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differences between EA82 and EA82T pistons etc?


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19 replies to this topic

#1 Tee Koo

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Posted 12 September 2005 - 05:39 PM

What are the differences between EA82 and EA82T pistons? How about rods?

#2 rallyrx

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Posted 12 September 2005 - 06:45 PM

i belive it's just compresion. I was going to put N/A pistons in my Turbo.
it changes somthing like from 7 to 9 but i'm no subaru god or anything so chances are i may be wrong

#3 Turbone

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Posted 12 September 2005 - 06:46 PM

The EA82T pistons are dished and produce a compression ratio of 7.7:1
The EA82 SPFI compression ratio is 9.5:1
The EA82 NA compression ratio is 9.0:1

#4 Snowman

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Posted 12 September 2005 - 07:10 PM

The rods, pins, crank, etc are all the same.

#5 Tee Koo

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Posted 13 September 2005 - 05:01 AM

Thank you for your help!

So is the piston the only thing that makes the difference between the compression, or is there also differences between the volume of the head's chamber?

And what kind of power would N/A engine's pistons handle? Are they as durable as turbo's pistons?

#6 Ross

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Posted 13 September 2005 - 06:32 AM

Thank you for your help!

So is the piston the only thing that makes the difference between the compression, or is there also differences between the volume of the head's chamber?

And what kind of power would N/A engine's pistons handle? Are they as durable as turbo's pistons?


Yes, it is only the pistons that change the compression ratio - the head makes no difference.

The N/A pistons should be just as strong as the turbo ones.

#7 Tee Koo

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Posted 13 September 2005 - 08:01 AM

Yes, it is only the pistons that change the compression ratio - the head makes no difference.

The N/A pistons should be just as strong as the turbo ones.

OK, thank you! :)

#8 oddcomp

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Posted 13 September 2005 - 09:30 AM

jumping on this thread anyone happen to know how much you would need machined off the piston dome to produce about ohh.. 8or8.5:1 compression?

#9 JWX

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Posted 13 September 2005 - 10:52 AM

just get new pistons

#10 oddcomp

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Posted 13 September 2005 - 02:13 PM

hmm know where i can get new pistons built to specs for cheap??

versus the potential to have stock spfi pistons milled down a smidge to achieve my goal for little money?

#11 JWX

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Posted 13 September 2005 - 02:38 PM

it just won't last very long is all I'd add to the turbo ones before I milled off teh SPFI ones

#12 Turbone

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Posted 13 September 2005 - 04:13 PM

The idea is to mill the turbo pistons to gain a little more comp, as compared to refitting with SPFI pistons. I think it might compramise the ring integrity if they were milled tho.
9.5:1 comp on SPFI pistons is alot for a turbo, altho theres a few running the setup. But its a interesting idea there Oddcomp.

#13 Ross

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Posted 13 September 2005 - 05:28 PM

If you want to lower the compression, you could try taking some material out of the head. There should be plenty before you hit the water jacket, you might want to try it on an old one first though.

#14 Turbone

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Posted 13 September 2005 - 05:36 PM

If you take material from the head surface, wouldnt this increase the comp ratio?

#15 Ross

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Posted 13 September 2005 - 06:32 PM

I'm not talking about planing material off the whole surface, just increasing the volume of the chamber where the valves and spark plugs sit. A die grinder does the trick - i've seen it done on a chevy 8 before.

#16 Snowman

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Posted 13 September 2005 - 07:16 PM

What about EA81 pistons? Those have a compression ratio of 8.7:1. I don't know if that is created by making the pistons a different height or if it's from head design. Anybody know?

#17 oddcomp

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Posted 14 September 2005 - 09:31 AM

i think some people are as confused as i am as to what i meant...

usally if you mill the whole head surface the comp goes up
if you increase the "bowl" in the head to a larger volume usually from porting and polishing ect then your cr goes down

if you take your turbo pistons wich are a dished type of setup and you mill down the ridge around the dish they become flat top pistons and since there is less "stuff" in the combustion chamber you lower the cr that way also

now going on the theory that the spfi/carb pistons retain the same wrist pin location and ring land locations they are just a taller piston resulting in higher cr so you have extra material
then you could safely mill those downa few thousandth of a inch or so and take
pistons built for 9. something to something and reduce it to 8. something to
something cr
so now we end up with a increase in compression for turbo motors but not a huge giant make things go boom type of increase going from 7. something to 9. somthing

also i suspect the things going boom due to hi cr in a turbo motor is mostly related to fueling issue's that the stock ecu just can't compensate for .. but thats for another thread :)

feel free for anyone to correct me if i was wrong on any of my points :)

#18 wrw166

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Posted 14 September 2005 - 09:50 AM

+++++++++++++++?
How about using thick head gsk?
+++++++++++++++

#19 Ross

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Posted 14 September 2005 - 03:31 PM

Not a great solution, any of the above methods would be much more reliable.

#20 kingbobdole

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Posted 14 September 2005 - 03:59 PM

I'm pretty sure that the CARBBED EA82 is 8.5:1 compression.....




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