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Should cats be taken out or left in, is there any real advantage by removing them from the stock headers if you are fitting slip on mufflers ?

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I took cats out of a set of Shotguns to put flame throwers in

did not make any difference !
and flame throwers didnt work as good as i wanted

All the Victory mechanics i have spoken to, say leave them in. Victory has to put them in by law when the bike is built and  have become experts at tuning and engineering the freedom engines around them being fitted.

I was also told that there is some toque loss at the lower end if they are removed ( Loyd's USA also say leave them in unless your doing some major engine rebuild  )removing the cats will make the engine perform differently to how it was engineered to run.

removal of the cats could also cause an erratic idle speed and stalling and a smokier star up. it was recommended to me that if i did remove the cats i would be wise to install a power commander 5 to smooth out the rev range, fuel and air mix and reduce popping , back firing and stalling.

The PC5 would be around $400 and $280 to install it and set it up properly,  in the opinion of the technician he said that i would end up with no better performance for all the expense than i would if i had just left them in.

Not sure that would be money well spent ? the top over all recommendation from mechanics has been, just fit some high flow slip on mufflers to your original headers as they have the best power performance over most after market full systems including Victory full systems  (leave the cats in) fit a high flow air cleaner with a vented cover and simply do a stage 1 remap. you will have a beautifully preforming trouble free engine that will deliver plenty of good usable power.

I've removed mine on both my Ness Vision and XCT.  I do run a PCV with A/T on both too so if if there is any power loss on removing them while stock it's made up for in with the PCV.

All is can say is from my differences and how they run.  It "appears" that both bikes are smoother throughout the rev range.  They definitely sound a tad different....smoother sound sort of speak.  

The biggest gain I see, which is why I removed them is the lack of heat that they create.  One is under the bike, just past the oil filter in the cross over pipe as it connects to the left muffler setup, and the other is at the end of the pipe on the right just at the joint to where the muffler connects.  In other words, pull both mufflers and both cats are at the end of each side.

IMHO, not having that darn thing heating up to 1500+ degrees, 2-3" from the oil filter can only be a good thing.

Both my bikes, even after a 1200 mile trip, have completely ZERO soot on the tailpipe.  They did before removing the cats and adding the programmer.  The cats burn off excess fuel/gasses before entering the air we breath.  My PC5's (more like the Auto Tunes) have got my bikes running perfectly.  And I mean perfectly!!!!!

Other forums have beat this almost to death.  Many many people have "facts" they throw out there for one way or the other on removing them.  I know why they are there.  I know how to compensate for them not to be there.  For me, it was a no brainer to pull them.  

With no cats in it's a safe thing to say that the exhaust will breath a bit easier.  With that in mind I added the 2nd air filter to my Vision and added the Lloydz big air cleaner to the XCT.  Easy in - easy out as far as the flow of air.  That may very well be one of the biggest reasons my bikes seem to run extremely well no matter the elevation (14k+ feet) or throttle position and VERY responsive. off topic a bit. opinion is if you can do it, pull them.  

Hey Mike,

That's great to hear, it's like they say mate, an opinion is always outweighed by an experience. I had the cats out of my Ness  Vision , stage 1 pipes and hi flow air filter but with no PC5 fitted and it also ran just fine, only very occasional popping on deceleration but my high Ball pops now with the cats in, slip on mufflers and hi flow air filter and it's also been tuned by a victory mechanic using digital wrench. I am now thinking i may be better off following the same set up you have done with your bikes.

Are you saying you run a PC5 plus an additional Auto tune plug in module ? or just a stock PC5 on its own ? i would be interested to hear more details about your set up as it sounds like its working well for you. Can you tell me more specific details on the modules your using.


I run the PCV and their AutoTune. The AT-300 version.

The AT is for dual O2 setups. Swap out (disconnect the Victory ones) the O2's with the ones provided with the AT and wire them into the AT. Few setting on the PV5 and your done.

I've dealt and talked to two different Dyno shops. They can't do better than the AT can. They install PC's but don't advertise the AT's for obvious reasons.

Never need a Dyno again. It will keep the bike in perfect tune all the time. Swap out pipes, change whatever, never worry about the tune again.

The AT can stay connected indefinitely or you can get it tuned then you can remove or turn it off via the PC5. The O2's are there only for the AT as that's what they use to check the PC5's tweaks.
Oh, I too have the stage 1 flash but with D&D pipes, the Vic high performance air filter PLUS the Lloydz additional high performance air filter under the center console. I also installed the Lloyd's adjustable intake tubes. Don't know what they actually did but I was looking for max gains without changing anything internally on the bike.

The PC5 and AT is what put everything together and made the intimate difference.

I tow a Bushtec trailer and travel 2 up when I tow. Performance is awesome and my mileage is between 42-49 all the time.

Thanks for the info Mike, i will be looking at doing exactly what you have suggested.



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