Performance intake runner diameter

[redblockpowered]

What if... intake runner flaps.

 

[spock345]

What if... intake runner flaps.

Like a 4AGE intake? I forget how they implemented the variable intake on that one.

 

[redblockpowered]

I was picturing like an N52 BMW but that too.

 

[MikeSr.]

There was a guy, Ronnie Hillmersson, who had a 16v in an Opel who made a slide throttle with a sliding plate with holes sandwiched between two manifold plates and controlled by cable with spring loaded bell crank . I think he had ball bearings spring loaded that the plate ran on with enough gap for an idle bleed

 

[redblockpowered]

I was picturing like an N52 BMW but that too.

Basically - different runner lengths instead of runner areas. I think the 4AGE setup like covers half the runner or something.

 

[spock345]

Basically - different runner lengths instead of runner areas. I think the 4AGE setup like covers half the runner or something.

Reminds me of the B20 dual butterfly manifold.

 

[cwdodson88]

I’m going to say no thank you. I just want to stay simple, and mill something that flows well and is somewhat affordable.

 

[redblockpowered]

Please ignore me I just like having more buttons to push

 

[Stiggy Pop]

I'm not unhappy with the port DIAMETERS on a B230F but I wish the runners on the intake were about 2" shorter. This would be if I were building a performance engine.

Interesting because when I was putting my top end together with Erland Cox his critique of the Nathan manifold was the runners being too short. I believe I have measurements and volume calcs in my stale build thread. I did pull in a ported KLR intake from him but haven’t used it yet. I think Tate is working on doing that swap and pretty interested to see the comparison data.

 

[shoestring]

Interesting because when I was putting my top end together with Erland Cox his critique of the Nathan manifold was the runners being too short. I believe I have measurements and volume calcs in my stale build thread. I did pull in a ported KLR intake from him but haven’t used it yet. I think Tate is working on doing that swap and pretty interested to see the comparison data.

Give me all the data.

I guess I have to clarify that I'm looking at it from a naturally aspirated perspective, that can compromise some below 3500 or so. Other applications may ask for something different.

 

[cwdodson88]

It’s interesting that there doesn’t seem to be a lot of data available about boosted engines with runner length tuning. And from my experience it tends to come back to compressed density effects on waveform velocity, etc.

In my time with AM Racing, working with former design leads for Cosworth, Williams, and a few others. There was quite a bit of discussion about how traditional intake tuning can dramatically improve turbocharged engines ability to ingest more efficiently. And along those lines, culberro has pointed out that more frequent places where valve frequency effects are helpful, rather than one pointed spot within the rpm range, not only delivers a stable output curve, but typically can provide longer duration of peak power.

That’s where my thoughts are on it. Tuning for multiple waves across 6k of usable rpm(2k-8k) makes sense, but it’s not easily possible. Now on a 16k 2.4l flat plane v8, with usable revs from 6-16k it’s a bit easier to do.

 

[cwdodson88]

Interesting because when I was putting my top end together with Erland Cox his critique of the Nathan manifold was the runners being too short. I believe I have measurements and volume calcs in my stale build thread. I did pull in a ported KLR intake from him but haven’t used it yet. I think Tate is working on doing that swap and pretty interested to see the comparison data.

I think some of this is from large runner dia combined with short radii in the velocity stack.

 

[Stiggy Pop]

Give me all the data.

I guess I have to clarify that I'm looking at it from a naturally aspirated perspective, that can compromise some below 3500 or so. Other applications may ask for something different.

We had the NIW at overall volume of ~5,445cc and the volume of the runners at 138cc per or 552cc total. This is based on a set of external measurements and math so it’s approximate not a big science project. Could pull numbers from the KL piece sometime I suppose.

 

[Sjeng]

The 8V intake port is approximately 100mm or 4",
adding 4 inches (possibly a little more due to trumpets protruding in the plenum) gives about 8-9" total intake tract length.

Even the 4th harmonic will be at 7000+ rpm.

https://racehead.com.au/wp-content/uploads/2018/09/Wave-Pulse-RPM-Chart.jpg

Ofcourse the chart is a simplification (probably blairs intake length calculations, constant speed of sound), but they are ballpark figures for intake lengths.

It’s interesting that there doesn’t seem to be a lot of data available about boosted engines with runner length tuning. And from my experience it tends to come back to compressed density effects on waveform velocity, etc.

Speed of sound is not affected by air pressure.

Speed of sound - Wikipedia

en.wikipedia.org

However, it seems as if turbo intake runners are often shorter than pulse tuned NA runners/intakes.
So good question, does a turbo engine require different intake lengths than a NA engine?

If so, what is the mechanism behind this?
Speed of sound increases with temperature.
According to the formulas, the speed of sound in an ideal gas is proportional to the root of absolute temperature.
However I do not think that with a good turbo/IC setup the intake temperature increase would be that significant as to affect the tuned intake length.

Any opinions?


Edit - A temperature increase (higher speed of sound) would actually require an even longer runner instead of a shorter one.

 

[cwdodson88]

Speed of sound is not affected by air pressure.

Speed of sound - Wikipedia

en.wikipedia.org

However, it seems as if turbo intake runners are often shorter than pulse tuned NA runners/intakes.
So good question, does a turbo engine require different intake lengths than a NA engine?

If so, what is the mechanism behind this?
Speed of sound increases with temperature.
According to the formulas, the speed of sound in an ideal gas is proportional to the root of absolute temperature.
However I do not think that with a good turbo/IC setup the intake temperature increase would be that significant as to affect the tuned intake length.

Any opinions?


Edit - A temperature increase (higher speed of sound) would actually require an even longer runner instead of a shorter one.

While the speed of sound isn’t affected by air pressure, the theories that have been discussed contribute waveform velocity changes under pressure to the changes in fuel density within the air charge. Having more so to do with what else is in the air when it’s compressed.

Now, like you say here, temperature will also change things. Getting those injection events positioned in a way that they aid in both physical strength of wave, and add to the cooling effect of phase changes.

Thats could be something to consider in design changes.

 

[shoestring]

Now we're talking. Too bad we can't all take a year off and build and test a bunch of stuff to get a better idea of what the answer is. Sounds like a job for retirement.

Keeping in mind that until recently all I was concerned with was N/A applications, the 13.5" total runner length of the F intake and 530 head (9.5" and 4.5", roughly?) was about the previously mentioned 2" too long. I'd have to go back over the math but I was probably shooting for a peak tuning effect somewhere from 5850 to 6000 rpm. Obviously a suction engine is highly dependent on intake and exhaust tuning effects, but my understanding of them in a turbo engine is pretty poor. I could see an effort to minimize overall volume in the intact tract to reduce lag and therefore reduce the length of the runner. Yes, I realize that's small potatoes, but when it's part of a grander overall design effort then every part needs to be scrutinized and adapted as appropriate.

I'm gonna go look for a Holdener video on this and review.

 

[culberro]

While the speed of sound isn’t affected by air pressure, the theories that have been discussed contribute waveform velocity changes under pressure to the changes in fuel density within the air charge. Having more so to do with what else is in the air when it’s compressed.

Density and moisture content definitely have an impact on wave travel speed in air. Higher density and higher moisture equals faster wave speed.

At around 10k ft elevation the speed of sound is roughly 60-70% compared to sea level.

The more molecules the wave can travel through, the faster it will be.

How does density affect the speed of sound in air?

Answer (1 of 5): The speed of sound in a gas is determined by the speed of the molecules in that gas, which in turn is determined by the temperature and their molecular weights. @What is the effect of air pressure on the speed of sound in air?

www.quora.com

 

[Sjeng]

It would be good to differentiate in the cause of the density change.

If the composition changes (injecting fuel) this is the case, yes the speed of sound is affected. However in the case of a density change due to a pressure difference, speed of sound is not affected.

"In the Earth's atmosphere, the chief factor affecting the speed of sound is the temperature. For a given ideal gas with constant heat capacity and composition, the speed of sound is dependent solely upon temperature; see § Details below. In such an ideal case, the effects of decreased density and decreased pressure of altitude cancel each other out, save for the residual effect of temperature."

 

[shoestring]

Density and moisture content definitely have an impact on wave travel speed in air. Higher density and higher moisture equals faster wave speed.

At around 10k ft elevation the speed of sound is roughly 60-70% compared to sea level.

The more molecules the wave can travel through, the faster it will be.

So what you're telling me here is that I need to do MORE MATH to determine how much my effective runner length is going to change depending on how much boost I run, and therefore which camshaft I choose and what kind of cylinder head numbers I need to get the effect I'll need for the results I want? Forget it I quit.

 

[cwdodson88]

It would be good to differentiate in the cause of the density change.

If the composition changes (injecting fuel) this is the case, yes the speed of sound is affected. However in the case of a density change due to a pressure difference, speed of sound is not affected.

"In the Earth's atmosphere, the chief factor affecting the speed of sound is the temperature. For a given ideal gas with constant heat capacity and composition, the speed of sound is dependent solely upon temperature; see § Details below. In such an ideal case, the effects of decreased density and decreased pressure of altitude cancel each other out, save for the residual effect of temperature."

And it’s not just one, two or three variables that we have here. It’s the combinations that bring us to the intriguing phenomenon that make up the discussion.

Throw in water meth, rainy days, or any other combination and it’s all over the place.