V-Twin Forum banner

1 - 15 of 15 Posts

·
Premium Member
Joined
·
188 Posts
Discussion Starter #1
I've read there is no HP benefit removing them using the stock pipe. Others say there is. Has anyone dynoed their bike to prove otherwise? It's a lot of work to get them out. I know the heat advantage, but would like to know the facts.
 

·
HATER OF THE GRAVEL!!!!!!
Joined
·
5,761 Posts
But if some local or state agency wants to be a butthead, you could get a 50,000 dollar fine.
(It's federal law and enforceable anywhere in the USA)

With that said, Vance and Hines makes a free flowing system and will equalize the flow side to side.
 

·
Registered
Joined
·
789 Posts
If changing to a higher flow air cleaner and free flowing mufflers can add horsepower, the why wouldn't anything that produces resistance for the exhaust reduce horsepower.

I'm no engineer but it"s my understanding that a motor is like an air pump. The more air you can pass through it, the more power it will produce. Obviously there are other factors. I realize that it's not just air flow that makes horsepower, but it's one important aspect.

Am I wrong or does just changing to a free flowing muffler add a little power? So trying to force the exhaust through a cat has to eat up a pony or two.
 

·
HATER OF THE GRAVEL!!!!!!
Joined
·
5,761 Posts
$50,000 really???
And or 5 years in jail. It's only been enforced in places like California, but this has been the law since the 1970's.

It's just been a law not applied.
 

·
Premium Member
Joined
·
188 Posts
Discussion Starter #7
Are you saying they did a good job sizing the cats to flow well enough? So the only benefit is a cooler exhaust? Sounds like the cats are staying on my bike.
 

·
Enjoying a great Ride.
Joined
·
807 Posts
Im wondering if there was anyone fined to that extream, and 5 yrs in jail and I thought Florida was a Police State damn.
 

·
Registered
Joined
·
789 Posts
Are you saying they did a good job sizing the cats to flow well enough? So the only benefit is a cooler exhaust? Sounds like the cats are staying on my bike.
If you spend good money on a set of slip ons and leave the cat in there, you'll barely hear a difference in the sound. I'm not telling you to take your cat out, especially if you're happy with the performance, but you'll never get the full sound from any slip ons if you leave it in.
 

·
?????
Joined
·
3,531 Posts
Thanks, I understand that the cats do a good job canceling noise
They sure do. I remember when I first saw a couple 2010 Ultra LTD's, one was bone stock and the other had Rinehart slip ons installed. There was very little difference in sound between the stock one and the Rinehart equipped one. The only thing I noticed was the Rinehart equipped one had just a touch deeper tone, volume was pretty much the same.
 

·
Premium Member
Joined
·
88 Posts
I've read there is no HP benefit removing them using the stock pipe. Others say there is. Has anyone dynoed their bike to prove otherwise? It's a lot of work to get them out. I know the heat advantage, but would like to know the facts.
OK a seat of the pants evaluation only but after removing the cat the bike seemed to run a little cooler and maybe a little better. Then I added the Rineharts slip-ons and I was definitely impressed. I know it's not a dyno but the performance was definitely improved with the slip-ons. I know most people will say it's just because they sound louder but the torque was much improved on my 2011 FLHTK.
 

·
Premium Member
Joined
·
171 Posts
The cat flows fine for motors up to about 100 hp. The only thing removing it will do is give better sound and cooler temps on the drivers and passengers right foot.
 

·
Registered
Joined
·
85 Posts
I had a customer take his pipe and remove the cat while I performed a 96-103 upgrade. It also received 211 cams and slip-ons. I don't know if I've done any other 103/211 upgrades with a factory 2into1 header before. Most, if not all, of them have had dual mufflers. I also didn't get numbers with and without the exhaust mod after I put the engine together, but it ran as good or better than any of the others.

However, every bike runs a little different. I haven't sat down and looked at them all together and compared correction factors, either. They can vary on my 250i by 2-3% on average. It depends on the conditions. Temp., humidity, etc. You can't compare runs from two different dynos or operators, really. There isn't enough information printed on a typical dyno sheet to do that.

The difference would be no more than 2% if closely studied. Maybe a couple HP on a stock bike. Not a big difference. Nothing you would feel seat of the pants. It wouldn't show any difference(or maybe a small loss) of power up until 5000 RPM or higher. So basically I imagine you'd probably lose a couple ft. lbs. of torque(1 HP) at low RPM and gain a couple HP at an RPM range most people rarely(some never) ride at.

... the performance was definitely improved with the slip-ons. I know most people will say it's just because they sound louder but the torque was much improved on my 2011 FLHTK.
You are correct. Slip-On mufflers alone will "improve the performance". About half of the performance gains are from the mufflers and air cleaner and the other half is from a properly calibrated ECM. The slip-ons will also increase the exhaust gas temperature resulting in higher engine temperatures.

99% of people will agree that a leaner running engine is a hotter engine. But not so well known is the fact that an engine with improved airflow(i.e. more HP) will also be hotter when running at the same AFR as it did with less airflow.

Just like blowing on the coals of a campfire. More air equals more heat. Removing the cat would raise exhaust gas temps slightly while also reducing heat on the right side of the bike. That's because the cat absorbs and radiates heat very well.

Many people would tell you that muffler x or y can be installed without needing tuned thanks to the closed loop EFI. The bikes don't noticeably leaner as far as the AFR goes, but you won't gain all your potential power without a tuner. As well as lower engine temperatures and make the engine run smoother. Even a stock motorcycle will benefit from a tuner. More than removing the cat would.
 
1 - 15 of 15 Posts
Top