[DeTomaso] SPC - Do headers affect scavenging in individual cylinders?

JDeRyke at aol.com JDeRyke at aol.com
Wed Feb 20 00:50:55 EST 2008


In a message dated 2/19/08 11:40:06 AM, kenn_green at yahoo.com writes:

> I was looking at some headers and it occurred to me that the interaction of 
> pulses in the collector might affect scavenging differently in individual 
> cylinders.  While it might not produce a noticeable effect on HP, it might 
> cause some cylinders to receive more fresh air than others.  That might not 
> matter with a carb which mixes fuel and air based on the air flow, but with direct 
> port EFI if the same amount of fuel is injected into each intake port, it 
> seems like some cylinders could run lean?
>      Might be an argument for equal length 180 degree headers on an EFI 
> motor.
>   Maybe use a second set of big injectors in a plenum that feeds all the 
> cylinders?
>   Maybe it's such a small effect that it doesn't matter?
> 
Can't tell without testing, but typically, exhaust ram-effects are smaller 
than intake effects in their power-adding capabilities. Adding wide-band o2 
sensors into all 8 primary pipes would tell you if a cylinder is lean or rich and 
the answer will change with rpms.. FWIW, this stuff is exactly what NASCAR 
dyno guys spend countless hours exploring. Street gys just dream..... Good luck- 
J Deryke (who can't afford ONE wide-band sensor, let alone the multichannel 
data logger!)




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