Straight Pipe... What do people need to know?

Cameron23

Cameron23

Skid Plates
Founding Member
Location
Kansas
So I was casually ripping out a heat shield off of my exhaust today when it hit me.... Why the hell is ripping off a heat shield casual!? I hate the exhaust on my X it's too quiet unless it is rattling a heat shield. I want to run my own pipe and cover it in rust proofing spray before install but I don't want to deal with cats and mufflers lol. I want loud growl. So I want to run just pipe from headers back along the same route as the current exhaust but without cats and without muffler.


Now I know there is something to know about back pressure and I know some might not be for the loudness but that is my preference. Kansas does not test emissions. I want to know:

Will this hurt my engine?
Should I instead do just pipe from the cats back?
What diameter?
What type of pipe?
What thickness of walls?
Will this work?
How would I bolt/weld (i have a welder friend) it to headers or cats?



Sent from my iPhone using Tapatalk
 
robcarync

robcarync

Sliders
Location
Raleigh, NC
Cameron23 said:
So I was casually ripping out a heat shield off of my exhaust today when it hit me.... Why the hell is ripping off a heat shield casual!? I hate the exhaust on my X it's too quiet unless it is rattling a heat shield. I want to run my own pipe and cover it in rust proofing spray before install but I don't want to deal with cats and mufflers lol. I want loud growl. So I want to run just pipe from headers back along the same route as the current exhaust but without cats and without muffler.


Now I know there is something to know about back pressure and I know some might not be for the loudness but that is my preference. Kansas does not test emissions. I want to know:

Will this hurt my engine?
Should I instead do just pipe from the cats back?
What diameter?
What type of pipe?
What thickness of walls?
Will this work?
How would I bolt/weld (i have a welder friend) it to headers or cats?



Sent from my iPhone using Tapatalk
Click to expand...

You have 2 exhaust manifolds and each has a cat. If you want a single pipe, you will need to custom bend some pipe into a crossover and connect the two exhaust streams with a Y-pipe. See magnaflow parts for y pipes.

And efficient exhaust needs efficient routing and high speed of gasses. That means you do not want to make the pipe too big...bigger pipes slow exhaust gas down...so it can have an adverse effect.

The easiest thing to do would be just to cut the muffler out after the cross over and weld or clamp a straight piece of pipe out the back. I used 2" pipe in the cross over section and 2.5" single outlet.

It really depends on what you want to do and how you want to do it. If this is a DIY project with no pipe bending capabilities, it becomes more difficult. You can buy pre bent exhaust pipe and cut it to fit if you want to deal with that.

All in all...it took a muffler shop 40 minutes to custom bend and weld up my exhaust excluding muffler cost. It was far better than anything I could have done myself.
 
robcarync

robcarync

Sliders
Location
Raleigh, NC
Also...midget 28 on here just went exhaustless. No pipes after the cross over. It broke off wheeling and he never fixed it. You could also look into an exhaust cut out.
 
Cameron23

Cameron23

Skid Plates
Founding Member
Location
Kansas
robcarync said:
You have 2 exhaust manifolds and each has a cat. If you want a single pipe, you will need to custom bend some pipe into a crossover and connect the two exhaust streams with a Y-pipe. See magnaflow parts for y pipes.

And efficient exhaust needs efficient routing and high speed of gasses. That means you do not want to make the pipe too big...bigger pipes slow exhaust gas down...so it can have an adverse effect.

The easiest thing to do would be just to cut the muffler out after the cross over and weld or clamp a straight piece of pipe out the back. I used 2" pipe in the cross over section and 2.5" single outlet.

It really depends on what you want to do and how you want to do it. If this is a DIY project with no pipe bending capabilities, it becomes more difficult. You can buy pre bent exhaust pipe and cut it to fit if you want to deal with that.

All in all...it took a muffler shop 40 minutes to custom bend and weld up my exhaust excluding muffler cost. It was far better than anything I could have done myself.
Click to expand...

I would have a shop custom bend depending on the costs if I went headers back the pipe would follow the current path of the exhaust including the y pipe section same would be said for cat back but I think I have heat shield rattling before the cats so I just wanna take it all out. I don't want to run cut off exhaust because I know engines require at least a little back pressure lol


How expensive was the bending and welding done by the shop

Sent from my iPhone using Tapatalk
 
Cameron23

Cameron23

Skid Plates
Founding Member
Location
Kansas
robcarync said:
Also...midget 28 on here just went exhaustless. No pipes after the cross over. It broke off wheeling and he never fixed it. You could also look into an exhaust cut out.
Click to expand...

He should post a quality sound video if he hasn't already


Sent from my iPhone using Tapatalk
 
robcarync

robcarync

Sliders
Location
Raleigh, NC
Engines do NOT need back pressure.

Engines need an exhaust with low backpressure and a high gas velocity. The most effective exhaust dumps the gasses as quickly as possible with the fewest number of bends.

The common idea is to reduce back pressure by going with a bigger pipe. Problem becomes that bigger pipes mean the gasses slow down and cool. Cool gas is more dense which means heavier...and creates resistance. This is where the myth comes from ... People think they need back pressure because bigger pipes did not increase power...contrary...bigger pipes lessen back pressure ...but the slower cooler gas creates more backpressure than the large pipes reduced it by...thus you gotta find a sweet spot on pipe sizing

Sure fire way to reduce pressure without hurting performance is shorter pipe routing, fewer bends, remove mufflers and cats. Pipe sizing mostly depends on engine power....so stock size pipe is good size, but you could also go up one size.

YouTube robcarync xterra. There are a few clips of midgets rig at MIOBI.
 
Last edited:
robcarync

robcarync

Sliders
Location
Raleigh, NC
Last edited:
robcarync

robcarync

Sliders
Location
Raleigh, NC
Sorry for replying like 5 times in a row...I was travelling the last several days and just typed up some stuff from my phone on the go. I will give you a few more details directly addressing your questions:

Will this hurt my engine?

No...Not many ways an exhaust can "hurt" your engine...unless it just doesn't get the gasses away like it should.

Should I instead do just pipe from the cats back?

It depends on what YOU want to do and how much MONEY you want to spend. If I were you, in a state with no emissions checks...I would get headers, run 2" pipes from each header into a Magnaflow Y-Pipe (2in pipes going in from each header, 2.5" pipe going out). I would keep the pipe as short as possible dump the gasses in the most efficient routing as possible.


What diameter?

http://www.xterraownersclub.com/forums/ubbthreads.php?ubb=showflat&Number=643144

http://www.exhaustvideos.com/faq/how...pipe-diameter/

Basically, 1.75" is stock on the single stream pipes, but you can go up to 2" from each side. Stock single pipe is 2.25" diameter, but you can bump up to a 2.5" single stream...but these details will help explain how to arrive at those numbers.


What type of pipe?

I would get an exhaust shop to use whatever pipe they have on hand. They can custom bend the pipe and mount hangers, etc. Look at some Google reviews in your area. I paid $125 for welding and custom bending the pipe for my application.

What thickness of walls?

See above response.

Will this work?

Sure it will.

How would I bolt/weld (i have a welder friend) it to headers or cats?

This is where it may cost you a bit more money at an muffler shop. The headers will have a flange on the end, designed to bolt up to another exhaust flange at the cross over section. You can spend the money...and have them cut off the flanges from the cross over, and have it welded onto new pipes that they bend up for you...that will give you a clean bolt on look to your headers.

You can go the cheaper route and heave them cut the header off right behind the flange, and weld new pipes directly to the header. I would have a hard time taking a sawzall to new headers though. I used the stock manifolds and cats, so I just cut off after the last cat, and welded directly to the pipe.

I have a welder at home, and can easily weld up pipes and tubes, etc. I went with the exhaust shop route, simply because I did not have capability to bend pipes easily. The exhaust shop has a hydraulic powered tube bender (not the hand pump bender), and it included the fitting to expand or contract pipe diameter. This meant they were able to expand 2" pipe so it slipped over the 2" inlet of the muffler before welding, etc. Also, welding under the truck is fairly difficult, even if you can weld. These guys had a lift, and were very skilled at 1 handed welding in the over head position. They did a MUCH better job than I could have done at my house.

Also, be forewarned, that many muffler shops may not deal with headers or cutting out cats. Maybe they will cut the cats out if you pay them cash and take them with you...but even with no emissions inspections, it is federal law (EPA) that states you have to have cats. Cats can be recycled, but shops that recycle them have to have documentation, blah blah blah to submit to the EPA for why the cats were removed. This part, I believe is not state-dependent.

I know my muffler shop would probably look the other way if I cut them out and got them to patch up the left over holes in the tubing...but they are not a full mechanic shop, so they won't install headers.

I would probably install the headers yourself, then cut the rest of the exhaust out yourself...and take it to a muffler shop to weld the straight pipe for you, and have them re-use the old flanges to bolt it up to the headers.
 
Cameron23

Cameron23

Skid Plates
Founding Member
Location
Kansas
You say the best option is the short exhaust.... Side exhaust? Not to look too ricey or ricey in any way


Sent from my iPhone using Tapatalk
 
robcarync

robcarync

Sliders
Location
Raleigh, NC
Performance wise, you want to the exhaust gasses out of the system as fast as possible with smallest amount of restriction. The length of pipe increases the back pressure...but so do bends...so it is a toss up. Is 5 feet of straight pipe more restrictive than a sharp bend with only 2 feet? I would guess that straight and long is better than bent and short... but without some complicates tests, it is hard to know for sure.

If you had to do a sharp 90 degree bend to do a side exhaust, I would say keeping the exhaust straighter would probably be better overall. I didn't go side exhaust because it would have to go down low to go under the frame rail, and would be very vulnerable to trail damage.

If you look at how my exhaust is routed, it is basically fairly straight, very few bends, and just has a simple turn down right behind the bumper...not even extending out past the bumper. I think this is a pretty good route, especially if you don't have a spare tire in the stock location. You can keep the pipes high and out of the way, and stick the pipe out further, or cut it back if you want. Having the small turn down generally keeps the exhaust from floating up and getting trapped under the cab area while driving.. Some people have done axle back exhausts that turn down right past the rear axle...It is all up to you how you want to go about it.

Basically, the gasses can only be restricted when they are "in the system"...the easier the exhaust gasses can be pushed out (exit the system), the less power the engine has to use pushing the gasses. The biggest restriction in the stock set up is the 1) terrible manifolds, 2) cats, 3) crossover

Replacing all of those should get you some considerable gains.

If you JUST want sound...you can go for an exhaust cut out. It basically just welds in every easily and allows the exhaust to bypass the muffler and exhaust system. That wouldn't replace the headers or cats though...just bypasses the muffler.

http://www.installuniversity.com/in...haust_cutout_explanation/exhaust_cutout_1.jpg
 

Attachments

  • 07-TailPipe.jpg
    07-TailPipe.jpg
    100.8 KB · Views: 30
Last edited:
Cameron23

Cameron23

Skid Plates
Founding Member
Location
Kansas
I think I'm gonna go your route but get Doug Thorley headers delete cats and muffler. Idk how that would sound though


Sent from my iPhone using Tapatalk
 
Mirage

Mirage

<img src="http://i164.photobucket.com/albums/u7/ra
Founding Member
Location
Greenville SC
https://www.youtube.com/watch?v=njFnRaTgZsE

My truck with AC headers, '99/'00 walker fed downpipes (no secondary cats, OE diameter piping) nismo catback. Loud, bit buzzy between 2600-2900 rpm. I am going to add another muffler/resonator eventually to quiet it down some, the 450sx will be my loud vehicle soon.
 
Nd4SpdSe

Nd4SpdSe

First Fill-Up (of many)
Location
Quebec, QC
robcarync said:
Engines do NOT need back pressure.

Engines need an exhaust with low backpressure and a high gas velocity. The most effective exhaust dumps the gasses as quickly as possible with the fewest number of bends.

The common idea is to reduce back pressure by going with a bigger pipe. Problem becomes that bigger pipes mean the gasses slow down and cool. Cool gas is more dense which means heavier...and creates resistance. This is where the myth comes from ... People think they need back pressure because bigger pipes did not increase power...contrary...bigger pipes lessen back pressure ...but the slower cooler gas creates more backpressure than the large pipes reduced it by...thus you gotta find a sweet spot on pipe sizing

Sure fire way to reduce pressure without hurting performance is shorter pipe routing, fewer bends, remove mufflers and cats. Pipe sizing mostly depends on engine power....so stock size pipe is good size, but you could also go up one size.
Click to expand...

Absolutely beautiful responce! Thank you!

Cameron said:
I think I'm gonna go your route but get Doug Thorley headers delete cats and muffler. Idk how that would sound though
Click to expand...

That's the setup I got on a 2.5" exhaust, no cats but with a muffler. It's pretty loud, but not too obnoxious (My KLZE Mx3 test piped was stupid loud in comparison), but enough to have fun and outrev people that rev their cars, and to show off my frustration. The only thing I don't like is it's loudless at highway speeds, especially around and above 115km/h because at 3000rpms it's is nice loudness "dying trombone" sweetspot. It's ok, just not ideal for having a good conversation, especially for 1000kms, but in town it's definitely OK.
 
robcarync

robcarync

Sliders
Location
Raleigh, NC
Depends on rust, PB Blaster, and torching...

I have always been a fan of destructively removing exhuasts. If you aren't re-using any of them...sawzall is WAYYY quicker and less frustrating as you bust your knuckles less than turning wrenches

Some can be easy, some can be tough
 
robcarync

robcarync

Sliders
Location
Raleigh, NC
That I can't really say. I have had no issues gaining access to the 2ndary cats, but I haven't done headers or the primary cats

Someone else would have to chime in
 
Cameron23

Cameron23

Skid Plates
Founding Member
Location
Kansas
KChurch86 said:
I didn't really think it was that bad honestly, I used some long extensions and at least one universal joint. I found the job 100% easier with the front drive shaft removed also.
Click to expand...

I don't want to remove anything except the exhaust and catsAlso what do I do about the O2 sensors


Sent from my iPhone using Tapatalk
 
P&P

P&P

Need Bigger Tires
Site Sponsor
Location
Middle TN
robcarync said:
Engines do NOT need back pressure.

Engines need an exhaust with low backpressure and a high gas velocity. The most effective exhaust dumps the gasses as quickly as possible with the fewest number of bends.

The common idea is to reduce back pressure by going with a bigger pipe. Problem becomes that bigger pipes mean the gasses slow down and cool. Cool gas is more dense which means heavier...and creates resistance. This is where the myth comes from ... People think they need back pressure because bigger pipes did not increase power...contrary...bigger pipes lessen back pressure ...but the slower cooler gas creates more backpressure than the large pipes reduced it by...thus you gotta find a sweet spot on pipe sizing

Sure fire way to reduce pressure without hurting performance is shorter pipe routing, fewer bends, remove mufflers and cats. Pipe sizing mostly depends on engine power....so stock size pipe is good size, but you could also go up one size.

YouTube robcarync xterra. There are a few clips of midgets rig at MIOBI.
Click to expand...

One thing we have noticed about the stock exhaust on the Xterra and many other vehicles that could pick up some power are:

Crush bends
Reductions in piping ID at connections.

I wish I could take credit for this but a friend had an aftermarket exhaust on a supercharged rotary engine making ~320whp. It had the same type of reductions in piping ID at all the connections/flanges. He went to an exhaust shop and had all those reductions replaced with the same size piping as the rest of the tube and from this picked up 15whp.

I don't think there is that much to be found with that modification alone on the NA Xterra, but it would be a place to start.


Sent from my iPhone using Tapatalk
 
P&P

P&P

Need Bigger Tires
Site Sponsor
Location
Middle TN
Cameron23 said:
I don't have one yet but it is doable without one? What if I took the front tires off?
Click to expand...

Do you have the primary cat that is integral to the manifold or the primary cat that bolts up to the manifold?


It really will save you time, energy and frustration to drop the front driveshaft. Otherwise you'll fight to get things past and around it.

Sent from my iPhone using Tapatalk
 
robcarync

robcarync

Sliders
Location
Raleigh, NC
It would be nice to see some exhaust options...It would be nice to see a re-engineered cross over section, or federal down tubes as they call them...pipes that replace the back cats on the cali Xs, but bolt up to the stock cross over...etc. I think most people on the exhaust front do a random muffler with custom bent tube from the cross over, or bolt on headers. It would be nice to see some attention in the middle...manifold back to the cross over.

Then you could get headers...bolt it up to the down tubes (would need O2 bung)...then bolts to the cross over....and finish the muffler and tail pipe however you want.
 
Cameron23

Cameron23

Skid Plates
Founding Member
Location
Kansas
My ultimate goal is to have DT headers Pipe coming straight off those meet with either a Y pipe or having it follow the current path but without the sharp 90 degree bends and then have it run into a flowmaster or no muffler. I didn't say cats because I don't want cats. You guys think that would net me some HP gains?

Also idk if I have the cats bolted to the headers (please gobble let that be the case) or if they are integrated into them.
 
Cameron23

Cameron23

Skid Plates
Founding Member
Location
Kansas
Does anyone know what the 2001s came with? I've heard 2 cats and I've heard 4 cats (even Cali Spec) are my cats going to be integrated into the headers?

Since the 1st set of o2 sensors measures gases coming out of the engine I would keep those but the second set measures gases after the cats and if I'm deleting my cats then what would I do to avoid error codes?


Sent from my iPhone using Tapatalk
 
Muadeeb

Muadeeb

Nissan al Gaib
Admin
Location
Dallas
Can't tell on mine because I have the heat shields on still, but I think mine are one piece. Hard to tell but I don't see any obvious mating flanges between the manifold and 1st cat.

As for the number, on mine (not Cali) I have two bulges under the vehicle after the 2nd sensor. I assume its a cat and not a dog, but it could be some kind of resonator.

As for the sensor, your best bet is to have a bung welded in, and use a CEL. The computer needs to see a certain signal change or it will throw a code. That, or you can ask someone to write a prom you plug into the harness that fakes a sensor. I don't know of any of those on the market today.

Sent via wild ferrets on crack
 
Cameron23

Cameron23

Skid Plates
Founding Member
Location
Kansas
Muadeeb said:
Can't tell on mine because I have the heat shields on still, but I think mine are one piece. Hard to tell but I don't see any obvious mating flanges between the manifold and 1st cat.

As for the number, on mine (not Cali) I have two bulges under the vehicle after the 2nd sensor. I assume its a cat and not a dog, but it could be some kind of resonator.

As for the sensor, your best bet is to have a bung welded in, and use a CEL. The computer needs to see a certain signal change or it will throw a code. That, or you can ask someone to write a prom you plug into the harness that fakes a sensor. I don't know of any of those on the market today.

Sent via wild ferrets on crack
Click to expand...

See I see the ones coming off the headers... Hard to think what's under the head shield because I can't find the bolts to remove the shield.


Sent from my iPhone using Tapatalk
 
robcarync

robcarync

Sliders
Location
Raleigh, NC
You use a spark plug defouler on your O2 sensor. It basically just spaces the sensor out of the exhaust stream so it doesn't actually measure the oxygen in the exhaust stream. It makes the computer think the exhaust is cleaner than it really is.

If I recall how it works...the first O2 sensor measures before cat, and the 2nd O2 sensor measures post cat...which just checks to see if the exhaust gas is getting cleaner. As long as those sensors think the exhaust is getting cleaner from one to the other, no CEL
 
El Robot

El Robot

Bought an X
Location
Frankfort Ky
Cameron23 said:
Does anyone know what the 2001s came with? I've heard 2 cats and I've heard 4 cats (even Cali Spec) are my cats going to be integrated into the headers?

Since the 1st set of o2 sensors measures gases coming out of the engine I would keep those but the second set measures gases after the cats and if I'm deleting my cats then what would I do to avoid error codes?


Sent from my iPhone using Tapatalk
Click to expand...

Here is what the stock manifold looks like with the integrated cats. You'll need to either buy or fabricate some light eliminators for your 02 sensors if you don't want to have codes. All that the light eliminators consist of are a simple tube that pulls the 02 sensor out of the stream. Also when it comes to gains remember, it doesn't necissarily help if you can breathe out well, if you can't breathe in first! So make sure you are doing things to the front side to compliment the back side.

2duv.jpg
 
You must log in or register to reply here.
Top