gt37vgt

A point missed in the 8v 16v discussion...and i feel more significant the points Chris made is that an 8v turbo basically bolts together and 16 v doesn't .
I think no money or development is saved in head of the engine by choosing 8v as 16v will give the same power with out porting or cam work ...
its the manifolding that's work or bucks

RPHARRIS

For the 16V my guess is that you need to do some re-engineering or at the very least swap out some parts in the valve-train to obtain durability when you start upping the boost. The 944 turbo valve-train already incorporates things like sodium filled valves and stiffer intake valve springs. On the plus side, the 16v components are smaller and lighter so if its rev's your looking for you've got a lot more headroom once you set everything up to handle boost.

Also, there are some idiosyncrasies that come into play with 16v cam designs when you start playing with boost that aren't so crucial on 8v engines (check out the intake duration on a 944S cam and consider that 4v heads generally have much more advanced timing on the intake cam compared to a 2v) You might also get away with opening up those exhaust valves a little earlier on a boosted 16v but not too early because the exhaust flow is insane on these things and your egts will get out of control fast. You WILL need to do some re-engineering if you want to run high boost on a 16v. Without going into any serious details, at the very minimum I would probably want to make some changes to the cam timing if I had a 16v ...but then you run into hood clearance issues with adjustable cam gears so re-machining the key-ways on the cams may be advisable. New cams would be ideal. Either way $$$

Making a 16v survive high boost may be a little more complicated than most people who haven't tried it think. In the end its pretty damn complicated and expensive to engineer something that's can take advantage of the power potential of the 16v head that will also hold together lap after lap at 18+psi, ESPECIALLY if you try to do it on the cheap and use an extra thick head gasket or unsuitable piston design. It's not just a matter of bolting an S2 head onto a stout bottom end, a lot of thought has to go into the top end as well. While we're on the topic, can anyone guess why the 16v heads like to be on strokers besides the obvious displacement difference?

Darwantae951

Tell me about it! If you were still in the DFW area, I'd offer you a drive!

porshhhh951

I'm going to be in August.

Darwantae951

I won't be home until November. Also the build won't start until then. If you're in town anytime in November or after April, gimme a shout.

ehall

Unless one is looking to spend 20k plus, on an engine build, I can't see any reason to build a 16 valve. It kind of just becomes an issue of "because I could".
I can't think of a single reason why one either needs nor can use the extra hp, of a 16 valve. At some point it becomes too much power to try to put to the ground. That can be done all day with a 3.0, 8 valve, for much less money.

Darwantae951

Speaking from new found experience...there isn't all THAT much of a price difference...

porshhhh951

I disagree. 4 valves per cylinder with breathe MUCH better and make more power doing it.

ehall

BUT, not enough for the additional cost. Where exactly does one use the extra power to drive it 195 mph? It's a waste of cash, in a road car. A 3.0, 8 valve is so much more than one can actually use, in a road car.
We've seen a 2.7, 8 valve, put down 400+ RWHP, with Vitesse gear and a top notch 8 valve head.

16 valves are only needed if one is insecure about their Vienna Sauasge length *****.

V2Rocket

howabout an 8v putting down 600+RWHP?

ehall

That should be the attainable, with the right management.

porshhhh951

RPHARRIS

The 16v head doesn't automatically mean you'll make (208hp/160)(1+boost/14.7) ...If only things were so simple. You can throw an 8v head onto a 3.0 bottom end and it will make loads of power at 17psi for years with next to no custom machine work. Try that with the 16v head and my guess is that you'll end up with some serious headaches after the first couple thousand miles ...after you've already busted your budget on the custom manifolds. Have you ever noticed that 16v guys rarely run big boost and their net power is much less impressive than expected, there's a reason for that. IIRC, George D. makes just as much power as DFASTEST. Plan to spend a lot more money than you expect on a well thought out 16v project ...there are so many little things that need to be dealt with.

Unless you're really clever, I don't think you're going to get that much more reliable horsepower out of a minimum budget 16v ...at least not enough to justify the work and cost and even then it's somewhat of a ticking time bomb. A lot of things go into finding a configuration that will survive years of punishment. With the 8v 3.0 you get to re-use most of Porsche's work. With the 16v you're back to square one unless you've already built a few of them.

Chris White

Sausage envy?

Chris White

Cresting the top of the esses at Watkins Glen at 110 and accelerating with a half a mile of straight you will always welcome a little more horsepower...if you are chasing a GT3 you will sell your mother for a little more horsepower!