TZR250 3MA
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The 0 curve

We talk a lot about the 0-curve but what is exactly the 0-curve
Here a small (basic) explanation what it is.

In the 3MA CDI YAMAHA stored four ignition curves, this was done to get the best performance at different throttle positions.
The four stored curves inside the CDI are active if the CDI receives a certain voltage from its TPS sensor.
It will calculate internally which curve to use.

   0 till 1/8 (throttle opening) is 3,75V till 4,50V (given by the TPS sensor) the 0 curve is active
1/8 till 1/4 (throttle opening) is 2,75V till 3,75V (given by the TPS sensor) the 1/4 curve is active
1/4 till 1/2 (throttle opening) is 2,00V till 2,75V (given by the TPS sensor) the 1/2 curve is active
1/2 till 1    (throttle opening) is 1,25V till 2,00V (given by the TPS sensor) the 1 curve is active

Why is this done? (in big lines)
The less load the engine is having the more advance it can handle the better the power outcome will be.

The components

1) Throttle Position Sensor (TPS) mounted on the carb's
2) 3MA-01 CDI mounted underneath the fuel tank.
The curves stored inside the 3MA CDI.

Ignition curves explaned (basic)
1/4 curve.
A good curve, nice high advange in the low rpm and backing it off around 6500rpm to four degrees.

1/2 curve
A good curve more load on the engine less advange in the low rpm but holding it longer at the end backing it off around the 7500rpm to four degrees.

1 curve
A good curve max load on the engine so least advange in the low rpm but holding it the longest at the end backing it off around the 9000rpm to four degrees.

Is a unlogical curve, its almost out off reach its way off compared to the others. That makes the 0-curve so special.
What makes the 0 curve so special

Of course YAMAHA makes sure the 0 curve is only active at a very very small throttle opening (to be save)
Lets face it, when do you use a 0 till 1/8 throttle opening? (perhaps when you kick start your engine when its warm?)
Its a area that hardy is used, we talk about a couple mm opening so they must done that for a reason

My guess YAMAHA did that on purpose.
Its a very very suitable ignition curve that works perfect on performance pipes peeking around the 10800rpm till 11000rpm mark
And that is exactly the rpm most performance pipes (at that time) where peeking (except the SUGO FIII pipes which will need the SUGO CDI)
It can't be a coincidence they mach that well.

To keep the TZR 3MA myths alive.
Lets say it was a secret (power) curve, for the ones knowing its existence.

To use the 0 curve you need to remove the TPS sensor and manually select the 0 curve by checking the voltage given at the CDI

But I strongly advice people not to use the 0 curve when you don't know the consequence off using a high advanced ignition curve.
It is not suitable for the stock pipes, and you ride in a danger zone when you use it on the street riding traffic.
Its only usable for a track bike with good pipes peeking around the 10800 till 11000rpm mark.

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