Budget Intake Manifold/TB Options

[dsm-onster]

If you move to langley, I will be about 1 hour from you .

We disagree on whether there is pulse tuning at 8000 rpms or whatever rpms on a short runner manifold. I think there still is, though its going to be weaker in the shorter runner manifold than the longer runner manifold. My point is with the long runner manifold you won't make it to 8000 rpms without volumetric efficiency dropping off the cliff. VE is a combination of ALL tuning phenomenon, both positive and negative. At the end of the day its VE that counts, not the pulse "tuned" rpm.

9000rpms for the 3rd harmonic. Even if there's a curved increase beginning 1000rpms earler to peak tuned runner returns, then a typical setup will only see a percentage of the 3rd harmonic assisitance for, what, 500rpms? Most with SMIMs don't need to rev to over 8500rpms to get the results they want. Even mid 10s. . . Something else is helping. Reducing the scrubbing losses are not apparently the benefit, because of the use of more bends in the ic piping makes minimal to no difference. Nor does resonance since a weak harmonic would be in play and only a portion of that would be seen, if it functions as you're stating.

VE is the sum of the results, yes. That I can agree with. I think the other differences are not ranked as high on the scale with you than it should. For example,radiused entry: that one difference can account for a 16% increase in flow alone. I'll email you the .pdf discussion by Gordon P. Blair, Senior Associate, Prof Blair & Associates and
W. Melvin Cahoon, Senior Engineer-Specialist, Volvo Penta of the Americas, on the subject; along with the paper by Michael Patton, hired by GM to solve the duramax overheating issue.

As for being an "on-off" switch. A tunned intake manifold has always had the negative side effect of being "on-off". It "hits" like a 16g. My graphs plot runner length, a MINISCULE variation moves the pressure peak from the valve to up the runner the wave is short and peaky: very exponential. A tuning fork and brass helmholtz resonator shows this effect. This is an exact science. I've driven a porsche 944 n/t. BIG on-off switch at 6.5K. The runners are tuned for a second harmonic at that point. The motor peaks out very accutely.

The typical 6" runner has a 4th harmonic at about 6750. . . But what is the signal strength of the 4th harmonic?

. . . I think were at the point in the conversation that only comparison results will help any more .

 

[pboglio]

Your right, depending on the design an intake manifold or header could cause the car to come on in a narrow band. However there are designs that spread that effect out over a much wider rpm band, even allowing an obvious double tuned peak. And isn't this what your trying to achieve in the first place, a tuned intake manifold with a wide torque band?

Agreed, time to get down to business and start the design and build phase and just see how it works

 

[deflator]

Agreed, time to get down to business and start the design and build phase and just see how it works

Sweet. Anyone have any noob-oriented articles on resonance and intake design so I can figure out where this discussion went

 

[pboglio]

Sweet. Anyone have any noob-oriented articles on resonance and intake design so I can figure out where this discussion went

Desktop Dynos by Larry Atherton is a good read. Its a companion for the "Desktop Dyno" software but it explains the theory decently without putting you to sleep. Its great, has alot of pictures of all sorts of intake manifold designs, I like pictures Goes into header design theory but nothing that'll bore you to death. Good condensed material though still very technical.

A must read is "Scientific Design of Exhaust & Intake Systems" by Smith & Morrison. I warn you on this one, you'll read it, put it down, then promptly fall asleep. You really have to keep going back to it cause the wealth of information and history is phenomenol. It is dry reading but the volume of experimental data, testing, dyno graphs for intake manifold and header designs is staggering. It was first published in 1962.

"Internal Combustion Engine Fundamentals" by Heywood is a fabulous book. It is so technical it would put me to sleep. But for a hot rodder searching for secrets on everything from turbocharger design, engine design, combustion chamber design it is a bible for automotive engineering. What is great about it is the references sited, which means you can access the SAE papers online to get even greater in depth technical information.

Here is a primer on Helmholtz theory and application:

 

[turbotalon1g]

Iroc g on here is doing testing of SMIM.
Check the link for more info on the ones he has tested and is receiving to be tested, might be a chance to test out these budget manifolds.

SMIM Showdown! Lets figure this out once and for all! - MitsuStyle

 

[dsm-onster]

Testing a SMIM with constant flow from a flowbench is showing a very narrow part of the picture. Intake valves open and close, and this changes the characteristics of the aircharge GREATLY from what a flowbench outputs. You need to swap intake manifolds on the same setup and hit the same track every time. Use a maf that outputs volume flow like a stock 2g maf to do away with the differences of baro and ambient temp from day to day. All that testing will be meaningless for an ottocycle-type engine.

 

[DSMunknown]

^ I would love to do that sort of testing, but I don't have an extra 2G head to work with.

 

[Street Surgeon]

For $440 to gain near nothing, thats not a budget intake manifold.

I like how for 10.00 more you can get a JMFab manifold