Simple idea for AR chamber off header collector

[digger]

Digger, It was validated on the dyno, many times. And with the exhaust system that fit back in the car.

so in effect the PWTB concept can be emulated by using a section of pipe that is 0.5" over size like an exaggerated stepped pipe?

[gmrocket]

In the op’s drawing of his tapered AR, it’s not as effective as a small bullet style AR...but it’s in the right direction to add power. On the dyno anyway

Do not taper your exit pipe , make it a blunt cut at 3/4 of the way into the bullet outer diameter.

take a look at the majorty of winning engine masters exhaust terminations...the winningest engine builder has used this exact AR design for years.

[Mikej26]

I placed my AR devices at the inlet side of my x pipe so that I still had a good amount of collector extension ahead of it.[/img]

[Mikej26]

Adding to my above comment. The AR devices I included in the pics are 3” inlet and outlet, but the internal portion tapers down to 2 1/2”.

[BradH]

That's what it looked like to me, but thanks for the confirmation.

Not sure the way my system is routed that I could put an AR chamber right before the X-pipe, although it could make sense given some of the comments above.

Also don't believe I want the ID to be any smaller than 3" it's already been necked down to from the 3.5" collector.

[BradH]

Double checked the system... any AR chamber added is only going to fit right after the collector flange, or after the exit of the X-pipe.

Is after the X-pipe worth considering?

[RevTheory]

Double checked the system... any AR chamber added is only going to fit right after the collector flange, or after the exit of the X-pipe.

Is after the X-pipe worth considering?

Probably, at least I would think so. How much length is there between where the primaries come together and where the x-pipe meets?

[BradH]

I'll have to take measurements to know for sure, but from the end of the primaries to the flange is probably 8- 10", then add another 18-20" to the entrance to the X-pipe junction. The dyno testing was done with straight 18" extensions bolted to the flange, for comparison.

[RevTheory]

I can't back my opinion up with an actual experience doing what you're talking about but I'd sure think that even if it's not a recommended Pipemax length and may be a little on the long side, I don't see how it can't be beneficial.

[BradH]

Found this older thread started by Mikej26 in which Calvin Elston "piped in" (yes, pun intended) w/ some guidance: viewtopic.php?f=1&t=55735

The one comment that got my attention after my last question on this thread: "Depends on where there is room but I have done AR final collectors and a Hendren Piece after the xpipe or final Y"

Sounds like my original idea and adding a couple of AR chambers in the highlighted section of the x-pipe pic below. Both Dynatech and Schoendfeld offer pieces that have 3" ID entries and 3.5" OD outlets (appear to keep the 3" ID through the chamber) would could be dropped down to the remaining 3" section of the exhaust system.
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tti_E-body_X-pipe-AR_chamber_locations.png

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Well, the possibilities are certainly interesting... even if not exactly functional or successful.

[MetricMuscle]

I hope this is still on topic but, I'm wondering about tail pipe size out of the PWTB or AR chamber which acts like one. I've read that it is necessary to have ample flow but I've also read that the farther back the exhaust travels, the more it cools and slows down and the tail pipe diameter/area can actually get smaller. This is why it's a good idea to locate any muffler which isn't a straight thru design as far back as possible.

If I'm running 2.5" collectors into the PWTB should I run 2.5" out or larger? How far back do I need to keep running 2.5"? Can I step down to 2.25" at the mufflers at the very rear of the car say 5ft from the PWTB?

[BradH]

Re reducing tailpipe size from the size used up to the muffler, this is an old article that still has very good information on different exhaust testing done by Jim Hand: https://pontiacstreetperformance.com/psp/exhaust.html

FWIW, once I read that article many years ago, I switched to a 3" x-pipe system that dropped down to 2.5" tailpipes after the mufflers. The car was a consistent low 11-sec street/strip ride (best ET in that config was a 10.97) and surprisingly quiet. When people would video my passes at the track, you'd usually hear the car in the other lane over mine, even if it was significantly slower, which I found amusing.

[408swinger]

A little off subject but does this have any effect on evac tubes ? More vacuum ? Less ? Less pulsation ?

Thx

[MetricMuscle]

Re reducing tailpipe size from the size used up to the muffler, this is an old article that still has very good information on different exhaust testing done by Jim Hand: https://pontiacstreetperformance.com/psp/exhaust.html

FWIW, once I read that article many years ago, I switched to a 3" x-pipe system that dropped down to 2.5" tailpipes after the mufflers. The car was a consistent low 11-sec street/strip ride (best ET in that config was a 10.97) and surprisingly quiet. When people would video my passes at the track, you'd usually hear the car in the other lane over mine, even if it was significantly slower, which I found amusing.

Thanks for the link!

How much HP were you making with that engine?

So from the collectors into a 3" X-Pipe then into the mufflers and tail pipe out to the back of the car. How far back from the X-Pipe were the mufflers and how long were the tail pipes, roughly.

I've wondered for many years why so many car manufacturers always have the main muffler at the very rear of the vehicle with only a resonator forward of that. Muffler flow is less critical and it can be quieter.

[BradH]

3700 #s with driver and 121 - 122 MPH... maybe 530-ish HP.

X-type about 20" from header collectors; mufflers another 30+" after that; tailpipes 60" after mufflers... all the way to the rear bumper.