TIMING: Ea81 8 Degrees, Ea82 20 Degrees, Fact or Fiction . . .

[kerandt]

I just want to confirm what approx number a person should be shooting for with timing their Subaru. And now might be a good time to share any of those Timing "tricks" for those of use who have only done it a couple of times.

 

I have been lead to believe the motor was the main factor in timing (as the title suggests). But with some of the more recent threads I have been reading it is suggested that fuel delivery is what determines what it should be. For example; models with SPFI = 20 degrees and those with a carb (ea81 AND ea82) would be closer to 8 degrees.

 

Can we get some clarification on this? It actually kept me up part of the night thinking about this.

 

Many thanks in advance!

 

-Keith

[obk25xt]

You are correct sir....

 

20* for SPFI

8* for carb

[MilesFox]

carb 8deg btdc. including ea81 thru 89 and ea82 thru 87

 

mpfi with mechanical disty 185-86 25 deg btdc.

 

spfi (1986 and up) and mpfi 1987 and up 20 deg btdc.

 

if, say, you swapped an spfi onto an ea81, the timing is still 20 deg.

[kerandt]

Ok. Thank you! This means I have my '87 (ea82) a bit too far (approx 20). Surprisingly it seems to run fairly good (has a Weber carb though).

Awesome. Thanks again!

[Quidam]

 

I have been lead to believe the motor was the main factor in timing (as the title suggests). But with some of the more recent threads I have been reading it is suggested that fuel delivery is what determines what it should be. For example; models with SPFI = 20 degrees and those with a carb (ea81 AND ea82) would be closer to 8 degrees.

 

Can we get some clarification on this? It actually kept me up part of the night thinking about this.

 

Many thanks in advance!

 

-Keith

 

The motor and timing...Compression ratio, combustion chamber efficiency are primary factors in base and total timing.

 

The fuel delivery thing...carb less initial timing because you're working with a vac advance and mechanical, spring controlled advance.

 

SPFI, the computer controlls the timeing, you're setting a reference point.

 

I doubt that the SPFI is at 20* advanced while cranking.

 

Just some thoughts off the top of my head.

 

Doug

[Crazyeights]

Some real life experience with the EA81 I built - FWIW:) Ea81 with EA71 pistons, ported heads (shaved .020), Delta torque cam, SPFI conversion running about 35PSI fuel pressure. Timing makes a really big difference with this engine. It will run fine at 20 degrees but the sweet spot seems to be about 28 degrees. I had to mod the distributor mounting plate to do this. Can't push it any higher than that though.