Crankshafts

[komodo]

I was just reading Rooz's exhaust thread and crankshafts were mentioned, and rather than going OT on his thread, I'm making this one to find out some more about it.

Someone mentioned it'll stroke your engine to 3.0 liters or whatnot. So it basically increases the displacement?

Can someone explain a bit more about upgrading these in your car and the advantages/disadvantages?

Thanks.

[94bmw325i]

yeah komodo with a m52 motor it strokes it out to a 3.2 I believe. I heard that doing this can make your engine's life be shortened a little bit, not in a huge way. Umm better performance, less mpg? better for your turbo setup!

I don't know a lot about them, I just heard the guy in a dealership talking to one of the parts people about it.

[voca]

a crankshaft with more throw will--yes, increase displacement and result in gained torque and horse. you'd need new pistons and maybe rods (not sure?).

I think the biggest disadvantage is that you can't safely rev your motor as high. but I guess it really depends on how big of displacement your going for.

[catalyst]

A crankshaft alone is not going to be something you want to do.

A crank +completely new upgraded valve train is the only way to do it right.

You can put an s52 crank in your motor and it will yeild almost 3.2L displacement, but your head was not made for that displacement. Uprated valve springs are needed to make the motor run decently and for any extended amount of time.

Basically the only reason to do this is if you already have a 2.8L in your possession and you want to fully build it for NA high revving. Many other internal engine components besides the crank are needed to do this correctly, along with many other mods, such as PNP, fully balanced and blueprinted crank, knife edged crank, custom cams (shrick?), valve tappets or solid lifters ($$$$$), ITB's, headers, exhaust, etc. You only want to go this route if you are FULLY building a high revving race motor, for street use an s52 makes much more sense, and will cost much much less.

An over-revved s52 can be had extremely cheap, and depending on internal damage can be repaired reasonably cheaply. Rebuilding an s52 is the cheapest way to go for the most NA power.

[xsperf]

haha catalyst, you know that komodo is planning on getting a turbo, right?

komodo, i wouldnt really do it, b/c when you replace your crankshaft, you have to replace everything else, seriously its just like rebuilding your engine w/totally new parts, so might as well get an s52(non over-revved) and just install that w/ a turbo if u want(or the euro s52, see, thats an idea)

[catalyst]

Originally Posted by xsperf

haha catalyst, you know that komodo is planning on getting a turbo, right?

komodo, i wouldnt really do it, b/c when you replace your crankshaft, you have to replace everything else, seriously its just like rebuilding your engine w/totally new parts, so might as well get an s52(non over-revved) and just install that w/ a turbo if u want(or the euro s52, see, thats an idea)

That is exactly why i went though all of that.

The euro s50 is not made to be run on american pump gas.

Why pay up to 4 or 5 grand for a low mileage s50/2 when you can buy and rebuild an over rev for 2500-3000 or less?

[xsperf]

^^ yea but for the over rev you gotta buy the engine too, and then rebuild it

[komodo]

Hum, a bit different direction for the thread, but what parts of the engine would need work/replacement if I wanted to increase the PSI of the turbo?

[xsperf]

pistons, piston rings.. thats about all i can think of but if ur replacing ur pistons and rings u are basically rebuilding your whole engine

[catalyst]

BMW's really are not the best cars for boost.. honestly.

Just a thought man.. i know you are set on the turbo an all, but this is what i would do if i was loaded like you :

Rebuild an s52
6 speed euro gearbox
3.73 LSD
cams
Headers
3.5 HFM, big bore TB, and CAI.
OBDI conversion if you wish.

Cost? most likely 7-10 grand. Possibly more. A turbo will probably end up costing the same, will be less reliable, and less driveable.


This will beat an e46 M3.. probably by alot.

[Spieluhr]

^^^
that would absolutely own.

only thing better is a EURO s52, now that would STOMP an e46 M3.

I agree that the turbo set up you are going after is going to cost an insane amount of money, and chances are you will break something because you are builing it, instead of buying a kit or something.

[94bmw325i]

Originally Posted by catalyst

BMW's really are not the best cars for boost.. honestly.

Just a thought man.. i know you are set on the turbo an all, but this is what i would do if i was loaded like you :

Rebuild an s52
6 speed euro gearbox
3.73 LSD
cams
Headers
3.5 HFM, big bore TB, and CAI.
OBDI conversion if you wish.

Cost? most likely 7-10 grand. Possibly more. A turbo will probably end up costing the same, will be less reliable, and less driveable.


This will beat an e46 M3.. probably by alot.

I don't think so.

[komodo]

I'm also questioning the amount of gain those upgrades would give me...

I've looked into dropping a 3.2 instead of turbo'ing, but the difference in my 2.8 and a 3.2 is so minimal, it's not really worth the thousands of dollars. Or am I wrong? heh

[xsperf]

well look, it would not stomp an e46 m3, it would probably be the same or a tiny bit slower, because if you drop a 3.2 in there, i think if you bore it, change crankshaft, camshaft, and a few things, you have a euro engine, or pretty close

however is it too late to back out of the turbo set up or not? ever think if 3.2L + supercharger?

[catalyst]

Gearing man.. gearing.. the 6 speed with the 3.73 LSD makes all the difference.

i THINK, the 3.73 puts 6th gear at the same ratio as 5th in the 5 speed trannys, so you have 5 gears that can be that much shorter, making you that much faster.

I know of a e36 M3 with a 6 speed swap only without cams and headers that can take an e46 M3, so with cams and headers.. you can most def. take one.

Dont forget about brakes, and suspension.. add on another 2 grand for those..