all the smoke coming from? I assume it is coming from the valve seals, which has been my thought all along. I added some Lucas Oil additive stuff on the advice of some of my friends that work at automotive shops, and it seems to smoke slightly less, and the compression remained the same. It still smokes at startup, high rpms, and stop sign burnouts http://www.nevac.nl/flensjes/images/smilies/burnout.gif

Any thoughts?

[Andrew Bohan]

how about suicide. that always worked for me

[RSP13-Sideways]

hrmmmmm maybe your piston rings are shot.....time to stop doing those burnouts I think.......you've successfully destroyed your motor.

[ledzeppelin240]

Not all piston rings are not shot. It would be the oil ring. Could be clogged, or just worn down. $20.00 says there is something wrong with the oil ring...

The valve seals should not burn too much oil unless there is oil pooled up there. They mostly burn oil on startup because of the sitting time and leak down.

[Rennen]

time to stop doing those burnouts I think.......you've successfully destroyed your motor.

NEVER! ;)

Actually, I was pleased with these results, I thought it would be worse. Since the FSM lists 142 as the minimum, 170 seems OK to me. This motor will be replaced by another KA24E in the next few months anyway, I was just checking compression to see how soon.



I am still thinking the oil is coming from the valve seals, because the compression isn't superbad. Also, it mostly smokes after it has been idling for a while. (ex. it smokes really bad on autoX launch because I have been sitting in grid for a while, and if I sit at a stoplight for a while on a warm engine, it will smoke when I take off) This leads me to believe that oil is "pooling" up somewhere and then getting burned once the air starts flowing.

[IvanAtSPRacing]

Smoke on start up is usually caused by valve seals. Smoke on WOT accel is usually from rings. I would say you have a combo of problems. You compression numbers are probably elevated by the fact that you have oil in the combustion chamber creating a better seal on the top ring.

My guess is your valve seals are hard as a rock and the oil scrapers on your oil control pack are not doing their job.