Full dual vs Y and X setups

[Celsiorous]

Hi, I have finally destroyed my standard exhaust on my 1st gen Celsior from being too low so I am basically forced to setup a new catback
I have called four different performance/exhaust shops, two of the shops are very familiar with 1UZ setups and have done conversions including custom headers and exhaust.
Out of the 4 places I called only one recommended using a X or Y setup, the rest suggested 2.25 or 2.5 full dual setups with Magnaflow superturbo mufflers on the rear.
I dont understand the benefits from the X and Y sections properly, is this to increase velocity as the exhaust evacuations from each bank flow through the sections one after the other?
Any opinions would be great, also does the X or Y sections change the sound of the exhuast?

 

[dogstar]

i dont claim to be an expert, but in american muscle cars, dynos generally show fairly good gains from using a proper H or X pipe.

it could be worth looking into, hopefully someone with more expertise can provide concrete information related to the 1uz

 

[JBrady]

Hi, I have finally destroyed my standard exhaust on my 1st gen Celsior from being too low so I am basically forced to setup a new catback
I have called four different performance/exhaust shops, two of the shops are very familiar with 1UZ setups and have done conversions including custom headers and exhaust.
Out of the 4 places I called only one recommended using a X or Y setup, the rest suggested 2.25 or 2.5 full dual setups with Magnaflow superturbo mufflers on the rear.
I dont understand the benefits from the X and Y sections properly, is this to increase velocity as the exhaust evacuations from each bank flow through the sections one after the other?
Any opinions would be great, also does the X or Y sections change the sound of the exhuast?

I have written extensively on this subject so please search for details.

The bottom line... DEFINITELY run a quality X or Y pipe. The stock system is basically two Y pipes. I suggest copying the stock system in either 2.00" or 2.25" pipe with the same size Magnaflow or equivilant style mufflers. The single center section should be 2.5" pipe if you are using the 2.00" for the duals and 2.75" pipe if you are using the 2.25" duals.

I would use a single center muffler in the single center pipe. I would run twin 4" round type mufflers (measurement of outside of the housing, internal pipe should match the rest of the tubing) in place of the stock middle mufflers. I would run twin oval muffler in the rear.

If you choose larger diameter pipe your system will be louder and loose power.

Most muffler shops and even many many "performance" shops do not understand proper exhaust systems. They recommend what they THINK will work or what is EASIEST for them to make money selling you. Quality X and Y pipes are not super easy to find. Search this site and Club Lexus and eBay for many options and choices.

 

[Celsiorous]

Thanks for the quick replys, JBrady what would your preference be between 2 and 2.25? Do you think the sound and volume of the exhaust will change alot between the two sizes of pipe?

 

[Lambo]

X And Y Exhaust Pipes

Hi Guys, i was just scanning an old HR mag to archieve away. It covers real tests of x and y pipes their effects and hp gains,also covers port flow etc, to big to post 785kb zipped ,if anyone wants it pm me with an email i'll send it over. Real usefull info. applys to any v8.

Regards
Lambo

 

[JBrady]

Thanks for the quick replys, JBrady what would your preference be between 2 and 2.25? Do you think the sound and volume of the exhaust will change alot between the two sizes of pipe?

PLEASE READ ALL DO NOT TAKE OUT OF CONTEXT

A single 2.00" pipe will support 200+hp. 2.25" will support 300+hp. Dual systems double that. Understand that the above are ranges and in fact some have engines making more than the above. The pipe itself is rarely the restriction. As you add transitions and bends and mufflers and catalysts the effective flow SIZE of the system drops.

Twin 2.00" on a stock 1990-1994 1UZFE engine is fine as long as the other variables are done correctly. Using mandrel bends and high flow mufflers (magnaflow, borla, other straight through perforated core mufflers) should be easiest, least expensive and quietest.

Twin 2.25" if you intend to modify your engine past 300hp may be a better choice but requires careful transition design to avoid loss of low RPM response efficiency and torque.

Exhaust is both an art and a science. That is why I recommend copying the stock layout with better mufflers and Y pipes.

 

[Celsiorous]

Thanks for the clarification JBrady

 

[SCV8]

When I did an upgrade to my SC exhaust, I was careful to maintain the original lengths from the manifolds to the point where the downpipes merged, this was not only to preserve any benefits from an exhaust tuning point of view, but also to keep the fuel curve as close as possible to what had been used. The ecu has a limited ability to correct, and exhaust tuning can upset the curve if you make larger changes.

 

[lspower]

this place has quality x pipes this is where i got mine

http://www.exhaustdepot.net/xpipes.html

65$ i bought the 12" universal, they are perfect on the inside no shitty welding top quality

just letting you know

 

[JBrady]

http://www.exhaustdepot.net/xpipes.html

65$ i bought the 12" universal, they are perfect on the inside no shitty welding top quality

just letting you know

I realize it is not easy to find a quality X or Y pipe for cheap but that unit is 2.5" which is too larger for best effect. Better than nothing but still too large.

 

[the highlander]

what do you recommend then jbrady? can you post pics of your setup?

 

[doey]

Here's an article that may be of interest.

http://carcraft.com/techarticles/69238/

 

[JBrady]

what do you recommend then jbrady? can you post pics of your setup?

Actually I just welded up some experimental 2-1 merge Y pipes tonignt. I will post more later but these should work very nicely. Currently my system is stock.

 

[Pro]

V6, V8, V10 - basically ANY engine with split banks of cylinders; an X, Y or H pipe is a good recommendation.

 

[JBrady]

V6, V8, V10 - basically ANY engine with split banks of cylinders; an X, Y or H pipe is a good recommendation.

Correct and I would add that virtually EVERY gasoline engine (most fuels) that needs a decent operating service range benefits from merging the exhaust gases together. The manifolds are merging individual cylinders together with 2,3,4,5 and occasionally 6 into 1 collectors. Merging 2 collectors together for the benefit of velocity and or accoustics generally improves the torque curve.

 

[akitamike]

I just replaced the exhaust on my 1998 sc400 from the cats back, taking out the stock middle muffler, and the other 4 mufflers/resonators. I put in 2.25" x-pipe in the siamese-joined-in-the-middle design of an x-pipe and not the kind of X pipe in the picture by highlander. The x-pipe then goes 2.25" to two high flow 2.25" bullet 4" mufflers. The sound is better now, but the low end torque/pull seems to be less than before. I tried to reset the ecu by taking the negative battery terminal off for a few hours, but seat of the pants it still feels less powerful when pulling from a dead stop. Should I try to reset the ecu again, or I was thinking of trying to change the x-pipe design to one like show by highlander in the picture after the headers. It seems that the stock system (with it's 5 mufflers) had a lot of backpressure which I've reduced too much, and thus it feels less powerful from a dead stop. Thoughts on changing the design of the x-pipe, or just going back to the restrictive stock system with the increased backpresure? I intuitively thought (coming from Porsche 928's) that better flow equalled better performance (than the stock system) but I may be wrong.

Here's a link to the siamese x-pipe design that I have in:
http://www.performance928.com/cgi-bin/page_display.cgi?page_nav_name=xpipe6c5&pass_parent=1128

[email protected]

 

[doey]

Leave the x-pipe, replace the middle muffler with a more free flowing one and put the original 4 mufflers/resonators back on. [just athought]

 

[JBrady]

I just replaced the exhaust on my 1998 sc400 from the cats back, taking out the stock middle muffler, and the other 4 mufflers/resonators. I put in 2.25" x-pipe in the siamese-joined-in-the-middle design of an x-pipe and not the kind of X pipe in the picture by highlander. The x-pipe then goes 2.25" to two high flow 2.25" bullet 4" mufflers. The sound is better now, but the low end torque/pull seems to be less than before. I tried to reset the ecu by taking the negative battery terminal off for a few hours, but seat of the pants it still feels less powerful when pulling from a dead stop. Should I try to reset the ecu again, or I was thinking of trying to change the x-pipe design to one like show by highlander in the picture after the headers. It seems that the stock system (with it's 5 mufflers) had a lot of backpressure which I've reduced too much, and thus it feels less powerful from a dead stop. Thoughts on changing the design of the x-pipe, or just going back to the restrictive stock system with the increased backpresure? I intuitively thought (coming from Porsche 928's) that better flow equalled better performance (than the stock system) but I may be wrong.

Here's a link to the siamese x-pipe design that I have in:
http://www.performance928.com/cgi-bin/page_display.cgi?page_nav_name=xpipe6c5&pass_parent=1128

[email protected]

Mike,

First of all, WELCOME to Lextreme.

Secondly, the Ott's performance X pipe is a nice design. We must keep in mind that his Porsche 928 is a 5.0 liter and has very different cam profiles than our 1UZFE. Regarding "backpressure"... this is a SERIOUSLY missunderstood dynamic and in fact more pressure at the valve means LESS power. Changing pipe size, transition designs and mufflers will alter pressures, harmonics and of course power and response.

That said, I think more than anything else you are feeling a loss of response. I donated a merge collector and mandrel parts to the first header install customer. He modified his system prior to the headers. He felt it lost power throughout the range. Dyno testing showed a GAIN of 1rwhp and 6rwtq. Obviously there is MORE than dyno numbers going on here. With the headers installed the car became VERY responsive.

Another header installer, SRQ400 from CL installed 2.25 duals WITHOUT any crossover from the SS headers to his stock rear mufflers and was VERY excited about the serious gain of both high end power but even more surprising his LOW rpm response and power. Here are links:
http://www.clublexus.com/forums/showthread.php?t=186633
http://mysite.verizon.net/res6pb6m/id11.html

Now, due to testing a data I have been gathering I have actually developed a different Y pipe design I call a "nozzle" collector. The concept is to accelerate the gas flow at the intersection without creating a backpressure bottleneck. This promotes one WAY flow and low RPM scavenging. These are the pipes I will be fitting to my 99 1UZFE engine. From the outside they appear to be standard racing style merge collectors. The modification is internal. The below Y pipe is 2.25 in and 2.50 out. It will be used with the reverse dimensions to duplicate the factory system design. Are these sizes optimal? That is undetermined but I would suggest that too large a center pipe will not be desireable so erring on the small size is better than too large.

 

[akitamike]

Thanks JBrady for the info. I called my exhaust shop and suggested going back to stock 2.0" pipe before the x-pipe (ie 2.0" from cats to x pipe) then maybe changing the design of the siamese-style x-pipe to the magnaflow true-x design as shown by doey in his picture above. He counseled against that, saying stock is 2.0" vs. the 2.25" he put on from cats to x-pipe and said the siamese style design is better for hp increases than magnaflow x-pipe design (as Louis Ott's research also showed). After the x-pipe we run 2.25" to new high flow 16" x 4" bullet mufflers, so given your post from SRQ400 I might put back on the stock larger chambered mufflers at the back - they are much bigger and chambered. My shop and I thought this might be something that could work to make it not flow so much over the stock system (at least we're taking out the restrictive middle muffler and the 2 resonators, and increasing the diameter of the piping to allow better flow.) That would be an inexpensive attempt at a fix. Your idea of going with a Y-pipe instead of the x-pipe in the middle - do you think that would help. My shop talked about doing a Lexus design similar to mine, but then the customer custom burned a new chip to change the fuel mapping characteristics (which in California will probably negatively affect smog readings too much to pass, so don't want to go that route.) Maybe I'll just try to to put on the stock back two mufflers, thoughts? Thanks.

 

[JBrady]

Thanks JBrady for the info. I called my exhaust shop and suggested going back to stock 2.0" pipe before the x-pipe (ie 2.0" from cats to x pipe) then maybe changing the design of the siamese-style x-pipe to the magnaflow true-x design as shown by doey in his picture above. He counseled against that, saying stock is 2.0" vs. the 2.25" he put on from cats to x-pipe and said the siamese style design is better for hp increases than magnaflow x-pipe design (as Louis Ott's research also showed). After the x-pipe we run 2.25" to new high flow 16" x 4" bullet mufflers, so given your post from SRQ400 I might put back on the stock larger chambered mufflers at the back - they are much bigger and chambered. My shop and I thought this might be something that could work to make it not flow so much over the stock system (at least we're taking out the restrictive middle muffler and the 2 resonators, and increasing the diameter of the piping to allow better flow.) That would be an inexpensive attempt at a fix. Your idea of going with a Y-pipe instead of the x-pipe in the middle - do you think that would help. My shop talked about doing a Lexus design similar to mine, but then the customer custom burned a new chip to change the fuel mapping characteristics (which in California will probably negatively affect smog readings too much to pass, so don't want to go that route.) Maybe I'll just try to to put on the stock back two mufflers, thoughts? Thanks.

When you make this statement, "to make it not flow so much over the stock system" it tells me you are looking in the wrong direction. Theoretically you would want unlimited flow capacity. If you restrict flow the engine must work against this restriction. However, the engine is a DYNAMIC system that has different exhaust needs at different power and speed ranges.

As RPM increases so does the flow capacity, obvious I know. Less obvious is the reverse, IE at lower RPMs the flow capacity requirement is less, MUCH less.

What you want is in fact a combination of TUNING and velocity.

Tuning is the way the system "sounds" to the engine. Reflected sound waves can either help or hurt the power at any specific point. Velocity is ALWAYS a good thing provided there is not a substantial increase in pressure at the exhaust valve(s). Backpressure is never helpful in a 4 cycle engine except to compensate for an inadequate fuel system.

So, what is the answer? Application of known components, experimentation with new ideas and lots and lots of testing. If you get it right on the first try you are very good AND very lucky.

There is no doubt that 2" pipes are sufficient for low RPM use and they certainly will have higher velocity than larger pipes. The question is will they present a bottleneck at the peak flow required for peak power? 2.5" pipes kill low RPM velocity and with it response and power. They are also much larger than needed for peak power and they take up more space and weigh more, not much help and in fact no good reason to use. 2.25 is a compromise between the 2 sizes. 2.125" may be better but hard to obtain.

Stock Lexus center pipe is 2.36" or 60mm and necks down further in the LS400 resonator. A single 2.50 pipe represents a 13% gain in flow area and probably a 20% gain in actual flow when boundary layer flow is included. Now, if 60mm supports 300hp in the GS400 how much will 2.5" support? Probably another 50hp. How much do you expect your system to gain total? The point is why go with over 50hp capacity gain on a system that may give you 20hp? All you do is sacrifice low speed velocity.

So, you could go back to 2" pipes which are SLIGHTLY larger than stock but MUST be carefully mandrel formed and each weld must be ideal or you could end up with less flow than the stock pipes. You could source 2.125" pipes. You have already spend the money on 2.25" pipes which can work very well. My suggestion was to try to go back to the factory DESIGN of dual Y pipes. I suggested trying my nozzle collector idea. 2.25" into a single 2.50 and back out into dual 2.25. Going back to the stock mufflers will probably not make much difference either way.

I emailed you so let me know if you didn't get it.