Dont know how many of you know this, but i actually own a flowbench.

Its a homemade job, could be painted / finished better, but its 100% solid, works great, and its (as i always do) complete overkill.
It has 4 huge ass motors, each able to pull a genuine 125cfm @ 28" H2O. When all 4 run, you get a loss, but its good for around 420ish CFM, i dont have a orifice plate to test higher. But for an idea of how much air that is, a stock 5litre V8 would pull around 450cfm thru the manifold. So if you are testing individual cylinders, i could go up to basically anything you can buy "commercially". Ive made accomodations for 8 motors total if i ever need it.. Which i highly suspect i wont.

Now the fun stuff. Throttle bodies. Ive made up some trumpets (long time ago) and finally got my ass into gear to do some testing on them very briefly. now please remember that my throttle bodies are from a TDM900, which are 38mm diameter, the same as the stock Mikuni that the TRX runs, except ive bored mine out to 41.2mm. Ive not finished them off as i have much blending work to do, which is where the flowbench comes into it. Note that this is for a EFI total conversion. I already have 100% control over the spark tables, i can increase / retard spark at my hearts desire. Its good for a few hp actually.

You can clearly see ive left a bunch of meat to be ground out. Anyway.. here are some flow pics.


You can see that the trumpet was good for around 5cfm increase in flow. Im hoping at the end ill be upwards of around 220cfm. I dont have velocity readings, but i want to keep that above the 340FPS range, id prefer more if i can get it, but i need some cfm too.
Ive also made a "flowbox" which is an exact mould of something, to play with. In my case, ive cast my ports (inlet, exhaust, cylinder chamber) in a soft silicone, and then put those pieces into a box. Cast it all in hard resin (think "bowling ball" plastic) and squared it up on a mill so it sits flat. I also made a valve opening jig, and for 3 valves, it was a bastard. but i did it.





This way, i can grind away on the flowbox, and if i screw up, find out im loosing velo / cfm, whatever, i can mix a bit of resin, paste it on with a paddle pop stick (popsicle stick ?), wait for it to set, and go in another direction.
Doing this takes quite a while to figure out what is best. There are some rules that people come up with, but everyone is different. There is no "right or wrong" method, its the end result. And fingers crossed, ill get some more time to play.
Anyway, enjoy, and hopefully by the weekend ill post a full cfm / velo plotted graph of the cylinder head. Might help someone one day for some tech data / cam design / exhaust design, etc..
Questions / comments, please dont hesitate to whinge at me.

