It seems to me that things become "fashionable" and, I repeated often enough - "true".

I have read a lot of threads about gutting cats from the 2010 and later bikes. Without trying to cast doubt on the benefits of this, the questions I would like answering, ideally substantiated by, for example, before and after dyno results:

1. Exactly how much reduction in temperature can one expect? Living in the UK I have never really had any complaints about the heat anyway but I am still interested

2. What is the effect on power? It seems to me that people make a whole bunch of changes in conjunction with this change so I wonder if anyone has done a before and after dyno test, making just this change

 

Do you have intl style exhaust with the valve?

most posts are from the US so do not.

The cat is shown to be an obvious obstruction and while there is no empirical evidence ( such as before after for gutted cats)--- I might suggest that some of the stock vs modified dyno charts out there confirm this ( although they also reflect hi flow cleaner and a tuner.

consider that US spec mufflers compliant for 2010 and up ( the cat years, 49 State) such as the S/E nightstick has a 2 inch core and is essentially open having 10 discs in the stack and an open 1.4" end cap.

those mufflers are way too loud and not as restrictive as would be optimal on my 09 bike by a factor of about 45%.
( I have 2 nightsticks on my bike now with closed endcaps and running a total of 23 discs between the 2- the stock configuration is equal to about 38 discs)

I'm sure there is science out there somewhere.

1.) ambient heat- easy to bag on the UK for being cool and moist in the summer, but we experience much higher ambient temperatures in the US--- and in city traffic ( most locations) motorcycles traffic is treated as a "car" and cannot split lanes or work through traffic as is common in the UK, so we get more time to experience and enjoy the warmth.

2.) common thought the past 25 years is that 7 to 10 easy horsepower are gained by "uncorking" the intake and exhaust- I would expect cat/no cat to fall in line with this.

3.) AFAIK tailpipe testing is only done in parts of Arizona, so modifications are unlikely to be discovered ( and the AZ standards are so loose you could pour gas up the sniffer and pass.)

4.) overtime, the catalytic media can break down, be contaminated or clog- which would cause reduced performance. I had this happen on a Nissan Sentra where after an accident the car would idle but not run well, the impact had loosened the media, which clogged the exhaust tract.
Wonder how it will do on a "Milwaukee Shaker"

mike

 

I am not sure exactly what exhaust I have fitted to be honest, my bike is a 2010 FLHTK. I know my '08 Ultra had cats in the slip on section as I have seen the cat in there.

I have just assumed that the cats are in the header as per the numerous posts on this forum. There certainly are O2 sensors in there. Is there an easy way I could check / compare?

It is the assumption in your point 2 that I am especially interested in. I guess I am working towards an argument that says "if you live in a cooler region the it's not worth gutting" - but would only want to reach that conclusion on proper comparative test results

 

per point 2: there were before after test on the 80" evos, and both my evos were dynoed after showing a huge increase from the stock evo 55 HP ( 45 HP in california due to camshaft)- the 95 FLHTC with hi flow air cleaner, tuned supertrapps and modded carb at 68 HP.
The 88 FXRP ( hi comp, police cam and module) added S/E air cleaner supertrapp 2/1 and modded CV carb turned over 74 HP ( this bike is tuned for torque as the final drive was a 15% overdrive)

That said I would love to see dyno cat/no cat with everything else left untouched or better yet, cat/no cat with a high flow air cleaner


you should have a cat, and it's location can be found by tapping the pipe with a biro.

also look at the photos on some of threads

of interest is many intl models have an active valve system on the exhaust which I believe opens the left pipe under certain rpm/vacuum conditions.

I think most EU market bikes are built to satisfy the Swiss

mike

 

Im sure if you do some searching on this forum you can find posts and dyno sheets that will indicate the improvement. I recall seeing dyno sheets from a stock bike only replacing the header with a aftermarket header with no cat and using the stock slip ons . I think it was either the FM , Fulsack or American Custom modified stock header.

Here is one article about American Custom. using the stock head pipe and mufflers modified, without the cat and stock baffles a small increase in Hp and Tq and with the loader baffles a greater increase. It does not say anything about a A/C or Download or tuner.
http://www.americancustom.com/media/news/AmerCustom.pdf

This is from Fuel Moto, same bike with PCV , A/C and stock mufflers only difference is stock head pipe or FM catless head pipe 4hp 6ft/lbs Tq difference
http://www.jackpotmufflers.com/2010E...ot212vsstk.jpg

This one is box stock only changed the head pipe 5 hp and 5 tq increase
http://www.jackpotmufflers.com/limit...jackpot212.jpg

Regarding heat I can only speak to it subjectively, my bike is cooler with the V & H that has no cat than it was the first few days when stock.

If I can find it Ill add to this thread as an edit.

 

Loads of interesting info in there, thanks. The differences seem to be fairly consistant across the 3 tests, namely around 4 or 5HP, although American Custom are declaring circa 7HP, but then they are stating that they add a "Power Chamber" in the area where the Cat was.

I am no authority on the subject by any stretch of the imagination, but I am intrigued to understand how "adding" something to the header can result in improved HP. I would be inclined to assume that any addition will result in some form of restriction, so how come better results?

 

flow--- changing flow will change something "somewhere"- so if you skew the tests for that "somewhere" you can advertise that gain.

just adding or subtracting a couple of inches to the total length of the exhaust tract can result in significant changes +/- as well.





Mike

 

....... man, if a headline like this doesn't attract the PETA folk, nuthin will.

 

Thats funny right there, I don't care who ya are...

 

I gutted mine due to heat. If heat is not an issue, I'd leave it alone. If you want more noise, gut it. If you want more power, don't waste your time, it's negligible.