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takai Forums Junkie Location: Adelaide Registered: May 2003	Re: 4A: G vs F heads Wed, 27 October 2004 07:58 From what i understand it the Yamaha G heads have a hugely wide valve angle in order NOT to use rockers. So far as i can figure, my 4AGE has similar properties to my old R6. As in they both rev like buggery. So if we go off the theory that Yamaha were developing the G series heads along the same design principles as their R* series bikes they woudl be developing them for high flow at high rpm, and not caring much about torque, because as Shraka has said torque changes as per RPM. This is how race bikes are designed. Now if they are developing for say a peak power at 7000rpm (4AGE) they would want as few reciprocating parts as possible, especially ones with large inertial mass actuated off the camshafts.... i.e. rockers. So they went to a shim/bucket design. Shim and buckets take up room, and hence the wide angles on the valves. This allows the engine to rev to higher rpm without large amounts of damage to the rockers. Now if we look at our rocker engine, namely the SR20 we can see that it makes peak power further down in the range at around 5500rpm, rather than the screaming 7000rpm which Yamaha have designed their head for. This is largely due to the rocker design in the head (or lash adjusters as they call them). And we notice that the CA18 which doesnt have lash adjusters can rev a lot higher 7200ish rpm. When people are building a high rpm and high power SR20 engine the main thing which is replaced are the lash adjusters/rockers. And not at any cheap cost either might i add. But the advantage is a narrow valve angle. How else can we get this narrow valve angle, well by using shim/bucket design but changing the cams to drive each other off the single camgear. Now this is a fairly good design, as you dont have any pesky rockers to get in the way of high rpm, but by the same token you also dont have the adjustment in the cam timing. Lets put that aside for the time being, and work on just the rpm. I think i can safely assume that one the F head's great limitations is not contained within the head, but rather within the engine itself. i.e. the static compression. The other problem i can see is with the airflow within the head, and so i guess it may be a combination of these. I think thats about it. Ive kind of tried to get into the heads of the designers and think about it from a completely seperate standpoint. As for the GZE i think that came about due to some development designs being thrown into production without being perfected. I think the best evidence of this can be seen in the design of the intake into and exhaust from the supercharger. [Report message to a moderator]

	Subject	Poster	Date
	4A: G vs F heads	Henn	Thu, 21 October 2004 13:47
	Re: 4A: G vs F heads	Norbie	Fri, 22 October 2004 00:06
	Re: 4A: G vs F heads	rob_RA40	Fri, 22 October 2004 00:09
	Re: 4A: G vs F heads	b1gb3n	Fri, 22 October 2004 02:26
	Re: 4A: G vs F heads	rob_RA40	Fri, 22 October 2004 04:51
	Re: 4A: G vs F heads	b1gb3n	Fri, 22 October 2004 06:15
	Re: 4A: G vs F heads	Bill Sherwood	Fri, 22 October 2004 04:01
	Re: 4A: G vs F heads	EVOSTi	Fri, 22 October 2004 06:15
	Re: 4A: G vs F heads	ae95	Fri, 22 October 2004 06:19
	Re: 4A: G vs F heads	SEXY 16	Fri, 22 October 2004 06:41
	Re: 4A: G vs F heads	wuzah?	Fri, 22 October 2004 10:51
	Re: 4A: G vs F heads	NuGeN	Fri, 22 October 2004 11:41
	Re: 4A: G vs F heads	Henn	Fri, 22 October 2004 13:34
	Re: 4A: G vs F heads	Bill Sherwood	Fri, 22 October 2004 14:16
	Re: 4A: G vs F heads	Henn	Fri, 22 October 2004 15:13
	Re: 4A: G vs F heads	cwhelan	Mon, 25 October 2004 01:59
	Re: 4A: G vs F heads	drift86levin	Mon, 25 October 2004 03:03
	Re: 4A: G vs F heads	b1gb3n	Mon, 25 October 2004 07:53
	Re: 4A: G vs F heads	takai	Wed, 27 October 2004 21:52
	Re: 4A: G vs F heads	SEXY 16	Mon, 25 October 2004 09:23
	Re: 4A: G vs F heads	Bill Sherwood	Mon, 25 October 2004 10:09
	Re: 4A: G vs F heads	SEXY 16	Mon, 25 October 2004 21:27
	Re: 4A: G vs F heads	Johnny	Tue, 26 October 2004 02:27
	Re: 4A: G vs F heads	Bill Sherwood	Tue, 26 October 2004 02:57
	Re: 4A: G vs F heads	Shraka	Tue, 26 October 2004 03:02
	Re: 4A: G vs F heads	Bill Sherwood	Tue, 26 October 2004 03:42
	Re: 4A: G vs F heads	Norbie	Tue, 26 October 2004 03:33
	Re: 4A: G vs F heads	mrshin	Tue, 26 October 2004 04:15
	Re: 4A: G vs F heads	Shraka	Tue, 26 October 2004 04:53
	Re: 4A: G vs F heads	Bill Sherwood	Tue, 26 October 2004 05:04
	Re: 4A: G vs F heads	b1gb3n	Tue, 26 October 2004 05:04
	Re: 4A: G vs F heads	Bill Sherwood	Tue, 26 October 2004 06:28
	Re: 4A: G vs F heads	Shraka	Tue, 26 October 2004 06:45
	Re: 4A: G vs F heads	mrshin	Tue, 26 October 2004 06:17
	Re: 4A: G vs F heads	Norbie	Tue, 26 October 2004 06:51
	Re: 4A: G vs F heads	Shraka	Tue, 26 October 2004 07:25
	Re: 4A: G vs F heads	Bill Sherwood	Tue, 26 October 2004 07:53
	Re: 4A: G vs F heads	Johnny	Tue, 26 October 2004 10:49
	Re: 4A: G vs F heads	mrshin	Tue, 26 October 2004 14:17
	Re: 4A: G vs F heads	oldcorollas	Tue, 26 October 2004 14:27
	Re: 4A: G vs F heads	mrshin	Tue, 26 October 2004 14:36
	Re: 4A: G vs F heads	quest	Tue, 26 October 2004 15:36
	Re: 4A: G vs F heads	b1gb3n	Tue, 26 October 2004 15:48
	Re: 4A: G vs F heads	4DaDrift	Tue, 26 October 2004 15:50
	Re: 4A: G vs F heads	Shraka	Wed, 27 October 2004 00:08
	Re: 4A: G vs F heads	Bill Sherwood	Wed, 27 October 2004 01:49
	Re: 4A: G vs F heads	oldcorollas	Wed, 27 October 2004 15:22
	Re: 4A: G vs F heads	Tofuboi	Tue, 26 October 2004 21:53
	Re: 4A: G vs F heads	Shraka	Wed, 27 October 2004 02:02
	Re: 4A: G vs F heads	quest	Wed, 27 October 2004 06:30
	Re: 4A: G vs F heads	quest	Wed, 27 October 2004 06:59
	Re: 4A: G vs F heads	quest	Wed, 27 October 2004 07:21
	Re: 4A: G vs F heads	oldcorollas	Wed, 27 October 2004 07:34
	Re: 4A: G vs F heads	Henn	Wed, 27 October 2004 06:58
	Re: 4A: G vs F heads	Shraka	Wed, 27 October 2004 07:31
	Re: 4A: G vs F heads	takai	Wed, 27 October 2004 07:58
	Re: 4A: G vs F heads	quest	Wed, 27 October 2004 14:32
	Re: 4A: G vs F heads	oldcorollas	Wed, 27 October 2004 15:08
	Re: 4A: G vs F heads	Tats	Wed, 27 October 2004 23:26
	Re: 4A: G vs F heads	Johnny	Thu, 28 October 2004 00:48
	Re: 4A: G vs F heads	Shraka	Thu, 28 October 2004 02:21
	Re: 4A: G vs F heads	Johnny	Thu, 28 October 2004 03:44
	Re: 4A: G vs F heads	Bill Sherwood	Thu, 28 October 2004 04:30
	Re: 4A: G vs F heads	b1gb3n	Thu, 28 October 2004 05:24
	Re: 4A: G vs F heads	koen	Thu, 28 October 2004 04:52
	Re: 4A: G vs F heads	Norbie	Thu, 28 October 2004 05:09
	Re: 4A: G vs F heads	justcallmefrank	Thu, 28 October 2004 05:24
	Re: 4A: G vs F heads	Bill Sherwood	Thu, 28 October 2004 05:17
	Re: 4A: G vs F heads	Bill Sherwood	Thu, 28 October 2004 05:29
	Re: 4A: G vs F heads	oldcorollas	Tue, 02 November 2004 08:10
	Re: 4A: G vs F heads	Shraka	Thu, 28 October 2004 07:05
	Re: 4A: G vs F heads	da_horse	Thu, 28 October 2004 08:36
	Re: 4A: G vs F heads	justcallmefrank	Thu, 28 October 2004 08:45
	Re: 4A: G vs F heads	Shraka	Mon, 01 November 2004 03:10
	Re: 4A: G vs F heads	justcallmefrank	Mon, 01 November 2004 03:11
	Re: 4A: G vs F heads	Shraka	Mon, 01 November 2004 03:18
	Re: 4A: G vs F heads	86tt	Mon, 01 November 2004 14:15
	Re: 4A: G vs F heads	takai	Tue, 02 November 2004 07:41

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