On Off Throttle

The trouble with starting is the urge to finish!

SAI elimination just cools the exhaust and stops exhaust fuel burn off for emissions compliance.

The snatchiness is lean fuelling - again emissions driven but not MoT tested. Conventional wisdom is to remove the O2 sensor that trips at 1500 rpm, fit a resistor and use Tune ECU to kill the error light. A richer re-map cures the entire problem.

So how much does it bother you and what is your budget? Read on.....

https://www.triumphtwinpower.com/bo...aster-efi-airbox-modification-removal-kit.php

 

https://www.thetriumphforum.com/threads/accelerator-off-on-effect.4447/

 

"The secondary air injection system reduces the level of pollutants emitted in the exhaust gases. The system is operated by the control valve assembly located under the fuel tank and functions as follows.
When the engine is running, the vacuum present in the intake port opens up the control valve diaphragm. Every time there is a negative pulse in the exhaust port, the control valve then allows clean air to be drawn from the airbox into the port. This air causes secondary combustion of the exhaust gases in the exhaust ports, reducing the amount of unburnt hydrocarbons released into the atmosphere in the exhaust gases.
The control valve assembly contains two reed valve assemblies (one for each cylinder) to prevent the exhaust gases travelling from the exhaust port back to the airbox."

It has no effect on off idle snatchiness.

 

Lesson 2!

https://www.dimecitycycles.com/brit...iumph-bonneville-t100-scrambler-thruxton.html

 

Start from the premise that the bike is tuned as lean as it will go at closed and stable throttle openings. Then remember it uses a very narrow band sensor. Bang open the throttle and it gets overridden.

My understanding of electronics is minimal but, from what I do understand, the switch from closed to open loop occurs at about 1500 rpm when a pretty lean idle flicks instantly to a richer fuelling - much richer if you whack open the throttle. The system is quite crude. The rough transition is the result.

Off idle I doubt the unburnt hydrocarbons exist in any great quantity because you are already in a highly lean condition.

Re-mapping provides the opportunity for bottom end enrichment as well as addressing any inlet and exhaust derestrictions.

So.......I doubt SAI removal is a significant factor in throttle response and when the SAI is at its most effective - in rich WOT conditions - the ECU will be ignoring the O2 sensor anyway.

 

Unless the Triumph ECU is radically different closed loop, O2 feedback will respond to a missing or failed sensor by running slightly richer fueling, this is a safety measure...however due to the closed loop only being used until 1500rpm is reached, i have no idea if there is a load cut off criteria as well?
Under normal circumstances i wouldn't ever expect a weakened mixture as a result.
SIA removal shouldn't have and effect on the o2 sensor if the air enters downstream of the sensor and in any case depending on the type of sensor used and the fact that the air is timed should stop the sensor reporting weak mixture and ECU adjusting it other than the fact that if its a narrow band sensor the mixture will fluctuate as the ECU adjusts to compensate.

 

Hi Jarra, here's a bit more for you to consider:

1. The SAI is only in operation from 0 to 6% of throttle opening;

2. The ECU switches between two tables of values, dependant upon throttle position, engine temp, MAP (manifold absolute pressure) sensor info, air temp and yes you guessed O² sensor info.

So as you can see, there are a significant number of parameters and variables used/analysed and applied in the second by second fuel calculations.

Re the relationship between the SAI and O² - at small throttle openings the sai is letting in fresh air after the exhaust vale and before the O² sensor. So if less oxygen is detected that will change the value reported by the O² sensor to the ECU and will impact on fuelling in the 0-6% throttle position.

So all of this is going on at small throttle openings when filtering/creeping through traffic for example. The ECU is swapping between tables and continually re-calculating.

However, if when the SAI is removed and there were to be some way to gttee that the O² sensor would still deliver the expected data, then that would be good wouldn't it? Use dummy plugs on the O² cables.

Or alternatively, if the bikes' O² sensors were removed and the bikes' ECU was remapped with the new map that DIDN'T need to use O² data, then that would work even better, because there would be less data being "chunked".

This is what I did to my bike and it ran smoother, freer, with better mpg.

 

Remap it with the TTP stage one map only way and this sorts it all out as there is no provision within that map for AIS or 02 sensors no more jerky throttle

 

It will work with standard air box and restricted pipes as i mapped it and ran it like this but worked better with the TORS pipes that i had fitted after it unleashes its hidden power and makes it smoother very noticeble difference as I really hated the snatchy feeling