Anyone with a flow book wanna put any creedance to this?

[Guest Anonymous]

URL: http://www.metricmechanic.com/pg28.htm

http://www.metricmechanic.com/pg28.htm

[Guest Anonymous]

I did some graduate work in compressible flows, and this is what I think. One area of flow loss through cavities and around bodies is separation of the flow from the cavity wall or the body. It creates low pressure areas that suck the flow back in an attempt to fill in the low pressure areas. Turbulent flow tends to separate from the cavity wall and body less than laminar flow (i.e. smaller low pressure areas), and the ribs here are designed to induce turbulent flow. However, since a fluid in turbulent flow does not flow straight in the direction of flow (more of a tumbling), and fluid in laminar flow does, turbulent flow is not as efficient at getting fluid from point A to point B.

Whether the ribbed valves etc. flow better than a conventional system is a question of whether the pressure drag in a conventional system (caused by separation of the flow from the valve and intake walls) is greater than the drag of the turbulent flow in the ribbed system. That I don't know. I guess another question is whether a conventional system even has any substantial laminar flow. If not, the ribs aren't doing anything anyway.

The best way to find out is to test a ribbed vs conventional system.

One thing that immediately jumps out at me is that those ribs look to be monster stress risers.

[Guest Anonymous]

I agree... they look like monster stress risers as well... I would think that if it was more efficent then teams like nascar and such would be using them.. I just have never seen such a valve or such a head cutting technique applied anywhere before.. hence why I asked the question.. I would definitly think with all those angles you'd get heat buildup and premature detonation vs the semi smooth head surface.. why would they do it in the head cause the flow is interupted by the engine cycle unless thats all for getting the exhaust out more efficently but again it's not even cut to enhance flow around the exhaust valve... like they took the same step idea and applied it to the combustion chamber...

[Guest Anonymous]

today at the shop. I kept the head with the schrick 292 to freshen and put on my sahara. You will be able to see better what they do to the chamber area. MM put a lot of time and testing into the design. They used to do the cuts by hand- took mucho man hours , now they have a computer driven machine that makes exact cuts quickly. Jim Rowe is working on a new web site and an article about his engine/head building philosophy. I am sending the old MM head to the machine shop today for freshening. ( if i can get the cam out in time). I will then have a nice E12 head with a Metric Mechanic 278 asymmetrical cam for sale when the swap is complete. That head and cam have worked really well with my 38/38 and my current 40/40 downdrafts. It is time to sell some extra stuff to recoupe some parts costs.

[Guest Anonymous]

I noticed that you said you are running a 40-40 downdraft.

I am at 60 idle, 165 main, 180 air, F2 emulsion. Just plugged up the coarse enrichment tubes, just waiting for the epoxy to dry.

-Justin

'76 02

'97 m3

http://www.bmw2002.net

[Guest Anonymous]

Looks fairly stock right? :-)

[Guest Anonymous]

I will ask PO who gave me the entire system from his 2.3 L stroker Touring that used to run this 40/40. I dont have any specs on components of the carb. We just bolted it onto the new engine last year and it has run great. It did really well at 7k plus feet in Tahoe last week. here is Sahara engine bay w/ 40/40

[Guest Anonymous]

(nt)

[Guest Anonymous]

If you get a chance to pop the top cover off, I would be very curious as to at least your main jet and air corrector (actually you can see the air corrector through the top of the carb).

I have a 2.2l metric motor. Still trying to dial the carb in.

If it has base as-delivered-from-weber (or metric mechanic) tuning: 180 Main, 185 Air, 60 Idle then you are giving up some power as it is way too rich.

Thanks!!

-Justin

'76 02

'97 m3

http://www.bmw2002.net

[Guest Anonymous]

I can testify to the qualities of Surface Turbulance. The motor could put out 300HP and 300 ftlbs of torque out of regular gazoline. Yes, the Surface Turbulance helps keep fuel particulres atomized for a better combustion.

Benefits are from less drag on the walls and better atomization.