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wideopenallthetime

stock exhaust mod

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wideopenallthetime
So I plan on buying a full exhaust kit soon but in the mean time I was thinking about doing some mods to the stock setup to see what if any more sound can be had. I found a forum where a fella cut the small diameter tip off and replaced it with a larger one for a "perfect" sound increase he claimed. But km thinking more along the lines of drilling several holes around the tip in the muffler and maybe even 3 larger holes on the bottom...I know I will lose a little torque around 6500 rpm from what I've learned but it's temporary and if I ruin the stock one oh darn I HAFT to buy exhaust haha and where I live loud bikes save lives...I don't care if my neighbors don't like it lol so what are your thoughts fellow riders ?

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MarylandFZ07
Interested to see if anyone who bought an aftermarket exhaust has tried it with thier old exhaust.

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NICKY NEON
don't drill a hole in the bottom you need back pressure. try doing something with the tail pipe.

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olderthandirt
 
 
 
 
 

 

Congress is the only whore house in the United States that loses money.

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MarylandFZ07
don't drill a hole in the bottom you need back pressure. try doing something with the tail pipe.
I was thinking something along the lines like this ....

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aeisan
...you need back pressure. 
Said no engineer, ever.  
 
No good exhaust system promotes back pressure. In fact, an ideal system has zero back pressure. It's all about exhaust velocity.  Trust me... I stayed at a Holiday Inn Express once. ;)
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Life is good on 2 wheels!

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wideopenallthetime
Well I went ahead and drilled 6 holes all together...no pics yet sorry but sounds way better and didn't lose any noticeable torque. Used a pilot bit then reamed them out to 3/8... I put two around the tail pipe just above where it's welded to the muffler and then one to the left and down about 3in. Then I put 3 in the tail pipe itself. Its way deeper and thumper sounding...not a permanent fix but works till I get my custom setup :)
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aeisan
Nice. Pics and/or sound clips would be appreciated if you get some time.

Life is good on 2 wheels!

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V8titanpwr
...you need back pressure. 
Said no engineer, ever.   
No good exhaust system promotes back pressure. In fact, an ideal system has zero back pressure. It's all about exhaust velocity.  Trust me... I stayed at a Holiday Inn Express once. ;)
Actually without the ECU being re-flashed or a power commander etc, you need the back pressure. Running with no back pressure on a stock system when the computer isn't set up to run it will run the back very lean, causing loss of torque and a few other issues. A lot of the systems with straight pipes either have to be re-flashed or you have to change the jet size in the carbs, But I do agree straight pipes are better, with the proper tuning of course.

Keep the rubber side down and the shiny side up.

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aeisan
No, you are confusing back pressure with proper exit velocity. No system needs back pressure, ever. What it needs is the right amount of exit velocity and with too much flow area you lose velocity. When you add holes or remove the restrictive silencer, you are not removing the back pressure as much as you are creating a larger flow cross section, thus reducing velocity. It's a common misnomer, and though I understand what you are trying to say and your intentions are in a way correct, back pressure is not technically what is needed.

Life is good on 2 wheels!

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planetwister
Wouldnt recomend any exhaust mods without getting your ECU re-flashed. even little holes in your exhaust will make it more lean

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wideopenallthetime
th_20140910_110605_zpsb19537f3.mp4
 
Bike was cold so I didn't wrap it out and it sounds way better in person... I know about the torque loss and I was nervous but I don't notice it at all I even think it made my throttle response quicker but maybe that's just cause I can hear it now lol

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PearlWhiteFZ
Need to make the DIY so we can all have some sound until we get an exhaust system

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olderthandirt
ghetto
cheap
wrong
too lean
shade tree

 
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Congress is the only whore house in the United States that loses money.

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rotaryryan24
No, you are confusing back pressure with proper exit velocity. No system needs back pressure, ever. What it needs is the right amount of exit velocity and with too much flow area you lose velocity. When you add holes or remove the restrictive silencer, you are not removing the back pressure as much as you are creating a larger flow cross section, thus reducing velocity. It's a common misnomer, and though I understand what you are trying to say and your intentions are in a way correct, back pressure is not technically what is needed.
4 stroke yes, 2 stroke not true. A 2 stroke needs back pressure to keep the incoming air fuel mixture from just going out the exhaust ports.

You do or don't
Then your dead.
 
To order a tail tidy click
One-off-fabrication.myshopify.com

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Guru
 

I can confirm. I started on a two stroke Yamaha FS1 and one of a popular mods was a so called high pressure exhaust (combined with some other things). It increased the back pressure and made a difference compared to stock.

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rotaryryan24
I recently acquired a stock exhaust, my plan is to install a o2 bung and wideband gauge, run it stock just to see the stock AFRs. Then cut off the stock section just down stream of the collector, and try out some different style mufflers. With the aftermarket wideband I'll know just how lean it will be.
 

You do or don't
Then your dead.
 
To order a tail tidy click
One-off-fabrication.myshopify.com

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Guest MXRider

I can confirm. I started on a two stroke Yamaha FS1 and one of a popular mods was a so called high pressure exhaust (combined with some other things). It increased the back pressure and made a difference compared to stock.
Yeah the FMF silencer I have on my YZ has a ring welded into the end of the baffle to add back pressure. It adds a bit of power in doing so.
 

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aeisan
I think at this point we are just arguing semantics and I'll just leave it alone. You guys have the right concepts, but it's just not true that back pressure is the reason for the better performance. I could go into sin waves and savaging and all the technical mumbo jumbo, but I won't haha.
 
 
48858d5d6eaf1f623808a6a2a04fa5d5.jpg
Hahaha ^^^

Life is good on 2 wheels!

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fechner
As a fellow engineer, I welcome technical details. I expect to see schematics and a thorough analysis this time tomorrow aeisan!

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hippiebikerchick
As a fellow engineer, I welcome technical details. I expect to see schematics and a thorough analysis this time tomorrow aeisan!
And we want a PowerPoint presentation of the findings.

Illegitimi non carborundum

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aeisan
Well, I'm in sales now, so yeah... PowerPoint won't be a problem! ;)

Life is good on 2 wheels!

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mikeyfz07
OP,
 
How is the bike running to date? Can you show us a picture of what you exactly did and where?

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mikeyfz07
After looking at the stock exhaust, I do not think its semi-wise to drill large 3/4th holes in the canister. Maybe the exhaust tail pipe but not the actual exhaust canister.

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