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Re: Mufflers... Any E.T gain from swapping?
[Re: WO23Coronet]
#1573486
02/04/14 02:53 PM
02/04/14 02:53 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
When you guys run open headers do you put collector extension on? Dulcich did an extensive header comparison awhile back on a hot 440 (Hooker super comp headers I think) and a proper length collector extension was worth a ridiculous amount of power over the factory collector length, something like 40-60 HP, but only in the lower to mid range level, it didn't seem to make a huge difference in the upper RPM's. I think the engine dyno'ed in the 600+HP range.
Yep... the proper collector length is for the torque...
a shelf header doesnt have anywhere near the proper
length collector(even if its the right diameter)...
shelf headers are basically made to fit and sure dont
make peak HP or torque... but they do get the exhaust out
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Re: Mufflers... Any E.T gain from swapping?
[Re: d3m0n]
#1573487
02/04/14 03:49 PM
02/04/14 03:49 PM
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Joined: Aug 2003
Posts: 43,287
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,287
Bend,OR USA
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Quote:
i have a demon with a 440 . i run pro parts headers an H pipe and 3" flows dumped at the axle. my car has tons of torque and bottom end . i droped the exaust and jetted up 4 sizes went to the track didnt get to make any changes but the car lost all bottom end it was very lazy . im going to run exaust next time i go but the car felt slower to me maybe i jetted up to much i dont know?
You probally did jet it up to much, go back and try it again with the same jetting with and without the exhaust system on it   Usually, when removing the back pressure of the exhaust, you jet the carb. down one or two jet sizes to make the car go faster   BTW, by jetting the carb. up with the open exhaust you did prove your fuel system has enough volume to slow the car down, which is a good test  It is far safer to jet the motor up to slow the car down first and then jet it down a little bit at a time(one jet size at a time, not four  ) until it starts to loose MPH in 1/4 Let us know your results
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Mufflers... Any E.T gain from swapping?
[Re: MR_P_BODY]
#1573488
02/04/14 03:56 PM
02/04/14 03:56 PM
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Joined: Jan 2003
Posts: 9,888
Weddington, N.C.
Streetwize
master
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master
Joined: Jan 2003
Posts: 9,888
Weddington, N.C.
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That's because the high velocity pulses of the tubes exiting into the collecter create a 'draw' (Bernoulli effect) behind them felt by the adjacent tubes. If there's not a sufficient amount of downstream volume the draw "scavenging" is minimized or negated.
flowmaster theory is also related to creating a low pressure area that draws (creates a negative pressure) on the upstream pipe, the CFM flow of pumping air through a muffler tells "A" story, but not the whole story....so just like flowing an intake port...take raw CFM data with a grain of salt.
Last edited by Streetwize; 02/04/14 04:02 PM.
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Re: Mufflers... Any E.T gain from swapping?
[Re: Twostick]
#1573489
02/04/14 04:03 PM
02/04/14 04:03 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
I think 18" give or take not very much was the magic number depending on what was less than ideal in your combo.
Kevin
Its usually in the 16"-18" range but each engine will
vary some... if you have a slip on or a bolt on extension
you can start long and make passes cutting off a 1/2"
at a time till you start to loose the 60'.. also
tweak in the jetting on each change to make sure your
in the proper tune... once you go to far then you
know the length you need... you can weld on any length
you cut off or buy new extensions... I make all my
extensions and weld them on when the job is completed ...
come spring time I'll be adding some electric dumps
to my exhaust... I'm lazy so a flip of the switch
I can reduce the back pressure
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Re: Mufflers... Any E.T gain from swapping?
[Re: WO23Coronet]
#1573490
02/04/14 04:05 PM
02/04/14 04:05 PM
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Joined: Jan 2003
Posts: 13,385
Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,385
Marion, South Carolina [><]
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Quote:
When you guys run open headers do you put collector extension on? Dulcich did an extensive header comparison awhile back on a hot 440 (Hooker super comp headers I think) and a proper length collector extension was worth a ridiculous amount of power over the factory collector length, something like 40-60 HP, but only in the lower to mid range level, it didn't seem to make a huge difference in the upper RPM's. I think the engine dyno'ed in the 600+HP range.
I did not add extensions on the 2 tests I did w/ my 440 motors.
On my hemi, I typically run a pair of 4" bullet race mufflers that I slip right onto the collectors...basically a low restriction muffled collector extension if you will. It runs basically the same w/ them or w/ open collectors. It makes a lot more power than the 440s I ran before though...the 440s would have probably benefitted from the extra collector length, whereas my hemi may not really need it.
CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax
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Re: Mufflers... Any E.T gain from swapping?
[Re: Streetwize]
#1573491
02/04/14 04:07 PM
02/04/14 04:07 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
That's because the high velocity pulses of the tubes exiting into the collecter create a 'draw' (Bernoulli effect) behind them felt by the adjacent tubes. If there's not a sufficient amount of downstream volume the draw "scavenging" is minimized or negated.
flowmaster theory is also related to creating a low pressure area that draws (creates a negative pressure) on the upstream pipe, the CFM flow of pumping air through a muffler tells "A" story, but not the whole story....so just like flowing an intake port...take raw CFM data with a grain of salt.
Yeah I know whats causing the increase and also the
effect from changing the lengths
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Re: Mufflers... Any E.T gain from swapping?
[Re: Streetwize]
#1573492
02/04/14 09:00 PM
02/04/14 09:00 PM
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Joined: Jan 2003
Posts: 5,895
Florida
Locomotion
master
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master
Joined: Jan 2003
Posts: 5,895
Florida
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Quote:
That's because the high velocity pulses of the tubes exiting into the collecter create a 'draw' (Bernoulli effect) behind them felt by the adjacent tubes. If there's not a sufficient amount of downstream volume the draw "scavenging" is minimized or negated.
flowmaster theory is also related to creating a low pressure area that draws (creates a negative pressure) on the upstream pipe, the CFM flow of pumping air through a muffler tells "A" story, but not the whole story....so just like flowing an intake port...take raw CFM data with a grain of salt.
Would it be logical to assume that a properly designed X-pipe creates the "Bernoulli effect" at the junction as well?
What is the theory behind "merge collector" styles manufactured by Lelchook, Burns, etc.?
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Re: Mufflers... Any E.T gain from swapping?
[Re: Locomotion]
#1573493
02/04/14 09:11 PM
02/04/14 09:11 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Quote:
That's because the high velocity pulses of the tubes exiting into the collecter create a 'draw' (Bernoulli effect) behind them felt by the adjacent tubes. If there's not a sufficient amount of downstream volume the draw "scavenging" is minimized or negated.
flowmaster theory is also related to creating a low pressure area that draws (creates a negative pressure) on the upstream pipe, the CFM flow of pumping air through a muffler tells "A" story, but not the whole story....so just like flowing an intake port...take raw CFM data with a grain of salt.
Would it be logical to assume that a properly designed X-pipe creates the "Bernoulli effect" at the junction as well?
What is the theory behind "merge collector" styles manufactured by Lelchook, Burns, etc.?
The X or H shuttles the pulse back and forth so it
doesnt really disrupt the flow... the merge if setup
proper for the engine will increase the velocity in
the primary to create a better draw on the overlap
in the cam for a better filling of the next charge
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Re: Mufflers... Any E.T gain from swapping?
[Re: Locomotion]
#1573494
02/05/14 06:10 PM
02/05/14 06:10 PM
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Joined: Oct 2004
Posts: 8,165
Left Coast
BobR
master
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master
Joined: Oct 2004
Posts: 8,165
Left Coast
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Quote:
Quote:
That's because the high velocity pulses of the tubes exiting into the collecter create a 'draw' (Bernoulli effect) behind them felt by the adjacent tubes. If there's not a sufficient amount of downstream volume the draw "scavenging" is minimized or negated.
flowmaster theory is also related to creating a low pressure area that draws (creates a negative pressure) on the upstream pipe, the CFM flow of pumping air through a muffler tells "A" story, but not the whole story....so just like flowing an intake port...take raw CFM data with a grain of salt.
Would it be logical to assume that a properly designed X-pipe creates the "Bernoulli effect" at the junction as well?
What is the theory behind "merge collector" styles manufactured by Lelchook, Burns, etc.?
The merge, if done correctly, increases exhaust speed. The pinch point is a venturi. It normally takes a lot of testing to see gain but there usually is some. Look at a pro stock header.
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Re: Mufflers... Any E.T gain from swapping?
[Re: 70Dustmite440]
#1573500
02/08/14 12:54 PM
02/08/14 12:54 PM
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Joined: Jan 2003
Posts: 9,888
Weddington, N.C.
Streetwize
master
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master
Joined: Jan 2003
Posts: 9,888
Weddington, N.C.
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The Pinch point in a merge collector acts sort of like a check valve or more accurately a "backflow preventer"....the 4 high velocity "slugs" of header pipe exhaust are "rifle shot" past the pinch point in a merge collector and directly into a larger diameter downstream pipe, so the pinch in effect works like a check valve since the expanding ( and as a result slowing) exhaust won't very easily push back very effectively against the narrow/smaller diameter upstream pinch. Not quite the same means of achieving the Bernoulli effect of a "conventional" header collector, but it seems to be more effective on higher RPM N/A Race motors that operate 100% of the time at RPMs above their torque peak. Mufflers, headers/collectors, the key is all the same, trying to get that slug of spent gas out of the cylinder and past the exhaust valve as efficiently (and quickly) as possible for AS LONG AS POSSIBLE (keep the VE up) in the RPM range you want/need the motor to run in. For a muffled true dual-purpose car the exhaust is always going to be a compromise in one way or the other (optimum sizing/routings/sound dB's/or overall weight) Open headers with an optimum length collector is going to be as good as you can get, Guys who have it right don't drop a significant amount of ET with mufflers or without, although the tune to get there may still wind-up being a bit different. A number of experts all told me thoughout the years (and I've found it to be true) that the first 4-6 inches of pipe past the head flange are far more important than all that happens beyond it. In a production chassis the bends required in the initial primary tubes (off the flange) are almost always a compromise.
Last edited by Streetwize; 02/08/14 01:02 PM.
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Re: Mufflers... Any E.T gain from swapping?
[Re: GTX MATT]
#1573502
02/08/14 05:44 PM
02/08/14 05:44 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Quote:
A number of experts all told me thoughout the years (and I've found it to be true) that the first 4-6 inches of pipe past the head flange are far more important than all that happens beyond it. In a production chassis the bends required in the initial primary tubes (off the flange) are almost always a compromise.
This is interesting, that sounds like it would make the best option fenderwell headers, which they don't make for any of us other than big block A body guys now. But everyone ran them back in the day. It'd be interesting to see the dyno results of a fenderwell vs an underchassis header of the same size and tube length on the same engine.
On a chassis car I always try to get 1 cyl volume
before I hit the tangent point of the first bend..
a production car thats pretty much impossible to do
so they sacrifice that part
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