A race bmw 316, m10, s14, m20, turbo, na, its been the lot!

[caprimentle]

Re: A race bmw 316, 240bhp Atmo M10

on heads like these bmw and pinto ones if you have a really long radius to the short turn the flow at low/med lifts is good as the air turns the corner nicely, at higher lifts the airs trying to skate across the back of the valve and that nice rounded shape actually obstructs teh air, a lower profile port allows better high lift follow but low med lifts are disrupted as teh air no longer has a nice rounded shape to follow,

the port shape that gave really high flow at big lifts leave a very tight turn if any are is going to go round the short side of the valve,

a multivalve head which has the flow better distributed in terms of where around teh valve head it goes will prob benifit more from valve seat angles

would that explain why big 8 valve heads seem more torquey compaired to a 16v head but the 16v usually has more power higher up the revs? or is what i just said bollocks and 16valve heads are better all round, coz 8v always seems more grunty to me.

[Tristan]

Re: A race bmw 316, 240bhp Atmo M10

Were you checking the flow with something under the head to replicate a Cylinder , Graham?

[Graham]

Re: A race bmw 316, 240bhp Atmo M10

yes

[Tristan]

Re: A race bmw 316, 240bhp Atmo M10

I thought you would be alright! Is bore shrouding much of an issue?

[Graham]

Re: A race bmw 316, 240bhp Atmo M10

i dont think so the valve angle is steeper than a pinto so the valve doesnt that close to the bore wall, espeically as the head was designed to work with a 89mm bore but in actual fact i have a 95mm bore

[Graham]

Re: A race bmw 316, 240bhp Atmo M10




anyone want to take a guess as to which head will make the most power?

they are all very different port shapes but if you take an average of teh flow figs they are all very smilar, infact one with least peak flow has highest average flow

[Group4_Mark2]

Re: A race bmw 316, 240bhp Atmo M10

Tough question to answer. I suppose that the only thing I can think of is to put the flow figures and other engine data into an engine simulator program and see what comes out of that. I have two that I use (engine analyser pro and dyno2003)


Tom

[Graham]

Re: A race bmw 316, 240bhp Atmo M10

your prob right tom, that said im not finished with the heads yet im sure i can find more flow with detailed seat changes etc, also im going to try a 2mm oversise valve next

[Tristan]

Re: A race bmw 316, 240bhp Atmo M10

what lift does that graph finish at? Wouldn't it be awesome if you could replicate the oscillating motion of a valve , to really see how the flow stacks up..

[Group4_Mark2]

Re: A race bmw 316, 240bhp Atmo M10

I have been reading a bit about high lift and low lift flow recently. It seems that high lift flow produces high peak power and torque figures but low lift flow produces a wide power band. It seems that as rpms go up a lot of the clinder filling happens later and later in the cycle and if the low lift flow is good then much more air can be crammed into the engine after BDC when the valve is nearly closed.

I put a few numbers into Dyno2003 to see what came out the other end.


HIgh Lift Flow Graph


High Lift Flow numbers



Low Lift Flow Graph


Low Lift flow nunbers

Looks like high lift flow wins with this setup
Regards
Tom

[Graham]

Re: A race bmw 316, 240bhp Atmo M10

It seems that as rpms go up a lot of the clinder filling happens later and later in the cycle and if the low lift flow is good then much more air can be crammed into the engine after BDC when the valve is nearly closed.

that makes a lot of sense, in particular if you take into account air has inertia, it takes a while to get it moving and once moving a while to stop, but then keeping air flowing into the cylinder after BDC is what ram tuning is all about and something these bmw engines really respond to

[Graham]

Re: A race bmw 316, 240bhp Atmo M10

what lift does that graph finish at?

0.500"(12.5mm) because thats what my cam lifts too

[caprimentle]

Re: A race bmw 316, 240bhp Atmo M10

i know by reading alot of pass threads you dont like them but is it not worth while to really consider a roller cam if possible? i know they can be a pig to set up but to those that have been succsesfull have had some real good results with the pintos.

[Graham]

Re: A race bmw 316, 240bhp Atmo M10

i guess a roller cam would be possible, but no one has made one for this engine so you'd spend a lot in time and money trying to devolop one, it would probably be better to try and tweek the current cam for a bit more lift

[RWD fords rule]

Re: A race bmw 316, 240bhp Atmo M10

Have you thought about ceramic coating the piston crowns, combustion chamber and valve faces, both isdes on the ex valve, with those mods the engine would have a lot less heat rejection throught those parts during combustion, + a dry film lubricant on the piston skirts will also help reduce friction, coating those parts would be an easy 7 to 12bhp with your 240bhp engine.

http://www.camcoat.com/

CBC2 and DFL1 is what you are looking for, you can buy the coatings from them and apply it yourself + bake it on in an old home oven for an hour.

I am saying this because you are at the stage where getting more bhp is becoming difficult, I believe thermal barrier coatings would really make your engine sing and also be more resistant to detonation, plus it would cost you very little if you did this yourself, I haven't used these coatings yet but I will be doing so on in hte near future, the coatings were not expensive.

Regards
Jason