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MrDangerUS

Variable Volume Intake Manifold and Tuning

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I was always wandering what are 910 turbo intake and plenum parameters.

Do you have any design parameters like frequencies or IM dimensions?

Where can I get stock dynoTQ/rpm and HP/rpm curves?

Has anyone tried any version of VVIM on Lotus?

Good example of VVIM:

The various valves in the 458 power-plant show the proficiency of (Ferrari) design in figuring out how to command and control the resonances. In the 458 version there are 3 valves. The center valve couples the two plenum air boxes (L&R) to broaden the TQ peak downward on the RPM scale. The other 2, located on the ends, provide even longer 'path' for the resonating charge, enhancing TQ even lower in the RPM scale. The air boxes do not 'create' power like the headers and velocity stacks, but they go a long way in broadening the power band so the engine is more tractable and user friendly at places in the RPM bands far from peak TQ & HP.

Edited by MrDangerUS

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I owe everybody an update on VVIM (slow) development.

Empirical results prove contrary to the popular misconception that forced induction negates any need or benefit of acoustical IM tuning. For a proof see: TQ curve on Dave’s (“Changes”) dyno which is a result of IM plenum volume optimization.

I took a summer “off’, but did not stop thinking about VVIM.

I am leaning toward a cylindrical shape for my variable, multi-chamber Intake Manifold, fitted with a mechanism enabling to adjust Helmholtz resonator volume in function of the rpm & MAP. Objective is to improve cylinder fill coefficient+ achieve flat “stretched” torque curve trough the wide rpm range. So far, I was exploring a variety of "barrel TB" gate mechanisms to connect main plenum with aux resonator chamber. Gate would be actuated by a stepper motor activated by a vacuum switch. Due to space limitations, I am also considering a “tube-in-tube” resonator chamber with integral door/gate. Prototype construction is planned for "after the Summer season", unless unexpected stimulus appear.

Edited by MrDangerUS

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A turbocharged engine still benefits from a tuned intake. After all, it's an engine operating under pressure. However, it does give you the opportunity to wind up the boost instead which is a lot easier.

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What he said - Turn the boost up instead.

All you are doing is creating a little bit of boost by timing the resonances on the chamber to coincide with the valves so you get a little peak pressure spike as the valve opens. However, this is a tiny effect when there is boost involved and it's much less effort to get this effect by winding up the boost by 0.1 bar. On an N/A intake tuning is the only way you have of gaining 'boost' pressure.

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It is not about the boost,

but it is very much about the engine volumetric efficiency by increasing the cylinder filling index in aspect of the IM plenum volume ratio (V=Vplenum/Vcylinder). Empirical testing confirms that the higher V values add second resonance peak above 4500rpm, that’s why TQ curve after adding the 1” spacer on Dave’s car is so "flat" and “stretched”.

(VVIM) variable volume manifold with a secondary (Vr2=180 cu in) resonator chamber coupled with primary resonator (Vr1=196 cu in, existing expanded plenum) seems feasible. I found pertinent information in Dr. Bertoluzzi's dissertation.

See chapter titled “Analysis of Intake Manifolds w/Sidebranch Resonators":

http://www.dinamoto.it/dinamoto/7_MDRG_papers/_MDRG%20Papers%20in%20PDF%20format/1998_03%20The%20effect%20of%20tunable%20resonators%20SAE.pdf

Since there are obvious packaging limitations on our cars, I decided to entertain an idea of adding a second (Vr2) chamber above the stock plenum, between the diffuser and the engine compartment cover. 3”H x4” D x16” long, rectangular AL tube packages well in the space available.

There is a 3.7" clearance between the top of the OE plenum box and the underside of the engine bay cover. On-demand coupling of two resonator volumes has to be executed with a solenoid air valve, or a butterfly valve located at the rear end of the current plenum box, or directly between two chambers (in up-down direction). It may be activated by a simple logic switch triggered by TPS switch at 3250 rpm.

http://www.planetsoarer.com/resonator/ResonatorsAcoustic.htm

The objective is to preserve the first peak, which requires lower plenum volume and add an advantage of the higher volume above 3500 rpm.

Initially I thought that the Saab/Volvo IAC solenoid valve may work, but diameter of the gate is too small. I need a rather large connecting tube diam, 2"-2.5” dia, to maximize the influence of Ar aux resonator chamber. I may have to make my own "sliding plate" valve.

Edited by MrDangerUS

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forced induction negates any need or benefit

and the NA region is too small a span to affect

 

1. Engine operates as a N/A pump untill onset of boost and certainly benefits from the first VE peak.

2. Higher MAP values do not negate laws of thermo-dynamics/fluid dynamics, just change the readings.

See: chapter 4,5 of "Design Techniques for Engine Manifolds: Wave Action Methods for Ic Engines" by D. E. Winterbone, Richard J. Pearson, ISBN-10: 0768004829

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Brake and indicated engine performance characteristics, coefficient of variation in indicated mean effective pressure (COVimep) as an indicator for cyclic variability, pulsating flow pressure in the intake manifold runner, and CO, CO2 and HC emissions were taken into consideration to evaluate the effects of different plenum volumes.

 

The results of an empirical study showed that the variation in the plenum volume causes an improvement on the engine performance and the pollutant emissions.

Volume 48, Issue 3, March 2007, Pages 961–966

 

The brake torque and related performance characteristics improved pronouncedly about between 1700 and 2600 rpm by increasing plenum volume.

 

First mock-up of the auxiliary resonator on my car.

post-11050-0-75028700-1431980543.jpg

post-11050-0-86873900-1431980593.jpg

Edited by MrDangerUS

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Have you looked up the system used on the gen 2 MR2's? They have a variable length runner setup.

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Variable tuned telescoping resonator
US 6698390 B1
 
Interesting concept, but difficult to seal under the boost. More applicable to the N/A induction.
Edited by MrDangerUS

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My development is not VLI, but VVI.

 

VLI found an application for N/A engine IM-s. Beside this, there is no room to engineer VLI for our engine.

 

VVI is more feasible for turbocharged engines.

the gist of it is here:

  http://planetsoarer.com/resonator/ResonatorsAcoustic.htm

 

and here

http://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleid=1425888

 

Chart below shows the same test engine equipped with different displacement plenums.

post-11050-0-64063100-1432146466.jpeg

Edited by MrDangerUS

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Here is the diagram for 1.6 L N/A 4-cylinder engine,

page 171  of Desmond Winterbone's book Design Techniques for Engine Manifolds, ISBN 186058179x

 

Obviously, larger plenum is better but too large may hamper the effort.

 

For turbocharged engines, this applies  before onset of the boost.

post-11050-0-23023400-1434035989.jpg

Edited by MrDangerUS

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Ha!

Finally!

My persistence was rewarded!

I have found what I was looking for!  A vacuum actuated VDI valve used on RX8 engines.

rotary_intake_manifold RX8.jpg

RX8 lower intake manifold SSV valve.jpg

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Little bit of science  in support of VVIM concept. Larger plenum volume improves relative air ratio in lower rpm range before the onset of

boost

 

 

Edited by MrDangerUS

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Interesting photo 

Regarding the plenum volume (achievable via spacer thickness), there's an interesting photo on page 48 of Corky Bell's book "Maximum Boost", that shows a plenum spacer on  Esprit engine, which seems to be about 3,5"+ thick.

That spacer is huuuge! I'd say, it is thicker than the cover (3.5" OD), so it must be 4" thick practically doubling the plenum volume!

Corky's book does not mention the spacer at all. This makes me think that he had used someone's else picture. I'm wondering whose car it might have been? It was a long time ago, because this book was first printed in 1997. ISBN-10: 0837601606  or ISBN-13: 978-0837601601

 

IMG_4757.jpg

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Spacer dimensions here look to be driven by the deletion of the throttle bodies, I wonder how long the stacks are inside that box?

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7 hours ago, snowrx said:

Spacer dimensions here look to be driven by the deletion of the throttle bodies, I wonder how long the stacks are inside that box?

Loren Stump's design extends ~25mm, but he kept OE individual runners/ butterflies.

Mine are extended ~23/4 above the stock plenum runner plate.

IMG_3667.JPG

PLENUM 2.JPG

Velocity stack 45mm ID.JPG

 

 

 

PLENUM 2.JPG

 

Velocity stack 45mm ID.JPG

IMG_3667.JPG

Edited by MrDangerUS

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On 09/02/2019 at 12:22, snowrx said:

 I wonder how long the stacks are inside that box?

If you're trying to determine an optimal runner length, this handy calculator beats all the charts   http://www.bgsoflex.com/intakeln.html

In order to benefit from the 3-rd harmonic, it seems the runner length should be 14", as measured from the valve to the rim of the velocity stack.

Edited by MrDangerUS

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I seem to remember when I first took the carbs off mine to switch to injection, the ram pipes (or whatever they're referred to as) were so long they left hardly any gap between the tops of them and the plenum chamber housing. I was surprised any air managed to get in at all before boost came in.

On the injection plenum, as on the photo above, they are just a lip more than longer pipes.

I guess injection doesn't benefit as much from having pipes as carbs do. This is way out of my league though when it comes to airflow and stuff. :)

Edited by Glyn Harper

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