Turbo on 2v versus 4v motors

[SamE30e]

I think the M10 will be more reliable though, they're pretty stout little motors. the M42 is a little bit fragile.

the M10 is also cheaper to build by a long shot. you could probably do a basic M10 rebuild for what the M42 timing chain system costs alone..

M42's timing systems suck, I found this out the hard way.

[Pinepig]

M50 swaps suck, I found this out the hard way.

Fixed that for ya.:D

[Quadrajet]

Essentially the m10/m42 was only being used as an example. It was the only example I could think of off the top of my head where displacement was equal and I assume, the only major difference was the heads. I haven't been in the BMW scene long enough to know of all the differences.
And the "question" asked to me was basically a very general statement. I just wanted some input from some folks who had "played" with the variables.
Thanks for your input guys.

[xwill112x]

it just hasn't happened yet. it's about as inevitable as breaking a rocker on a 200,000 mile M20.

just another excuse for a s52 swap ;)

[Lurker27]

2 or 4 valves doesn't matter, volumetric efficiency does. If the 2 valve motor has a greater VE than the same sized 4 valve motor the 2v will win ( highly unlikely to find a 2v with more VE than a 4v but I'm sure there are examples )

You guys are asking the right questions, your just not using the proper terms.

Right, for the purposes of my post (as would be obvious to those reading it with the knowledge) it is assumed that a 4v engine is more volumetrically efficient than a 2 valve engine.

[rThor432]

i've dropped the oil pan, found no bits of chain rollers or guide rails so i think i'm good :up:

You might not have seen the bits, but if you take off the front timing cover and look at the rail you will be scared by what you see. Doing timing chains in 10 M42's with between 130k and 230k has taught me that.

The plastic on the guides begins to deteriorate and crack into bits. The chain eats away at the guide and eventually starts to take the guide out in big chunks.

For all of the people who are arguing about the efficiency increase of a 2v vs. 4v with a turbocharger, you should know that when you are forcing air into the combustion chamber the head flow numbers pretty much go out the window. As stated, the head flow still affects the efficiency, but not at all like it does on a normally aspirated motor.

[Danny]

M10s are easier.

[David Alejandro]

they aren't the same basic engines though, completely different.

also, there are good 4v designs, poor 4v designs, and exceptional 4v designs, so that still doesn't hold. the M50 is a good design, the honda S2000 would be exceptional..

I still think the M42 is the worst $/hp of any BMW engine.. even worse than the M20. I would own an M42 car now if the cost to do the work it needed wasn't several times more than what the car was worth. :p

and if M42's where not KNOWN to have a "reliability problem" with the bloody head-gasket!
Now for a simple truth: identical engines, 2v vs. 4v. The 4v would win. BUT the 2v will see a greater improvement, PERCENTAGE WISE, over the 4v, because the 2v is restrictive and the turbo can (and most definitely DOES) overcome much of this restriction! THIS TRUTH DOES NOT TAKE INTO ACCOUNT VVT/VANOS/(add your brand of variable valve timing here..). It is only identical engines, 2v vs. 4v, without any additional electronic wizardry thrown in. End of story.

[Pinepig]

and if M42's where not KNOWN to have a "reliability problem" with the bloody head-gasket!
Now for a simple truth: identical engines, 2v vs. 4v. The 4v would win. BUT the 2v will see a greater improvement, PERCENTAGE WISE, over the 4v, because the 2v is restrictive and the turbo can (and most definitely DOES) overcome much of this restriction! THIS TRUTH DOES NOT TAKE INTO ACCOUNT VVT/VANOS/(add your brand of variable valve timing here..). It is only identical engines, 2v vs. 4v, without any additional electronic wizardry thrown in. End of story.

The VE of an engine does not magically change when you throw boost at it.

[92 mtechnic cabrio]

2 valve heads have less shit to break ;)

[nando]

The VE of an engine does not magically change when you throw boost at it.

what?

Yes it does, it changes dramatically. Where do you think all that power comes from? :roll:

[Pinepig]

what?

Yes it does, it changes dramatically. Where do you think all that power comes from? :roll:

The base normally aspirated VE is constant you can then use the law of thermodynamics to make a decent estimation of HP by a multiplication of PSI, but the base VE does not change.