Catalytic Converter removal/elimination - Yamaha FJR Forum : Yamaha FJR Owners Forums
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post #1 of 9 (permalink) Old 09-05-2019, 11:48 PM Thread Starter
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Catalytic Converter removal/elimination

Hey all,

Curious as to what would happen if the cat was removed and a straight through exhaust system was installed on a gen 1 FJR1300? Would the ECU need to be re-programmed or flashed? Would performance improve? Worse/better gas mileage? Have any of you done this mod?

I'm not actually planning on doing this to my gen 1, just totally curious if anyone has done it, and if so what benefits or problems did you encounter.

Thanks!
Jay
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post #2 of 9 (permalink) Old 09-06-2019, 07:50 AM
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Jay, there is NO advantage to removing the cat, no performance gain at all. The fjr uses a honey-comb brick style cat that only restricts exhaust by the pipe size, nothing to gain by removing it and may actually kill your fuel economy.

I used to drag race my 94 dodge Dakota and was always looking to gain more power and all the internet experts claimed at least a 25hp gain by removing the cat so I did and found nothing, zilch, nada. The only thing I gained was a 4mpg loss of fuel eeconomy and a louder exhaust.

So I called the guy’s at More-flow who specialize in high performance cats and talking to the owner he started laughing at me as I told him my sad story, he said that that removing the cat performance gains was pure Internet myth and that pipe diameter affected things more than the cat did. So I would recommend not removing it since there’s nothing to be gained, which is the case with most modern emissions these days.
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post #3 of 9 (permalink) Old 09-06-2019, 08:24 AM
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A certain amount of back pressure is necessary for an ignition engine to run well. Is more closely related to valve timing than fuel injection. When back pressure is lessened (and valve timing to accommodate) to maximize peak HP it comes at the expense of a narrower torque band. In other words, lower HP at lower RPM in exchange for higher HP at higher RPM. Perhaps in a racing environment this would be acceptable but is the opposite of what I want on the street.

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post #4 of 9 (permalink) Old 09-06-2019, 10:09 AM
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there are a few posts on it if you search. Delkevic also has a header system pretty cheap. I googeled fjr cats removed and a few posts came up.
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post #5 of 9 (permalink) Old 09-06-2019, 11:43 PM
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The modern Japanese motorcycle is a carefully designed system. Unlike an old Harley, you just aren't going to find much bolt-on power. Even going the usual route: pistons, cams, exhausts, and a remapped EFI system (if you could afford it), wouldn't get you much. Displacement might, if you could figure out how to do it.


Even if you could do all of that, I suspect the limiting factor would be the air box.

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post #6 of 9 (permalink) Old 09-06-2019, 11:54 PM
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when some one mentions exhaust, some one wants to poop on it. If you custom paint a bike, it does nothing for performance or comfort. It's just something to spend money on. Some like to play, some don't. I'm not gonna remove my cats, but if I could find some whitewall tires
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post #7 of 9 (permalink) Old 09-07-2019, 01:58 PM
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Quote:
Originally Posted by JohnC View Post
The modern Japanese motorcycle is a carefully designed system. Unlike an old Harley, you just aren't going to find much bolt-on power.
Even a modern Harley-Davidson is designed like a coat rack: Deliberately detune the stock engine so as to sell Screaming Eagle Stage II, III, and IV kits.

I enjoy the effortless quiet power of my FJR. If I was willing to tolerate finicky uneven behavior in exchange for more power then I would have bought a KTM or similar.

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post #8 of 9 (permalink) Old Yesterday, 11:39 PM Thread Starter
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Thanks for all the replies. Sorry for beating a dead horse. I should have done a search first. In retrospect, obviously this would have been discussed previously.

Kind of wandered a bit as usual with most forum postings, but still curious if anyone has done this and what their results or experiences have been with a complete new exhaust SYSTEM that eliminates the cat. I think someone mentioned removing other bits, and using a PCIII. Seems like a sensible approach to the possible problems of engine running different after removing all those parts.

My interests are mainly academic, because the FJR is a plenty powerful bike, so I'm not interested in more power. Heck, I've been 140 on mine a few times; that's plenty fast! I like the fact it's a reliable bike too, so making changes to the bike that would affect it's reliability don't interest me.

I think we can let this thread die. It's all been said before.

Jay
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post #9 of 9 (permalink) Old Today, 10:13 AM
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Quote:
Originally Posted by N4HHE View Post
Even a modern Harley-Davidson is designed like a coat rack: Deliberately detune the stock engine so as to sell Screaming Eagle Stage II, III, and IV kits.
Well, yes. Really big bucks there. But a lot of it is also a successful attempt to pass Federal noise requirements. If yo want to take a step backwards, look at an old, pre-EFI, German Harley. In Germany, insurance costs are (or at least, were up to the '90s), governed by BHP, not displacement. That is why I used to see hordes of little bikes and quite a few liter bikes, but not much in the middle.



Insurance costs were a large portion of the total cost of ownership. The step was at 27 bhp. Harley dealers there sold a carburetor restrictor plate that limited horsepower to 27 bhp. Can you imagine a 27 hp Harley? It wouldn't be able to get out of its own way.



Quote:
Originally Posted by N4HHE View Post
I enjoy the effortless quiet reliable power of my FJR.
Much more accurate.

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