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Old 04-22-2010, 10:30 AM   #1
CastIron
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Default 97 LGT - Replacement Engine Compatibility

The engine in my '97 LGT just imploded, so I'm looking for a replacement. Is it safe to assume that all four-cam non-turbo EJ25s will wire up without a problem? Is there anything else that will work without too much headache? Any of the SOHC motors perhaps? I'm just looking for something cheap and easy.
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Old 04-22-2010, 05:47 PM   #2
Patrick Olsen
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You're basically stuck with the EJ25D (DOHC non-turbo), as the SOHC engines used a different ECU and the harnesses aren't interchangeable.
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Old 04-23-2010, 12:37 AM   #3
Jonathan
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Originally Posted by Patrick Olsen View Post
You're basically stuck with the EJ25D (DOHC non-turbo), as the SOHC engines used a different ECU and the harnesses aren't interchangeable.
You can however put the DOHC heads on to a later model "Phase II" SOHC with no major issues although you will be significantly increasing the compression ratio. In fact, Subaru did build several DOHC Phase II hybrid motors when SOA's inventory of EJ25D engine blocks ran out late in the 1999 model year. This to me suggests that Subaru likely produced a number of lower compression pistons to work in such a hybrid motor. Correct ?

Cam sensors, knock sensors, etc... these should work fine in both motors, right ?

It is basically an issue of using the Mass Air Flow (MAF) sensors in place of the Manifold Absolute Pressure (MAP) sensors, right ?

What other issues are there ?

Yeah, I know that the conversion between these two motors is far more complex than you might at first think. But before one can seriously consider such a swap it might be smart to identify what the major stumbling blocks are.
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Old 04-23-2010, 09:00 AM   #4
Patrick Olsen
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You can however put the DOHC heads on to a later model "Phase II" SOHC with no major issues although you will be significantly increasing the compression ratio.
If you use the stock DOHC head gasket the CR is hardly changed at all.

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Cam sensors, knock sensors, etc... these should work fine in both motors, right ?

It is basically an issue of using the Mass Air Flow (MAF) sensors in place of the Manifold Absolute Pressure (MAP) sensors, right ?

What other issues are there ?

Yeah, I know that the conversion between these two motors is far more complex than you might at first think. But before one can seriously consider such a swap it might be smart to identify what the major stumbling blocks are.
All of this has been covered repeatedly in the Normally Aspirated forum and the Subaru Conversions forum.
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Old 04-23-2010, 11:17 AM   #5
Jonathan
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All of this has been covered repeatedly in the Normally Aspirated forum and the Subaru Conversions forum.
Sounds like these are both great forums to check out.
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Old 04-25-2010, 07:33 PM   #6
CastIron
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I thought that would be the case, but I just wanted to check.

Regarding variation within the EJ25D line, however, I have a couple more questions. First, how does one distinguish the 165hp version (97+ here) from the 155hp version (96 here)? I'd like to avoid inadvertently purchasing the latter. Also, some are designated EJ35DE; what does the DE designate? Lastly, did the 155hp/165hp change happen between 96/97 in other markets as well, particularly the Japanese market?
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Old 04-25-2010, 09:25 PM   #7
Patrick Olsen
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Based on my experience and that of someone else on the forum here (I can't remember who it was), the lower power rating seemed to be a matter of the '96 ECU's overly conservative tuning, and not a matter of the mechanicals of the engine. The Ebay engine that I had in my car for a while was an HLA EJ25D and it put down very respectable numbers on the dyno and ran just fine at the couple track days it went to.

As for visually distinguishing the two variants, I think that the HLA engines have "DOHC" in big letters cast across the valve covers, and the non-HLA engines don't. At least, that was the case with mine. That's a pretty small sample size, though, so I can't definitively say that was always the case.

Not sure on the EJ25DE thing. I've seen some listed like that on Ebay, but just chalked it up to incorrect labelling of the engine designation by the vendor.

Pat
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Old 04-26-2010, 12:09 PM   #8
CastIron
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Originally Posted by Patrick Olsen View Post
Based on my experience and that of someone else on the forum here (I can't remember who it was), the lower power rating seemed to be a matter of the '96 ECU's overly conservative tuning, and not a matter of the mechanicals of the engine. The Ebay engine that I had in my car for a while was an HLA EJ25D and it put down very respectable numbers on the dyno and ran just fine at the couple track days it went to.

As for visually distinguishing the two variants, I think that the HLA engines have "DOHC" in big letters cast across the valve covers, and the non-HLA engines don't. At least, that was the case with mine. That's a pretty small sample size, though, so I can't definitively say that was always the case.

Not sure on the EJ25DE thing. I've seen some listed like that on Ebay, but just chalked it up to incorrect labelling of the engine designation by the vendor.

Pat
I was suspicious of the same thing for the "DE" designation.

Out of curiosity, was your Ebay engine USDM or JDM? It seems like most of the cheap ones are JDM. Is there any difference? I just don't want to end up with any extra trouble during install.
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Old 04-27-2010, 12:19 AM   #9
Patrick Olsen
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It was a JDM engine. I don't think I've ever seen one on Ebay that was not a JDM engine. The only somewhat weird thing was that the engine didn't have EGR; the port on the back of the driver side head was there, but it wasn't drilled and tapped, and the intake manifold didn't have any provision for EGR. That meant I popped a CEL for no EGR, but I was constantly resetting CELs anyway (for "misfires" due to the aluminum flywheel) so that didn't really bother me.

Apparently some of the JDM engines have EGR and some don't. Not sure if there's any rhyme or reason to it.
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