I'm posting this here because it applies to every generation of motor, and because I figured that this section may offer unique perspective on the topic, such as if it's even necessary with forced induction engines.

Anyways, I'm just scratching the surface of the whole resonance tuning thing, and have a question or two that happen to be quite applicable in this section.

For a street/strip car, weekend warrior, whatever... Just not max effort, dedicated track car... Would it behoove you to put the best intake and exhaust optimized for 2000-3000rpms where you aren't in boost?

Resonance tuning really doesn't apply to a boosted motor, or at least not in the same sense as it does in a naturally aspirated application. So, wouldn't it be best to choose the intake and exhaust that is most efficient for your particular engine in its daily driver operating range?

On a vehicle that may see boost 20% of the time it is running, it seems silly to set up the intake and exhaust for such a small fraction of how it will be used.

Meanwhile, for the other 80% of your engine's "life", idle-to-3000rpms, it's breathing through a less than optimal intake/exhaust for that operating range.

Given that resonance tuning is designed to maximize naturally aspirated efficiency, it makes sense (to me) that you would plan to capitalize on this in the naturally aspirated section of your powerband, where such things matter.

Your boost at redline will still be there. You don't need a special "capitalize on boost at redline" intake on the car that spends 80% of its time running, below 3k in traffic or at the Starbucks drive through.

I know it's difficult, at best, to optimize the exhaust if your power adder of choice is a turbo. And likewise, equally difficult to optimize the intake on a positive displacement blower motor.

But, for the sake of this discussion, we will say that a centrifugal blower is being used on a daily driver vehicle, light to light and freeway roll racing, random track day or autocross.

Custom cam set up for the centri blower, boost is there @ 3k, full boost by 3500, cam carries out to 7000rpms. Just for the sake of discussion.

So, in this example, do you adjust your intake runner length for best resonance tuning in the 2000-3000rpm range for the most efficient naturally aspirated breathing possible before boost?

Do you likewise tune your exhaust primary length and diameter for best resonance scavenging during the operating range the vehicle will see the majority of its time running?

 

You use a stock truck intake for the torque and power you need, because blowing your money on a custom intake isnt going to make you faster than the guy who turns boost up 1 or 2 more PSI to compensate.

Exhaust primary length matters even less than intake runner length on a boosted setup. There is no scavenging effect in boost unless you achieve a 1:1 pressure ratio.

 

Oh, by no means am I saying that tuning the intake and exhaust for optimum naturally aspirated efficiency before boost will make you faster than anyone.

From a driveability standpoint, or efficiency standpoint, would it make sense? You spend 80% of your time driving idle-to-3000rpms. Your engine is naturally aspirated, not in boost, during this time (80% of the time your engine spends running). So, why not capitalize on resonance tuning for that part of the powerband? If there are ways to increase your VE, why not apply those tricks to the part of the powerband that it actually matters, which also just so happens to be where the engine is running for 80% of its "life".

Once boost kicks in, who cares about resonance tuning? Boost takes care of itself. An intake with runners optimized for your engine's displacement at 2500rpms isn't going to be a hindrance in any way once boost occurs. Same with a set of headers with primaries optimized for your engine's displacement at 2500rpms. They will flow better than stock manifolds, and people boost stock exhaust vehicles all the time.

This particular question is directed towards boosted street driven vehicles. This doesn't apply to max power builds, or racecar engines.

It just seems silly to optimize your whole engine for boost that it may see 20% of the time.

 

And on that same note, why optimise the low end unless you will actually use large throttle openings at those lower loads where you will really use any airflow/torque improvements ?

But what you're saying does make sense.

Boost at the top end will overcome a lot of things, whereas off boost....you're totally reliant on the intake airflow so it does make sense to optimise this, perhaps more so with turbos than any of the superchargers.

And a lot of the big intakes etc dont really seem to shine until over 6k, so for many who dont rev say beyond 6500-7000rpm...they almost seem wasted too.