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loki

3valves

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when and where will this show up in GM's engines?

i'd just take a guess at "09my (or before) with the v6's, because they could have the best responce for the midsize power and efficency boosts,

the v8's should be close behind, w/ the 5.3 making closer to 340-350 hp

any articles anyone found on this subject, that isn't the idea pdf on gm's media site?

edited for a few spelling corrections

Edited by loki

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We haven't heard much about it recently, and I wouldn't be surprised if it got put on hold given GM's current money problems.

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We were told that all the new high value engines were going to get 3v heads, and they were capable of adding 30hp over the same engine with 2v head. They'd also be available as over the shelf upgrades to existing 2v head engines.

I'm guessing either it's the money issue, or they found a compatibility problem that shouldn't be released on production cars, like the 3900s that make noise when fitted with VVT, or something like that.

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VLE's have traditionally been reluctant to go for the added cost of the 3-valve heads, even in the Corvette. A "270-hp 3.9L V-6" was in the GMPD's G6 Performance Coupe at SEMA last year.

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Screw 3 valve angines. Look at the Z06... it seems GM si doing a fantastic job of making the LS series engines breathe super-efficiently wiht just one intake valve. I say don;t fix what's not broken.

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real good detail on how it was going to work.

Starting on page 5. (From september 2003?)

http://www.sae.org/automag/techbriefs/09-2003/1-111-9-26.pdf

With D.O.D and VVT

Positioning intake and exhaust valves

on opposite sides of the combustion

chamber leaves space in the center for

the spark plug, which improves combustion

efficiency. Together, these improvements

boost power output by 10-15%,

according to the company.

The three-valve heads are about 1 in (25 mm) wider than

the two-valve heads, but they maintain the low profile that is

an advantage of OHV engines. The new heads will work with

the displacement-on-demand (DOD) cylinder-deactivation

system that will arrive on the two-valve Generation IV engine

and High Value V6 for even better fuel economy.

”The three-valve design adds complexity but uses the type

of components with which GM is very familiar, so reliability

shouldn’t be a problem,” said Frederick Rozario, Development

Engineer, Advanced Powertrain at GM. “And while the added

mass in the valvetrain might seem to be an obstacle to highrpm operation,

the Corvette engine will rev to 7000 rpm with a

30% margin of safety. It can go to 8000 rpm safely,” he added. A

special jig will hold the parts together so the whole valve actuation

assembly can be installed as a unit on the head.

“A weakness of single camshaft engines is the inability to

separate intake-cam timing from exhaust-cam timing for

maximum efficiency and minimal emissions. But a cam phaser

that adjusts the advance or retard of even a single cam,

depending on conditions, is still very valuable,” Rozario said.

“The cam phaser on this engine provides 80% of the benefit

of a system with separate intake and exhaust phasers.”

The DOD system and cam phaser increase the demand for

oil pressure, so both the V8 and V6 engines get improved oil

pumps. The V8’s is a two-phase oil pump, switching between

high and low flow as needed to maintain the necessary oil

pressure without suffering excessive parasitic losses when

lower pressure is sufficient. The V6 is even more efficient,

with a variable displacement oil pump that continuously

adjusts its output for maximum efficiency.

The engines also feature optimized exhaust manifolds with

equal flow runners for each cylinder.

Would have been Sweet.

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