Street Twin Intake Mods Etc.

RHB

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Sep 4, 2017
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Cebu Philippines
My Ride
Triumph Street Twin
I added the following (and deleted) to my Street twin.
DNA high flow filter
Booster plug
snorkel removal

Test results sans dyno
Adding the Booster Plug to my totally stock ST yielded no advantage, in fact it decreased its performance. (Due to a pre-existing rich A/F I found out), so I removed it and...

After adding a DNA filter and going for several long rides to clear the excess oil from the filter I noted the following;
The DNA filter alone seemed to add a boost to the torque curve freeing up some RPM's especially above 6,000 RPM.
Re-adding the booster plug to the mix did tend to smooth things out and improve throttle response. But not a lot, however it was very noticeable.
After removing the snorkel plus DNA filter there was a relatively big change in the performance, I could realize faster revving, and an a definite increase in pull. Adding again the booster plug after snorkel removal yielded mixed results but it's effect was, in my opinion diminished. I should note when I removed the snorkel the intake noise increased significantly, the snorkel basically exists in order to comply with Euro 4 noise constraints and chokes up the intake flow in the process. However, noise does not necessarily equate to power, one must be careful in assessing the performance after removing the snorkel, because it sure sounds like it is going faster.

In the final analysis, I would say the Booster plug while very effective on other bikes (I have used it successfully on a stock Yamaha MT07), has little value on the Street twin. Why? Well after doing some reading, asking some questions, and finding a dyno chart or 2 on the WCTwins, these bikes actually run rich, well below Stoich (A/F 14.7) For whatever reason Triumph has succeeded in making a Euro 4 compliant bike without over leaning the mix, especially on the open loop circuit.
The Booster plug is a simple device that enrichens the A/F in the open loop circuit approximately 6% using an accurate temperature probe to regulate this percentage across the rpm range regardless of outside air temp.
So you can see, at least on the Street Twin and cousins, there is little advantage to using this device on a stock bike.

It should be noted, that tuning or adjusting the A/F ratio will not necessarily increase performance, it will only either lean or enrichen the fuel mixture to achieve a more efficient or safe A/F range along with the other Discrete modifications you have done, IE: free flow air filter and snorkel removal. But by finding the A/F sweet spot(on the open loop) you can make the bike feel more user friendly, better throttle response down low, smoother acceleration, shifting, and engine braking where it is noticeable. The Street Twin suffers none of those things, except perhaps a little sluggish initial throttle response.

Myths encountered on other forums:
You cannot readjust or reset the A/F by performing an ECU reboot, it is only for clearing various error codes by going through 3 heat cycles.
You can not in any regard affect the closed loop A/F ( cruising speed) because it is hard wired into the ECU. But O2 sensors can make minor adjustments.

The WCTwins have a "self learning ECU" which will adjust your A/F. BS

All modern bikes that use O2 sensors in the exhaust adjust for an over lean condition, but have a very limited range of about 14-15 to one. Just below Stoich to just above. They are narrow band. They do not redefine the A/F, they make small quick incremental adjustments only. (and in some cases timing adjustments)

The secret of the water cooled twins is they run rich all the time and because they are low revving shall we say de-tuned or re-tuned for maximum torque at relatively low RPMs. Adding any intake or exhaust mod won't make them run dangerously lean. However you see many exhaust manufactures saying a remap may be necessary. In my opinion, this is just said to cover their collective butts, but not saying if you want to invest in a remap it may have a smoothing effect by slightly adjusting the A/F ratio.

Power commanders?
A very good product, but in my opinion useless unless you want to invest in dyno time with a very skilled technician to set up you're A/F ratios. (because now you have negated the factory settings) you can do more damage than help if your not careful. preset maps are only a guess or starting point. Really it comes to cost, 400 bucks plus dyno time gets expensive.

Since the ECU is locked, an ECU flash which is an alternative solution and much more comprehensive than a simple remap is not possible.

The upshot is, if you add a DNA filter or similar High performance filter, AND remove the snorkel, you will be pleasantly surprised with the results. Adding a Booster plug on top of this adds a very little bit, but for 150 bucks, I’d go buy a wind screen.
 

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Rocky

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2WHEELST100

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Eric
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22-T100, 14-800Tiger, 99-Trophy900
I added the following (and deleted) to my Street twin.
DNA high flow filter
Booster plug
snorkel removal

Test results sans dyno
Adding the Booster Plug to my totally stock ST yielded no advantage, in fact it decreased its performance. (Due to a pre-existing rich A/F I found out), so I removed it and...

After adding a DNA filter and going for several long rides to clear the excess oil from the filter I noted the following;
The DNA filter alone seemed to add a boost to the torque curve freeing up some RPM's especially above 6,000 RPM.
Re-adding the booster plug to the mix did tend to smooth things out and improve throttle response. But not a lot, however it was very noticeable.
After removing the snorkel plus DNA filter there was a relatively big change in the performance, I could realize faster revving, and an a definite increase in pull. Adding again the booster plug after snorkel removal yielded mixed results but it's effect was, in my opinion diminished. I should note when I removed the snorkel the intake noise increased significantly, the snorkel basically exists in order to comply with Euro 4 noise constraints and chokes up the intake flow in the process. However, noise does not necessarily equate to power, one must be careful in assessing the performance after removing the snorkel, because it sure sounds like it is going faster.

In the final analysis, I would say the Booster plug while very effective on other bikes (I have used it successfully on a stock Yamaha MT07), has little value on the Street twin. Why? Well after doing some reading, asking some questions, and finding a dyno chart or 2 on the WCTwins, these bikes actually run rich, well below Stoich (A/F 14.7) For whatever reason Triumph has succeeded in making a Euro 4 compliant bike without over leaning the mix, especially on the open loop circuit.
The Booster plug is a simple device that enrichens the A/F in the open loop circuit approximately 6% using an accurate temperature probe to regulate this percentage across the rpm range regardless of outside air temp.
So you can see, at least on the Street Twin and cousins, there is little advantage to using this device on a stock bike.

It should be noted, that tuning or adjusting the A/F ratio will not necessarily increase performance, it will only either lean or enrichen the fuel mixture to achieve a more efficient or safe A/F range along with the other Discrete modifications you have done, IE: free flow air filter and snorkel removal. But by finding the A/F sweet spot(on the open loop) you can make the bike feel more user friendly, better throttle response down low, smoother acceleration, shifting, and engine braking where it is noticeable. The Street Twin suffers none of those things, except perhaps a little sluggish initial throttle response.

Myths encountered on other forums:
You cannot readjust or reset the A/F by performing an ECU reboot, it is only for clearing various error codes by going through 3 heat cycles.
You can not in any regard affect the closed loop A/F ( cruising speed) because it is hard wired into the ECU. But O2 sensors can make minor adjustments.

The WCTwins have a "self learning ECU" which will adjust your A/F. BS

All modern bikes that use O2 sensors in the exhaust adjust for an over lean condition, but have a very limited range of about 14-15 to one. Just below Stoich to just above. They are narrow band. They do not redefine the A/F, they make small quick incremental adjustments only. (and in some cases timing adjustments)

The secret of the water cooled twins is they run rich all the time and because they are low revving shall we say de-tuned or re-tuned for maximum torque at relatively low RPMs. Adding any intake or exhaust mod won't make them run dangerously lean. However you see many exhaust manufactures saying a remap may be necessary. In my opinion, this is just said to cover their collective butts, but not saying if you want to invest in a remap it may have a smoothing effect by slightly adjusting the A/F ratio.

Power commanders?
A very good product, but in my opinion useless unless you want to invest in dyno time with a very skilled technician to set up you're A/F ratios. (because now you have negated the factory settings) you can do more damage than help if your not careful. preset maps are only a guess or starting point. Really it comes to cost, 400 bucks plus dyno time gets expensive.

Since the ECU is locked, an ECU flash which is an alternative solution and much more comprehensive than a simple remap is not possible.

The upshot is, if you add a DNA filter or similar High performance filter, AND remove the snorkel, you will be pleasantly surprised with the results. Adding a Booster plug on top of this adds a very little bit, but for 150 bucks, I’d go buy a wind screen.
Very nice review of your hard earned time, efforts and expenses. I have just purchased a 22 T100 and may be looking into simple mods by next year.
 
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