greasyfj Posted December 31, 2015 Report Share Posted December 31, 2015 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 1 Quote Link to comment
scooter Posted December 31, 2015 Report Share Posted December 31, 2015 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 1 Quote Link to comment
greasyfj Posted December 31, 2015 Author Report Share Posted December 31, 2015 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? Quote Link to comment
datzenmike Posted December 31, 2015 Report Share Posted December 31, 2015 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 Quote Link to comment
Stoffregen Motorsports Posted December 31, 2015 Report Share Posted December 31, 2015 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. 1 Quote Link to comment
greasyfj Posted December 31, 2015 Author Report Share Posted December 31, 2015 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. Quote Link to comment
greasyfj Posted December 31, 2015 Author Report Share Posted December 31, 2015 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. Quote Link to comment
greasyfj Posted December 31, 2015 Author Report Share Posted December 31, 2015 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, Quote Link to comment
datzenmike Posted December 31, 2015 Report Share Posted December 31, 2015 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 1 Quote Link to comment
Laecaon Posted December 31, 2015 Report Share Posted December 31, 2015 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. 1 Quote Link to comment
Doctor510 Posted December 31, 2015 Report Share Posted December 31, 2015 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! Quote Link to comment
datzenmike Posted January 1, 2016 Report Share Posted January 1, 2016 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* Quote Link to comment
Laecaon Posted January 1, 2016 Report Share Posted January 1, 2016 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 Quote Link to comment
datzenmike Posted January 1, 2016 Report Share Posted January 1, 2016 But it says under compression....8.7 A confusing way to sell pistons. Nothing marked... is it mm? or inches? Quote Link to comment
scooter Posted January 1, 2016 Report Share Posted January 1, 2016 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. Quote Link to comment
datzenmike Posted January 1, 2016 Report Share Posted January 1, 2016 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 Quote Link to comment
greasyfj Posted January 2, 2016 Author Report Share Posted January 2, 2016 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 Quote Link to comment
scooter Posted January 2, 2016 Report Share Posted January 2, 2016 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. Quote Link to comment
datzenmike Posted January 2, 2016 Report Share Posted January 2, 2016 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. Quote Link to comment
greasyfj Posted January 3, 2016 Author Report Share Posted January 3, 2016 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: Quote Link to comment
datzenmike Posted January 3, 2016 Report Share Posted January 3, 2016 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. 1 Quote Link to comment
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