Mongo

While this would be great, this would take tens to hundreds of hours of engineering a variable intake manifold. I believe Greg's current setup is very well suited and designed for our application. Somewhere in here is a dynosheet showing a 50HP gain on (I think) a GTS. Keep in mind this design does not incorporate any type of variable length runner.

Mongo

I just had a random thought. If there is a new iteration of an intake manifold, can we please for the love of God have the ISV located somewhere we don't have to perform major surgery to replace it?

GregBBRD

The higher the rpm potential of a given engine, the more beneficial variable length intake systems become. The greatest increase in cylinder filling potential is associated with the second harmonic (intake pulse), although the third harmonic is only slightly less beneficial. Taking advantage of both pulses (obviously at different rpms) is a very beneficial thing to achieve, when designing an intake system.

Imo000

Yamaha, not Kawasaki.

Porsche did have a variable (two length) V6 engine that was originally developed for the Boxter and then they decided to sell the engine to Ford and use a smaller version of the M96 engine that eventually went into the 996. Mainly the Ford Contour/Mercury Mistique V6s ended up with these engines and some other Ford models too. With a manual transmission the little 2.5L V6s were surprisingly powerful. I had one in a Contour.

ptuomov

With the caveat that I can't read dead people's minds and thus my opinions on this issue are just opinions, I think the designers of the S4 manifold were very proud of their achievement. This is because they were engineers, they had requirements, and engineers take pride in meeting requirements. I'm guessing that the engineers had the following main requirements: cost, hood line clearance, maintenance access to fuel rail and spark plugs, torque number at some low rpm that would allow them to use the same intake for manual and automatic cars, and peak power number below a given redline. I think they met the requirements, celebrated, and were celebrated. It's a great solution that leverages the patented S3 manifold geometry.

The engineers had the access to a single plane long runner manifold already, but it didn't meet these requirements. I'm talking about the cast FIA Group B S3 manifold. I'm guessing that the Group B manifold didn't meet their low rpm torque requirements, which in turn were driven by the requirement to use the same intake for automatic and manual cars.

I believe that for a manual transmission only 5.0l car, the single plane Group B intake would've been cheaper to make and overall probably a bit better. But that I believe wasn't allowed by the requirements.

For a hot rodded normally aspirated manual 928, of course headers, high overlap cams, high compression, and long straight runner single plane intake (preferably with ITBs) is going to result in a more powerful, faster, and sportier car than anything that the factory contemplated in the 1980's.

Imo000

The S4 manifild was pattented?

Mongo

What does the Group B intake look like?

ptuomov

S3 was and S4 is covered by that but may also have some independent patents.