mk e wrote:
I'm really confused about what length stacks I need now. Dynomation6 has had a couple more updates but continues to insist shorter tuned lengths are better for hp, about 10.25" is about the best...i need to confirm that is posdible to build. It seems though like it's assuming flow losses build with length, which is true for a straight tube but I'm pretty sure that with enough taper its not true so the answer is suspect.
The other place -5 and -6 differ is the strength of the pulses with 6 really showing peaks as the stacks move in and out of tune.....im going to need to dyno a few options. But first I need to modify the printer to make the z more reliable and I'm not allowed to run it in the basement so I need windows and doors on the new garage.....some day
Here's what I was taking about. The line on top is the 10.25 stack, on the bottom is 16.75. Both tuned to the same rpm but the shorter stack is much smoother due to lower energy in the tuned pulses, that makes some sense. What I'm not sure about is the short stack makes more power.....
I checked last night and I'm about 9.25 valve to the bottom of the recesses in the TB where the stack sits, maybe 9.75" valve to the top of the TB, so 10.25 total is a doable length and give plenty of room for a nice airbox to fit under the hood. The new software also says that ITBs are the best setup for hp and when I go to something with a plenum (like say adding an airbox) I need to shorten the runners a bit or the tuned rpm drops...so 9.5" with a "flat tunnel ram" intake which is the best flowing plenum design choice and results in a not really a doable runner length.
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2018_01_15 10_25 vs 16_75.JPG [ 166.46 KiB | Viewed 11938 times ]
Now in the older version DM-5 things were different. Around 18.5" stack gave what looks like about the same result as the 10.25 stack in the newer -6 version and a shorter 11" stack was smooth but down on power because while it is in tune at 9500 it really wanted to to make power up at 11k and with the headers tuned to match would crush the long stack at that rpm...that made sense to me because there is enough air and cam for this thing to pull to around 11k so 9k is really the cross-over from mid to high rpm...or so my theory went.
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2018_01_15 DM5 11 vs 18.5.JPG [ 207.78 KiB | Viewed 11938 times ]