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ed_ma61 Forums Junkie Location: Lost in the K hole Registered: May 2002	Re: How does the 7m-gte boost retard ?? Fri, 29 November 2002 12:32 SUPRAGTE wrote on Fri, 29 November 2002 17:38 Measuring the pressure in the intake manifold doesn't give you how much air is going into the engine. It merely gives you pressure. What happens when you do some porting? The pressure in the intake manifold stays the same but more air is going through the engine. Your theory doesn't work on using the pressure isn't the best. no, youre right about the calculation of airflow, but im talking about timing...when you increase intake pressure, you're effectice compression ratio increases, and this needs to be compensated for by timing rertard. trying to calculate this effective CR simply through predicitve RPM, TPS and AFM signals is not an optimum solution... SUPRAGTE wrote on Fri, 29 November 2002 17:38 CR has got something to do with AF ratios. How could it not? There is less volume in the combustion chamber for higher compression engines. Agreed???? Thats why they are higher compression. If you put the same amount of fuel with the less volume you will get richer AF ratios. Its obvious. not so. just think about it again the volume in the combustion chamber of a high CR engine still contains the same amount of air and fuel as an identical lower CR engine... but at higher pressure. thats it. (ok maybe ~5ml less total volume, but this 5mls is NOT manifested in a change in the volume of air ingested. it's contained within the dead space of the cyl, and does not come into AF calculation) perhaps in a turbo application, the extra 5mls of volume will be pressurised to yeild say an extra 7mls total volume over a hi comp... BUT relating back to your original point that a high comp doesnt suck in as much air and fuel as its lower comp counterpart, thats still incorrect. a highr CR engine may also require more fuel simply to keep the compustion temperatures down, but that is a deliberate tuning allowance made in the ECU, and nothing inherent to the engine's physical design. SUPRAGTE wrote on Fri, 29 November 2002 17:38 If it were such a good idea wouldn't everyone be running higher comp pistons on their turbo engines instead of lower? because its hard to pull off. magin for error in manufacture, tuning, fuelling and maintenance is extreemly low, and the engine is very highly strung. not the kind of car manufacturers want mom and pop driving around. as for hi performance modifications... again, its just easier to drop CR in order to run big boost. much harder to run hi static CR and then run mid/low boost. but, when it is done, look out, she does go... cheers ed [Report message to a moderator]

	Subject	Poster	Date
	How does the 7m-gte boost retard ??	ed_ma61	Wed, 27 November 2002 03:51
	Re: How does the 7m-gte boost retard ??	SUPRAGTE	Wed, 27 November 2002 04:22
	Re: How does the 7m-gte boost retard ??	inferno	Wed, 27 November 2002 13:36
	Re: How does the 7m-gte boost retard ??	Norbie	Wed, 27 November 2002 04:33
	Re: How does the 7m-gte boost retard ??	scottee78	Wed, 27 November 2002 04:44
	Re: How does the 7m-gte boost retard ??	Norbie	Wed, 27 November 2002 05:27
	Re: How does the 7m-gte boost retard ??	scottee78	Wed, 27 November 2002 05:40
	Re: How does the 7m-gte boost retard ??	ed_ma61	Wed, 27 November 2002 08:24
	Re: How does the 7m-gte boost retard ??	SUPRAGTE	Wed, 27 November 2002 13:15
	Re: How does the 7m-gte boost retard ??	ed_ma61	Wed, 27 November 2002 13:41
	Re: How does the 7m-gte boost retard ??	gianttomato	Wed, 27 November 2002 20:52
	Re: How does the 7m-gte boost retard ??	humble	Wed, 27 November 2002 22:20
	Re: How does the 7m-gte boost retard ??	Norbie	Wed, 27 November 2002 22:42
	Re: How does the 7m-gte boost retard ??	gianttomato	Wed, 27 November 2002 23:05
	Re: How does the 7m-gte boost retard ??	SUPRAGTE	Thu, 28 November 2002 12:19
	Re: How does the 7m-gte boost retard ??	ed_ma61	Thu, 28 November 2002 13:25
	Re: How does the 7m-gte boost retard ??	SUPRAGTE	Fri, 29 November 2002 06:38
	Re: How does the 7m-gte boost retard ??	ed_ma61	Fri, 29 November 2002 12:32
	Re: How does the 7m-gte boost retard ??	justcallmefrank	Sat, 30 November 2002 07:28
	Re: How does the 7m-gte boost retard ??	SUPRAGTE	Sun, 01 December 2002 06:13
	Re: How does the 7m-gte boost retard ??	Esteban	Mon, 02 December 2002 06:56
	Re: How does the 7m-gte boost retard ??	SUPRAGTE	Tue, 03 December 2002 02:50
	Re: How does the 7m-gte boost retard ??	1G-GTEFreAk	Thu, 02 January 2003 17:05

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