This video came through my youtube feed, it's a guy building an intake system for a miata which appears to work on the same concept as the tpi. He's added venturis between the runners to supposedly shorten the effective runner length, but maintain the harmonic effect. In the video he describes what sounds like a possible resolution to the power drop off at the top of the rpm band, and maybe adjust-ability depending on where the venturi is placed along the runner. If you have 15 minutes please take a look, or maybe just long enough to see that it's BS, and give an opinion.
Edit: You can probably skip to like 3 min for the goods. The first part is kinda long winded.

 

Ford tried that as well. In addition to the long runners of a stock TPI, they also have a relatively small cross section. While that helps maintain velocity and maximizes the pulse wave charging effect, it doesn't do much to support higher flows. Thus, gating the port runners could make sense to increase the resonant RPM band, the flow required to make power at higher RPM is not very well supported.

The factory solution to that was the "neutral" port style of the LT1 and a different cam grind. That carried over to the Gen III and later engines with only a slight increase in runner length (nowhere near the TPI design), and seems to work fairly well with a slightly lower torque at the lower RPM ranges.

 

Thanks for looking, and explanation.

 

My 2004 BMW 545 has a variable intake, it is said to be the first of its kind ever mass produced. It basically changes the lengths of the runner based on lots of inputs, including RPMs. The car is so fun to drive, the torque is unending, Pits you back in your seat all the way up to the 6500 shift point and maintains it during the shift to the next gear, the torque curve is seamless. The intake size is simply a beast, but it fits in a large car like an E60. I have a 2009 BMW M6 has is a V10 with another 150 horsepower over my 545, it is scary to drive, but I have to say, the 545 is funner to drive, simply because of the torque curve. My 1990 Formula on the other hand, is the funnest of them all !

 

If you really want a thorough explanation I suggest you post on www.firebirdnation.com and ask a guy with the screen name injuneer. I guarantee you'll get a lot of explanation.......probably more than you want. That gentleman is a wizard!

How far south of Dallas are you, and are you a member of NTTGA on FB?

 

Almost 15 yeas before that "first" Fiat and Honda were doing variable intakes, in 1989. Just about everyone else tried it well before 2004. Early 1990s Ford (V-6 SHO), GM (LT5), and a host of others from Audi to Volvo had either staged or variable intakes. These were in general production, not just experimental engines. Experimental versions of variable intakes go back to the 1930s.

The hill-Germans were the first to implement in their way, however, so their marketing wasn't a complete lie.

 

I left out a key word - "continuously variable" if you look inside the N62 intake, a pivoting mechanism that is operated by an electric motor. The SHO for example, seems to turn on either the short side, or the long side. There are simply 2 lengths, but not something that adjusts as the RPM's fluctuate. https://link.springer.com/article/10.1007/BF03227525

 

This thread reminds me of the 1990-'95 Corvette ZR1 engine that used a 2-runner/2 injector-per cylinder intake system. Different in concept from OP's setup, but still unique.

 

30 or so miles, outside of Waxahachie, and no I don't do any social media. but I'll check that site, thanks.

 

Ok so now that guy has changed it up, and added solenoids and a dual runner setup- one long and one short per cylinder. If anyone is still interested take a look. Is this looking promising?
3d printing different runner sets in plastic for easy experimentation sounds too good to be true too, is that feasible on top of a 350 with current filaments?
EDIT: If you guys already described exactly what he's doing above and I didn't pick up on it I apologize.