thats a je piston yes. I now have accralite pistons. Most forged pistons are much the same at the level we are at.
Well, final seat blending and chambers done, set it all up on the flow bench ready for some testing tomorrow... but could'nt resist a quick lift curve The previous best before the seats was 125.3cfm @ .500, with 121.5 @ .450. I expected the final seat shape to add a couple of cfm, with a secret hope that 130cfm would be nice, today's results were........... 130.9 cfm @ .500 Feeling slightly smug I thought I'd better check the real world figure where the cams will lift, so I backed off the dti to .435 and took another reading... 130.1 cfm @ .435 Not that I like to push my estimates to the limit or anything.. Exhaust testing tomorrow, along with some basic porting of the Dbilas manifold to see if it can be brought up to close to the bare head, (it's lost 10cfm in previous tests) or if we need to scrap that idea and move straight onto the custom manifold... watch this space.
Great work! So if the theory holds true, your flowed head (with an extra 9 or 10 CFM flow) should have 9x0.43x4 = 15.48 hp, provided you've got a similar increase on the exhaust side. Have you gone for a different grade of finish on the inlet and exhaust sides? Bill Blydenstein was adamant that a rougher finish on the inlet side was a good thing, on anything except a full race head. I'd be really impressed, and a bit surprised, if you got that on a dyno. It would be really interesting to compare these heads on the same engine, on the same dyno, to see how the flow rate compares to the HP and torque curve. A lot of work though.
So the headline figure is impressive..... But this is the one of real interest of course, and very impressive, how does it compare at even lower lift? Mike_H, the thing about this is not the peak figure (though as we can all see IF it translates across the peak figure will be good) but the area under the curve... If the CFM's are up like this at all lifts (i.e. just off the seat) this head will offer impressive area under the curve gains Cheers Simon
Absolutely, and it'll be interesting to see how it pans out. Back to back comparison of the different heads would be great! Mike
Excellent results. So in this instance you would not have to run huge lift cams in this head for it to perform as shown by the tiny increase in flow between .500 and .435 A steep ramp on the cams and long hold at full lift would be sufficient Out of interest, do you have a bare-port-flow figure now the seats are finalised? I am interested to see if the head flows more with the valve in or not (a few manufacturers heads do) I will be very interested in the manifold tests too. If you can get the losses down to zero, I may change from DTH... Keep up the good work, N.
Just a quickie... work beckons... After a morning on the bench some very positive "and" interesting results have come about. First, just to touch on the above... airflow is up at all points over standard (+ 5cfm @ .050, + 10@ .250, + 18@ .350, +23@ .450 etc). But the biggest smile for me today was something else... a certain head company advertises their 16v head at 142cfm peak. When you look at the bore adaptor used (3.9 inches, or approx 100mm)) you begin to see a possible reason why. The biggest bore adaptor we have is 93mm (Ford Pinto), so a quick test just with my head on the bigger bore resulted in a peak gain of 9cfm over what I've seen when tested on the "correct" 82.5 adaptor. I'll leave someone else to do the maths on the above by searching back through this thread... but it makes you think... Also, the airflow is likely to go up a little more when tested on the 100mm bore as others have done... but I'm happy with my "real" 130 ish cfm. As for the manifold, I added plasticene to the base to make it match the head.. no gain.. i then flowed the lip at the top, 1-ish cfm gain... but either way, the Dbilas dropped the flow to 123cfm at best over the bare modded 130... guess what's on the drawing board next.. No bare port test on the final shape (may do one just for you Neal if time premits nxt week ), and I'd stick with the DTH's. Thanks for the positive comments chaps.
So what you are saying is there is a bore shrouding issue with the inlet valves, or that the other 142 cfm company had an air leak on their adaptor? 100mm would overlap into the combustion chambers in the other cylinders wouldn't it, so those would have to be sealed too? Either way, correct to use the actual bore size - 82.5mm If you get those BPF numbers that would be a useful source of information and could help with selection of valve shape for others. Again, great work!!
top job - the way I work it out is that you have pretty mutch matched 'the other head company' which gives great faith in both of the datasets dth's do rock
Any plans on tesing bulleted guides or 1mm oversized inlet/exhaust valves? Fantastic work by the way & it's nice to see undselfish people share their knowledge.
remember Dave walker doing a ferrari 328 quarter-of-voles head and getting around 142, so maybe VW aren't as bad as advertised what does an XE flow at similar lift?
