building a 24v DOHC engine

[formula driver]

thanks for the support :D

definatly, its getting harder and harder to surf through all the bullshit to find some real answers.

and Im not talking about R3V solely...

[lifeiskaos]

thanks for the support :D

[formula driver]

You people suck at life.

Threads like this are never worthless, at the very least we can learn what not to do.

Hypothetically speaking, some chap thats been working on lame ass fords forever, gotten VERY good at, but finally see's the light and wants to move over to bimmers. Come's here for advice and you guys bash him. He's been putting motors together his entire life yet he has NO knowledge of BMW's, who's to say he cant get it all put back together with a little guidance.

My point is, why the fuck do you loser's have such a problem with people trying new things? Nothing is impossible and everybody has to start somewhere.

btw... goodluck to ya man, hope you get it all sorted. Working on engines isnt brain surgery.

[z31maniac]

well that is what i'm not sure of. i know 1.45 rod ratio (130:89.6)

Like nando said, and from the research I've done motors with low rod ratios seem to run out of breath up top.

Old Z28 Trans Am Cars used 302s with a 2:1 rod ratio, giving them phenomal top end pull, but not much low end torque.

From what I've read, you want to get the rod ratio as close to 1.75:1 as you can for the best compromise.

[lifeiskaos]

thanks for the link

[JGood]

Here:

http://books.google.com/books?id=UtxI5gXM1yQC&pg=PA213&l

Start reading 8-)

[lifeiskaos]

haha well thanks anyways

[JGood]

no, i havent taken much of that into account at all. i'll do more research on that, but any insight is much appreciated

I'm not the guy to go to. Hell I can't even spell right 'squelch' should = 'squish'. Or Quench area. Or something along those lines, I'm not an engine guy...

[lifeiskaos]

Getting the correct CR is only part of the big picture. Is the rod ratio, squelch area, swirl effect, etc... all ideal with the parts you are throwing together? One thing that always had me curious with people mix and matching parts from various engines is the above questions. Sure, it fits, but is it worth it? You spend all that money to build an engine, when custom parts for a little more money (maybe less?) could net you much better results.

Not that your combo won't work well, because I have no idea, and it very well could work great. But you seem to be doing all kinds of calculations that aren't focused on other important aspects of a custom build.

no, i havent taken much of that into account at all. i'll do more research on that, but any insight is much appreciated

[lifeiskaos]

physically? sure, but I don't see why you'd want to do that. the rod ratio is going to be very low leaving you with very high piston velocities and higher wear on the cylinder walls. Not to menition it's going to change the CR (piston will be .6mm lower in the deck) but not likely a full point. They are also really heavy.

why not use the M54 crank with it's rods and pistons?

well that is what i'm not sure of. i know 1.45 rod ratio (130:89.6) isnt the greatest, but i really dont know enough to argue. if that's really a bad idea, then i suppose i'll get pistons. im just trying to work with what i have and what i know, neither of which adds up to a whole lot. the pistons will actually be 2.2mm lower than stock at TDC, which is required to lower the c/r, especially with the added stroke

[JGood]

Getting the correct CR is only part of the big picture. Is the rod ratio, squelch area, swirl effect, etc... all ideal with the parts you are throwing together? One thing that always had me curious with people mix and matching parts from various engines is the above questions. Sure, it fits, but is it worth it? You spend all that money to build an engine, when custom parts for a little more money (maybe less?) could net you much better results.

Not that your combo won't work well, because I have no idea, and it very well could work great. But you seem to be doing all kinds of calculations that aren't focused on other important aspects of a custom build.


Edit: Nando kinda beat me to it...

[nando]

physically? sure, but I don't see why you'd want to do that. the rod ratio is going to be very low leaving you with very high piston velocities and higher wear on the cylinder walls. Not to menition it's going to change the CR (piston will be .6mm lower in the deck) but not likely a full point. They are also really heavy.

why not use the M54 crank with it's rods and pistons?

[lifeiskaos]

after several hours of research and calculations today, i've seem to come up with a final plan. the numbers, work out to be perfect, almost too good to be true.

according to my calculations, using an 89.6mm crank from an m54b30 or an s52, stock m52 pistons, stock headgasket, stock bore, i'll get 2.97L, so my goal of 3L shall be done. now i also determined that if i use 130mm rods, which i happen to have laying around in the garage, i can lower the compression from 10.2:1 to 8.9:1, which will be very suitable for boosting. is it physically possible to use said crank, 130mm (eta) rods, and stock m52 pistons?

[Massive Lee]

stay the fuck out of my threads

The initial post is soooo funny. :giggle:

In fact, not just the initial post. I knew there was no meat around the bone.

[lifeiskaos]

You should be banned for your outright laziness in this endeavor.

stay the fuck out of my threads