NowhereFast

Seems as if anyone going true dual runs them both through the stock location. The exhaust is definitely gonna get pinched here no?

novaderrik

the exhaust system in that pic is now the suspension bump stop on that side.

mjdavis68

iTrader: (1)

looks "mocked'' up as it only tack welded and yes i would say it would get crushed to me

tealman92

Thats not gonna work

MoJoe

iTrader: (5)

It sure looks like the exhaust will get squished at the next big bump. And if not squished, definitely bent up until it hits the PHR-brace, then squished.

Take out the exhaust, take out the rear spring(s) and see how close the axle and PHR is to the PHR-brace. That is your exhaust clearance on the driver's side.

deadbird

Exhaust pipe run over the drivers side works just fine without getting crushed if you build it properly.

Ozz1967

iTrader: (4)

My single 3" goes up and over the axle on the drivers side. that's factory routing.

tealman92

You might want to go look under your car. All are on the passenger side

Ozz1967

iTrader: (4)

Your right, passenger side. Sorry, its late lol

sofakingdom

iTrader: (1)

That kinda reminds me of an employee I used to have, who sawed a limb off of a tree about 30' up in the air while he was sitting on it. Fortunately when he hit the pavement below it didn't break anything that took more than acoupla months to grow back.

Sometimes the crap you see in cartoons mimics real life, eh??

mk1431

youll be fine wont compress that far. spring will only compress so far plenty of room

novaderrik

the stock good IROC springs are only something like 120 lb/in rating- if i sit on the quarter panel over one of the wheels, my 240 pound mass will push that corner down 2"- which, to me, looks like it's enough to hit that pipe... driving down the road will cause a lot more travel than that, and just doing a low speed turn into a steep driveway will put it at or near the stock bumpstop, which is farther up than this exhaust..

if it was this easy to run real duals under these cars without having issues, everyone would be doing it..

deadbird

Where is the claim it is easy ?

novaderrik

nowhere... it was a response to the pic in the OP: if it was that easy to run exhaust on that side of the car and not have interference issues, everyone would be doing it.

customblackbird

iTrader: (15)

I had to make my full exhaust from scratch, this includes 2" primary 3.5" exit long tube headers, into a 3" xpipe into 18" SS jones max flow mufflers which I dumped before the rear axle. I just finished running dual 3" over the rear axle (over pass and driver side). My whole kit is 3" and used All mandrel bends, I utilize Vband clamps and accuseal band clamps at the back of the mufler. I got a founders panhard bar relocation kit and my 3" dumps behind the bumper for a clean look (no exit tips). Painted in high temp header paint and wrapped in lava wrap. I should have plenty of clearance on the driver side. The rear is set at less than ride height so its already in the compression area and I have a few inches left, ride height will lower the rear even more than what is pictured. I always wanted the exhaust to run to the back bumper and its been years... maybe even will change the tone/loudness.

Literally just finished it this past weekend.

2slow5.0

iTrader: (2)

I saw an exhaust like this on a 4th gen a few years back, I think it was In GM HiTech magazine. Real clean install, the installer used spin tech oval piping to gain even more clearance. I'll try to dig the article back up

Thirdgen89GTA

iTrader: (5)

Just an honest question here.

If you were spending all that time building a custom exhaust, why didn't you build something similar to what Willie did with his dual over the axle setup. He ran true duals, but with the factory routing and kept a ton of ground clearance.

novaderrik

because it looks goofy to have both pipes on one side.. it's a symmetry thing.. and if you are putting both pipes on one side, why not just go with a single pipe to really open things up: which might flow just as well as the true duals, but it will never, ever sound as good..

Thirdgen89GTA

iTrader: (5)

I don't think two on the left is goofy at all. Duals following the stock exhaust routing would sound just like true duals. You get to keep all your ground clearance and eat your cake too.

-=Z28=-

iTrader: (3)

Maybe its me, please correct me if Im not thinking correctly this morning. Doesn't the exhaust go over the axle on the pass side and not get squished?? So whats the difference if it goes over the axle on the drivers side? Pass side will compress just like the drivers side doesn't it?

I think my set up only calls for a 3" main pipe,but instead of duals, Id like to finish it with a single, but looking like how you finished yours customblackbird.

Thirdgen89GTA

iTrader: (5)

Stock most of the factory and aftermarket 3" over the axle pipes are either crushed or oval depending on the quality. Mine is oval and doesn't cause any restriction.

There are also Panhard kits (founders, which CustomBlackBird has pictured) that would allow dual 3" over the axle on the passenger side per factory routing.

customblackbird

iTrader: (15)

I agree with Nova on this one and its the main reason. Running both pipes over the passenger side of the axle wont work for me... I run 3" true duals, LT headers, and a 3" Xpipe before the dual 3" 4.5x18" mufflers on the floor pan. Mysetup isn't even close to stock and I need to run 18" mufflers with a 521 otherwise you wouldn't believe how loud it is lol. Even with the 18" mufflers its very loud. I had some 14" chambered Thrushes on before and couldnt take it for long periods, the 18"s brought it down nicely and its a great loud tone.

You can clearly see the Xpipe and the rest of the exhaust routing in the pics under the car. I had to make the headers too from scratch and they are 2" primary and 3.5" collectors, all the piping is true mandrel bent 3" so it flows ALOT! and I kept a good bit of my ground clearance by knotching the stock subframe by the transmission (I run 2 sets of SFC). The mufflers being the lowest point.

Also even if it were stock routed Its counter productive to run the pipe all to the pass side to and then back over to the driver side (alot more work) and having unequal lengths in the exhaust will cause slight differences in tone, flow and savaging.

customblackbird

iTrader: (15)

This can be achieved but really depends on the fabricator and the skills, not to mention the pipe size. Dual 3" by the tranny tunnel will hang low... there just isn't that much room for dual 3" and keeping room for the driveshaft etc. While its prob much better than most dual 3" jobs (not in the factory location) its also alot more work. So you will loose some ground clearance, dual 3's in the stock location I would rather just run a single 3.5 - 4".

Also like i said the uneven lengths in the exhaust will and could affect sound, flow etc.

customblackbird

iTrader: (15)

Thank you, I'm assuming you mean how it turn downs behind the rear bumper so the tips aren't seen? I think the Tips sticking out the back of 3rd gens are crap, Doesn't flow with the car lines, usually has to below the bumper (bumpers aren't setup with cutouts etc) and looks like its been "added on". I like the stock how it terminates behind the bumper for a cleaner look and that's what I was going for but tucked higher.

Different things going on at both sides of the rear end. The PHB is fixed on the passenger side, driver side it moves up and down with the suspension and it will crush on the driverside before:

1.) Axle tube hits the bump stops
2.) PHB hits the PHB support bar
3.) PHB squishes the exhaust between it and the PHB support bar.

Only way to gain clearance would be to increase ride height (stock setup) or run a PHB relocation like I did and allows you to mount the PHB lower on the driver side.

Another thing to mention and I notice no one does is weld (or Bolt on) a new PHB mount on the driver side axle that is shorter (Closer to the pass side) and then run shorter PHB from the new mount to the stock frame mount. This would give you ALOT more room for exhaust over the axle. Now that I think about it that would prob be better than the PHB relocation and prob cost less than the PHB relocation (not Founders but like UMI/BMR etc). Prob less than $100

http://www.speedwaymotors.com/Panhar...lamp,3382.html

http://www.speedwaymotors.com/BSB-Ma...lamp,3392.html

They have custom length PHB kits for like $30-$50. measure the length or make it yourself.

MoJoe

iTrader: (5)

Shortening the PHB has negative effects on suspension performance. You want the PHB as long as possible.

-=Z28=-

iTrader: (3)

Got it. All the morning cob webs are gone. I can clearly see how the phb would hit the pipe now.

Yes, I like that finish as you stated. I have seen some exposed tips that look nice, but not many on 3rd gens and are usually built into/around the bumper better. Only thing I question about how you have it is how bad it resonates under the car, compared to tips that get the exhaust out and from under the car..

customblackbird

iTrader: (15)

Well u can't see them in the pics bit the new tips are turndown facing the corners of the bumper, gases and sound will shoot down and out at a 45* angle to help with interior noise so it should be much quieter than it was lol.

Before I had dumps (basically turndowna off the mufflers in the first pic) so the back of the car was a echo chamber. I played with angling the tips outward at 45*, straight down and then towards eachother at 45* which is how I kept it last year. Pointing them towards themselves helps cancel some of noose and resonance... picked it up off yellow bullet. Either way the new exhaust should be 100x better than the dumps before the rear axle. I'm excited to hear if it changed the exhaust note at all since I have 4ft of tubing after the muffler.

customblackbird

iTrader: (15)

Hmmm got it. I wonder how much it would hurt IF it was like 4" shorter?

ASE doc

There is atleast one better alternative to the PHB altogether. I forget the name for it but there is a system using two links and a bell crank that pivots around the center of the rear diff. If designed right, it could increase clearance at the points where exhaust pipes would pass over the axle, this design is better than a PHB because axle centering is not affected by vertical movement of the axle.

I plan to run my duals following the stock path because all things considered it is the easiest way. This plan works best for my shorty headers that exit in the stock locations. While I have had the same concerns about unequal lengths of the pipes, the X-pipe will balance pressure between the two banks and pretty well resolve this issue.

I like the PHB relocation bracket that customblackbird built for his axle. I plan to rob that design for my own car. Since I plan at least at this point to run dual 3" over the axle, I'll need the added clearance provided by the Founders PHB relocator kit. The problem with the kit is that it does alter PHB geometry and without lowering the PHB bracket on the axle side, you will affect cornering. From what I can tell, as long as the PHB is level to the axle at ride height, geometry is good, regardless of whether it's above or below axle centerline.

customblackbird

iTrader: (15)

Your referring to a Watts Link. It has its advantages and its tradeoffs.

The xpipe only equalizes the pulses/scaveging and smoothes out the tone. This is usually based off equal length exhausts (Most cars that employ them are tuned exhausts) ours are not for the most part and I don't know how much affect having 1 side longer than the other would have. Also why are you so concerned with the dual 3" exhaust? The edelbrock headers have a 2.5" collector flange right? Running 3" after that wouldn't do anything as your bottle neck is right at the collector. Unless I'm mistaken and its a 3" collector but I don't think it is. From a performance standpoint the 2.5" collector means 2.5" after would be best for flow, increasing to 3" after the 2.5" collector will do nothing flow/performance wise.

There is a negative to running a PHB relocation and that is the affect on the suspension geometry and the rear roll center. Lowering the PHB (even if its level) will affect just about everything else. Keeping the PHB level just keeps the rear centered for most of its suspension travel. Also from what Ive read you need to run stiffer rear springs to help with wheel hop and keeping the rear stabilized with a lower PHB. For the most part lower the PHB is a "nono" as its negatives outweigh the positives massively. People do it bc 99% of us dont push our cars to that point where it would really matter, and bc dual exhaust is more important to us. It is what it is.... I will never autoX, I dont even DD my car so the negative affects weigh even less on me. But I do run stiffer rear springs (175lb) and I can account for lowering with all my LCA, PHB, and TQ being adjustable and adjustment mounts.

ASE doc

Thanks customblackbird, I see your point, but I also have a slightly different view of some of your points. Actually, going from 2.5" to 3", if done properly, should increase flow capacity. The point to remember is that flow capacity of any length of pipe is dependent not only on the CSA but on the overall length of the pipe(hydraulics 101). Running exhaust by the 3rd gen's stock routing, especially with dual mufflers crossing each other in the rear of the car, the total length of the pipe gets pretty long. Keeping the length of the 2.5" pipes balanced at somewhere between 24 and 30", then a smooth transition(cones) to 3" will not only take advantage of the 2.5" pipes greater velocity and improved scavenging through the headers, but it will also have the same flow increasing effect of shortening the total length of the system. As far as I can tell from my math, as long as the pressures are balanced between the two banks(X-pipe) the lengths after the crossover won't effect performance. There will certainly be some effect to exhaust tone. The longer pipe will have a lower frequency. May actually create a nice exhaust tone, especially if the two channels harmonize.

Through peak VE and torque of let's say a 500hp engine, the 2.5" head pipes should actually increase VE and torque through improved scavenging, if the lengths are correct for the engine's flow at that point.

With your beastly 521, the pipe sizes needed are much larger. Even dual 3" is on the small side.

I need to sit down and do some math on PHB dynamics. I am aware of the effects of raising or lowering the chassis end of the bar. This is why race vehicles using three link have an adjustable mount. While there may well be some effect from moving the bar up or down from axle center, I think it would be minimal as long as the bar and axle are kept fairly level. The key, as far as I can tell, is how lateral force is transmitted to the chassis from the axle. Whether it is parallel to the axle, and the ground, or whether it is at an angle to the axle which will transfer some the force into either up or down force, causing either a loose or tight effect in the rear of the car. In circle track racing the choice is simpler, because all the turns are left.

customblackbird

iTrader: (15)

I appreciate your input! While I would agree that velocity is directly related to exhaust size it is also directly related to exhaust temp. The temp of the exhaust gas in the header is hot (hot gas has more volume) and moving quickly... but it cools very quickly, therefore reducing volume and speed. Since after the header the flow of the exhaust reduces/diminishes very quickly the size of the exhaust does not need to be as large to keep the velocity high. Cooling gas/less volume and speed would need a smaller DIA pipe to keep velocity up. So moving from a smaller DIA collector (at hot gas/high speed to a large DIA pipe with cooler/slower moving gas would slow the velocity down even more. I dont know your application so I can't be sure but putting 2.5" collectors on a car that would need a 3" exhaust would be counterproductive. Although the 3" will be louder you will loose velocity, and low - midrange power.

Here is some more basic reading on the subject of exhaust backpressure and velocity.
http://www.gomog.com/allmorgan/exhaustbackpressure.html

But the general consensus is that dual 2.5" exhaust will flow enough for 500-550hp before it becomes a restriction while keeping exhaust velocities high. There is a point where DIA and velocity become the restriction and then a larger DIA pipe should be used.

I run a 3" system bc my motor although large is a low RPM street motor. Peak power should be in the 5500rpm range. The Lower DIA pipe also increases velocity as well as backpressure to help with low end tq. Since I dont spin the engine over 5500K I really wouldn't benefit from a larger pipe DIA and I would lose more of my low end street fun grunt. I dont need to go above 4K ever to really get in trouble lol.

I read a few threads on lowering the PHB and its affects, vetruck/slicktrackgod (nascar crew cheif) and a few others posted the affects of the PHB relocation. One of the main things is keeping the balance of the lowered rear RC compared to front, and using higher spring rates or larger sway bars to compensate for the increased body roll created by a lower PHB.

ASE doc

I am aware of the constant reduction in temperature as the exhaust passes through the pipes, thus reducing mass of the gas(made a rhyme). I won't likely be going past 550hp, since I plan to stick with my current cyl heads that flow 280cfm. I probably will just go 2.5 dual. Will sure make the install easier. But, it is my way to over think and over engineer the pee out of everything. A close look at this car I built from scratch will show you that.

Part of my thinking was that the larger pipe will cool the gases faster due to larger surface area and slowing of velocity. The drop in pressure at the transition to 3" actually increases velocity through the short section of 2.5". Is it worth the added hassle? Probably not.

I see what you mean also about the lower PHB increasing body roll in the rear. More weight above the point where lateral force is transmitted. I have seen one dual 2.5 install in the stock routing( arcticwhiteZ) in the exhaust stickies that was done without PHB relocation. I still need to do something with the PHB since my car is lowered. I'll have to think about it. I also have the LCA relocators, really improved traction with the lowered ride height.

I suppose with 521 cubes, you don't need to turn it past 5,500 to be fast.

83 Crossfire TA

iTrader: (2)

Honestly, I can't quite figure out the finer details of what you're hoping to do, but if you're talking about the larger pipe cooling better than 2 smaller pipes... well a single larger pipe with the same cross section as 2 smaller pipes will have less surface area. It will cool less and flow more than 2 pipes because less of the exhaust will be in contact with the metal.

I have thought about manipulating exhaust flow by cooling (increasing the density of the exhaust), but have never had the opportunity to test the results, and I've wondered if the decrease in velocity might hurt some setups worse than the increase in potential flow might. 2 thoughts I had about testing this are just duplicating the existing exhaust in aluminum, which would dissipate heat better than steel, or just welding a fin or 2 down the length of the pipe to increase the area to dissipate the heat without changing the flow path presented to the exhaust gas at all.

ASE doc

Aluminum pipe would certainly dump heat. I think you would really need to watch clearances as the heat transfer might be enough to damage components. As far as my plan goes, it has been to go from dual 2.5" to dual 3" through cone transitions, not into single 3". I would then go back to dual 2.5" after the mufflers. Now, dual 2.5" into single 4" would have the same basic effect, as long as the y-pipe transition is smooth.

I am determined to have dual exhaust and prepared to do the work installing it. It's worth it to me simply for the sound full dual exhaust. I'm sure that dual 2.5" will work just fine for my power goals and it will certainly make the install much easier.

customblackbird

iTrader: (15)

Why would you want to build an exhaust out of aluminum?! The shedding of heat has a negative affect on exhaust velocity. Hence why ceramic coating the inside and outside of the exhaust header keeps the heat in an keeps it from escaping, thus keeping the exhaust gases hot and moving faster.

You want to keep exhaust temps hot and in the tubes. Reducing radiant heat and keeping it in is like having your cake and eating it too.

ASE doc

Yeah. Aluminum wouldn't be a good choice for exhaust material. Radiant heat transfer would be severe.

ASE doc

You know, I've been thinking so much about increasing flow capacity, I forgot the role of thermal dynamics. As I remember, racers coat and wrap their exhaust, not to protect components from radiant heat, but to keep the pipes hot for increased velocity. Maybe there's good reason nobody goes from 2.5" to 3" pipe. I'm glad I have people here to bounce these ideas off of. Maybe save myself from more expensive redos down the road.

customblackbird

iTrader: (15)

Your welcome!

customblackbird

iTrader: (15)

I just wanted to inform this thread that the exhaust worked and sounded great. Unfortunately I'm going to be selling it as I decided to pull the motor and go a different route. So The full exhaust as you see in the pic will be for sale. All you would need to do is fab 2 small sections of pipe to connect your headers to the inlet to the Xpipe and your good to go. PM me if interested.