Tony

Jerry Feather

This was a long time ago, but I still wonder why you think so; probably because I don't really understand much about the S4 Flappy in any case. My loosely related intake project is also going to be absent any kind of Flappy, and I am using the S4 dual outlet TB. Just curious.

dr bob

That was a tongue-in-cheek comment, hopefully evidenced by the ellipses and the smiley.


For the lower-displacement engines (5L), using a binary resonance-switch like the factory flappy is a simple alternative to dynamic intake valve timing. The V6 in my Honda DD has some of each, 30 calendar but 4 brazzilion technology years later. Take a look at the intake and cam/valve technology in a new Panamera for example. Would a "new" 928 intake benefit from a variable intake diverter along with VVT technology? Um, yes?

GregBBRD

Pretty sure that Bob was joking when he posted this.

However, virtually all intake systems on naturally aspirated engines can benefit from runner length changes, as the engine runs at various rpms. Many (most?) manufacturers are now building manifolds with methods to increase/decrease runner lengths at various rpms to optimize engine efficiency and performance.

hacker-pschorr

This Audi intake has been around for quite a while, three stage intake manifold on their V8's. These engine also have oil controlled variable camshafts:

ptuomov

This was all the rage for about a decade or two. However, I think that over the last decade or so the variable geometry intakes have gone out of style. It has been replaced with highly flexible variable valve timing systems. In a sense, the variable geometry intake and variable valve timing are different solutions to the same problem. Each of them can help with the problem. Importantly, if you have one of them that is really well designed, the other is usually not worth the cost. For example, BMW now has variable valve timing and lift systems that I'd expect to make variable geometry intake a relic. Combine that with almost all new high-end engines going turbo, the variable geometry intake era is basically over.

This doesn't mean that variable geometry intake wouldn't be nice to have in a 928. It would, as we don't have variable valve timing system. And we do have it, in the S4 and later intake manifold.

GregBBRD

Agreed that variable cam timing makes runner length changes almost moot. And turbo charged engines make variable runner lengths just extra weight.

However, this thread is about 928's.....30 (plus) year old engine designs.

The 928 5.0 and 5.4 engines engines were far, far from being optimized in the form that was delivered. The delta in runner length and individual cylinder filling capability is extremely high. I understand that they were trying to "package" many things in a fairly small area....which is part of what has made building a better intake so time consuming. While I can (and have) cobbled up prototypes for testing, optimizing each little detail has been a real challenge.

Personally, on the stock intake, I consider the flappy in the intake to be more of a "patch" than anything else....I think the engineers were sitting around asking: "What can we possibly do to help this crazy intake design function better?"

Mongo

And what about GM? Do their engines incorporate variable runner intakes? I think Gen IV engines start to show more advanced engineering such as varied cam timing but I think they never explored the variable runner route.

V2Rocket

would be cool to see a newly-fabricated "S3-style pipe organ" intake optimized for the S4 engine..what that might do.

they tune via "cubic inch adjustments"...
"how do we get more torque into this Silverado?"
'buy the 5.3 instead of the 4.8'

The Forgotten On

I know Ford did it with the help of Kawasaki when they built the V6 Ford Taurus SHO back in the late 80s. It would be cool to have a design similar to that.

Mongo

Or you buy the 4.8L LR4 and run 3.90s like us.

928s have the displacement (S3-on) so an intake similar to an LS1/6/7/etc. must yield some sort of gains over the stock.

Strosek Ultra

Ferrari F1 Variable length intake actuating by hand

Strosek Ultra

Animation better showing how variable telescopic intake works.
Åke

Mongo

Wow. It is so simple, yet so complex at the same time.

The Forgotten On

This seems pretty similar to the Varioram system Porsche used in the 993.