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· Premium Member
941 Posts
Discussion Starter · #1 ·
Now that DJ is releasing their PCV. There has been a lot questions, posts, emails and PM's asking.. "What's the difference between the Autotune and the Z-AFM.

So, Here is a more complete explanation for how the DJ Autotune and Bazzaz Z-AFM work.

First off, they both use a Bosche Wide Band O2 Sensor.
This is pretty much an industry standard top quality sensor.
The Sensor mounts in your exhausts and measures the A/F ratio of your bike (how much fuel per parts of air)
"Mathmatical" perfect A/F measurement is said to be 14.7 to 1 known as (stoich) <-- Huh?
That's 14.7 parts Air for 1 part fuel

But, reality is Stoich doesn't make the best power.

Dyno tuning centers have shown for year and years.......... MAX Power, normally is made around 12.4 :1 - 12.7 : 1 A/F

This "Max HP" A/F varies of course depending on a LOT of factors. (Fuel being used, Temp, Altitude, Relative Humidity, Barometric pressure, the Bike, what mods have been done to it, what it's used for.....etc..etc )

So now that has been explained, here is how the units work

1) They both require YOU... the owner to put in what your target A/F ratio is. Because, they don't and can't know what's the best A/F for your bike, with your mods, where you live. So you have to enter that.

2) Then you go out and ride, and the Sensor and unit figure out what map changes need to be made to obtain this "Target A/F ratio" you are wanting.

3) While you are out riding, It's very important that you do your best to hit as many areas of the fuel chart you can.
0 -100% Throttle, at all RPM's

Example.... While doing the "Learning Process" ... if you never ride the bike at 60% TP at 3000 rpm ....... the Sensor won't know what your A/F is in that area, and won't be able to recommend a change.
That's not the end of the world, But it makes your map less complete.
Obviously the most important areas...... specially on the Grom..... are 80-100% TP, as that is where most of us are, since the bike only has 8-10 hp.

4) So, now that you are done with your "Learning" process, you come back to your house and view the "recommended changes"

The Bazzaz Z-AFM only allows "apply changes" it cannot automatically make them for you.

The DJ Autotune allows "Apply changes" and then it can also be switched to AUTOTUNE Mode, "Closed Loop" where it keeps monitoring and adjusting all the time while you ride... attempting to obtain the target A/F in every part of your fuel map.

Now, the advantages and Disadvantages.

If you leave the AUTOTUNE Mode on all the time, ..... Eventually your Sensor will crap out over time.
How much time you ask ? Well that depends on a bunch of factors (Fuel quality, Ride time, Temps, and start and stops....etc) Lots come into play.
If it does crap out, that can mess up your map. There are fail safes in place to prevent it from going too far +/- with the fuel. But, still.. your bike will run like crap until you change your map back.

So most of the time the common practice is ....... make your map. And then disconnect your sensor, and put the plug back in Bung on your exhaust, and go ride.

Now, if you live at sea level, and decide to go to the mountains...... then most likely the map will change, in that case you probably want to turn the Autotune back on. Or make a "Mountain Map" to save for the next time. Which both units can do... That is Save a 2nd map.
And you can add an optional Map selection switch to allow you to toggle between two maps.

Hopefully this helps explain the units a little better.


· Premium Member
941 Posts
Discussion Starter · #2 ·

Please NOTE...... all this above refers how these units WORK on a "Normal Motorcycle"

You have to take that into consideration.......... as the GROM and it's "crazy" O2 sensor are not.. "NORMAL"

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