I know the at least the rod bearings are bad because of severe knocking and shavings in the previous oil and oil filter. Adjusted values and knocking persisted. Used stethoscope on top and bottom of engine and sound is worse near the bottom around the oil pan.
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2.7i Pros and Cons
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Originally posted by nando View Postit's only 0.2l of displacement - it doesn't really even make that much difference.
if you already have an eta, fine, slapping a B25 head on makes some sense. Pros: it's cheap.
Cons: If you started with a B25, putting in the B27 block is hardly worth the effort. I collected a ton of 2.7i dyno graphs and most of them made the same or less power as a stock B25. They peaked torque a little earlier but really didn't make much more torque (often less) either. The displacement gains are mostly lost in the fact that the pistons don't match the shape of the 885 combustion chamber and you lose almost a full point in compression ratio.
The lower CR for boost doesn't even really make any difference either because the B25 already has a fairly low CR and it works great for boost out of the box. it's going to make what, 10ft/lbs more at 15psi? what's an "assload" of torque? blunt? :p
Now the car is making 53wtq more than whp at 15psi and the only things changed during the rebuild was an equal length manifold (not sure if it matters much on a 6cyl) and a bigger downpipe (from a 3" to a 3.5") because blunt said my pipe was too small for his liking.
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2.7/2.5 is an 8% increase, at a given low rpm you gain a higher % than this though.89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...
new build thread http://www.r3vlimited.com/board/showthread.php?t=317505
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Originally posted by IronFreak View PostYou do realize that motor in that video was probably 700+hp.....
The car was then wrecked I believe but the heart was saved and it turned into this.......
The Blue Monster
Little fun fact.
But the fact that you can squeeze that power from that teeny displacement is incredible.
Gotta hand it to the Swedes.1989 325i Lachssilber Sedan
5-Speed Swapped
M30B35 Swapped
MegaSquirt MS3X
1987 325i Lachssilber Sedan
260k OEM Automatic Daily Baby
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Originally posted by digger View Post2.7/2.5 is an 8% increase, at a given low rpm you gain a higher % than this though.
the 2.7i doesn't have the same VE as a 2.5. the fact is they both make basically the same peak torque, only the 2.7i does it at a lower RPM. So it has larger displacement, same torque, which means it has to have lower VE. An engine with lower VE N/A will also have lower VE with boost.
It's not going to make a lick of difference in the end. in fact, I'd put my money on the boosted B25.
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Originally posted by nando View PostI don't think so, it's not a straight displacement increase = more power, and you know that.
the 2.7i doesn't have the same VE as a 2.5. the fact is they both make basically the same peak torque, only the 2.7i does it at a lower RPM. So it has larger displacement, same torque, which means it has to have lower VE. An engine with lower VE N/A will also have lower VE with boost.
It's not going to make a lick of difference in the end. in fact, I'd put my money on the boosted B25.sigpic
Rebellion Forge Custom Fabrication
1988 325is - TrackRat in progress
Instagram @rebellionforge
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Originally posted by nando View PostTrue - but even the seta engines with 885 heads don't really end up with that much more power than a B25.sigpic
Rebellion Forge Custom Fabrication
1988 325is - TrackRat in progress
Instagram @rebellionforge
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^ you missed the point man, people here are discussing whether to go 2.7i or rebuild his cammed m20b25, I think it would be difficult to find anyone claiming the 2.7i build is not an improvement over an ETA, and even more difficult to find someone who has done the conversion and wants to go back.
just read the 2.7i thread, its stickied in the m20 section
unless i missed you checking the sarcasm button?
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You can't get any worse than a stock eta.......A 2.7i should make about the same power as a b25 if it's not high mileage and you fit the same induction as a b25 with a custom tune. Many m20 builds even big $$$ ones never get a custom tune and that's where many seem to lack. If you want more power you need breathing mods but the low compression means you need to limit how much duration you throw at it.
Also a small amount of compression doesn't make much difference at all, it's not like going from 8.8 to 11:1,people seem to get hung up on it89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...
new build thread http://www.r3vlimited.com/board/showthread.php?t=317505
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I'm in the same boat as OP. Bearings are shot - I also get the dreaded knocking. Took it to GAS in Berkeley, they told me the bearings are on their way out, but head is good.
So if I understand correctly:
- an ETA engine with an i head is bad, because the compression drops, due to inadequate pistons?
- a SETA engine with an i head is good, no compression drops or other problems? Do the 15lbs injectors keep up with the increase in displacement? Need to update the ecu map?
From what I've read up until now, the bottom end swap can cost you from 2-3k, but most of those estimates are based on the fact you're upgrading a SETA engine with an i head. What about our case? If you already have an b25 engine with everything, but just need to swap out the bottom end?
Edit: nvm, found this: http://www.e30tech.com/forum/showthread.php?t=48288Last edited by crappycoco; 09-30-2015, 01:22 PM.
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