Replacement Engine 'Feels' Different

[RichE]

Last time I posted was about the knocking in my engine. Long story short, spun rod bearing in 110k mile engine (2004 2.0L unmodified WRX) warranted replacement. So I just got this (supposedly stock) replacement (55k mile) engine (and turbo) put in by a mechanic and the car is driving great, but it feels a little bit different.

The first thing I noticed was I could hear the turbo spooling, which I thought was odd, since I never heard that in the old engine. I think it is spooling up sooner, around 2400-2500 RPM, which is why I think I can hear it - the engine noise at the normal 2700RPM starts to drown it.

The second thing I noticed was considerably less mileage per gallon. I was getting an average of 25 MPG on the original engine and now I think I'm getting about 20 MPG. I think I have to try a few more fill-ups to know for sure, since it's possible I could be getting a wrong measure, but I don't think so.

From a more anecdotal perspective, I definitely notice more pep in the 2500-3500 RPM range and considerably less turbo lag, but don't notice anything different in the lower engine range. So my question is, was this engine or turbo modified in some non-obvious way (I don't think a engine can really be modified without it being obvious, right?), could it be a 2.5L engine (can that even fit easily?) or is there something else going on?

It's not really the worst thing in the world since it drives well and turbo lag is gone, but the lag never bothered me and I'd expect a lot more performance for a 5MPG cost. Any thoughts/suggestions would be helpful.

[zax]

When I was stock, I never got better than 20 MPG city consumption...

The 2.5L motor SWAP would require full ECU harnessing, a new ECU, and more. It's a very involved process, doubtfully performed by a dealership. Could you provide pictures?

It's possible that this motor swap was a motor with a catless UP. This would influence how quickly the turbo spools. It's possible that the UP was "hollowed" and the dealership might not even know...

[RichE]

Here's a picture under the hood. Just to clarify, it was done by a mechanic, not a dealership, but it was supposed to be the same engine. Is it common to include the up pipe on engine swap? I didn't look too closely on the old engine when he showed it to me (it does kinda look different when it's sitting on the floor), but did mention that the only the engine swap was straightforward except for some (pvc?) shielding that was missing on the donor turbo and ended up taking that from the original. BTW, I'm doing mostly highway driving and based on my latest fill-up averaging 21 MPG.
Does that help?
https://picasaweb.google.com/lh/phot...eat=directlink
https://picasaweb.google.com/lh/phot...eat=directlink

[zax]

Here's a picture under the hood. Just to clarify, it was done by a mechanic, not a dealership, but it was supposed to be the same engine. Is it common to include the up pipe on engine swap? I didn't look too closely on the old engine when he showed it to me (it does kinda look different when it's sitting on the floor), but did mention that the only the engine swap was straightforward except for some (pvc?) shielding that was missing on the donor turbo and ended up taking that from the original.
Does that help?

That's definitely an EJ205 Longblock (could have the 2.5L shortblock and I'd never know). If it had a "donor turbo" it probably had the headers and uppipe included.

[RichE]

So should I keep the upgrade or try to go back to stock? Heresy, I know, but I've never driving a non-stock car so I don't know the implications. Is this a big plus in the long term or more trouble than it's worth?

The car is 6 years old and fully paid off, so the reduction in MPG isn't going to kill me. That is, of course, if oil prices don't go through the roof in the next year or 2.

[zax]

So should I keep the upgrade or try to go back to stock? Heresy, I know, but I've never driving a non-stock car so I don't know the implications. Is this a big plus in the long term or more trouble than it's worth?

The car is 6 years old and fully paid off, so the reduction in MPG isn't going to kill me. That is, of course, if oil prices don't go through the roof in the next year or 2.

Honestly, that was just a conjecture. If the new motor has a catless/hollowed uppipe, consider that an improvement. The cat did little more than present a possible mode of failure for the turbo

[anxiouz]

It kinda sounds like the turbo has been ported. In my first Evo I had the turbo ported and it did change the sound a lil (more whistle/whine when spooling).

Also keep in mind that the "new" engine has half of the mileage the old one had. So there's 50k less mileage on the turbo (in theory), 50k less wear, etc.. So it's possible that the old engine had lost some pep in it's step and now you're back to normal so to speak.

If you're starting to boost earlier then you're likely IN boost more which would decrease MPGs.

[dbya rx]

the only reference you have is of a motor and turbo that had 110k miles on it. i would assume you can't remember what your car felt or sounded like when it had 50k miles on it. it may just be that the car feels different b/c the motor and turbo are half the age of the one you had replaced. i would ask the mechanic if he noticed anything that was out of the ordinary or not stock. where did the motor come from? most reputable used/remanufactured vendors disclose any modifications made to the motor beyond stock b/c it affects their warranty...unless the motor was from a junk yard or something...then i wouldnt really know how to verify anything beyond what your mechanic saw