How exactly do you increase compression?

Post by **Zebrahead** » Wed Aug 07, 2002 7:18 am

Among getting the usual I/H/E, I was thinking about getting a new ECU and having my compression increased. How exactly do you increase the compression? What's involved? How much will it cost?

Nick

Post by **Daunttless** » Wed Aug 07, 2002 7:18 am

By changing your combustion chamber, the easiest way is to get domed or dished pistons, and/or change the size of the headgasket.

Do you have a KA24DE or KA24E?

Post by **biggie** » Wed Aug 07, 2002 7:18 am

Hey, Daunt have you looked into pistons that much. I was thinking about the performance ones from Nismo---or maybe the racing ones(they might be a bit too much). What would be the ideal compression with a rebuilt NA motor and all the bolt ons.

Post by **Daunttless** » Wed Aug 07, 2002 7:18 am

10.5:1-11.6:1 is about as high as you want to go on 92-93 octane gasoline. : )

Wed Aug 07, 2002 7:18 am

I've seen these offered somewhere, they are the pistons offered in the first batches of '89 240's. Do you think they'd be worthwhile?

Post by **Daunttless** » Wed Aug 07, 2002 7:18 am

The first batches offeredin the KA24E were 9.1:1

The later were 8.6:1

The KA24DE comes with 9.5:1 pistons.

If you put the E 9.1:1 into the DE, you get 11.6:1 compression.

If you put the E 8.6:1 into the DE, you get 11.1:1 compression.

Post by **Zebrahead** » Wed Aug 07, 2002 7:18 am

I've got a 93. That would be a DE. I'm looking for the best/cheapest way to increase compression. How much am I looking at for parts/labor?

If I do this, should I just get cams and get it done at the same time?

Nick

Post by **YochTown240** » Wed Aug 07, 2002 7:18 am

I was thinking of changing my piston in my 1990 SOHC to the 9.1:1 nissanmotorsports and i was wondering is there any boring or anything i need to do or just change the pistons and rings??? Also did the 1990 KA come with 8.6:1 pistons or do i even know what im saying??

Post by **Daunttless** » Wed Aug 07, 2002 7:18 am

To my knowledge the KA24E in the 240SX comes with 9.1:1, and the KA24E in the Nissan half tons came with the 8.6:1

Also, you can get them in either 89, stock, or 90, overbored. : )

Post by **YochTown240** » Wed Aug 07, 2002 7:18 am

So if i did buy the pistons from nissanmotorsports the 9.1:1 it would dropping the same exacty pistons in i already have giving me nothing??

Post by **TrunkMonkey** » Wed Aug 07, 2002 7:18 am

YochTown240 wrote:So if i did buy the pistons from nissanmotorsports the 9.1:1 it would dropping the same exacty pistons in i already have giving me nothing??

i believe all 90s have 8.6:1 compression. check your engine serial #. if it falls after 012039 your compression is 8.6:1.

Post by **Daunttless** » Wed Aug 07, 2002 7:18 am

Thanks for the update demcj, I know you've done a lot more research into this than I have. A few quick statements and questions for ya.

The 89 and 90 have the same rated power output, therefore I had thought that both had the 9.1:1 compression pistons, whereas the Nissan Half-ton with the KA24E has a lower rated power output, thereby pointing to the 8.6:1 pistons. If the 89 and 90 have the same rated power, but different compression ratios, what makes them balance out? : )

Post by **TrunkMonkey** » Wed Aug 07, 2002 7:18 am

Daunttless wrote:If the 89 and 90 have the same rated power, but different compression ratios, what makes them balance out? : )

they don't have the same ecu. i've seen a copy of the service bulletin on the web. when i find it i'll post it.

YouTube · Post by **EZcheese15** » Wed Aug 07, 2002 7:18 am

demcj wrote:
they don't have the same ecu. i've seen a copy of the service bulletin on the web. when i find it i'll post it.

Thanks, please post it. I was on the same page as Dauntless. I'd like to see the TSB.

Post by **Daunttless** » Wed Aug 07, 2002 7:18 am

thanks for the update demcj, I'll be waiting. : )

Post by **TrunkMonkey** » Wed Aug 07, 2002 7:18 am

http://wac.addr.com/auto/240sx/240sx.html

if you click on the service bulletin halfway down the page you can enlarge it.

note: the compression ratio stayed at 8.6:1 through 1990 for emissions purposes. if anyone has an FSM for a 90, it should say 8.6:1.

Post by **Zebrahead** » Wed Aug 07, 2002 7:18 am

Daunttless wrote:The first batches offeredin the KA24E were 9.1:1

The later were 8.6:1

The KA24DE comes with 9.5:1 pistons.

If you put the E 9.1:1 into the DE, you get 11.6:1 compression.

If you put the E 8.6:1 into the DE, you get 11.1:1 compression.

Wait wait wait. With risk of sounding dumb, according to this, teh DE has the highest compression pistons at 9.5:1. Could someone fill me in?

Thanks,Nick

Post by **TrunkMonkey** » Wed Aug 07, 2002 7:18 am

Zebrahead wrote:Wait wait wait. With risk of sounding dumb, according to this, teh DE has the highest compression pistons at 9.5:1. Could someone fill me in?

the DE's pistons have a deeper dish than the 8.6 E's. it still has a higher compression ratio because it's combustion chambers are smaller (different head design).

Post by **numatik** » Wed Aug 07, 2002 7:18 am

Does anyone know a place where one could aquire a set of 9.1 or 8.6:1 pistons for a reasonable price?

Post by **YochTown240** » Wed Aug 07, 2002 7:18 am

u didnt really just post your Sticker, cobra eye and tire flys did you?? man doin stuff like that around here will piss alot of people off. post real mods.....

Post by **numatik** » Wed Aug 07, 2002 7:18 am

It's a joke man.... wow

Post by **YochTown240** » Wed Aug 07, 2002 7:18 am

aight cool i was kinda thinking it might be but yea my bad either way......

Post by **ash1y1** » Wed Aug 07, 2002 7:18 am

How can I tell if what type of motor I have?I have a 1995 240sx SE

Post by **uno** » Wed Aug 07, 2002 7:18 am

you have the ka24de if it's the original motor... maybe you got lucky and somebody made it a silvia for ya hahaha j/k manit's the dohc ka24de

How exactly do you increase compression?

How exactly do you increase compression?

What about the 9.5:1 pistons from Nissan?

How do I know if I have a KA24DE or KA24E etc?

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