Advice/Opinions? 2.8l stroker or stay 2.5l?

[Spaz!]

I was leaning more towards Miller's war chip than MS.
I cant help but think that ~200/200 is feasible on a fresh, n/a, 2.5 or 2.7. In all honesty I think I would rather fore-go the 200/200 mark and just see how far I can push a basic build from OEM parts. Surely if a stock 2.5 is pushing the 160/160 mark I can get pretty close to 200/200 from a well executed build and tune. Especially if I can get a decent CR out of a 2.7i with just a custom head gasket. You still have head and block dimensions to play with as well as cams, valves, porting, intake and exhaust, etc, etc.

[Spaz!]

On a side note:
I have been tinkering with the idea of a new TB for some time but have never really gotten off my rump and done some real R&D.

So.... can any give me a formula for calculating fluid velocity through an orifice?

[nando]

there's a much simpler way to figure out if your TB is too small - get a vac gauge. You need to test this without an airbox (pick a dry, non-dusty day). if you aren't seeing atmospheric pressure at WOT, then your intake/TB is a restriction. If you're seeing full atmospheric pressure, then it isn't. no fluid dynamics required..

However I can gaurantee you that the stock intake manifold could use a lot of improvement. This is where I got stuck, though. the "budget" upgrade would be an extrude honed B25 intake at a cost of $700. Beyond that you're looking at $2k minimum for an ITB setup plus you really need standalone to use it which is another $1k easily. I already had the standalone but I decided it wasn't worth going another $2000-$2500 into this motor..

My opinion: if you want an M20 budget stroker, do the 2.8 using an M52B28 crank, 130mm eta rods, and b25 pistons. you'll probably need to clearance the block and piston skirts for the crank. however this will give you a decent CR (9.8:1 I think?), and the piston crowns will have the proper shape for the 885 combustion chamber. I'd go with a schrick 284/272 or similar cam (catcams?), leave the ports alone (unless you know what you're doing, you'll only make them worse). Put it together and then decide if you want to do more (headers are a GOOD thing on these motors, intakes are $$$$). that will easily be 200bhp, though (tuned, of course). the upper limits will be more defined by how good your exhaust is, how restrictive your intake manifold/throttle is, and how good your tune is.

[Spaz!]

Thanx for the info Nando. I understand that the factory TB is a bit restrictive and that I will probably need to replace it eventually but I will worry about that after I get the engine in and can see how it does then. At this point I am considering going ITB anyway. Has anyone used motorcycle TB's on their Bimmer? I have seen this done to a few other vehicles and with good results but I haven't noticed anything in the bimmer circles yet.

Will Miller's WAR chip give me the tune-ability to deal with ITB's?

I'm actually working on a new type of throttle body which is why I need to calculate velocity through an orifice.

At this point I think a budget build is out the window. I just dont see any way to do this right on the cheap. If I am gonna get into swapping rods, pistons, crank, etc etc. I may as well just go through the whole thing, I dont really see that I have a choice...