Catalytic converter?

[Orangeman]

Originally Posted by bira

You're right orange, the point of the O2 sensors is to maintain close to stoichiometric fuel/air ratio, at low loads anyway, in order to get the cleanest, or most complete, combustion and most out of the catalytic converter for emissions reasons. The stoichiometric point would/should be the optimal air/fuel ratio for performance as well but it's too hot burning and at high loads can cause detonation and damage to the engine which is why the fuel maps are rich at high loads and fuel system is not in closed loop mode at high loads.

Yes sir.....

For emmisions purposes the goal is to burn the fuel completely, leaving some traces of oxygen in the exhaust typically an AFR between 14.1/14.7

Many have a hard time wrapping their head around that it's not burning all the fuel that makes the most power, but rather stuffing as much O2 as you can in the cylinder and providing enough fuel and correct conditions to use it all, leaving traces of fuel in the exhaust. Typically an AFR between 12.8/13.2 for a naturally aspirated engine which is outside of the range allowed by the O2 sensor.


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[Wayne's Striple]

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

[bira]

Originally Posted by Wayne's Striple

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

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.

[Dave73]

I know after i removed the cat and fattened the mixture i was able to hit the rev limiter in 6th, which want possible before.

[hatfielddj]

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

[Orangeman]

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.

[David L.]

Originally Posted by Orangeman

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.

It is possible to put D675 cams on the street? But if it is, i suppose that we have to put the D675 ECU too?

[Orangeman]

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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[David L.]

I'll not ask you to post any other information, but let me know if this mod worth the money? Is the beautiful torque curve of the ST3 is lost for a little boost in top end???
And if it's possible and you know the link for this post, let me know please ;-)

[Orangeman]

http://www.triumph675.net/forum/showthread.php?t=51431