A Exhausting question

Smileyshaun

Bought an X
So when I was putting the clutch in my rig I noticed that the Y pipe before the muffler to me at least seems the be almost squashed in half on one of the pipes . Is this how all xterra Y pipes look seems to be overly restricted to me 954175EC-C13B-4979-A4B4-D8F730308870.jpeg
 

TerryD

Total Tease
Supporting Member
Location
Covington, Va
That's how they all are. Some believe there are gains to be had by changing it but I don't personally think it makes that big a difference unless you are spending a lot of time over 4k RPM like a prerunner.
 

TerryD

Total Tease
Supporting Member
Location
Covington, Va
There was an article in Hot Rod or Car Craft where they put new headers on engine and dynoed it. Then they proceeded to beat and smash them and redyno it.

They actually gained power if I remember correctly, in the long run and the headers looked horrible when it was all said and done.
 

IM1RU

Skid Plates
Supporting Member
Location
SLC, UT
^This... That was an hilarious article. At some point during the smashing of the headers, they did indeed gain HP.
 

Smileyshaun

Bought an X
I was more worried about the imbalance between the two banks on the exhaust, not sure if it’s just coincidental but the previous owner replaced both cats on the drivers side and with all my free time under there putting the clutch in it just had me wondering if there was a reason for it . It’s probably nothing but anytime something looks out of the norm it catches my eye and I want to know why .
I remember seeing that whole test on engine masters , I’ve always been a fan of small pipes . I would much rather have more low to mid power that’s usable rather than a couple more ponies up near redline .
 

Just a Hunter

Bought an X
Location
Georgia
A post of mine from long ago.
.....
Ask yourself, how much do you feel the single small dent on one side of the Y pipe affects our exhaust performance.

I'm guessing not noticeably at all.

For example,
AFE has a nice looking exhaust comprised of 2.5" into 3" mandrel bent stainless steel tubing and a 409 stainless dual in single out muffler.

For a msrp of $786 ( + installation cost if your not mechanically inclined) you can brag to all your friends that your now making 5 extra HP.

This is a shockingly small jump in hp when you consider your removing the dent in your Y-pipe, receiving a high-flow muffler and gaining a larger diameter pipe.

https://afepower.com/afe-power-49-4...3-409-stainless-steel-cat-back-exhaust-system

My point is even with the y pipe dent, our exhaust's is not as restrictive as some people may believe.
 
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Smileyshaun

Bought an X
I’m not so much thinking the restriction as a power robber more the fact it almost necks down to half the size of the other pipe causing a imbalance . I know by looking at the Carfax that it failed emissions and that’s the reason both cats on the driver side where replaced . Most people wouldn’t replace 2 cats unless there was a good reason , just odd to me it just the cats on one side , if it was both forward cats I could just say it’s a normal thing . The rig has just over 100k on it so to even need cats at this point to me is almost unheard of . Like I said it’s probably nothing but my mind just wonders sometimes .
 

Just a Hunter

Bought an X
Location
Georgia
A couple years back, I ran some calculations to determine what size pipes would be optimal fo a 4.0 re 244ci engine with 260hp.

Basically, my conclusion was the Xterras exhaust is for better words over built.
To be clear, I found our exhaust could support the flow needed of an engine with much more hp than our own.
Yes, there is a dent in the y pipe , but our engine didnt need a pipe of full size to flow appropriately to start with.

This can be seen in the post I recently shared.
AFE went out of their way to build the best exhaust possible.
They removed the y pipe dent, went up in exhaust pipe diameter, included a straight through muffler , mandrel bent their pipes and used stainless steel in its construction.

In the end, everything was optimized to deliver a properly balanced, first class exhaust focused to achieve a performance gain.

However, the best AFE claims is you may see up to a 5hp gain. I could gain this much power by replacing my air filter

If there had been a real issues regarding the dent in the y-pipe or how it effects exhaust flow, you would have noticed more of a difference in hp gains than what was advertised

Ps, I suspect the previous owner failed to maintain your vehicle properly which led to a misfire on bank 2 of your engine. This detail combined with it having higher mileage on the factory catalytic converters assisted with the emission failure. In so far as the owner having replaced both the front and rear catalytic converters, I would suspect this is the result of a good salesperson at the repair shop he visited
 
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Smileyshaun

Bought an X
A couple years back, I ran some calculations to determine what size pipes would be optimal fo a 4.0 re 244ci engine with 260hp.

Basically, my conclusion was the Xterras exhaust is for better words over built.
To be clear, I found our exhaust could support the flow needed of an engine with much more hp than our own.
Yes, there is a dent in the y pipe , but our engine didnt need a pipe of full size to flow appropriately to start with.

This can be seen in the post I recently shared.
AFE went out of their way to build the best exhaust possible.
They removed the y pipe dent, went up in exhaust pipe diameter, included a straight through muffler , mandrel bent their pipes and used stainless steel in its construction.

In the end, everything was optimized to deliver a properly balanced, first class exhaust focused to achieve a performance gain.

However, the best AFE claims is you may see up to a 5hp gain. I could gain this much power by replacing my air filter

If there had been a real issues regarding the dent in the y-pipe or how it effects exhaust flow, you would have noticed more of a difference in hp gains than what was advertised

Ps, I suspect the previous owner failed to maintain your vehicle properly which led to a misfire on bank 2 of your engine. This detail combined with it having higher mileage on the factory catalytic converters assisted with the emission failure. In so far as the owner having replaced both the front and rear catalytic converters, I would suspect this is the result of a good salesperson at the repair shop he visited

I get what your saying but I wouldn’t call when they where replaced at 80k high mileage.
 

Smileyshaun

Bought an X
And I’m not saying there is a simple dent in the Exhaust , it is crimped down to half the diameter of the other pipe and concaved in .
 

TerryD

Total Tease
Supporting Member
Location
Covington, Va
Cat failures on these are not uncommon. I don't know if it's faulty materials or poor design but it does happen.

Occasionally a misfire will lead to a failed cat so it's possible they lost a spark plug or coil on that side and the excess unburnt fuel wasted them as well.

But a single failure like yours has experienced isn't common without an ignition issue (usually both age out).

I had 170k on mine when I replaced both primary cats and O2 sensors preemptively.

There is some disagreement in the ranks as to the exact cause but there seems to be a phenomenon where the primary cats plug/disintegrate and by some function of that, the rear most cylinders begin really using oil. FAST. In incident that caused my concerns, the engine to begin using a quart in a couple hundred miles after the faulty cats were gutted and the vehicle driven for testing afterward.

He wound up having to replace the engine due to that level of oil consumption.

To that point, my early 2nd gen had checked all the boxes for Xterra Bingo (SMOD, secondary timing chain tensioner) and I didn't think it was worth chancing a $4k engine for a couple hundred in parts. The piece of mind was worth it in my book.
 
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