| [ Total Views: 1253 | Total Replies: 19 | Thread Id: 79082 ] |
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 matt
A.k.a.: Choco
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| posted on September 15th, 2009 at 07:20 PM |
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stingers
probably a silly question but, why do most drag cars run stinger (straight out) exhausts??? do they run better without the back pressure a muffler
provides????
matt
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Brian
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| posted on September 15th, 2009 at 07:24 PM |
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define exhaust back pressure please , its always confused me
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matt
A.k.a.: Choco
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| posted on September 15th, 2009 at 07:32 PM |
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i dont know much about it i just assume a motor will run better with a bit of back pressure. back pressure is the resistance of the gasses to flow
through the exhuast, some one else may explain it better
matt
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Brian
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| posted on September 15th, 2009 at 07:36 PM |
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if all other things are equal (ie air /fuel ratio etc) the muffler will slow it down
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matt
A.k.a.: Choco
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| posted on September 15th, 2009 at 07:41 PM |
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oh ok, you learn something new every day!!!
thanks
matt
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chunks54
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| posted on September 15th, 2009 at 07:51 PM |
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Plus there's nothing like waking up in the morning at a drag strip listening to a flat four barking through a stinger 
Happiness is a Hot VW.
1954 Bug, 2276/Turbo
Turbo lag - that split second when the other guy thinks he has a chance
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trickysimon
A.k.a.: Simon Azzopardi
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| posted on September 15th, 2009 at 07:55 PM |
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Why not just have no stinger or muffler at all?
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bajachris88
A.k.a.: Chris Leete
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| posted on September 15th, 2009 at 08:07 PM |
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You need backpressure of some kind. But in a drag racers case, the extractor tubing alone towards the flange for the stinger is sufficient.
But i dont know if backpressure is the right term. See... from what i'm aware of, its to do with air velocity. Smaller diameter tubing with same rate
of air flow has greater velocity of air going through than a larger diameter tube.
A wider diameter exhaust tube with same rate of air flow as the smaller diameter tube has larger volume, slower air flow.
By finding a 'balance' to create maximum air velocity, by manipulating tube diameter without large restriction (and too much back pressure) it
results in a 'relative' vacuum at the exhaust port as the momentum of the air exiting the exhaust (due to its velocity) continues to 'suck out'
exhaust gas inside the tubing as it goes the exhaust pipe.
Extractors take advantage of this, by lengthening the pipes correctly to collaborate with the timing difference of the exhaust ports. They work with
the 'pulses' of the exhaust gas to maintain a continuous flow and continuous forward momentum of the exhaust gas exiting, to keep 'sucking' out
the gas from the port.
Eva seen how shizzy any motor runs without any exhaust manifold at all? 
Its a mess. efi or carby...
Load like a tractor on the dub though haha.
its similar, but opposite to velocity stacks on a heads intake, choosing the right size for best possible air velocity. or even TVIS, taking advantage
of the 'natural supercharging' effect.
(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears. 
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta! |
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colonel mustard
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| posted on September 15th, 2009 at 08:28 PM |
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they make the car pretty useless for driving between o and 2k-ish but rock after that...
and they sound awesome  I got one fro my thunderbird from action day,
spent 2 hours cleaning it up.. and it looks sweet... under my bed with the rest of the exhaust. all ready for the set up!
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Duanepipe
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| posted on September 16th, 2009 at 07:13 AM |
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I ran several runs with the stinger and several with just the open header on my drag bug. It definately ran stronger with the stinger.I think it has
some sort of scavenging effect too especcially at speed.
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fish26
A.k.a.: benito
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| posted on September 16th, 2009 at 02:54 PM |
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stingers
Best person to chime in would be Brad "westi" from Westside, but the way I see it is:
Stingers work because we need some sort of exhaust tail section after the collector to help with wave scavenging, there is less loss of velocity and
would probably work even better if they were the same dimension from flange to exit as there are no expanding gasses past the collector therefore
continuing velocity.
They sound great because they simply exaggerate the sound of the exhaust pulse.
Mufflers are just that, used to soften the sound and pulse of the exhaust gasses.
Think of it like running your tap to fill a cask, the water traveling through the small pipe is traveling at a fast rate and losses velocity as it
fills the cask, although exiting at the same volume but a slower rate through a larger hole.
Your engine has 15 psi (1 Bar) of atmospheric pressure sitting at the inlet and another 15 psi lurking at the end of the tailpipe. The inlet stroke
creates a pressure differential and the atmosphere goes rushing inward. The exhaust valve opens and there is a pressure rise in the tube followed by a
strong "vacuum signal" as the gases head down the pipe. The vacuum signal or low pressure that follows an exhaust event can be used to help scavenge
the cylinder during overlap when both exhaust and inlet valves are open. Conversely, during this overlap period, the increase in "backpressure" can
cause these burnt gases to re-enter the combustion chamber and contaminate the inlet charge. Result...loss of power. The way to look at exhausts is to
view them as a way to maintain the highest velocity that will not impede flow. As velocity increases the pressure drops and the engine can become more
efficient. As bajachris88 pointed out, there's all the variables of length, diameter, rpm, collector size, etc. There is no "one answer".
bitten by the bug..........several times
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Duanepipe
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| posted on September 16th, 2009 at 06:56 PM |
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At the end of the day they look good ,sound good, make people ask "whats that for" and people trip over them.
All good for me.
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bajachris88
A.k.a.: Chris Leete
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| posted on September 16th, 2009 at 07:05 PM |
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hahah people trip ova them... lol
I definitely gotta make it to the drags then!
(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears.
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta! |
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colonel mustard
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| posted on September 16th, 2009 at 10:36 PM |
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I nearly tripped over Craigs on the dray rat at action day....... don't tell him.
Awwwwwwwwwwwwww YEAH!
Pardon the messy room... lots of assignments going on. hahaha
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 matberry
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| posted on September 16th, 2009 at 11:02 PM |
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| Quote: | Originally
posted by Duanepipe
At the end of the day they look good ,sound good, make people ask "whats that for" and people trip over them.
All good for me.
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Couldn't have put it better....All good here too :-)
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE
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rose
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| posted on September 18th, 2009 at 09:07 AM |
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I have one to put on Buz at Warwick but you wont trip over it as Buz isn't lowered
[img][/img]
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HappyDaze
A.k.a.: Greg Mackie
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| posted on September 18th, 2009 at 09:47 AM |
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Exhaust systems are a 'Black Art' - just look at 2 strokes and their expansion chambers. In 1969 I drove a Vee, which came with 4 separate pipes,
1.25" dia. After talking with Bruce Peters of Sonic Speed Equipment (they made a VW exhaust system), I made a 4 into 1 using smaller (1.125"dia.)
primary pipes, and a single 1.25" dia. tail-pipe. This gave a 4HP increase on the Dyno! That's an extra 10%!!!!!!! Bruce told me that they (Sonic)
virtually threw away their books on exhaust theory, and used the Dyno to experiment with different ideas.
Cheers, Greg
I'd rather wear a Beetle out by racing it than by polishing it!
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pete wood
A.k.a.: figure itout
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| posted on September 18th, 2009 at 09:52 AM |
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greg, doesn't surprise me, but exhaust design has come a long way since 69'. I'm sure there are a few good books you could get to help these days
.
speaking of stingers on Fvees. I saw a whole bunch of Vees running stingers last weekend at Wakefield. A few were running hotdogs, but the one that
got my attention was this setup...
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bajachris88
A.k.a.: Chris Leete
23 Windows of Awesome
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| posted on September 18th, 2009 at 10:23 AM |
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its like the dual cannon motorbike stylin kinda thing.
me likes
(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears.
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta! |
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fish26
A.k.a.: benito
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| posted on September 18th, 2009 at 04:48 PM |
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Best guys to learn from are engineers in F1, lots of R + D on N/A.
bitten by the bug..........several times
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