methods of raising compression ratio
03-11-2005, 04:36 PM
#16
Registered User
Join Date: Nov 2004
Posts: 3
I get all of my information direct from nissan, or from my personal experience and race contribution. I am a distributor of nissan parts and have access to all factory information. I am also a L/Z/KA enthusiast like mentioned above, I work mainly with these engines or race specific applications allowing variants of them.
There is only progress in using correct information.
As far as compression ratio is concerned, only things of interest (besides known specifics of this engine, bore/stroke etc) Is the combustion chamber volume, piston compression distance, and dome or dish volume of the piston. Difference in cylinder heads otherwise is of no concern.
The 91-98 240sx, 98-04 Frontier/xterra, and 93-02? Altima KA24DE share the same combustion chamber volume assembled with oem valves/oem valve height. This is not what your really arguing, I was just pointing it out.
From 1998 on (excluding 1998 240sx) Nissan produced only one piston for both the Altima and Frontier/Xterra. This piston has the difference in ring assortment i mentioned above, as well as a very minute increase in the piston dish volume (I forgot about this in earlier post but difference is miniscule). This lowers the compression slightly from 9.5:1 (98 and earlier 240sx, altima) to 9.2:1, not nearly a full point increase to 10.3? if thats what you said.
The rings are not interchangable between pre 98 pistons and 98+ pistons. .25mm difference in thickness for both compression rings and .3mm thickness difference in total oil ring. Also the oil ring depth is different, 3 different depths changes starting in the 95-97 altima (although these used earlier type compression rings).
I am well aware of all KA24DE differences in casting and components. There are actually 7 different KA24DE cylinder head castings including those cast in japan, mexico, and USA. Some are only minor differences.
As far as pistons, with sohc and dohc combined, there is 8 different oem offered pistons. This does not necessarily mean that dish and rings are completely different between each, Ive already explained some of that, I can go into further detail if necessary.
If you would like to "debate" ever further as you say, about L/Z/KA specifics and hybrids, be sure you know what your getting into
I pioneered it bro. Actually, id imagine youd like what I have to say. I could fill up many pages on "newschool" nissan/datsun hybrid racing engines, but due to basically non-existent copywrite on internet forum, I will not.
On that note, I do not argue what you mentioned about L/naps-z/KA. There is much more to that topic, thats just a tidbit. One little "oldschool" bit you forgot, l20b head or block used with a napz or ka must have the block plugged in one spot (or head modified whatever youd like) depending on configuration. An oil passage can cross to water. I just mention that because it fits in with what you said just there. Most 720 or other datsun tuners skip this step when doing L/Z single cams for instance but problem has been surfaced in race community. This does not apply to napz and ka deck layout.
But like I said, not here specifically to argue. Its all about the facts.
Gabe Z.
There is only progress in using correct information.
As far as compression ratio is concerned, only things of interest (besides known specifics of this engine, bore/stroke etc) Is the combustion chamber volume, piston compression distance, and dome or dish volume of the piston. Difference in cylinder heads otherwise is of no concern.
The 91-98 240sx, 98-04 Frontier/xterra, and 93-02? Altima KA24DE share the same combustion chamber volume assembled with oem valves/oem valve height. This is not what your really arguing, I was just pointing it out.
From 1998 on (excluding 1998 240sx) Nissan produced only one piston for both the Altima and Frontier/Xterra. This piston has the difference in ring assortment i mentioned above, as well as a very minute increase in the piston dish volume (I forgot about this in earlier post but difference is miniscule). This lowers the compression slightly from 9.5:1 (98 and earlier 240sx, altima) to 9.2:1, not nearly a full point increase to 10.3? if thats what you said.
The rings are not interchangable between pre 98 pistons and 98+ pistons. .25mm difference in thickness for both compression rings and .3mm thickness difference in total oil ring. Also the oil ring depth is different, 3 different depths changes starting in the 95-97 altima (although these used earlier type compression rings).
I am well aware of all KA24DE differences in casting and components. There are actually 7 different KA24DE cylinder head castings including those cast in japan, mexico, and USA. Some are only minor differences.
As far as pistons, with sohc and dohc combined, there is 8 different oem offered pistons. This does not necessarily mean that dish and rings are completely different between each, Ive already explained some of that, I can go into further detail if necessary.
If you would like to "debate" ever further as you say, about L/Z/KA specifics and hybrids, be sure you know what your getting into
I pioneered it bro. Actually, id imagine youd like what I have to say. I could fill up many pages on "newschool" nissan/datsun hybrid racing engines, but due to basically non-existent copywrite on internet forum, I will not. On that note, I do not argue what you mentioned about L/naps-z/KA. There is much more to that topic, thats just a tidbit. One little "oldschool" bit you forgot, l20b head or block used with a napz or ka must have the block plugged in one spot (or head modified whatever youd like) depending on configuration. An oil passage can cross to water. I just mention that because it fits in with what you said just there. Most 720 or other datsun tuners skip this step when doing L/Z single cams for instance but problem has been surfaced in race community. This does not apply to napz and ka deck layout.
But like I said, not here specifically to argue. Its all about the facts.
Gabe Z.
03-13-2005, 11:35 AM
#17
Well I don't want to be counter productive so out of the assortment of heads and pistons for the KA, what would you recomend as a combo Devious KA?
I'm looking for a compression of 10.1 or 10.5 nothing lower, and nothing higher.........
Do you have an email that I can reach you at so I can order these parts, I am in the process of building a 240+CHP KA.. I have a 1991 KA24de.......
That would be great THANX
Vinnie
I enjoy what you have to say, but I also like to play devils advocate in the FORUMS I like to test people and see if they REALLY know what they are talking about.....
I'm looking for a compression of 10.1 or 10.5 nothing lower, and nothing higher.........
Do you have an email that I can reach you at so I can order these parts, I am in the process of building a 240+CHP KA.. I have a 1991 KA24de.......
That would be great THANX
Vinnie
I enjoy what you have to say, but I also like to play devils advocate in the FORUMS I like to test people and see if they REALLY know what they are talking about.....
Last edited by BigVinnie; 03-13-2005 at 11:58 AM.
03-13-2005, 08:04 PM
#18
Registered User
Join Date: Nov 2004
Posts: 3
Combo recommendations are goin to be a bit slim, honestly, a lot of information I must keep hush hush in regard to full race engine building.
So you are looking for 10-10.5:1 compression ratio using 2.4l ka rotating assembly and 240sx de head?
Are you planning to invest in a custom forged piston?, If not, ka24e pistons which yeild 11.1:1 compression ratio are best bang for the buck option. This is a good compression ratio for your 240chp. If your planning to hit your hp wheel mark, you will want a very high compression ratio. Id suggest something more along the lines of custom forged 12-13:1 CR with redesigned and matched combustion chambers.
Personally I like to run a shorter light weight flat top piston with smaller volume combustion chamber on smaller displacement ka's (unlimited), but dome top pistons work well (mainly used in race form when rules prohibit modified chambers or major rotating assembly weight drop).
For 10.5:1 in KA24DE, you will need 5cc of dish volume in a piston with stock (34mm) compression distance. You can also run pure flat tops and drop them down in the deck .020" or so for same ratio, but concidering this combustion chamber has "quench" area, reducing proximity at TDC can lead to un-effectiveness and even induced detonation. Best to keep the pistons within .030" (at piston edge, if dished) from the quench area for best result.
I attached a compression ratio chart for ka24de. All verified using proper method/tools/calculations and factory components.
I have a very poorly made website at the moment, made by myself. A new version that is complete with my full inventory and custom components will be up soon.
http://www.hybridka.com
email.
gabe AT hybridka.com
So you are looking for 10-10.5:1 compression ratio using 2.4l ka rotating assembly and 240sx de head?
Are you planning to invest in a custom forged piston?, If not, ka24e pistons which yeild 11.1:1 compression ratio are best bang for the buck option. This is a good compression ratio for your 240chp. If your planning to hit your hp wheel mark, you will want a very high compression ratio. Id suggest something more along the lines of custom forged 12-13:1 CR with redesigned and matched combustion chambers.
Personally I like to run a shorter light weight flat top piston with smaller volume combustion chamber on smaller displacement ka's (unlimited), but dome top pistons work well (mainly used in race form when rules prohibit modified chambers or major rotating assembly weight drop).
For 10.5:1 in KA24DE, you will need 5cc of dish volume in a piston with stock (34mm) compression distance. You can also run pure flat tops and drop them down in the deck .020" or so for same ratio, but concidering this combustion chamber has "quench" area, reducing proximity at TDC can lead to un-effectiveness and even induced detonation. Best to keep the pistons within .030" (at piston edge, if dished) from the quench area for best result.
I attached a compression ratio chart for ka24de. All verified using proper method/tools/calculations and factory components.
I have a very poorly made website at the moment, made by myself. A new version that is complete with my full inventory and custom components will be up soon.
http://www.hybridka.com
email.
gabe AT hybridka.com
03-13-2005, 09:05 PM
#19
I'll probably go with the 11.1:1 ratio then. I live in cali and need to stay within 91 octane. Any higher is cause for knock and ping, and detonation.....
Seems pretty safe I have a buddy with the s2000 that runs 11.1:3 compression on 91 octane.......
Need to keep the car street legal.......
Looks like I'm going to be using Iridium spark plugs also........
Seems pretty safe I have a buddy with the s2000 that runs 11.1:3 compression on 91 octane.......
Need to keep the car street legal.......
Looks like I'm going to be using Iridium spark plugs also........
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