Doing a big bore 2.3L compression ratio help.

Engine, Transmission and related drivetrain.
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gumby510
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Doing a big bore 2.3L compression ratio help.

Postby gumby510 » 31 May 2017 14:50

Hello everyone,

I tried the ozdat calculator and it stated my combo doesnt work ( jason gray 2.3L big bore)

I have a few questions.

1. Whats a "safe"cr for a 2.3L L series with efi running on 91oct. Id like to run around 10:1cr or a little more if possible. (In Wisconsin so I have a wide range of temp and humidity to deal with)..... Answered....

2. Math check: z22s crank, rods and block with 2mm overbore. A87 peanut head and ka24de pistons with 10.5cr would that equal a 11.1cr?

3. I have 3 options for a mls headgasket. 1mm 1.5mm and 2mm. Anyone have the formula or know how much the cr is effected by the different sizes..... Figured out.....

4. With the jason gray engine specs are the ka24 pistons used in the data the sohc or dohc. I know using a sohc piston in a dohc will give you 11.5cr

Ill be running the aem infinity for fuel control and my matchbox dizzy for ignition (for the time being) and getting that sorted before the new block goes in.

Originally I was going to supercharge this setup but after riding in Jordan's ecotech 510 with 164whp before he turbocharged it, I re-evaluated what I really wanted.
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Last edited by gumby510 on 03 Jun 2017 08:36, edited 1 time in total.
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funwithmonkeys
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Re: Doing a big bore 2.3L compression ratio help.

Postby funwithmonkeys » 31 May 2017 17:19

I have a 2.3L with 10.5:1 and can run 91 if it has some ethanol in it without detonation. My builder suggested I run 94 to be safe. She makes 178.778 WHP. The only time I have had detonation is on 94 when we were having problems with crappy fuel from the Chevron refinery up here.
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Byron510
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Re: Doing a big bore 2.3L compression ratio help.

Postby Byron510 » 01 Jun 2017 06:23

A stable ignition system goes a long way....
When I switched over to a stand alone EFI with a crank fire ignition, the stability of the crank fire was amazing, and really does help when you are pushing the CR envelope. It may be something to look into. Can your AEM system support the full ignition set up as well as the fuel management?

I run 10:5:1 without issue. I do generally run 94 as it's available locally, but I have had to run 91 on road trips as it may be all that's available.

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gumby510
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Re: Doing a big bore 2.3L compression ratio help.

Postby gumby510 » 01 Jun 2017 09:24

Alright 10.5cr it is. 93 is available but 91 is most common.

It is something i plan on doing just not right away. Yes the aem can support full ignition control 3d trim maps based on coolant and air temp, even down to the individual cylinder trim if you want it. http://www.aemelectronics.com/products/ ... inity-6-8h
71 PL510
01 s2000 aka skidmark
04 is300 manual
03 wrx winter car
Want to add a RA21 celica

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gumby510
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Re: Doing a big bore 2.3L compression ratio help.

Postby gumby510 » 01 Jun 2017 09:49

I also found this http://www.eatsleepboost.lt/tech-info/s ... alculator/

With changing some numbers the difference in cr from 1mm to a 2mm headgasket is about .7cr so i can fine tune things a little bit that way also.
71 PL510
01 s2000 aka skidmark
04 is300 manual
03 wrx winter car
Want to add a RA21 celica

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gumby510
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Location: Appleton wisconsin

Re: Doing a big bore 2.3L compression ratio help.

Postby gumby510 » 03 Jun 2017 07:36

Should I email rebello about the ka24 pistons on which ones produce what cr or maybe just have them build me a set?
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datzenmike
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Re: Doing a big bore 2.3L compression ratio help.

Postby datzenmike » 03 Jun 2017 15:28

I don't like the Ozdat 'computerÈ for just that reason. It argues with you. I do my own thing.


KA24DE piston dish is, I believe 9cc, so if it isn't, then this is all for nought.

Z22 crank/rods, 89mm bore, 47cc DE pistons, 41cc closed chamber head.... 9.52 compression

Why DE pistons???

The above with KA24E pistons..... 10.39


Who cares about higher compression? Run the 9.5 and save yourself any headaches. The difference between 9.5 and 10.3 on a stock 2.3 is maybe 6-7 HP at top RPMs. Much less lower down where you drive it.


Get a ported out U-67 head. Larger valves and ports.They are all open chamber. Use KA24E pistons. .... 9.81 compression. You are not going to have any quench area with dished pistons anyway so no advantage to it with DE pistons in this application.
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gumby510
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Re: Doing a big bore 2.3L compression ratio help.

Postby gumby510 » 04 Jun 2017 08:05

datzenmike wrote:I don't like the Ozdat 'computerÈ for just that reason. It argues with you. I do my own thing.


KA24DE piston dish is, I believe 9cc, so if it isn't, then this is all for nought.

Z22 crank/rods, 89mm bore, 47cc DE pistons, 41cc closed chamber head.... 9.52 compression

Why DE pistons???

The above with KA24E pistons..... 10.39


Who cares about higher compression? Run the 9.5 and save yourself any headaches. The difference between 9.5 and 10.3 on a stock 2.3 is maybe 6-7 HP at top RPMs. Much less lower down where you drive it.


Get a ported out U-67 head. Larger valves and ports.They are all open chamber. Use KA24E pistons. .... 9.81 compression. You are not going to have any quench area with dished pistons anyway so no advantage to it with DE pistons in this application.


Thanks for the response,
I already have a ported and polished with larger valves in my A87 peanut head upgraded valve springs and an agressive streetish cam.

With the ka24e piston I was looking at some that arias make and there specs are
Bore: 89mm
Comp. Height: 1.340
Dome CC: -11.5
Compression Ratio with Stock Head: 8.7:1 (ka24e)
Weight: 360g

If I were to use those my cr would be right around 10:1 correct?

I still may contact rebello and see what the cost would be for some flat top pistons in the cr im looking for to properly utilize the peanut chambered head.
71 PL510
01 s2000 aka skidmark
04 is300 manual
03 wrx winter car
Want to add a RA21 celica


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