[Zmagnette] Stub stacks

charles durning durningcharles at gmail.com
Fri Nov 15 11:18:44 MST 2013 

Just my 2 cents.  The extra noise from a fan or an engine is just the noise
made from  air movement.  Though our engines do make more power at
the higher rpms (thus more noise) it's actually not as efficent at
processing the air movement as it is at a slower speed.  I believe that the
most efficent engine in the world has an 8 foot stroke and maxes out at102
rpm.  It's most efficent speed is 100rpms.  That gives plenty of time to
extract all of the engergy from the fuel/air misture.  When the heater fan
is turning at 3 times the low speed it is not moving 3 times the air, just
moving more air.  Noise is just unused energy.

In my case I really don't care one way or another.  I have pancake air
filters with no air flow enhancements.  A nice throaty sound from a MG
exhaust is a plesant sound no matter how it gets there.


Charlie Durning

If you are using Google or Gmail, Big Brother is watching.



On Fri, Nov 15, 2013 at 11:08 AM, Wayne & Isabel Hardy <
gwhardy at suddenlink.net> wrote:

>   Yea that sounds nice all that about efficiency, but fact of the matter
> is that the big old factory cleaner was much quieter than the small
> cleaners or just velocity stacks...more air seems to make more noise, just
> turn your garage fan from low to high speed and tell me which setting is
> loudest or sit in the car and turn the heater / ac fan up to high and
> compare it to the low setting and see which one you like best.
> The intake roar doesn’t bother me in the least nor does a nice hum from
> the exhausting gases but some folks do not like gaseous noises from either
> end.
>
>  *From:* Gene deRuelle <deruelle at att.net>
> *Sent:* Friday, November 15, 2013
> *To:* Michael Anderson <mjamgb at sbcglobal.net> ; List for the Z Magnette
> Group - North America <zmagnette at autox.team.net>
> *Subject:* Re: [Zmagnette] Stub stacks
>
>  If you run the little stacks, aren't you subjecting the fuel/air mixture
> to whatever is IN the air?  In other words, you can't run the stacks and an
> air cleaner, can you?
>
> Gene D
>
> ----- Original Message -----
> *From:* Michael Anderson <mjamgb at sbcglobal.net>
> *To:* List for the Z Magnette Group - North America<zmagnette at autox.team.net>
> *Sent:* Friday, November 15, 2013 6:58 AM
> *Subject:* Re: [Zmagnette] Stub stacks
>
> I respectfully disagree that more air = more noise by default. "Noise" to
> a mechanical engineer (or most any engineer) is an undesireable by-product
> of inefficiency, i.e. whatever is causing the noise is sapping energy from
> whatever the machine is supposed to do (unless it's job is to make noise).
> Having said that, stub stacks should reduce noise -all else being the same
> - because the efficiency of the system is increased.
>
> To that end, Allen opens up the issue of Bernoulli. In our carbs Bernoulli
> is working hard for us at the piston/bridge, not the inlet throat. Without
> some kind of "stack" Bernoulli is screwing with us at the carb inlet as the
> "apparent" inlet diameter gets smaller due to the air having to make a hard
> 90-degreee turn... turbulence is also introduced before the piston/bridge
> which is not a happy thing for nice even fuel induction.
>
> Those two reasons are what makes the mixture "change" when you put a stack
> on. Not more air, per se, but quality of air flow.
>
> Mike!
>
>
> Michael Anderson
> One of a Kind Stuff/AEU
> 775 772-2056
>
>   ------------------------------
> *From:* Wayne & Isabel Hardy <gwhardy at suddenlink.net>
> *To:* List for the Z Magnette Group - North America <
> zmagnette at autox.team.net>
> *Sent:* Friday, November 15, 2013 1:19 AM
> *Subject:* Re: [Zmagnette] Stub stacks
>
>   If the carbs are tuned again to compensate for more air to the inlet,
> then more power should always be the result. If more power is “Better”,
> then the answer is yes. But you must adjust for more airflow to get a more
> better running motor..ie more air will need more fuel too if a result is to
> be more power. Maybe a new, slightly richer needle is the ticket to heaven.
> I know the K&N filter people caution that their filters flow so much more
> air than the usual paper ones, that a richer needle, or jet, or slight
> enrichment adjustment may be desirable for best running.
> Of course all this extra air flow is also likely to create more inlet roar
> under acceleration. Is that “Better” or not???
> I personally run the MGA cleaner assemblies rather than the Magnette one
> for better access to the carb adjustment screws for keeping up with summer
> 100 degree days now swinging to winter 50 - 60 degree days and the
> resultant changes in idle speeds due to cooler, denser air, and the need to
> richen the mix by about 1/8th of a turn.
> MG put on the big old ugly oil bath filter for better engine life in a
> variety of dirty dusty operating situations around the world, and for more
> civilized operation in a quieter manner. Their true race motors ran with
> velocity stacks and no filters usually.
>
> Wombat
>
>  *From:* Allen Bachelder <bachldrs at comcast.net>
> *Sent:* Thursday, November 14, 2013 10:21 PM
> *To:* List for the Z Magnette Group - North America<zmagnette at autox.team.net>
> *Subject:* Re: [Zmagnette] Stub stacks
>
> I'm cautiously venturing beyond my paygrade here, but are we not talking
> about the Bernoulli Principle: stating that as air enters a conical tube
> the air pressure is maximized, but as the tube diameter conically
> diminishes, air pressure decreases as air speed increases inside the carb.
> Without a conical stub stack, there is no acceleration in the air entering
> the carb inlet.  How much lift would we get from a cross-sectionally flat
> airplane wing-top with a squared-off leading edge?
>
> That being said, how can the original Magnette intake plenum perform any
> of this function? Same question for the intake plenums on T-series cars. I
> would think they would be Bernoullian disasters.  Would a Magnette engine
> always run better with stub stacks rather than the original plenum?
>
> Curious in Michigan.
>
> (Allen)
>   ******************************************************************
>
> *Allen & Florrie Bachelder       =iii=<Spring Creek Home for Wayward MGs*
> *'57 ZB, '65 B, '69 C/GT, '73 B/GT*
> *North Street, MI 48049, USA*
> *http://www.mgexperience.net/member/bachldrs
> <http://www.mgexperience.net/member/bachldrs>*
>
> ******************************************************************
>
>  On Nov 13, 2013, at 7:33 PM, John Park wrote:
>
>   Depending on length it can produce a much smoother flow, some say a bit
> of a ram effect which increases power and torque . Longer stacks as in
> longer runners means more torque while shorter ones mean more power.  Not
> lots, but it all contributes to a freer flowing intake which helps your
> freer flowing exhaust to make a bit more power/torque and slightly better
> fuel economy.  You note vintage racers usually have anywhere from2.5 to 6
> inch stacks. Some with a stocking for a coarse filter, most just hoping
> nothing of consequence enters the throat… I have a set of 2.25 inch stacks
> in my 3.25 inch K&N’s on my MGB and they seem to help. Just the ho hum
> stock setup on my Magnette.
>
>  *From:* zmagnette-bounces at autox.team.net [mailto:
> zmagnette-bounces at autox.team.net] *On Behalf Of *Richard Greenberg
> *Sent:* Wednesday, November 13, 2013 12:34 PM
> *To:* List for the Z Magnette Group - North America
> *Subject:* Re: [Zmagnette] Stub stacks
>
> What is a stub stack? Would it allow for a filter that lies closer to the
> engine than a regular pancake filter?
>
>  On Nov 13, 2013, at 9:53 AM, Allen Bachelder wrote:
>
>
>  I've always just used the item #54 from the Moss catalog:
> http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=28996#top Are these from APT or Rimmer better?
>
>  Always anxious to learn...
>  Allen
>   ******************************************************************
>
> *Allen & Florrie Bachelder       =iii=<Spring Creek Home for Wayward MGs*
>  *'57 ZB, '65 B, '69 C/GT, '73 B/GT*
>  *North Street, MI 48049, USA*
> *http://www.mgexperience.net/member/bachldrs
> <http://www.mgexperience.net/member/bachldrs>*
>           ****************************************************************
>
>  On Nov 13, 2013, at 4:10 AM, monster at caverock.net.nz wrote:
>
>
>  Hi everyone,
>
> I'd like to get a pair of 1.5" H4 stub stacks and I've tried emailing
> Steve Ash several times to see if he would make some more, but I haven't
> got an answer from him.
>
> So... from a light scour of the internet there appears to be two types
> available at a reasonable cost:
> $32.50 ea -
> http://www.aptfast.com/ShowItem/101221%20Billet%20Alloy%20Stub%20Stack%20SU%20HS4.aspx
> $57 pair - http://www.rimmerbros.co.uk/Item--i-RL1396ALT
>
> I've excluded the K&N ones as they are very rough, by all accounts.
> Are there any others that people would recommend?
>
> They're going to fit inside K&N filters that are 2 1/8" thick.
>
> regards,
> --
> Robert (in NZ)
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