Among multiple performance upgrades in progress to make this a perfect track car, here are some pics of what I have done to the exhaust, again and some thoughts.

High flow 2.5" 200 cell cats to 2.75" piping with new X immediately after cats, then 3" piping to another X before Magnaflow 3" resonators. I have not yet come up with a tip solution as I've been looking for something unique - carbon fiber or something.

Obviously the exhaust is louder but not a lot louder, it's just very different. Cold start is a very deep rumble, rasp is gone and downshifting causes a bit of a pop but not overrun. You can also feel a lot of flow blowing out the rear indicating the OEM back box is restrictive. However, noise inside the cabin at anything above 1500 RPM is a bit deafening, especially during a 2 hour drive to Sebring. There's gobs of room now in the rear so I may come up with some piping solution to help with what may be drone and I may eliminate the cats all together.

As for power gain, the car is WAY more responsive off the line and at lower RPMs it will jerk you back, but at the top end, 6-7K RPM at high speeds 130mph + it feels like a bit of power may have been lost.

 

I really appreciate a good craftsman and someone that takes pride in their work, the install looks oem... Well Done!!! You just reminded me of how bad I want the CF rear diffuser and to change the oem tips as well...

 

Muffler shop "quality"... No thanks.

 

Ranchero, school me, since I don't know what I'm looking at. Because to my untrained eye it looks like a well thought out and executed job?

 

Not a muffler shop...

 

Interesting. I don't think I've ever seen two xpipes used before. What's the thinking behind that?

 

Two to three X or two X and one H should theoretically help with drone and remove rasp when removing mufflers. It is done frequently with high performance exhausts as I have read.

 

This system ignores the laws of thermodynamics (heat loss) and energy control (exhaust pulse energy). A finely tuned header uses the exhaust pulse from one cylinder to help evacuate another cylinder. A correctly designed and located X pipe does the same from bank to bank as well as double the effective area for a pulse downstream of the X pipe where its energy is no longer needed. The problem once poorly engineered crinkly bent bends are introduced in the system is each crimp creates a ridge that reflects and dilutes the pulse energy as well as where it's crimped in the bend the diameter is reduced to @ 2/3 or straight pipe. Changing pipe sizes up and down at the crossovers (not a true X pipe) dilutes the energy as well. The further from combustion, the cooler the exhaust pulse is so it doesn't require larger diameter further away and just works to amplify the noise and adds unnecessary weight to the system.

Above 500 hp I'd do a 2.5" mandrel bent system with a true X pipe behind the trans and whatever noise mitigation was needed further downstream. Below 500 I'd keep it 2.25"

 

I read somewhere that one way to find the best location for the X-pipe is to paint your exhaust after the cats and run the car. Where the paint bubbles/burns, that's where you put it. No idea if that's true or not.

I agree with Ranchero50's pipe diameter suggestion. Otherwise you're just adding weight.

 

The stock pipes are about 2.25" and horsepower is probably at or above 500 by this point. You don't think having 3" pipes helps with better flow? I'm also planing on increasing the TB inlet size and porting the inlets and outlets on the supercharger and intake headers. Are you suggesting the Magnaflow X pipes are not X pipes? Everything I have read indicates the first crossover should occur as close to the headers as possible. I was told the crush bends were irrelevant because they were less than 90 degrees and the piping diameter was increased beyond factory diameter so velocity restrictions were a non-issue. And this is all specific to an air pump, forced induction motor.

 

Download a copy of the "2 stroke tuners handbook" and read the sections on exhaust pulses. It's free all over the net anymore and in spite of being written in the '70's is still relevant in exhaust design and tuning. Basically a 2 stroke uses the expansion pipe to 'supercharger' the intake charge via exhaust pulse manipulation. Apply it to a dual bank exhaust system via a correctly designed X pipe where only part of the pressure pulse can be transmitted into the off pipe which as it flows downstream causes a negative pulse to travel back up towards the off pipes header collector (or cat in our emissions friendly case) to help draw gasses through the cat. There's a lot of hydrodynamics involved too but it'll get you started.

Visualize Magnaflow X pipe from above and consider what various particles of exhaust gas are going to do as they approach and flow through the joint. The particles on the outside are going to hit the outer curve and bounce into the inner ones. The inner ones are going to want to go straight but get pushed into the middle where they collide with the back wall of the X and either bounce back into the original pipe or eddy in the middle colliding with other particles. There's no positive control of the pulse and the lost energy means the design is inefficient. That it's 1 foot behind the required bend from the cats means any exhaust needs to turn an extra time so you lose energy there.

I thought I did a pretty good write up in my rebuild thread. This pic shows my X pipe. Again, visualize what the particles are going to do on this pipe. The inside is going to bend a little right before the opening and shoot through the 2/3 base diameter crossover hole between the pipes to the off pulse pipe as a straight shot. The pressure pulse moving through the crossover opening will create a negative pulse that will travel back up the off pipe to the cat. The outside particles are going to have more room around the corner to flow through the entire diameter of the pulse pipe. Instead of two exhaust pulses per revolution on each pipe, after the X you have four smaller pulses. This is why you can use smaller diameter pipe and still get the same volume of air through an X pipe system. It'll also change the sound coming out of the back because you've doubled the sound pulse frequency for any given RPM.



Here's a little bit of thermodynamics side:
https://www.omicsonline.org/open-acc....php?aid=69626

One of the neat dynamics of my exhaust is the sound coming out the exhaust shifts from pipe to pipe in a very '70's stereophonic way. I wish I could record it because it sounds really cool.

Oh yeah, a too large sized pipe actually hurts performance.

 

Ranchero,

Best Exhaust Statement I have read here on this whole forum!

That last statement is dead nuts on, especially on a Supercharged System based on my 10+ years working with a similar configuration (5L SC). Dyno proven over and over X pipe gets more power closer to headers as possible, wouldn't additional X just create more confusion to the air, you want it smooth and consistent all the way out. Multiple X pipes, of which I have never heard of nor seen before now, well to me its like phase correcting your speakers and then switching it all up again, literally no difference between the 2 in my head.

100s of dyno tests by myself and at least 3 other competitors all came up with the same location...completely independently of each other's work.

Here was my resulting product, note the X location...as close to the bell housing (no tranny there, in back) as possible.just as you stated.


Happy Friday,

Dave

 

Those Xs look just like the ones used on my car. FWIW, the original X pipe I made was just like Ranchero's, 2 pipes cut and welded together parallel but I was told the Maganaflows were "real" Xs. I have no expertise with any of this and rely on "experts" opinions and guidance. I was told that was as far forward the X could go but when I remove the cats, I think the left and right can be pinched together right before they travel down the tunnel together side by side.

 

I prefer the Magnaflow "X" sections over a sliced together section of 2 pipes like a lot of custom Xs are done. Those are great also, but the welds inside are not as smooth and consistant as the Magna X stamped sections. Also from a production perspective the Magna Xs are going to be dead on accurate from product to product so tuning becomes easier across the production runs vs the hand made X sections that are rarely exactly internally, fine for a one-off build and tune, but not so much for a production run tune.

Just keep going at it, you will find the sweet spot eventually. Just don't get seduced by the noise...think back to when the Audi Diesels took over LeMans...all that power to spank everyone over and over again....and the only sound was a whoosh as it went by. Power ain't always about the sound or whine an engine makes.

Have a great time at Sebring,

Dave

 

10XKR, When I saw your production pics I was wondering about the choice to use prefabs. Figured it was a simpler, more consistent production step. Curious, did you see much difference between the two designs on the rollers?

 

Hi,
I never saw anything beyond the normal tolorance between Dyno runs (2-5hp), but I always had closer tolorance with the stamped X.

Look close at the stamped X it actually maintains the combined volume of the 2 inlet/outlet pipe sizes, whereas the "sliced" siamesed welded X actually reduces the combined volume. No way around that, if you cut sections off of 2 pipes and weld together it is now smaller.

Hope that makes sense,

Dave

 

It does. I remember back when Dr. Gas was selling these to NASCAR and his explanation was with the partial opening between pipes that only a portion of the high pressure exhaust pulse went to the off side pipe where there should be a lower pressure from the prior driven puls going by. The goal wasn't to allow them to mingle and balance out themselves like the stamped X does but control the amount of mingling threw the port. It's kind of neat that time has passed that idea on and the stamped part performs the same. Of course it helped the siamesed design when the firing order kept pulses alternating banks which I don't think the 4.2 does.

 

If you look closely at the current offerings, a Dr Gas $300 Handmade Welded X pipe starts to look way more like the flow of the Stamped X than the Siamese X .....and the Stamped X has no internal welds to trip the air, just a smooth surface for all the magic to happen.


Cheers,

Dave

 

The one on the left started as two bends. Both of these show the weldment too:

X-Pipe Crossover (Junction Only)

https://www.classicindustries.com/product/a7700138.html

 

Engine Masters made a video comparing X-pipe to an H-pipe.... and they were remarkably close. If I remember right they were within 2 on both HP and Torque, with the H-pipe getting more torque, X-pipe more HP.