Does removing the cat require remapping of the computer because of reduced backpressure?

 

Bob???

 

Welcome to the forum.

Give the folks at Fuelmoto a call, tell them what you've done, plan to do and they will be able to tell you what you need.
Good Luck
Bill
Here's the link:
http://www.fuelmotousa.com/

 

not so much "backpressure"- which is often a misnomer.

the idea is to control the velocity of the exhaust gasses- a smaller pipe will require the gasses to go faster...but you don;t want to reach the point where the gasses back up...a too wide pipe will make for slow gasses.


you see this on a cold morning when the vapour is lazily coming out the muffler of the other car idling in traffic...and then as the car accelerates, the vapour has to move faster to get out the pipe

fast gasses are good for performance, and on many exhaust designs allow scavenging ( which you can look up)- which will give "free power" power gains with no penalty.

sorry, lotso coffee today.


on many motorcycles the motor has the potential to flow more air into the motor and out the exhaust...but 1 or both of these may be restricted to control noise emissions.

removing those controls will give about 10 HP gains- 15% over stock...the classic "stage 1"

on models before 2014, a high flow air cleaner was typically required, this would allow more air to flow faster into the motor- on demand. the 2014+ air cleaner flows much better and esp with a high flow filter- like a clean stock or a K&N will flow to demand.

on models 2010+, the cat in the header is the other bottleneck to flow-removing that is needed- or replacement with an aftermarket header it's $150 vs $600...your choice for same same result. many rider stay with stock mufflers with no cat and are happy with sound and power.

but hey, now we have 15% or so more air flowing into the motor- in MOST cases that means you need more fuel to match...that is where the idea of a tuner comes in.

there are expensive complex devices, mid-price compromise devices--- on most of these the results depend crucially on the settings entered by "someone"- so can be great or suck...I've seen both extremes.

and on the cheap end of the scale are nightrider.com XIEDS, which can be closer to $130 and will suffice for many.
I used these for over 5 years to good result on my 2009.
I am playing around with a "free" V&H fuelpak and am on settings revision #5, the operation is pretty good for 80% but problematic for the other 20%..V&H is still trying to help sort this ut.
It's an experiment for me, and I may just put the XIEDS back on ( 10 minutes)

there are riders here who have $2000 stage 1's, and riders who have $300 stage 1's in depends how much DIY you can do and how well you understand the whats and whys of a motor.


and...on a Harley I stay at stage 1, more"performance" work often leads to mechanical failures further down the road- I keep my stuff along time

mike

 

No you won't have to remap,and your motor will thank you when you remove it.

 

I like bobbers, oh you are talking exhaust. Never mind

 

Just to clarify without giving any offense, what you are saying is not really right. OP, your question has to do with more than back pressure. Some back pressure is essential to prevent reversion and improve scavenging(The thermodynamics and wave theory here is way beyond me!), however if you change the header or decat it, you have changed the essential balance of cylinder pressure, intake pressure and the back pressure. So you get a situation at low to midrange rpm where you could have exhaust gas mixing with the cylinder that is in the intake cycle which is not good obviously. If you ever take your bike to get dyno'd, you might see it as a flat spot on the dyno chart. Now, if you change the cam along with the header, you got additional complication with valve overlap etc.
Now to answer your question, just changing the header or decatting it is not as severe as changing the air intake and cam at the same time. You can probably get by with a simple fuel management device like mkguitar is talking about.

 

You rang?

 

Is it required? No. Should you? Yes. These thing run lean stock, freeing up flow leans it more...

 

No. But if in addition you ever change the air intake and the mufflers, then you really should do something to manage the fuel otherwise you will be running way too lean.