Compression of EJ25D - What is it really?

[wtdash]

Came across a CL ad for '98 OB that has a LOT Of upgrades - HERE and attached.

 

I'm not here to Dis on the owner, but he states the stock CR of these engines is 8.1:1 not the claimed 9.7:1 (Edit*):

 

The stock 2.5 DOHC from 97-99 is billed to be 9.5:1. This is very misleading, I have measured it many times and it is a consistent 8.1:1 ratio this is why these cars are so sluggish off the line

 

Anyone confirm this is the case? Just based on my limited info, there's no way the stock engine makes 165HP/Torque if the CR is that low. And personally, I don't think they're that 'sluggish' compared to other cars of that era. But i'd agree the DOHC requires some RPM's to get to the power curve.

 

 

*I edited to be what the Owner's Manual states. The '96 EJ25D was the 9.5:1.

Thanks

1998 Subaru Outback, Expedition - CL.pdf

Edited November 27, 2017 by wtdash

[ocei77]

The FSM's for the 96-98 EJ25D lists it as 9.5.

 

 

O.

[Fairtax4me]

The pistons in the block in the pic are not 25D pistons. Might have low compression pistons installed and just doesn't know?

Not enough detail for me to tell if that's a 25D or 251 block, so can't say for sure what setup he actually has.

 

"Sluggish off the line" is a relative term. Anyone who can read a dyno chart can see that the 25D doesn't make peak power until the 5k rpm range. Torque is also a slow rise until higher RPMs, and that's all due to the cam setup. Twin cam engines are tuned to make better power at higher RPMs, the trade-off of that is less power available at low rpm.

[wtdash]

Ok...i'm going to take the CL poster @ his word that he's referring to the '97-'99* STOCK EJ25D engines he worked on as noted in the CL ad.

 

The pics in the ad are of the upgrades he's done - Not stock.

 

Regardless, I'm still  just curious if any of you engine gurus have come across this assertion he made about the STOCK EJ25D not being 9.7:1 CR.

 

 

*The '96 is listed as 9.5:1 in the Owner's Manual, the '97-'99 are 9.7:1, but the '99 is the Phase 2 block w/different pistons to work w/the Phase 1 Heads - I think.

[wtdash]

The FSM's for the 96-98 EJ25D lists it as 9.5.

 

 

O.

Yeah...I just looked that up, too.....but I don't believe that's correct as the '97-'98 were NOT the same as either the '96 nor the '99.

 

'96 had the HLA valve train and weird (Ok...different) combustion chambers, and the '99 EJ25D was a Phase 2 block w/different pistons than used in the EJ253 versions (from what I've read). The '99 does have the same 9.7:1 CR per the Owner's Manual.

Edited November 27, 2017 by wtdash

[GeneralDisorder]

No way are the 25D's in the 8's. They are around 9.5

 

GD