2.3 big bore Compression ratio using forged pistons

[greasyfj]

I'm building a 2.3 big bore motor and recently i came across a deal for a set of arias forged pistons that was to good to pass up.  Stock ka24e pistons are 8.6:1 compression ratio but aftermarket Arias # 3520300  forged pistons are 8.7:1.

 

Using Jason Gray info and http://www.ozdat.com/ozdatonline/enginedesign/Calculator, i get a compression ratio of 9.9:1 using stock Ka24e pistons -2.8cc dish(ie 8.6:1) and a 1mm head gasket.

 

Question: will using The arias pistons(ie 8.7:1) increase the compression ratio to 10.3:1??  would I be able to run 91 nevada octane safely?

 

Head -U60

Block L20B +4

Camshaft Web Cam 155 (252/.488) http://www.webcamshafts.com/pages/automobile/datsun/install_data/tc_001858_002399.html

Crankshaft Z22

Rods L20b

Pistons http://arias-pistons.myshopify.com/products/nissan-ka24e-2-4l-sohc-12-valve

[scooter]

When I did mine, I got 12.3:1

 

Don't forget to factor in the head being shaved and piston protrusion.

 

Mine are flat tops with valve reliefs, sticking 15 thou out of the deck, and a open chamber head. My cam is 306 duration 530 lift. It runs on 94, but pings. Runs good on avgas though.

 

Canada needs E85 badly

[greasyfj]

When I did mine, I got 12.3:1 Don't forget to factor in the head being shaved and piston protrusion. Mine are flat tops with valve reliefs, sticking 15 thou out of the deck, and a open chamber head. My cam is 306 duration 530 lift. It runs on 94, but pings. Runs good on avgas though. Canada needs E85 badly

wow that's high :thumbup: , is yours a l series 2.3 big bore, and is it still carbureted or FI?

[datzenmike]

1/ First a 2.3 using stock KA24E pistons (2.8cc dish), open chamber 45.2cc head, crushed gasket thickness of 1.2mm (per Jason Gray) has a compression of 9.7878
 
 
Hard to understand these numbers. http://http://arias-pistons...l-sohc-12-valve
 
Dish is 3.5 cc's? I guess???
Compression height?? c/l of pin to top of piston??? 1.34 WTF is this in inches??? This is 34mm

 

2/ Same as 1/ above except the forged pistons, the compression is 9.6943.

 

Take note that the only difference between the stock KA24E piston and the forged Piston is that the Forged piston dish (3.5cc?) is larger by 0.7cc. This makes the combustion chamber 'larger' by this amount and drops the compression slightly. Almost nothing... less than 0.1.

 

 

With your 1mm gasket, stock piston............ 10.2766

With your 1mm gasket, forged piston.......... 10.17....... again about 0.1 difference

[Stoffregen Motorsports]

10:1 is perfectly fine on pump gas. Any more than that and it really depends on the cam.

 

Generally speaking, the larger the cam, the more compression you can run. I ran a 2200 at 12:1 on pump gas, but it had a monster cam. It was barely streetable.

[greasyfj]

1/ First a 2.3 using stock KA24E pistons (2.8cc dish), open chamber 45.2cc head, crushed gasket thickness of 1.2mm (per Jason Gray) has a compression of 9.7878

 

 

Hard to understand these numbers. http://http://arias-pistons...l-sohc-12-valve

 

Dish is 3.5 cc's? I guess???

Compression height?? c/l of pin to top of piston??? 1.34 WTF is this in inches??? This is 34mm

 

2/ Same as 1/ above except the forged pistons, the compression is 9.6943.

 

Take note that the only difference between the stock KA24E piston and the forged Piston is that the Forged piston dish (3.5cc?) is larger by 0.7cc. This makes the combustion chamber 'larger' by this amount and drops the compression slightly. Almost nothing... less than 0.1.

 

 

With your 1mm gasket, stock piston............ 10.2766

With your 1mm gasket, forged piston.......... 10.17....... again about 0.1 difference

Datzen those Arias figures are way confusing to me also, but i understood it as 11.5cc dish for the set.  If I divide 11.5 by 4 pistons(total noob guess here), then i get 2.875 which is same as stock.  Do you think this is the case? if so to play devils advocate what would compression be with 8.7:1 pistons, 2.875cc dish and 1mm gasket and 1.2mm gasket?

 

https://drive.google.com/file/d/0BwGUz3GGZ1bAUHVrY1FNemM4YW8/view?usp=sharing

 

thank you for help, i dont think this specific question has been asked before.

 

I know the figure wont be exact because of milled head and milled block, although in my case they are both virgin items and this will be their first time to the machine shop.

[greasyfj]

10:1 is perfectly fine on pump gas. Any more than that and it really depends on the cam.

 

Generally speaking, the larger the cam, the more compression you can run. I ran a 2200 at 12:1 on pump gas, but it had a monster cam. It was barely streetable.

thanks, yea that what i figure, the cam i bought has lots of overlap, so i feel safer the more i think about it.

[greasyfj]

Im not allowed yet to post pics, maybe someone can re-post my link and embed it so everyone can see.

 

https://drive.google.com/file/d/0BwGUz3GGZ1bASFVxb3hub0Y4T1U/view?usp=sharing

 

 

the picture is the job card for the Arias pistons

 

the job card says 8.6:1 compression ratio, so that might answer the question

 

 

 

***Thread jacking question***  in the picture the piston on the left is the KA24e ARIAS forged piston (3520300) and on the right is a Nippon NPR KA24e hypereutectic piston(10-600). Notice the dish on each one; it seems like the Arias has more dish which is why i am still confused as to what it may be.  The NPR piston actually says 2.88 on the box but the dish is a teeny tiny bit.  Doesnt "seem" dished at all.  

 

Is it the case, that at the end of the day they are both 8.6:1 compression ratio while the design of the more expensive forged pistons are designed to work safer under boost than the cheaper NPR "dish"?   That's my guess, what gives, can someone explain this to me,

[datzenmike]

Datzen those Arias figures are way confusing to me also, but i understood it as 11.5cc dish for the set.  If I divide 11.5 by 4 pistons(total noob guess here), then i get 2.875 which is same as stock.  Do you think this is the case? if so to play devils advocate what would compression be with 8.7:1 pistons, 2.875cc dish and 1mm gasket and 1.2mm gasket?

 

https://drive.google.com/file/d/0BwGUz3GGZ1bAUHVrY1FNemM4YW8/view?usp=sharing

 

thank you for help, i dont think this specific question has been asked before.

 

I know the figure wont be exact because of milled head and milled block, although in my case they are both virgin items and this will be their first time to the machine shop.

 

 

11.5cc for the set is an insane way to list the dish volume... but they have cc's and inches mixed also.

 

 

Lets assume the Arias set is 2.8cc volume dish. This makes them basically identical to the stock pistons. Thus the compression is...

9.8787 with a 1.2mm gasket and...

9.9535 with a 1mm gasket

[Laecaon]

Read more on the spec page. On a ka its with a .045mm head gasket. This is to drop compression on a ka for a turbo. The numbers then make sense. So yes -11.5cc per piston.

[Doctor510]

Read more on the spec page. On a ka its with a .045mm head gasket. This is to drop compression on a ka for a turbo. The numbers then make sense. So yes -11.5cc per piston.

Might want to check your math bud    .045mm  =  .00177"  that is human head hair territory!

[datzenmike]

 0.045" is only 1.145mm not enough difference from 1mm to bother calculating.

 

 

 

The link provided...http://http://arias-pistons...l-sohc-12-valve    does not say turbo pistons but turbo rings. This is a forged piston which will expand with heat more than the stock pistons. Says right there the compression is 8.7

 

 

If 11.5cc* dish and used on a KA24E the compression would drop to 8.14 (this assumes the head volume is 62cc my info shows 65cc so it would then be 7.9

 

A 2.3 using these Arias KA24E pistons, open chamber 45.2cc head, crushed gasket thickness of 1mm and substituting an 11.5cc* dish would have a compression of 8.8

 

This is unknown*

[Laecaon]

Might want to check your math bud    .045mm  =  .00177"  that is human head hair territory!

 

Oh I know, I am a machinist... but uh, if you crunch the numbers they provide (unit less .045 gasket...) and assume incorrectly the .045 is mm then you get 8.7-8.8:1 CR on a KA E (depends on rounding).

 

Realistically though, these pistons are for turbo applications, and as such would drop the CR on a stock KA E to 8.1:1.  Kinda like how CP pistons drop the E to 8.0:1 and the DE to 9.0:1

[datzenmike]

But it says under compression....8.7

 

A confusing way to sell pistons. Nothing marked... is it mm? or inches?

[scooter]

If I were to do mine again I wouldof welded my head to a closed chamber and got cp to build a dish piston for maximum quench area at 10:1 compression.

[datzenmike]

You don't want dish if looking for quench. The KA pistons are almost flat at 2.8cc. Trouble with a 2.3 build is the pistons stop 1.55mm below the deck so this equates to 9.63 cc of added volume below the head + the 2.8 cc of the piston. But not all a bad thing, without it the compression would be off the charts high with an open chamber L head. IF the KA piston was flush with the deck the compression on an open chamber head would be 11.31 on a closed chamber head... 12.15

[greasyfj]

so since i'm no planning to turbo the build im going to use the Nippon pistons and sell the forged, thanks for the knowledge

[scooter]

What? Use the forged ones if your turboing it. Cc your pistons properly and your head and open the head up if you need to.

 

 

[datzenmike]

The stock pistons are good for up to 8 PSI of boost if careful. They are hyper-eutectic and almost 1/5 silicon (glass) so they do not swell from heat, making them very quiet in operation and ready to go at the turn of the key, very strong but brittle. Most stock turbos do this. Trouble goes up exponentially as you get excited and add more and then more boost. It's addictive and the pistons won't take this abuse for long.

 

If building a really hot street engine... high compression, big cam, ported head, header... blah blah blah, then forged pistons are still a good option as they can take huge abuse. The down side is noisy start up until the pistons swell from the heat or letting them warm at least. Not the best for a daily driven slightly 'warmed over' stock engine.

 

It all depends on the end use. 

[greasyfj]

i have a Web Cam 155 (252/.488) http://www.webcamsha...858_002399.html, going to do head work. i have all ready accumulated all  the bells and whistles,  im planning a hot street engine L2.3, so using the hyper-eutectic pistons will give me 9.9 compression.

 

not planning to turbo and the forged pistons would only give me 8.8 or so,  i will be cc'ing the head and block after the machine work and assembly is done, but seems like the best bet for me in my build would be to stick with the stock 2.8 cc stock ka pistons. 

 

sucks that i bought those expensive arias but im willing to pass them along to somebody who is going to take advantage of what they were intended for and build a turbo ka beast :thumbup: 

[datzenmike]

It's still not clear what the compression would be on these... http://arias-pistons.myshopify.com/products/nissan-ka24e-2-4l-sohc-12-valve  Very confusing data. Even says 8.7 compression with stock head. I mean what in the fuck??? some measurements in inches some in cc some in mm.