Let's try that again..
----------
From: DANIEL RAY
Sent: Monday, January 19, 1998 10:59 AM
To: 'michael j robson'
Subject: RE: aftermarket air-cleaner assemblies
Ok, well, pardon my total confusion after seeing this go back and forth.
I had planned on eventually putting on K&N filters and a Peco exhaust =
(not the header but just pipes). Is this a wast of time and money with a =
stock engine? My stock filters are in good shape, but the exhaust needs =
replacement. I just wanna do the right thing, if this "increased hp" =
thing is a myth, than I might as well just stay with the way it was put =
together in jolly ol' England!
Thanks
Dan
'73 B
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From: michael j robson
Sent: Sunday, January 18, 1998 7:46 PM
To: gofastmg@juno.com
Cc: tboicey@brit.ca; mgs@autox.team.net
Subject: Re: aftermarket air-cleaner assemblies
On Sun, 18 Jan 1998 17:37:40 EST gofastmg@juno.com (Rick Morrison)
writes:
>
>On Sat, 17 Jan 1998 23:36:59 -0500 Trevor Boicey <tboicey@brit.ca>=20
>writes:
>> I'm not sure I would agree with this.
>> Obviously, improvement to both systems is important. The best
>>triple webers will not really pay off with a stock exhaust
>>and stock cat.
>>
>> However, I can't see how the intake and exhaust could be
>>so tied. They aren't part of the same system, like the cat
>>and the muffler which can be matched for best performance. As
>>well, they don't handle the same air flow anyways, since a lot
>>more gas comes out of the exhaust than is drawn into
>>the intake.
>>
> Honeymoon's over Trevor, I'll dis agree with you here
> The exhaust and intake are so tied. Simply put, what goes in, must=20
>come out.
> If you increase the intake volume (increase volumetric effeciencey),=20
>and nothing to the exhaust, the resulting intake charge will be=20
>contaminated with burnt gases that cannot exit the chamber due to=20
>higher exhaust pressures. =20
> Result - little or no increase in performance, and possibly a=20
>decrease.
> (Remember that exhaust back pressure increases with RPM, but in a=20
>non-linear maner - ie, the slope of the graph curves upward.)
> Now, haveing said that, a little disclaimer. On an MGB the exhaust=20
>is, in stock form, superior to the intake in flow characteristics. So=20
>a marginal improvement to the intake side will generally result in a=20
>performance increase (assuming a well thought out and viable=20
>improvement), even with no exhaust modification. But a point of=20
>dimishing returns quickly sets in where continued intake improvements=20
>soon overwhelm the stock system ability to cope.
> At this point, an exhaust upgrage is in order.
> When planning induction improvements, one is forced to consider the=20
>effect of the intake changes on the exhaust flow, if the objective is=20
>to maximize the result of the improvement.
>Rick Morrison
>72 MGBGT
>74 Midget=20
>
Guess we learned at the same school Rick- and in my experience the
theory is borne out - Skips original point was that the carbs are
basically too small but having tried all sorts of combinations its =
still
a question of balance (obligatory Moody Blues ref)
mike robson
69 roadster (stock filters and exhaust, had stock filters performance
exhaust)
70 BGT (K+N filters Monza exhaust)
72 roadster (pancake filters and a bloody great stainless steel pipe =
with
no box!)
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