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I don’t understand what the benefit of eliminating intake runner multi-tuning, in favor of a single un-tuned intake, is supposed to be. Help?
 

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I don’t understand what the benefit of eliminating intake runner multi-tuning, in favor of a single un-tuned intake, is supposed to be. Help?
Here are some resources for you




 

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I read the “summary” section of the first link. It’s sort of like an abstract. It says that it’s beneficial to engine output to be able to tune intake manifold geometry vs engine rpm, which I already knew. IOW, what Honda has done on the Ridgeline intake manifold is good for output.

So at the risk of repeating myself: I don’t immediately see the benefit of using this mod to eliminate the variable intake manifold geometry that Honda has spent a lot of engineering time on.
 

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In a lot of engines, the shape of the cylinder head ports and piston head, create a swirling effect in the combustion chamber, this 'compacts' more air in the chamber during the intake stroke.
During low engine speed, the airspeed is maximized by utilizing the longer channels (with smaller diameter) and due to the venturi effect you are able to 'speed up' the air through them improving engine torque in the lower rpms. At higher engine speed, the secondaries open to create a more 'short' pathway for high velocity air to enter the cylinders for maximum power output.

Also another design objective with the 'dual stage' manifolds is taking advantage of pressure waves within the plenum. The air flow through the throttle body is 'free flowing ' but the second stage of this is the intake valves; they open and close during an engine's revolution. When they close, and the air is still moving, it hits the back of the valves and bounces back in a pressure wave form. This wave is a sound wave, and thus travels at the speed of sound, clashes with the incoming air and slows it down. This is a lose-lose situation as the engine is already in its lower volumetric efficiency operation. So turning the intake runners to capture the returning waves to 'force' the incoming air into the cylinders is key. This effect results in what we call Dynamic Pressure. The free flowing air past the TB has a pressure that we reference as 'static pressure'. The dynamic pressure is proportional (usually) to the square of the inlet air speed so by making the runners narrow or longer, you increase the pressure and thus increase the air speed.

So yes, on a bone stock (no internal engine modification), any un-calculated plenum modifications will have drastic effects in power production. From the above basic explanation, you can see why eliminating the longer runners will negatively affect power production.

What Will did was eliminate the longer runners completely, but also installed an 80mm throttle body which flows more than stock. I am not sure how he drives the truck (engine speed), and thus cannot be 100% compared to our stock engines with stock TB. It looks like he also deleted the EGR system and unless he gives us a full breakdown on how these systems were defeated and how that translates to the ECU looking at these parameters (though coding and emulation were mentioned) to adjust fueling and timing, it is hard to tell where the increased fuel economy and 'realized' power comes from. You will see the Holley EFI manifolds of the J-series block (J32 & J35) is on race motors that are full NA or forced induction; though many boosted guys run this manifold as the air velocity negates the need for precision plenum tuning.

Food for Thought:
  • In our J35 engines, the piston speed at 4000RPM is 40.68 ft/second (27.74mph). At 5750 (max power rpm) the piston speed is 58.48ft/s (39.87mph).
  • So at 4000RPM, the piston travels from the BTC to TDC in 0.0075 seconds (7.5 millisecond). At 5750rpm, it does that in 0.0052 seconds (5.2 millisecond).
  • Imagine the monumental task of designing optimized systems in fueling and ignition timing, when we are working with such low travel-time constraints.
  • A great flowing NA head will be also great for boosted application. However, a great flowing intake manifold under boost, will not flow that great for NA.
 

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Thanks. I understand both the theory and at least most of the math involved just fine. That's why I keep asking the questions. I have a very good idea what the outcome of a direct comparison will be, in terms of what is given in exchange for what is gotten from the intake manifold change. Now, if this is really about a bunch of internal mods, that's different, but I think I still have a very good idea of what the basic trade will be.
 

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Discussion Starter #27
Thanks. I understand both the theory and at least most of the math involved just fine. That's why I keep asking the questions. I have a very good idea what the outcome of a direct comparison will be, in terms of what is given in exchange for what is gotten from the intake manifold change. Now, if this is really about a bunch of internal mods, that's different, but I think I still have a very good idea of what the basic trade will be.
No I still have a fully functioning EGR to keep the nitrogen in check and combustion chamber temperature lower while cruising as the EGR was intended for


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No I still have a fully functioning EGR to keep the nitrogen in check and combustion chamber temperature lower while cruising as the EGR was intended for


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I will keep everyone in the loop , I work 80 hours a week so it’s hard to play with the truck , I am also currently trying to see how the setup handles different fuel octanes to see what the ECU likes as far as in my area that I drive


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Something else I came across.............. Just when you think this Holley EFI is the one of the expensive units than PrankParts $1400 manifold, I came across ASP's $2650 carbon fiber J series manifold. Looks real pretty and takes a 105mm TB. It really looks like an Holley EFI mold.

 
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