Exhaust TECH Mufflers, Headers and Pipes Issues

          
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  #21  
Old 11-13-2022, 01:41 PM
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In the early 90's, my cousin had a '78 T/A, daily driver, 400, lots of mods, ran mid/low 13's on his daily driver tires (drag radials didn't exist, and we couldn't afford slicks). I had a '79 T/A daily driver, mild 455, and about the same performance. We both had the same headers and exhaust systems.

One day my cousin decided to open his headers at the track - he ran 12.9's! Several tenths faster than the car had ever ran.

Encouraged by his success, I opened my headers a few weeks later. My car stumbled off the line and ran a couple tenths slower.

We later realized his carb was too rich with the exhaust connected, but AFR was about perfect for open exhaust. Mine was about perfect for full exhaust, but leaned way out too much when I opened it.

To make any test fair, you have to correct the AFR.

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  #22  
Old 11-13-2022, 01:43 PM
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Thanks, will monitor the AFR.

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  #23  
Old 11-14-2022, 03:16 PM
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Engine Masters has had some good episodes on this subject and determined that a 3" diameter extension from the collector. 18" long is the ideal setup for maximizing torque. They also tested a 3" single pipe system against 2-1/2" duals and found the single to be as good as long as the y-pipe was far enough back from the engine.

In another episode, they evaluated cut-outs, especially how the dump pipe was spliced into the main and got some very surprising results. Low rpm performance can be impacted very negatively because of pulse reflection back towards the engine from the dump pipe.

In all cases though, A/F ratio needed to be adjusted with rejetting.

  #24  
Old 11-14-2022, 05:10 PM
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Originally Posted by srmmmm View Post
Engine Masters has had some good episodes on this subject and determined that a 3" diameter extension from the collector. 18" long is the ideal setup for maximizing torque. They also tested a 3" single pipe system against 2-1/2" duals and found the single to be as good as long as the y-pipe was far enough back from the engine.

In another episode, they evaluated cut-outs, especially how the dump pipe was spliced into the main and got some very surprising results. Low rpm performance can be impacted very negatively because of pulse reflection back towards the engine from the dump pipe.

In all cases though, A/F ratio needed to be adjusted with rejetting.
I don't believe 18 inches is the "ideal" setup...it is the more common length. Every engine combo and header combo will have a different length.
3 single pipe vs 2.5 duals is fine for smaller hp builds I'm sure..but either is grossly small for higher hp.

I did take interest in the cut out video, it for sure showed there is an ideal spot for cut outs...many street guys will just do it for sound not realizing it is a hp loss but sounds "cool"

The test I'm interested in and have never seen is the X pipe vs the collector extensions

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  #25  
Old 11-15-2022, 10:23 AM
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Many times, cutouts are installed where it's feasible under the car. Each car being different with floor clearance and other obstacles.

What I've always done is make sure the cutouts are at least 18 inches from the header collectors, as in the picture I showed above. Sometimes that varies a few inches, again because of other obstacles. This mimics what has been shown time and again that open headers with some sort of extension is more beneficial than just having headers open at the collector.

The only issue I see with cutouts after an X, as I have on one car here, is the cutout ends up being even further back. That one, by the time it exits the cutout and makes the turn, ends up being at the front of the mufflers, which is basically at the rear end housing of the car. X placement also varies per car.

Is that too far back? Don't know. Haven't tested this one yet, but it does at least remove the rest of the system from the equation when the cutouts are open, meaning no more mufflers and no more over the axle tail pipes, and tailpipes on this car are super long too.

I can say cutouts as I pictured above, which end up being about 20" from the header collectors and are a straight shot before they hit any bends in the system, work exceptionally well at the track vs the full system, and that's not a restrictive system by most standards with 3" pipe, Dr. Gas X and Dynomax mufflers with torque tech 3" tail pipes.

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  #26  
Old 11-19-2022, 01:25 AM
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I ran my car with the Y type cutouts between the headers and exhaust. 3" Torq Tech pipes and Walker dynomax mufflers. Car was 12.0 @ 110. Open vs exhaust was less than 1 mph and a tenth. I did run 18" extensions with the old paint stripe to try to find length. Wasn't any faster. When my 1 3/4 headers shot craps I put on Heddman Hustler 2" primary 3 1/2" collector I had sitting for years with 18" extensions. Ran the 1/8 and hit 91 mph forget et but first time over 90 in 1/8th. Have to get to !/4 to see what happens. Also have an X pipe to try but it's tight going 3 1/2, reducer to 3, X pipe, mufflers etc.

  #27  
Old 11-19-2022, 01:52 PM
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An additional comment about track time. When racing through the mufflers vs someone with open headers I don't like not being able to hear my engine and having to rely on the tach/shift light. I like it better if both cars are quiet or both loud.

  #28  
Old 11-19-2022, 02:24 PM
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An additional comment about track time. When racing through the mufflers vs someone with open headers I don't like not being able to hear my engine and having to rely on the tach/shift light. I like it better if both cars are quiet or both loud.
Yes, also the first burnout with no exhaust is pretty intense!

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  #29  
Old 11-19-2022, 06:21 PM
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Not identical but on my 70 gto back in the day I had 1.75 hooker headers, 3" x pipe,3" to 2.5" reducer cones,2.5" ultraflows and 2.5" tailpipes. Unhooking the headers with no collector made no difference really in ET.. Ran 11.7 at 115mph at 3950 race weight.

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  #30  
Old 11-20-2022, 11:10 AM
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When I race the cars muffled I can't hear much anyway with the helmet on so doesn't matter much to me.

Racing the auto cars is of no consequence, I let the trans do the shifting, all I have to do is stab and steer.

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  #31  
Old 11-20-2022, 11:11 AM
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Quote:
Originally Posted by cjs64goat View Post
An additional comment about track time. When racing through the mufflers vs someone with open headers I don't like not being able to hear my engine and having to rely on the tach/shift light. I like it better if both cars are quiet or both loud.
Staging isn’t to bad for me with the noise I don’t like starting it in the lanes surrounded by open exhaust cars.

  #32  
Old 11-20-2022, 11:30 AM
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Quote:
Originally Posted by cjs64goat View Post
I ran my car with the Y type cutouts between the headers and exhaust. 3" Torq Tech pipes and Walker dynomax mufflers. Car was 12.0 @ 110. Open vs exhaust was less than 1 mph and a tenth. I did run 18" extensions with the old paint stripe to try to find length. Wasn't any faster. When my 1 3/4 headers shot craps I put on Heddman Hustler 2" primary 3 1/2" collector I had sitting for years with 18" extensions. Ran the 1/8 and hit 91 mph forget et but first time over 90 in 1/8th. Have to get to !/4 to see what happens. Also have an X pipe to try but it's tight going 3 1/2, reducer to 3, X pipe, mufflers etc.
In case you're not aware, Dr. Gas still makes a nice "X" that reduces the exhaust for you from 3 1/2" to 3" so you can keep the 3 1/2" size come from the header collector all the way to the X, and then run a 3" size after, into the mufflers and 3" tails.

That's how dad's GTO is configured, with the electric cutouts in the 3 1/2" section.

Fits nice on any A-body without issue. F-body would be a little tighter, depends on what you're working on.

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  #33  
Old 11-20-2022, 02:23 PM
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In high school we used to have "Open header Fridays" If a cop was around shut it off and coast-most were stick cars back then! At night letting off the gas and the flash/pop back in the collector was quite a show!

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  #34  
Old 11-30-2022, 04:11 PM
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Originally Posted by ta man View Post
I don't believe 18 inches is the "ideal" setup...it is the more common length. Every engine combo and header combo will have a different length.
3 single pipe vs 2.5 duals is fine for smaller hp builds I'm sure..but either is grossly small for higher hp.

I did take interest in the cut out video, it for sure showed there is an ideal spot for cut outs...many street guys will just do it for sound not realizing it is a hp loss but sounds "cool"

The test I'm interested in and have never seen is the X pipe vs the collector extensions
I'll look later but i believe pipe max says around 18" also, but that is from where the primary pipes end in the collector and not 18" from the end of the collector!

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  #35  
Old 11-30-2022, 04:53 PM
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That's been tested a bunch. Most recently on the engine masters show.

They did in fact find that about 18 inches from the end of the collector to be about optimum. Any shorter hurt power and longer didn't seem to matter at all.

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Old 12-01-2022, 12:42 PM
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Originally Posted by Formulajones View Post
That's been tested a bunch. Most recently on the engine masters show.

They did in fact find that about 18 inches from the end of the collector to be about optimum. Any shorter hurt power and longer didn't seem to matter at all.
What intrigues me is the "longer doesn't seem to matter theory"..and will an x added on create power.

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373 gears 3200 Continental Convertor
best et 10.679/127.5/1.533 60ft
308 gears best et 10.76/125.64/1.5471
  #37  
Old 12-01-2022, 04:54 PM
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What intrigues me is the "longer doesn't seem to matter theory"..and will an x added on create power.
Yeah I thought for sure longer would have an affect, but the back to back testing they did as they increased the length had no real affect on it. I'd have to watch that again, I think they started around 36-40 inches and then started chopping off short sections. It wasn't until they got below 18" they started seeing power fall off, and that was primarily the torque curve if I remember correctly.

We only have one car at the moment with cutouts that are actually behind the "X" cross over. I'd like to test that one out sometime.

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