Author Topic: Why your injection bike is jerky  (Read 1121 times)

Offline MarkCR750

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Why your injection bike is jerky
« on: October 01, 2017, 10:05:07 AM »
Some fuel injection machines are a bit jerky on the throttle at low revs, including my scrambler, I actually quite like the sudden "jerk" of acceleration, and having to use precise throttle control etc to counter it, but if you don't, here's why your bike does it and how to fix it, I've copied in a response from Jens at Booster plug below.


The internet is a great source for information, but it can be bloody hard to separate true and false information - not everyone out there is an expert :-)

The BoosterPlug will cover all combinations of aftermarket filters and exhausts (With or without the cat installed) - as long as you keep the O2 (Lambda) sensor installed in the exhaust. (Which you should for several other reasons.)

Here is why this is possible:

Most aftermarket filters and exhausts will flow a lot more air at higher RPM, but at low RPM's the difference between the resistance in the original exhaust and the aftermarket system is minimal - so in low RPM conditions, the AFR (Air/Fuel Ratio) is almost the same.

In a modern fuel injected bike, there's no risk of damaging the engine by running it too lean when you install an aftermarket exhaust or K&N filter - because the O2 sensor in the exhaust will adjust the mixture back to the original AFR in all closed loop situations (Higher RPM)

(Constant medium and high RPM are closed loop operation, and the O2 sensor is in charge here. The BoosterPlug is active in open loop conditions which is idle, low RPM and during acceleration and engine braking. - See the BoosterPlug.com website for a full explanation on open loop and closed loop)

But as the aftermarket parts will flow slightly more air in low RPM conditions too, the drivability will be even worse than on the stock bike. Normally we see the open loop AFR go from around 14,4:1 to 14,5:1 with the aftermarket exhausts, and now you really need the small controlled fuel enrichment from the BoosterPlug to restore the smooth throttle action and to prevent the engine to stall easily.

Because the AFR difference (between the stock system and the aftermarket parts) is relatively small in open loop conditions,makes it possible for the BoosterPlug to cover all combinations of exhausts and filters on the bike. (The BoosterPlug is only active in open loop)

You are far worse off if you installed a Power Commander, where the O2 sensor is removed/bypassed and then changed the exhaust. Now you would have to dyno and set up the Power Commander correctly again to avoid running the engine too lean all the time - with the risk of damaging your engine.

So the fact that the BoosterPlug works in cooperation with the O2 sensor in the exhaust makes it possible for our device to cover all combinations of exhausts and filters.

Sorry if this got a bit technical.


Best Regards


Jens Lyck

BoosterPlug.com
Slotsgade 3
4880 Nysted
Denmark

 
Mail: jens@boosterplug.com

Web: www.boosterplug.

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