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Guest Message by DevFuse

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EA81, EA81T questions

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5 replies to this topic

#1 Scoobywagon


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Posted 02 October 2004 - 01:39 AM

Ok...so I recently scored an 83 Turbo Wagon. Anyone care to guess how much I paid? (hint: not a fickin' thing! :headbang: ) All I have to do is go pick it up. It was running before it got parked, has a 3AT with pushbutton 4x4. The "fluid" in the front diff looks like something I might keep either to add to my hall of shame or to maybe patch my roof. :) Guy says it ran great and made good boost but had no guts when he parked it. I suspect that it was all that poor engine could do just to turn that tranny! So...I'm trying to hook up with a buddy of mine to get that thing towed to my house so I can start tearing it down. The body is pretty beat up and it is missing the glass in the windshield and tailgate. Oh yeah...his 10-year-old cousin rolled it over playing rally driver in the back yard (100+ acres).

So...my question is this...I know you EA82 guys like to put the Turbo top-end stuff on SPFI longblocks, but that you don't necessarily like to put it on a carbed block because the compression ratio is a bit high for the standard EFI system to deal with. Does this hold true with the EA81? Would I be able to run it if I put the EA81T goodies on my 83's bottom end, or would I be better off to just do a complete engine swap? If THAT's the case, then I'm thinking I'll wait until I get my hatchback....got some evil plans for a hatch! :grin:

#2 JWX


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Posted 02 October 2004 - 03:07 AM

dude you've got the SPFI/turbo/carb'ed think backwards. its Turbo on carb'ed block, where as some think the SPFI comp is too high.

#3 CIS Subaru

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Posted 02 October 2004 - 07:30 AM

dude you've got the SPFI/turbo/carb'ed think backwards. its Turbo on carb'ed block, where as some think the SPFI comp is too high.

I agree. CRs go as follows:
EA71- 9.0:1
EA81- 8.7:1
EA81T- 7.7:1
EA82 MPFI or carb- 9.0:1
EA82 SPFI- 9.5:1
EA82T- 7.7:1

As I understand it, raising the CR of a turbo engine helps the low RPM power, but hurts (or at least doesn't help) the high RPM power because the ignition has to back off the timing to avoid knock when the boost comes on. On the other hand, reducing CR allows you to crank up more boost and get more peak hp while sacrificing some low end power. Which way you want to go depends on how you plan to drive the car. This is just general info I've picked up, not soob specific.

#4 archemitis


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Posted 02 October 2004 - 10:16 AM

but alot of the time if you run a higher compression block, you plan on runing low amounts(stock) boost, and good fuel all the time, and enjoy a little bit of both worlds. 8.7 isnt bad for a turbo with stock boost, but if you want to boost it hard, get low comp. in my opinion/experience



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Posted 02 October 2004 - 11:04 AM

so along the same question, can you put EA82T stuff on a EA81 long block? and what would be the wiring madness?

#6 MilesFox


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Posted 02 October 2004 - 12:06 PM

the NA block wont have the 'case breather for the pcv system, but you can bypass that. the na case should have the boss for the crank angle sensor though, but it may not be tapped

as far as ea82's go the only difference between a turbo and na case is the one half that has the crank case breather

one thing to note as far as compression goes, the idea of a lower compression cylinder will allow for more air/fuel mixture VOLUME to be squeezed in under boost

as far as what i can tell you from experience, with the rx carb bottom end, we have had NO problem with 87 gas and stock timing. here in indiana with an average elevation of 900 ft above sea level

i recommend porting of the intake and exhaust ports with a dremel and the snake atatchment. use the "roto-ziip" style bit to take the metal away, the cone and drum STONES to even it all up, and finish with a sanding drum. remove thevalves when you do this.

one more thin that i would recommed, for the sake that our motor has this, is to take the dremel and blend in the valve reliefs on the N/A pistons to reduce hot spots and slightly lower compression. sane for theheads, we took the sharp edges off the circumfrence of the combustion chamber with the sanding drum

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