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post #1 of 66 (permalink) Old 06-26-2009, 12:55 AM Thread Starter
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deleted mufflers=power loss???

I finally cut off my mufflers off today and put straight pipe in. It sounds awesome and I love it!!! The only thing is, it seems like I've lost some power. It will still break the tires loose, but I have to get on it harder to get it to do it. I would've thought that the opposite would've happened. Has anyone else experienced this??

Mike
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post #2 of 66 (permalink) Old 06-26-2009, 01:12 AM
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Quote:
Originally Posted by mh68 View Post
I finally cut off my mufflers off today and put straight pipe in. It sounds awesome and I love it!!! The only thing is, it seems like I've lost some power. It will still break the tires loose, but I have to get on it harder to get it to do it. I would've thought that the opposite would've happened. Has anyone else experienced this??

Mike
No back pressure= No torque

Jim

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post #3 of 66 (permalink) Old 06-26-2009, 01:13 AM
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I did... i dont know if its the placebo effect or what, but I immediately noticed a difference in low end torque.

I think somewhere on this site there is a chart showing the differences of mufflers and no mufflers and power loss, etc...

What size tips did you use btw? mine were 3.5x22 and i LOVE the low, hollow sound lol

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post #4 of 66 (permalink) Old 06-26-2009, 06:33 AM
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Quote:
Originally Posted by Canadian_LX View Post
I did... i dont know if its the placebo effect or what, but I immediately noticed a difference in low end torque.

I think somewhere on this site there is a chart showing the differences of mufflers and no mufflers and power loss, etc...

What size tips did you use btw? mine were 3.5x22 and i LOVE the low, hollow sound lol
The chart you're referring to is in the second post in this thead.

Mods? Yea, I got mods ...
Air silencer delete, warp drive, dilithium crystals, flux capacitor, Slingshot Rubber band power adder, Moonshine & Gas, Leaf Blower Supercharger, Hamster Wheel & Hamster, Energizer Bunny generating 1.21 gigawatts, Mr. FusionŽ Home Energy Reactor, hover conversion and a sextant celestial navigation system (The original GPS)
Best 1/4: 1,320 nanoseconds @ 670,616,629.2 miles per hour

"There isn't that much difference anymore between spacecraft, aircraft and modern automobiles..." - Keith Henry, NASA's Langley Research Center
See a list of my real mods and pictures of my car HERE. The true performance of my car was made possible by the Carolinas Crew Chief, RobertP at Rob's Tire & Auto
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post #5 of 66 (permalink) Old 06-26-2009, 08:00 AM
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^^ Ah yes, gracia senor

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post #6 of 66 (permalink) Old 06-26-2009, 09:42 AM
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Borla XR1's look pretty nice. I'd suggest those b/c of the torque which is great for shredding tires. Now if only I can scrounge up some $$$.......

Michael M. ASE P2 Automobile Parts Specialist.

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post #7 of 66 (permalink) Old 06-26-2009, 09:58 AM
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if you just removed the mufflers it shouldnt have that much effect. you would loose some low end torque but barley noticeable. if you ran straight pipes like i did in my old bird then yeah you would definitely loose low end but gain some high end

-Patrick
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post #8 of 66 (permalink) Old 06-26-2009, 10:13 AM
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torque is not lost.....it is now in a different place in the power band....in the higher rpm's.

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post #9 of 66 (permalink) Old 06-26-2009, 10:49 AM Thread Starter
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Quote:
Originally Posted by Canadian_LX View Post
I did... i dont know if its the placebo effect or what, but I immediately noticed a difference in low end torque.

I think somewhere on this site there is a chart showing the differences of mufflers and no mufflers and power loss, etc...

What size tips did you use btw? mine were 3.5x22 and i LOVE the low, hollow sound lol
I know, I love the low rumble too, it's reminding me of my old big block fords i used to have. I just put straight pipe in with turndowns almost tucked up under the bumper, I like the clean look
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post #10 of 66 (permalink) Old 06-26-2009, 11:07 AM Thread Starter
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So are borla turbo mufflers the same as XS that's on the chart? I went to borlas site and they don't list an XS and they are more than I wanted to spend. I cut mine off for sound and cheapness BUT, I have noticed the shift in the power band and I want it at lower rpms. So to achieve the no muffler sound with lower torque, which muffler would be better? I know I don't like the sound of flowmasters on a 4.6. Thrush turbos don't sound too bad and are cheap but will I get the performance out of them that I'm looking for?

Thanks
Mike
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post #11 of 66 (permalink) Old 06-26-2009, 11:11 AM Thread Starter
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I found the borla pro XS mufflers on a separate section of their site. How close would these sound to no mufflers?

Mike
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post #12 of 66 (permalink) Old 06-26-2009, 11:44 AM
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IMO if you want to get a good amount of performance and sound you should run a true dual setup with either a mid-mounted magnaflow or a set of borlas out back, if your not looking to spend a ton of money then I would just throw a cheaper set of mufflers out back, something like dynomax or anything along that line.

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post #13 of 66 (permalink) Old 06-26-2009, 11:46 AM Thread Starter
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Quote:
Originally Posted by MikeyB View Post
IMO if you want to get a good amount of performance and sound you should run a true dual setup with either a mid-mounted magnaflow or a set of borlas out back, if your not looking to spend a ton of money then I would just throw a cheaper set of mufflers out back, something like dynomax or anything along that line.
That's what I was thinking. I figure a cheaper set like Thrush turbos which are dynomax would keep me around factory torque so I'm leaning towards those for now. Am I right, would a cheaper set like that bring my torque back to the lower end?

Mike
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post #14 of 66 (permalink) Old 06-26-2009, 12:23 PM
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That's what I was thinking. I figure a cheaper set like Thrush turbos which are dynomax would keep me around factory torque so I'm leaning towards those for now. Am I right, would a cheaper set like that bring my torque back to the lower end?

Mike
Yep those should bring you back to where you were before with a little added tone.


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post #15 of 66 (permalink) Old 06-26-2009, 12:34 PM
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On a basically stock engine. The point is moot. Exhaust is one of the last mods you should look at making. The torque differences between Thrush, Dynomax and Borla would be minimal on a stock engine.
The sound difference would be the defining determining factor.

I went with the Borla Pro XS mufflers for my new set up for the following reasons:
  • I always wanted Borla
  • They're the quietest of the choices out there (according to the chart I cited earlier)
  • They're 4th highest rated in terms of HP gains (according to This post)
  • They rated highest in power gains in six RPM ranges on the PDF spreadsheet.
  • They're reasonably priced. I purchased mine from Wicked Nicky's Exhaust in the 2.5" size in the offset in / center out configuration for only $84.00 each. They're also available in 2", 2-1/4", and 3" sizes.
  • OX said he regretted selling his Borlas.
  • The Great Obucina recommended them and I heard a set on his F150 (Very Nice Sound!)

Quote:
Originally Posted by _95badbird View Post
Torque is not lost.....it is now in a different place in the power band....in the higher rpm's.
Agreed. Torque loss due to loss of back pressure is an urban Legend/Myth.

Here's another good explaination from a fellow member here.

Quote:
Originally Posted by MadMikeyL View Post
ARGGH! The whole "backpressure in the exhaust" thing is another one of my pet peeves!

You never want backpressure in the exhaust, plain and simple. If you had any pressure in the exhaust at all, your power would drop like a rock. Ever drive a car with a plugged-up cat? It probably wouldn't go more than about 30mph, right? THAT is backpressure in the exhaust, and as you can tell, it didn't help the power of the engine at any point along the way.

You want that vacuum I was talking about for the scavenging effect, and vacuum is the opposite of pressure. The thing is that vacuum is only created by the velocity of the exhaust gases leaving the pipes. If you open up the pipe without increasing the quantity of exhaust gas that is going through it, you have just decreased the exhaust gas velocity. Decreased velocity causes decreased vacuum for scavenging, which is technically the same as increasing the pressure in the exhaust. So going to too large a pipe is technically increasing the pressure in the exhaust system. I bet nobody on the internet has ever told it to you that way before! Increased pressure (or decreased vacuum, since they are really the same thing) means that the exhaust has to be pushed harder to get out of the engine. This means more of the power the motor made is wasted pushing the exhaust out the tailpipe instead of pushing the car forward.

So, ANY pressure above ambient atmospheric pressure is going to drastically hurt your power and torque curve all the way across the line. While it is true that putting too large an exhaust on a car can hurt low end, the reason is not because the stock system has backpressure, but quite the opposite it is because the stock system has enough velocity at the lower rpms to create a scavenging effect. On a high perfrormance car, it might be beneficial to you to sacrifice a few lb-ft of torque down low to gain a few hp up top, and that is what the larger diameter pipe does for you because it moves both the rpm at which the scavenging occurs and the rpm at which the exhaust becomes a restriction up higher in the powerband. If you have a completely stock engine, and you don't rev it higher than the factory set rev limiter, and you go put dual 3" exhaust on it, you have just lost some low end torque, but you haven't gained anything up top because the operating range of your engine and the operating range of your exhaust system are now nowhere even close to each other.

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Air silencer delete, warp drive, dilithium crystals, flux capacitor, Slingshot Rubber band power adder, Moonshine & Gas, Leaf Blower Supercharger, Hamster Wheel & Hamster, Energizer Bunny generating 1.21 gigawatts, Mr. FusionŽ Home Energy Reactor, hover conversion and a sextant celestial navigation system (The original GPS)
Best 1/4: 1,320 nanoseconds @ 670,616,629.2 miles per hour

"There isn't that much difference anymore between spacecraft, aircraft and modern automobiles..." - Keith Henry, NASA's Langley Research Center
See a list of my real mods and pictures of my car HERE. The true performance of my car was made possible by the Carolinas Crew Chief, RobertP at Rob's Tire & Auto

Last edited by Trunk Monkey; 06-28-2009 at 08:23 AM.
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post #16 of 66 (permalink) Old 06-26-2009, 12:51 PM Thread Starter
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Originally Posted by Trunk Monkey View Post
On a basically stock engine. The point is moot. Exhaust is one of the last mods you should look at making. The torque differences between Thrush, Dynomax and Borla would be minimal on a stock engine.
The sound difference would be the defining determining factor.

I went with the Borla Pro XS mufflers for my new set up for the following reasons:
  • I always wanted Borla
  • They're the quietest of the choices out there (according to the chart I cited earlier)
  • They're 4th highest rated in terms of HP gains (according to This post)
  • They rated highest in power gains in six RPM ranges on the PDF spreadsheet.
  • They're reasonably priced. I purchased mine from Wicked Nicky's Exhaust in the 2.5" size in the offset in / center out configuration for only $84.00 each. They're also available in 2", 2-1/4", and 3" sizes.
  • OX said he regretted selling his Borlas.
  • The Great Obucina recommended them and I heard a set on his F150 (Very Nice Sound!)

I considered the borlas but I listened to them on a 96 t bird and really didn't like the popping and crackling, but that could've been specific to that car and also, they are quieter than no mufflers according to that chart. I'm wanting the no muffler sound but without any power loss. Thirdly, I can get the thrush mufflers $56 for both, which right now, is the deciding factor for me. Eventually I will do true duals with good performance mufflers, but I have other stuff to do first on my car

Mike
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post #17 of 66 (permalink) Old 06-26-2009, 03:06 PM
 
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I've read (here) that using slightly smaller diameter pipes in place of the mufflers will allow the exhaust velocity to remain the same as with mufflers, hence not losing any power, but as mentioned above, I don't think you really do lose power. I haven't noticed anything less, and I'm using straight pipes too.

I love the sound, but I don't think it's loud enough
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post #18 of 66 (permalink) Old 06-26-2009, 03:31 PM
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i agree. that set up sounded great in my 4.6L. but as soon as i swapped it out for my 351, it sounds like ****! but i also now have 1/3 of my cats- but i doubt that makes a difference
Sorry to thread jack... but in regards to ontario emissions laws, are you testing your car as a hotrod or still the stock numbers? Are you still able to pass? I was thinking of getting rid of my third cat and replacing the other two with high-flow ones but im afraid i'll fail on the nox readings.

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post #19 of 66 (permalink) Old 06-26-2009, 03:38 PM
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Originally Posted by BigJohnny View Post
I've read (here) that using slightly smaller diameter pipes in place of the mufflers will allow the exhaust velocity to remain the same as with mufflers, hence not losing any power, but as mentioned above, I don't think you really do lose power. I haven't noticed anything less, and I'm using straight pipes too.

I love the sound, but I don't think it's loud enough
I didnt notice/feel any loss of power with either of my cars when they were straight piped. With my tbird I did notice a slight increase in throttle response (or so I thought), but on my cougar I havent noticed the slightest difference except the exhaust tone. Thats not saying much though since the blowmasters that were on there when I got it were completely rotted out.

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post #20 of 66 (permalink) Old 06-26-2009, 03:40 PM
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lol. They're also affectionately called Rustmasters for obvious reasons...

Mods? Yea, I got mods ...
Air silencer delete, warp drive, dilithium crystals, flux capacitor, Slingshot Rubber band power adder, Moonshine & Gas, Leaf Blower Supercharger, Hamster Wheel & Hamster, Energizer Bunny generating 1.21 gigawatts, Mr. FusionŽ Home Energy Reactor, hover conversion and a sextant celestial navigation system (The original GPS)
Best 1/4: 1,320 nanoseconds @ 670,616,629.2 miles per hour

"There isn't that much difference anymore between spacecraft, aircraft and modern automobiles..." - Keith Henry, NASA's Langley Research Center
See a list of my real mods and pictures of my car HERE. The true performance of my car was made possible by the Carolinas Crew Chief, RobertP at Rob's Tire & Auto
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post #21 of 66 (permalink) Old 06-26-2009, 03:43 PM
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lol. They're also affectionately called Rustmasters for obvious reasons...
Ahhh yes thats the word I was looking for! lol

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post #22 of 66 (permalink) Old 06-26-2009, 03:44 PM
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i was thinkin crapmasters..

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post #23 of 66 (permalink) Old 06-26-2009, 04:01 PM
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i love the sound of my flowmaster delta flow 40, but all this talk about rust is worrying me. can i do anything to keep it from rusting?

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post #24 of 66 (permalink) Old 06-27-2009, 11:13 PM
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Most auto parts stores sell hi-temp paint. The stuff I use is the "ceramic" and about $8 a can. It holds up good. As for some good cheap mufflers, try Summit Racing Mufflers. I have these:
http://www.summitracing.com/parts/SUM-638222/ They are chambered similar to Rustmaster and have a similar sound without the (annoying) ping. They come dressed in primer, so paint is a must. If anyone uses them, the inlets and outlets are 2.5 inside diameter and it makes getting a proper fitting tip tough. As for performance, they are identical to the Summit Fully Welded, but are not bi-directional. I asked on line about the fully welded and was told these are identicle in performance but would give a lower tone (and they do!). Here is a copy (cut and paste) from Car Crafts comparisons a couple years ago:
I have listed here a muffler shootout test done by CAR CRAFT, they show the best bang for the buck, and show the db's

The Mufflers
MAKE MODEL Part No. COST
SUMMIT Turbo 630125 $14.75
THRUSH Magnum Glasspack 24214 $16.50
THRUSH Boss Turbo 17718 $23.95
HOOKER Competition 21006 $25.95
DYNOMAX Super Turbo 17733 $28.50
DYNOMAX Race Magnum 24215 $31.95
HOOKER Super Competition 21106 $35.95
SUMMIT Fully Welded 630325 $38.69
FLOWTECH Afterburner 50322 $39.95

MUFFLER FLOW TEST

MUFFLER Flow at 28-in H20
DynoMax Race Magnum 528.64 cfm
Thrush Magnum Glasspack 507.40 cfm
Summit Fully Welded 343.38 cfm
Flowtech Afterburner 342.20 cfm
DynoMax Super Turbo 333.94 cfm
Hooker Competition 232.46 cfm
Hooker Super Competition 320.96 cfm
Summit Turbo 331.16 cfm
Thrush Boss Turbo 297.36 cfm

MUFFLER Idle dB WOT dB
DynoMax Super Turbo 89 123
DynoMax Race Magnum 94 133
Flowtech Afterburner 92 124
Hooker Competion 92 122
Hooker Super Competion 90 125
Summit Turbo 89 124
Summit Fully Welded 92 125
Thrush Boss Turbo 90 123
Thrush Magnum Glasspack 92 128

DYNO TEST
All mufflers were dyno-tested on a 355-cube SBC with 10.0:1 compression, Air Flow Research 190 aluminum heads, a CompCams 292 hyd. a Victor Jr. intake, a Holley 750-cfm double-pumper, and 1 5/8 Headman headers.


MUFFLER HP TORQUE 2,500-6,000rpmAverage
Hooker Competition 397.4 381.1 286.8hp/351.9 lb-ft
Thrush Boss Turbo 407.1 384.9 292.1 hp/357.5 lb-ft
DynoMax Race Magnum 409.5 394.3 298.8 hp/366.9 lb-ft
Flowtech Afterburner 409.7 391.2 294.8 hp/361.7 lb-ft
Thrush Glasspack 409.5 389.8 297.7 hp/365.3 lb-ft
Summit Turbo 411.5 386.3 291.5 hp/357.4 lb-ft
DynoMax Super Turbo 412.7 387.2 292.6 hp/358.6 lb-ft
Hooker Super Comp 413.8 387.2 292.8 hp/359.0 lb-ft
Summit Fully Welded 415.4 390.7 295.6 hp/362.4 lb-ft

These aren't too shabby!

Mods? Do the ones in the garage waiting to go on the car count?

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post #25 of 66 (permalink) Old 06-28-2009, 05:53 AM
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i love the sound of my flowmaster delta flow 40, but all this talk about rust is worrying me. can i do anything to keep it from rusting?
Nope. There's nothing you can do to protect them. If you absolutely have to have that sound just replace them with another set when they go bad or switch to another brand. FYI the Borla's are stainless steel.

Mods? Yea, I got mods ...
Air silencer delete, warp drive, dilithium crystals, flux capacitor, Slingshot Rubber band power adder, Moonshine & Gas, Leaf Blower Supercharger, Hamster Wheel & Hamster, Energizer Bunny generating 1.21 gigawatts, Mr. FusionŽ Home Energy Reactor, hover conversion and a sextant celestial navigation system (The original GPS)
Best 1/4: 1,320 nanoseconds @ 670,616,629.2 miles per hour

"There isn't that much difference anymore between spacecraft, aircraft and modern automobiles..." - Keith Henry, NASA's Langley Research Center
See a list of my real mods and pictures of my car HERE. The true performance of my car was made possible by the Carolinas Crew Chief, RobertP at Rob's Tire & Auto
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post #26 of 66 (permalink) Old 06-28-2009, 12:39 PM
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Quote:
Originally Posted by warmaster259 View Post
No back pressure= No torque

Wow, the myths are rampant aren't they?

Any back pressure in the exhaust is bad, any.

The goal of all exhaust systems is to remove the exhaust. The goal is not to play with it, speed it up, slow it down, or twirl it around etc.

The goal is to get it out of the engine, an engine is just an air pump. The more restrictions are in the exhaust(for any reason), the less air is pumped through the engine. Less air coming out means less air going in, less fuel is needed, and less power can be made.

The bottom line is simple, and this is what people do not get. Any defined air flow through the engine needs a specific amount of fuel to make the most power.

If you decrease(smaller pipes, mufflers) the airflow with the same amount of fuel, you get less power(running rich).
If you increase(bigger pipes, mufflers) the airflow with the same amount of fuel, you get less power(running lean).

The answer is always to correct the air/fuel ratio. You have altered the A/F ratio by removing the mufflers. The power is down not because back pressure is needed. Power is down because the engine is running leaner, it needs more fuel.

The only part of the exhaust which critically needs to be a certain size for the given application is the exhaust manifolds, the headers. Those need to be sized for the rpm band of the specific engine. The entire rest of the exhaust can be made as large as you wish, the bigger the better. If you tune the engine(PCM or carburetor), then no power is lost at any rpm, none. There is not any power lost at lower rpm's if you properly tune the A/F ratio. In fact, the power goes up at all rpm's.

Why is this stuff so magical to people, doesn't anyone spread this knowledge around, instead of letting the myths grow? Regards,

_________
Don

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98 Mountaineer, A4WD, Big brakes - 12.75" x 1.25" rotors
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post #27 of 66 (permalink) Old 06-28-2009, 01:55 PM
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Uh, yea. I covered that back in post #16.

Mods? Yea, I got mods ...
Air silencer delete, warp drive, dilithium crystals, flux capacitor, Slingshot Rubber band power adder, Moonshine & Gas, Leaf Blower Supercharger, Hamster Wheel & Hamster, Energizer Bunny generating 1.21 gigawatts, Mr. FusionŽ Home Energy Reactor, hover conversion and a sextant celestial navigation system (The original GPS)
Best 1/4: 1,320 nanoseconds @ 670,616,629.2 miles per hour

"There isn't that much difference anymore between spacecraft, aircraft and modern automobiles..." - Keith Henry, NASA's Langley Research Center
See a list of my real mods and pictures of my car HERE. The true performance of my car was made possible by the Carolinas Crew Chief, RobertP at Rob's Tire & Auto
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post #28 of 66 (permalink) Old 06-28-2009, 02:05 PM
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No, you didn't cover it in post #16, no one here did prior to my post.

You did post several quotes, many of which erroneously support the myth that low end torque(or power) is lost, again with no explanation of why.

The A/F ratio is critical to power, so is the ignition timing. A stock tune is not the best for maximum power(and torque) of any engine when you start altering the exhaust. Read it again, read yours and your quotes. Then you may see that no mention is made about the air and fuel ratio except by me.

I'm not trying to claim sole knowledge of these facts, I don't care who does or when it was discovered. I just want the truth to be posted, all so that anyone can understand how to get the most power out of their exhaust.

The key should be to go bigger with the exhaust after the headers. Always go bigger, but always be sure to retune the engine with more fuel to correct the A/F, to gain power. Regards,

_________
Don

91 Mark VII LSC SE, Griggs and MM suspension soon
98 Mountaineer, A4WD, Big brakes - 12.75" x 1.25" rotors
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post #29 of 66 (permalink) Old 06-28-2009, 02:18 PM
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Mufflers aren't the restriction for 1. Its the cats and compression bends all over the place.

All you get from straight pipes in place of mufflers is a swarm of bee's sound. I had the ART true dual system on my car with high flow cats and it was an improvment over stock definitly but now im running NO carts midmount magnaflow and 3 inch piping. Talk about flow. And the sound is incredible. And of course low end power isnt noticeable for me with the stall im running and supercharger. If anything I have to much low end power for the street.

04 PI swap,SVO Supercharger 8-9 psi,Alcohol injection,39lbs Cobra injectors,XCal2-Walbro 255 LPH fuel pump,4.10 T-Lok,2003 4R70W built to withstand by RobertP,450hp JMOD,3800 circleD stall,trucool 4739 Trans Cooler,Dynotech 3.5 Driveshaft,70mm T/B,SCP Cold Air Intake,90mm LMAF,JBA headers,Magnaflow Midmount,No cats with 3inch piping,Vogtland 1.6inch drop,Cobra R's and xenon body kit.

Its slow, Really.
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post #30 of 66 (permalink) Old 06-28-2009, 02:27 PM
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Trunk Monkey, this quoted section below is part of your post #16 quote above.


Quote:
Originally Posted by MadMikeyL View Post
ARGGH! The whole "backpressure in the exhaust" thing is another one of my pet peeves!

You never want backpressure in the exhaust, plain and simple. ...


If you have a completely stock engine, and you don't rev it higher than the factory set rev limiter, and you go put dual 3" exhaust on it, you have just lost some low end torque, but you haven't gained anything up top because the operating range of your engine and the operating range of your exhaust system are now nowhere even close to each other.
There is a little truth in there, but this last sentence is really bad. That is at the core of myths about exhaust.

That one sentence is wrong badly on two points. It states that you lose low end torque with a bigger exhaust(stock engine). It follows that error by saying that above the low end there is nothing gained up top.

I call that BS, period. There is no mention of the air/fuel ratio, which is absolutely critical. No one should be altering the inlet and outlet restrictions on any engine without consideration of the tune of the A/F ratio. The A/F ratio must be adjusted, without it you might as well be swapping injectors without adjusting the PCM.

If you bolt on a dual 3" exhaust onto a bone stock Mustang 302, and adjust the PCM, the power will go up from idle to maximum rpm's. All of the power at every single rpm will be higher, but only if you adjust the air/fuel ratio properly.

_________
Don

91 Mark VII LSC SE, Griggs and MM suspension soon
98 Mountaineer, A4WD, Big brakes - 12.75" x 1.25" rotors
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