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Catalytic converter?

21K views 21 replies 11 participants last post by  street675wize 
#1 ·
I read in the Tiger forum that a guy had removed his cat and the bike ran WAY better afterwards. Does the Street3 have a cat in North America?
 
#3 ·
I've been reading on this and had it on my mind for a while. I know it violates US emission standards to remove the cat unless it is registered as a track only bike...All that aside though, does anyone know if it really would increase performance? I'm getting ready to put her up for the winter and do some upgrades while she's resting:

New exhaust, haven't decided on which yet
Modifying the air intake
new air filter
iridium plugs
Michelin PR3 tires front and back

and possibly removing the cat and replacing it with a equivalent SS pipe with a tapped hole for the O2 sensor.

Thoughts?

-Dan
 
#4 ·
The ECU needs the O2 sensor for proper fuel mixture; only race-track professional tuners should mess with that IMO. On my STR I have drilled a lot of extra holes in the plastic air intake, installed a K&N air filter, iridium plugs (same power as the originals but keeps gap integrity longer), titanium DanMoto GP exhaust with baffles ($300, weighs less than 5 lbs and LOUD - use tight fitting ear plugs), and Triumph tune 20589 for aftermarket exhaust. Bike runs flawlessly from idle to redline. Leave the cat in cos it is not worth the hassle just for a hp or two. Also installed a Vortex 520 conversion with 49T rear sprocket; shortens the wheelbase by almost a half inch (axle in middle of slot). A Shorai 18Ah lithium battery cranks like crazy and saves 5 lbs. Btw blow the bucks for the Triumph Quickshifter; you won't regret it! Oh yeah go to the TuneEcu site and order the OBD2 cable with correct ftd chip ($17 using Paypal), and download the program and files and study up while you are waiting for the cable, and you can install the tune yourself. - Wayne
 
#7 · (Edited)
The ECU needs the O2 sensor for proper fuel mixture
I am sorry but that is not actually correct. The narrow band O2 sensor and the way it is used by the ST3's ECU is to maintain emissions standard tuning, not proper engine tuning if by proper we are talking about the most power and best running engine. Tuned correctly the bike runs better without it. For the regular street rider there really is no advantage to removing it except for much smoother throttle response due to elimination of the lean off throttle condition caused by the O2 sensor.

EDIT: As a side note you can only remove it if you have also removed the CAT and turned it off in the ECU programming. Do not turn it off and leave it installed, it will quickly ruin the costly sensor.
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#6 ·
If I remember right, the O2 is before the cat so yes, I believe the CAT can be removed while retaining the O2 sensor.
 
#12 ·
Exactly my point (Orangeman is right on); the O2 sensor is needed for proper engine performance within emissions parameters, but removing the cat and sensor for maximum engine hp requires dyno/racer-tuning knowledge beyond the scope of the average rider (and is certainly not legal for the street). Like a previous post said, after the considerable hassle of removing his cat he could tell no discernible difference in performance cos further tuning is needed. The Arrow 3-1 and map is the way to go for the average street rider for lighter weight and a few extra horses (although still not street-legal). My very light titanium Dans and the 20589 map works quite nicely if one is keeping the cat. - Wayne
 
#13 · (Edited)
Yep, removing the CAT and keeping the O2 Or not) will not do much of anything for you unless your CAT was blocked. Modern CATs are fairly low in exhaust resistance. Removing O2 will result in the ECU resorting to the fuel map to ensure that you don't damage the engine by getting a lean condition, that is, the system goes into open loop mode reading the map and not using the O2s input for fuel mgmt. This map is probably the same as what is used when the system is in open loop due to high load, etc. Your bike is not in closed loop very often in all honesty. I used to tune my car and when running the analysis software monitoring the PIDs while driving, the fuel system was mostly in closed loop (relying on the O2) at idle at stop lights and at cruising at high-way speeds. If even close to asking for performance by stepping on the throttle it would exit that mode and rely on the programmed fuel maps.
 
#15 ·
Along the same lines, but not really...

Thank you all so much for your answers and explanations. In keeping with the thread subject (in a way) I'm curious about air intake modifications, and adding a cold air intake or ram intake. Any thoughts? In my limited experience so far I'm imagining an engine that can breathe better will run better, and an engine that is have air shoved down it's throat whenever it wants may run even better? How far off am I?

Thanks again.

Dan
 
#16 · (Edited)
The bike already has the intake right in the nose so has a "cold air intake". Even with a modified bike the only gains to be found are with removal of the plastic intake baffle located in the headlight bracket casting. It is only there for noise reduction and on a stock bike gives you all of 1 to 2 measurable HP all the way at red line but IMO better mid and high RPM throttle response and a noticeable increase in intake noise. Dyno runs show a measurable decrease in time to max power. With a modified bike it starts to get a little more significant. Even those that are running D675 cams find little can be had by completely removing the headlight casting so that the intake through the frame is completely exposed. Some of us have experimented with additional ducting to the air box, replacing the bolts for the headlight bracket so that the air intake is uninterrupted with no more effect than just removing the baffle and installing a high flow filter. There is a company in England that produces a race nose that has a "ram air" duct in it like the D675 fairing but eliminates your headlights, without tuning specifically designed for a pressurized air box you would have to prove to me that it makes a difference with the stock engine and that kind of tuning is very difficult to do. Unless you are running the Daytona cams it is my opinion from the modifications and Dyno work that I have done and even with the custom tuned velocity stacks I have installed on my bike it is a futile path. With a high flow filter and the baffle removed the stock intake track with the headlight bracket in place will easily support over 110 RWHP.
 
#18 ·
Yes it is, I have done it (and gone back), Mac Bandit has them in his, as well as a few other here. It requires dropping in the cams and custom tuning of your Street Triple ECU. It has been discussed in length here as well as on other Street Triple forums so no need to re-post the information here ;)

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#22 ·
Hi folks. This info is VERY interesting and informative. Thank you. After mulling whether to de cat my 2016 675 ST R which has an Arrow cat back can I think I have decided, seeing as It's just for street use, even though it gets ridden pretty hard to leave it be. I had a 765 Street Triple previously and, I found anyway that apart from a tremendous top end, which can rarely be used on UK roads, it didn't have an awful lot over the 675. If I want more power maybe I should go back to Super sport 1000's.!! Having ridden but not owned Triumph 675 Daytonas. The extra 1000 rpm redline is handy, as in the 765's top end rush, but I found the Daytona, on the road anyway needing more revs to get a move on. In my opinion.? The chassis on the Daytona R though. O yes, that is worth having. Maybe that is the route to take. Cheers to you all.
 
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