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Yes and then some! Extremely helpful post...! Wicked video of the run down the strip...
If you think about measurement of power and volumetic efficiency, the peak torque of the engine is when it is the most efficient - it's the maximum mechanical output. Remember that horsepower is a mathematical figure; Torque is a unit of work. The more work (output) that is done at a lower RPM (fuel input), the more efficient the engine is.
On the manifold volume, the kegger (which I cut runners down on the 2001 years back) or any manifold with long runners, the greater the plenum volume, the better filling of the cylinder on the intake stroke...?
tossing this in here before I loose this thought... if the added volume to the plenum (from the 1 1/2" tube) is reduced, torque should go up in the rpms. If the pvc cylinder had a piston in it to adjust the volume against the vacuum signal from the manifold then wouldnt it start to adjust on the fly? The thinking is to get the torque peak to move up in rpms under acceleration when the vacuum signal is lower with the goal being to move the torque peak on the fly.
this mod (pic below) gave the ram (diesel) a good bump in mid range (for a diesel ~2500 rpms) power while keeping the bottom end torque high (motor is in boost @ ~800-900 rpms). It, along with some other mods, allowed me to get mpg's up in to the 22~24 mpg range (7000# truck optimized to death lol). That mod opens the boost controlled exhaust cutout valve (3.5") at approx 6 psi for the reduced restriction in the air box. Testing on the Dak with the inlet piece to the air box mirrored what I saw on the Ram, lower restriction = better upper end (2500 & up in my case) performance. Doing that mod to the dak air box should give me the same results, or similar.
So for day 3 with the pvc pipe mod in place, fuel gauge vs miles driven is pretty positive. @ 100 miles now on the tank & the gauge is at the 7/8 mark. No where in this trucks history with me has it ever been that good. Previously I'd been seeing 70ish miles at that point in the tank. Pretty happy about that and cant wait to get the turning vanes back in the intake tube... (Wednesday afternoon), recall that the vanes got me a ~1.4-1.7 mpg bump. Once that is done I will see what could be done on the air box with the limited space it has.
So my dakota has a similar boost activated cutout called a LoudValve.
As far as dynamically adjusting plenum volume/runner length...it's been done several times. Some manufacturers call it an Intake Runner Valve. Mopar calls it a Short Runner Valve.
Understood on the variable runners being implemented... I'd seen it on several cars in the past. The air box mod, that was done on the old R53 mini cooper JCW models back in ~2004-2006. Found that after having already done the airbox mod with the V3.0 version on the Ram.
The overall goal with doing that mod (pvc pipe for IM expansion) seems to have worked, mpg's on this tank are up into the 19's from 18's... so about a 1 mpg bump guestimating fuel used vs fuel gauge position. Will be filling up today for an accurate number. I will say it has been tough to keep the foot out of it for a good comparison. Today, the turning vane goes back in for the next setup to compare against. Knowing how it affected performance before the above mod, cant wait... (like a child @ christmas lol)
Under consideration is a ball valve to disable the add on and see how the restricted flow in & out of the mod effects performance. If a piston setup of some kind could be fabbed up to control the volume in the pipe, I think that would be ideal. The current thinking is to somehow use the last vacuum port off the IM on the other end of the tube. Not sure yet how that would be done with both being equal... the goal would be to get the best of both worlds, upper end performance when needed and bottom end torque for daily driving.
Wondering if I could do something similar with the exhaust (tune it & the IM tweeks for the most power in the area's I want it...
The thinking is to get a custom y-pipe to eliminate the crimped sections and have it bolt to the cat-back section with the intent to adjust the flow at that point. I did this years back on the 2001 Ram I had to bring back some low end torque lost after a 3" exhaust upgrade.
Once the exhaust is set then I'd go back and tweek the intake again to get the torque peak where I want it.
