Thundermax Deceleration Pop - Tuning Methods and Other Info User Manual download pdf

The Deceleration Pop Problem

Decel Pop is many times a nasty issue to deal with. Any time the exhaust is “opened up” the

condition of deceleration pops is MUCH more noticeable and problematic. An open exhaust

allows additional air to be “sucked up the pipe” during closed throttle and any unburned fuels,

then ignite and “snap/crackle/pop”!

The cure is the engine either needs to turn off the fuel during deceleration or continue to run to

burn it off.

There are Pros and Cons to both methods. After tuning is established as well as it can be, it

then comes down to “rider preference”.

Some exhaust/engine combinations can totally tune out and eliminate deceleration pop and

NOT use the Decel Cut Feature. Other exhaust/engine combinations are very problematic and

the best that can be done is to minimize the deceleration popping.

There are no magical methods to “cure” ANY tuning system. Any system can only make the

best that can be made out of engine/exhaust combinations which may be totally “wild and

unruly”.

LOUD and OPEN exhausts are much worse.

Remember the last time you heard a race car decelerate into a turn, pop-crack-bang.

Straightpipes, loud and open!

In the majority of cases, nothing has to be done as most engine/exhaust combinations will, over

time, tune themselves. If after a period of time the level of “exhaust pop/talk” is unacceptable

to the rider then the Decel Cut Feature can be activated (set to 1) using the default settings.

Several factors affect what happens during deceleration. The Stock OEM module uses what is

known as a Deceleration Cut feature which, during deceleration (declining rpms with closed

throttle), from some higher rpm (above 2300) down to 1796 rpm, "Turns the fuel off". As the

rpm passed below 1796 Rpm the fuel is again "turned on".

This “feature” is only activated AFTER the rpms exceed 2300 Rpm. You can easily detect this by

accelerating to 2100 rpm then closing the throttle. You will notice that the engine appears to

burble and run during the deceleration all the way to 1280rpm or so. If you then accelerate to

2500 Rpm then close the throttle, you will notice an immediate “flat jake brake sound” like the

engine is OFF during the deceleration. In fact, it IS off. The fuel has been turned off!

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The Deceleration Pop Problem Decel Pop is many times a nasty issue to deal with. Any time the exhaust is “opened up” the condition of deceleratio

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As the rpm declines below about 1796 Rpm, you will hear the engine begin to softly fire and may even “feel a slight bump forward” as the engine, o

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Repeat the above process using slow feathering of the throttle position from closed to just open or even a little more at times. What we are trying

The Decel Fuel Cut Rpm Low/High values normally end up within two ranges. If you just can’t live with the exhaust “talking to you” as it burns off

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Thundermax Deceleration Pop - Tuning Methods and Other Info User Manual