About Valves

yaubrandon · 06-19-2007, 06:44 AM

Why did Audi discarded the 5 valve design in their engines?

Maybe an old and silly question though~

Just can't think of why. As what I can remember, before FSI is introduced, the 5 valve series in the VW group used to enjoy the highest fame and prestige.

martinbo · 06-19-2007, 03:10 PM

We have had this discussion elsewhere on the forum, I'm just too lazy to go and look for it.

To the best of my knowledge, you've answered your own question. With the adoption of FSI, which necessitated placing a high pressure injector nozzle in the middle of the cylinder head, this meant that there was not enough space for the centrally located "5th" valve (the centre valve of the 3 inlet valves actually...) and the gains achieved by FSI would more than make up for the omission.

yaubrandon · 06-19-2007, 03:16 PM

Quote:

Originally Posted by martinbo

We have had this discussion elsewhere on the forum, I'm just too lazy to go and look for it.

To the best of my knowledge, you've answered your own question. With the adoption of FSI, which necessitated placing a high pressure injector nozzle in the middle of the cylinder head, this meant that there was not enough space for the centrally located "5th" valve (the centre valve of the 3 inlet valves actually...) and the gains achieved by FSI would more than make up for the omission.

Now the Audi is becoming homogeneous...

martinbo · 06-20-2007, 12:06 PM

Quote:

Originally Posted by yaubrandon

Now the Audi is becoming homogeneous...

Or it's just that 5 valve heads don't offer the performance gains to justify the extra engineering costs. To my knowledge 5 valve heads have been dropped by those that were using them bar one. Ferrari and Audi no longer use a five valve head and only Toyota uses one in the high-revving NA 2.0 litre 4 cylinder.

06-19-2007, 06:44 AM	#1 (permalink)
yaubrandon Enthusiast Join Date: Jul 2006 Location: Hong Kong Posts: 120 Thanks: 5 Thanked 0 Times in 0 Posts	About Valves Why did Audi discarded the 5 valve design in their engines? Maybe an old and silly question though~ Just can't think of why. As what I can remember, before FSI is introduced, the 5 valve series in the VW group used to enjoy the highest fame and prestige.

06-19-2007, 03:10 PM	#2 (permalink)
martinbo Fanatic Moderator Emeritus Join Date: Sep 2005 Location: Johannesburg Posts: 1,250 Thanks: 136 Thanked 202 Times in 114 Posts	Re: About Valves We have had this discussion elsewhere on the forum, I'm just too lazy to go and look for it. To the best of my knowledge, you've answered your own question. With the adoption of FSI, which necessitated placing a high pressure injector nozzle in the middle of the cylinder head, this meant that there was not enough space for the centrally located "5th" valve (the centre valve of the 3 inlet valves actually...) and the gains achieved by FSI would more than make up for the omission.

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