VVIM Plenum Volume in turbocharged 4 cyl engine

[MRDAGERUS]

Hello,

I'm prototyping a variable volume(NOT variable runner length) intake plenum for t 2.2L 4-cyl turbocharged engine and have a few questions.

Analyzing Italia 458 IM design, one can notice 3 various valves showing the proficiency of engine designer in figuring out how to command and control the resonances. 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 stronger coupling 'path' for the resonating charge, enhancing TQ even lower in the RPM scale. The defined volume air boxes, when connected/coupled, broaden the power band so the engine is more tractable at the lower(?) RPM band far from peak TQ & HP.

Although there are several research papers on N/A engine VE increase whilst the plenum volume is increased, I could not find too many in regards to super/turbo charged engines. Could you give me any pointers?

Surprisingly, I have even encounter an opinion, that "forced induction negates any need or benefit and the NA region has too small a span to affect".
IMO, turbocharged engine still benefits from a tuned intake. After all, it's the same engine/principles, but operating under pressure. Tuned IM does give the engine an opportunity to wind up the boost more effectively.

Among the other, I found papers which inspired me to proceed with this project
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

Any thoughts would be appreciated.

Thank you.

Mater artium necessitas

 

[BrianPetersen]

While the same tuning principles apply regardless of the intake manifold pressure, if you have forced induction it's easier to just bump up the boost pressure a little bit if it's needed to achieve your performance objectives. Keep in mind that mass-production engines aren't tuned to get every last bit of possible power output in (generally) one narrow RPM range.

Additional plenum volume in a turbocharged application has disadvantages in terms of response time, particularly if the throttle is upstream of that plenum. A small-volume manifold without tuned-length runners (i.e. too short) and a turbo set to make just a wee bit more boost pressure, may end up being the better overall package when you take into account operating at engine RPM outside of the tuned range, throttle response, etc.

 

[BrianPetersen]

The other thing is that the cam timing that works better in the turbocharged application (i.e. mild) may not lend itself to having intake resonance ram tuning accomplish much.

A common OEM approach is to use mild low-end-torque-oriented cam timing in conjunction with a fairly small turbo. The engine itself has good response off the bottom, off idle, and the small, light turbo spins up quickly and takes over. This is absolutely NOT a recipe for maximum top end power ... but it is a recipe for an engine that drives nicely day-to-day and has a friendly low-end-and-midrange-oriented torque curve.

Tuning the cam timing and the intake manifold and the turbo all for maximum top end power is a recipe for what I call a dyno queen: Big horsepower on the dynamometer but it's a dog off the bottom and pretty much sucks for day-to-day operation. If you are building the car for something that specifically wants top end power and the mid-range doesn't matter then perhaps it will work.