Excuse the rough 10 second sketch, but you get the idea..... Basically it's the same setup I have until you get to the over-axle pipe. I'm thinking about cutting off the spintech single 3 1/2" inlet / single 3 1/2" outlet muffler and running 2 Borla XR1 bullet mufflers instead and also having it exit out the center. Do you think there will be a power gain by doing this?

Thoughts anyone?

 

Why not just 1 muffler, then do the split to 2 tips afterwards?

Besides that....With the depth of the tire well in the middle. a muffler is gonna hang pretty low.

 

Plenty of room there to tuck them both up but i dont see a huge gain in power. MOre of a reduction in sound while keeping up flow when compared to a single case muffler. BUT if that spintech was somewhat restrictive, then two xr1's will help. Just a rather pricey option. Two bullets would do a similar thing for half the price

 

your going to have to mod/notch the trunk well or the mufflers are going to hang down and not look real good. there's a pic on here somewhere of someone who did it w/ out modding the trunk well and it didn't work to well.

 

From what I've read in the past from several people, the spintech was great for sound but rather restrictive for HP. I've heard of gains of upto 3/10ths in 1/4 by switching to a different muffler. I think the Borla's would eliminate that problem.

I'm not opposed to modifying the trunk area. I don't ever use it anyways.

The reasons for choosing two mufflers instead of one is, my system is 3 1/2" and I don't want to choke it down to one 3 in. muffler and a single 3 1/2 in. muffler would be too fat to put there (hang too low). Also 2 mufflers may be slightly more noise friendly than one...

Kinda like this, tilted slightly up, but without the notch in the rear bumper.

 

Thats really similar to my exhaust.

Since I've only got a 350 pushing about 300hp I decided to stay with 2.5's before the y-pipe though. a single 3.5 pipe is almost exactly the same as a dual 2.5 in cross-sectional area.



I decided to lower the car so having the muffler in this location wasn't good enough for me, so that's why it's now run over the axle.



Mild BFH'ing necessary to fit it over the axle, though. Makes me wonder how mufflex does it, because there's just no more room.







You may want to try a single 4 inch, but I'd be curious as to exactly how Mufflex fits a 4 inch over the axle. And I agree a split-tip arrangement is quite cool, but I didnt want to notch my trunk pan to get them to sit evenly. I wanted that C4 look with mufflers pointed straight out the back. But if you can do the rectangle offset tips, you can just offset them the same direction and they will appear even even though your pipes are not. But I didnt think I'd like that very much.

 

I dont have any pics of my bullet mufflers, just a few of the piping from downpipes back. I mounted the one bullet right up against the trunk well. I had to beat it in alittle bit to get the tips to somewhat match up with the passenger side out the rear. I think there is some room to mount two in that spot, but i'd maybe suggest putting 2 where the stock muffler goes an then running the dual 3" out the back with tips

 

Well, here's a couple of pics of my current setup, 1 3/4" hooker longtubes, dual 3 inch Y-pipe into mufflex single 3 1/2 inch cat-back...

I'm probably going to cut off the muffler and tail pipe to use that 3 1/2" 90* mandrel bend then scallop out the trunk area in the center (weld metal boxed area back in). I'll try to photoshop something soon and show a better visual...

 

Also thinking about putting a pair of random tech bullet cats here....

Trying to make the car back to barely "legal" standards..

 

I think it would sound badass!

Does any have these mufflers on their car? Any chance of a sound clip?

I think it looks pretty good, here's a rough photoshop of the end product....

 

i just had a single 4" XR1 clone muffler on my 383. Dynatech split flow muffler but same construction as a XR1 with a split core. It was very very loud but sounded amazing

two 3" cases would tame it down alittle more than a single 4 but still going to be loud without the cats

bullet cats will help tame down sound. I got those bullet style cats on my LS1 car and it passed fine down here. Really helps tame the loudmouth 2 catback

 

Did you use the metal matrix or ceramic bullet cats?

I think I'm going to do the mufflers first and take a video of it. If it's too loud, I'll throw on the cats.

 

thats gonna look awesome if nothing hangs down like your photochop

 

Didnt realize you were going for center outlets and wondered why you had the pic of the lambo up... thats gonna be much harder to do with the trunk well in place. You could try to do something like the SLP exhaust on 4th gens


But it mounts around the trunk well, not sure where you could put mufflers on that setup unless its in the I pipe which would require 3.5" and lack of ground clearance


As far as the bullets, i am not sure what core they are. I have to check the box and paperwork. Looking through it, it looked like ceramic honeycomb style

 

I did think about that, but I dont really care for those flat oval tips and I would still be limited to using a restrictive crossflow muffler design with that 4thgen setup. I posted the Lambo pic because the mufflers/tips are 4 in. round and are angled slightly upward (which is how I would mount the XR-1's).

I'm pretty decent at fabricating, so I could mod the trunk area sheet metal with no trouble...

I'm still debating on the cats. After I retune the PROM when I rework the exhaust, I'm going to have the car test sniffed to see how far off it is. Then I'll talk to random tech. and see what they recommend I guess.

I'm trying to get the car back in a passable state without losing too much power and ground clearance. Well at least until 2016... then it shouldn't matter anymore with classic plates!

 

Thats the best way to split the trunk well up. box it out with some metal.

I dont know how you will do tips 4" because most tips are like 12" long plus the long muffler length, not sure there is room to do all that. Have to cut down the tips alittle I'm sure.

If you use those little cats, they work best hot naturally, so keep them close to the collector as possible.

I've seen rumor that there is a 5K mile a year or less emissions exemption now in texas? Is this correct?

 

That will look good! Now, just lower the car once you're done with the exhaust

I talked to Random Tech about using their cats on my car and what really matters is the amount of overlap in the cam and how well your car is tuned. If you are running too rich, you'll blow out the ceramic catalyst and the cats will be finished. I can't remember how much overlap your cam has but I think you will be fine so long as your AFR is dialed in.

 

There are a few companies that make shorty 4 inch tips... Corsa has some nice ones.

Yea, I will probably buy the wide-band meter and re-tune the PROM before installing the cats...

 

Wow, and I was worried how close I ran my pipe to the trans pan! Have you Looked at a mufflex 4" single pipe cat back? I'd go with one of those and just modify the exhaust tip to come out in the center if you really want it that way. Can't beat big ole four inch pipe!

 

I don't have a trans pan, I run a six-speed.

4 in. would hurt velocity IMO...

 

"velocity" he says?????? Why are you worried about that? The car never moves anyway

 

True!

HOWEVER.... Your's has not moved in a long while (due to being in a fabrication shop where it's costing you $$$). Mine is in a garage where the dollar signs aren't ticking off by the hour!

 

OUCH

 

Hey 1bad91Z,

Dude I have the same idea as you but I believe you'll be please with my idea lil more here's a couple of pics so you could get what im talking about.

* Pic Belongs To ****** Heres a quick photoshop of what im talking about.


And here's a pic of the way I would be running the exhaust.


But instead of the chamber exhaust I'll be using the Dynomax Bullet mufflers and I'll be making a dual exhaust. But I would have route the same way like in the picture.

Let me know what you think. Ohh yeah does anyone know where I could get those tips?

Tony.

 

How about from GM, since are are.....From GM!

 

Hey Stephen,

I thought those tips were aftermarket?

Tony.

 

Nope. CME (Center Mount Exhaust) tips.....I believe those are the stock set ups & the stainless ones are the optional tips.

http://gmmginc.net/Exhaust/

 

ME LIKY !!!!!!!

 

Yea but there are a few flaws IMO with that design..

Even if you run dual exhaust (2 mufflers instead of a crossflow), that's alot of extra pipe that the exhaust has to run through in order to reach it's exit.

Those flat oval tips are from SLP.

I like the round 4 in., straight cut, polished stainless tips a little better and in my design, the exhaust would exit quicker with less bends to hamper the velocity.

 

They look a lot different that CME SLP ones I've seen.

Those look like the STOCK tips I've seen on the 4th gens with the rear ground fx & center exhaust.

 

http://6litereaterdesigns.com/store/...roducts_id=120

 

These are the SLP tips I've seen.....

 

I LIKE THIS BUT IT SEEMS LIKE YOU COULD FIND SOMETHING LESS RESTRICTIVE.Sorry for the caps.Im talking about the white car btw.

 

Yeah no problem its just an idea I have in my head at the moment.

Tony.

 

Yeah my buddy direted me to their website and I over looked it I mean it will work but those tips them selves are expensive.

Tony.

 

Damm there expensive just for the tips. One of my local shops is going to build my idea for $350 thats almost the price of the tips.

Tony.

 

What to you mean by hamper the velocity?

Like my idea will cover up the pipes really well and the mufflers too. I'm still throwing ideas at it before I acctually get it done.

Tony.

 

Velocity issue...
The more pipe the exhaust gas has to travel through in order to exit, the slower the flow will be. (Alot of extra pipe to travel arround the trunk pan).

Those flat oval SLP tips and the square 4thgen tips are only 2 1/2 in. pipes at their inlets. Mine would connect two 3 inch pipes to the 3 1/2 in. over the axle pipe.

Besides, with my idea, I wont have to hack up the rear bumper.

 

I think both of your ideas are nice.
i do like the white camaro square tips better and all the pipe will be hidden.
I don't think there is going to be any issue ,since the muffler is not there and the flow will not be restricted at all.
U take a 2inch pipe and dump a gallon of water int that is 10 feet long, and take a 3 inch -5 foot long pipe . At the end both will let the gallon back out....LOL
Also the tourqe will be better on the longer smaller pipe unless u have a 500 + CI engine .....

 

Well, this is where you get into an exhaust technology debate...

By no means am I an expert on the subject, but this is what I understand from the things that I have read...

From everything I've read on the subject, velocity matters just as much as volume. The faster the gasses exit the system, the more power it will yield.

The longer length of pipe that the gasses have to travel through, will slow down the speed of the exhaust flow due to two reasons. The longer pipe will cool the gasses more (due to length of metal that the gasses travel through). Hotter gasses will travel faster and exit quicker.

Also, the more bends you have in the system (before the gasses exit), will slow down the gasses as well. Every extra radius added to the system will slow down exhaust velocity.

As far as volume, just because water and exhaust for that matter, will flow or pour out of a 1 inch pipe (because it's hollow), doesn't necessarily mean it would be ideal for modded small block. This is where a program like pipemax would come into play in order to tell you the correct diameter pipe you would need vs. length in order to meet the demands of your current power level of your motor.

Therefor, these are the reasons why I came up with the plan I posted. It doesn't restrict volume via pipe diameter, and it reduces the number of bends that the exhaust gasses have to pass through before exiting. Plus, I think it looks good!

If you prefer looks over maximum performance, by all means run the pipes in a configuration that fits your appearance requirements. I on the other hand am trying to squeeze every last bit of power from an exhaust system.

If there are any experts out there, please feel free to pick apart the theories and setup and if there is anything to add or change to make more power, please let me know, I'm always open for suggestions!

 

U need to hqave a certain amount of backpress. , or u will actually loose tourqe( power ) HP is not what turns your tires or tranny, its tourqe !!!!!

 

Its not backpressure, its tuneable length. Longer length of pipe tunes the exhaust pressure pulses differently than short pipe and will boost power at different parts of the rpm range while sacrificing power at other areas.

The exhaust system for max power would have a certain header primary diameter, a certain primary length, and certain collector length which is all dependent on the motor build from heads/cam/compression/intake manifold etc

There are programs to calculate the optimum collector lengths for max power or max torque and the lengths that really hurt power rather than help it. The gains made from having optimum length will vary but it does work.

The more bends in the system will slow gasses down because of cooling reasons, but also increase backpressure because there is more resistance from the pipe walls with longer spans of pipe. Between backpressure and poor tuned length, you can have poor power production.

Exhaust needs tuned length just like intake manifolds have tuned runner lengths for differnt rpm bands

 

Thats basically what I stated more or less....

Pipemax figured my optimal setup at 3 1/2" diameter from the Y-pipe back to the rear of the car. That's why I have the current system that I do.

However, many people have stated (that have had my exact setup), that by changing to a different muffler, they were able to increase power and lower 1/4 mile E.T.'s by ditching the Spintech muffler (and keeping everything else the same).

This is why I figured that the dual XR-1's would eliminate the problem and look cool at the same time.

And, it's something different that would set the car apart a bit from the rest of the herd...

 

So where would u find the programm to calculate the length or so ?????
Good post, THANKS

 

Its called pipemax. Its a great program and I have yet to buy it....dont know why i'm so delayed I will have it soon.

Its an accurate program only if you truly know your inputs. From cam timing events, exact flow numbers, etc and etc. The more you know the more accurate the results. Pretty straight forward.


I have heard the same but the only way to know for sure is to calculate the flow of each muffler to get an idea if one is restricting flow or not. I can tell you tho, the flow of 2 3" XR1s will destroy any straight through 3.5" at the same test pressures. Also the design of the mini-y pipe splitter you need to make to split the 3.5" into 2 3" pieces can have an impact on flow and sound. The better flow transition will sound better with less rasp and create less turbulence as the air goes through.

 

I have a flowmaster Y-adapter (dual 3 inch in / 3 1/2 inch out) connecting my cat back to the 3 inch pipes going to each header collector. I was thinking of using the same flowmaster Y-adapter only flipping it backwards then directly connecting it to the XR-1's, then using a piece of the current tailpipe only for the mandrel 90* bend to connect it to the over-axle pipe.

The flowmaster Y piece is pretty nice inside.

 

those are what i have used for my builds. They are designed to flow dual in, single out but will work ok for the opposite effect

 

Are there any better alternatives for the reverse Y ??

I just checked measurements for the muffler area. I have right at 24 inches from the edge of the rear bumper to straight part of the over-axle pipe. If I run the 8 inch long XR-1's, flowmaster Y, and the shorty 4 inch tips, everything should fit fine....

 

You dont have to hack up no bumper if you dont want I just wonder how it would look like the slp setup.

Tony.

 

I have a lil story for you guys, lol.

When I had my exhaust from cat back with a 2 1/2 inch pipe with a Y right over the axle with 2 I chamber mufflers was awsome at lower rpm's but was a bit harsh on top end.

So what I did I cut the pipe right next to the drive shaft and added just 1 1 chamber muffler. I notice a big difference right away from sound to power I guess if you want to call it that. I t felt as if my car lost torque on the launch but when I raced people on a 50 mph roll damm i loved it it was just a straight pick up and off I go.

Correct me if i'm wrong in any of this but thats just what I notice from my experience.

Tony.