The Timing Retard and Speed limiter override.




This mod ONLY applies to a fuel injected Suzuki
and can be used with bikes equipped with a Power Commander.

EXPLANATION:

Your ECU (the bike's fuel injection computer) takes readings from the sensors on the bike, for example, RPM, intake air pressure, throttle position, and the Gear Position. It then computes how much fuel to inject into the cylinders to make the bike run correctly.

As I understand it, the European Union and US government got involved with the manufacturers to sanitise Superbike power delivery so that when you are in 1st, 2nd, or 3rd gears, the computer figures out how much fuel to inject as usual, but, to limit torque, it backs off this amount and/or closes the secondary throttles a bit and retards the ignition to limit your power. This is to keep torque down when you are in the lower gears but it doesn't do this in the higher gears, because if you're in 4th gear or higher at low RPM's and give it the beanz, you don't have *that* much torque anyway.

The gear position sensor is a variable resistor. When in 1st gear it's around 500 ohms. When in 6th gear, it's about 15,000 ohms. So, if you clip the wires going to the ECU, and hook up a 15K ohm resistor, the ECU *THINKS* you are really in 6th gear all the time because it is sensing 15K ohm (6th gear) of your resistor rather than what the GPS is actually reading. So, when you roll on the throttle, it puts out the full amount of power the engine is capable of.

That's basically the gist of it and it makes a difference in the feel of the bike. Ever notice that in 1st gear when you rev it to around 3,000 RPM then nail the throttle wide open the bike hesitates? That is because of this built in retard. With this mod, you get power quicker and smoother. Also, when going slow on the road or in a car park when you close the throttle you get a real hard engine braking, it's a lot less with the mod.

It's just smoother all around. Also, there's a bonus with doing this mod on the Hayabusa and the GSX-R1000 by actually fooling the bike into being in 5th gear, not 6th you override the top speed limiter. To do this use a 6,800ohm resistor, the bike will then think it's in 5th. Actually it's the same map as 6th gear but without the speed limiter.


INSTRUCTIONS:

You can do this mod several ways, you can either hard-wire it, which will cause the bike to be in "permanent" TRE override mode. Or, you can wire it via a switch to change between factory mode and the TRE mode. The bike will idle SLIGHTLY lower when the throttle is closed in TRE mode, so the bike can be hard to start when cold in TRE mode. You can overcome this by using the choke or increasing the idle speed.



PARTS NEEDED:

Tools- You will need a small tip soldering iron and solder.
You will also need heat-shrink tubing to make it look nice. You can pick it up at Maplin for a couple quid for an assortment, or any auto parts store should stock it. You can use electrical tape in a pinch, but it looks crap.

If you do the switched version, I HIGHLY recommend you have a hot glue gun (use non electrical conductive glue though - regular hot glue off the shelf is non conductive). This is to seal the switch properly.

Parts-
You can find all the parts you need off the shelf at your local Maplin or Tandy.

1 - 15K ohm Resistor for non speed restricted bikes and 6800 ohm for the GSXR1000 and Hayabusa.

For the switched version you will also need:

1 - DPDT (Double Pole, Double Throw) toggle switch

For the switched version, you'll also need some 22 GA wire, preferable in 2 different colors so you don't accidentally cross wires.

DIAGRAMS:

(Substitute the 15K ohm resistor with a 6.8K ohm to eliminate the speed limiter)
An alternative diagram.
If you do the switched version, here is the diagram of how to wire the switch:

(Substitute the 15K ohm resistor with a 6.8K ohm to eliminate the speed limiter)




PROCEDURE:

Prop up your fuel tank. You'll find several bundles of wires just in front of the rear shock & spring, behind the engine block. The bundle you are looking for has 3 wires - they are BLUE, PINK, and BLACK/White Stripe. The end going down into the nub at the transmission is the GPS end, and the end that goes back up into the wiring bundle is the ECU end.
Solder the connections as per the diagram. " Use hot glue to insulate the solder connections on the switch. Just pump it in between all the posts with the glue gun. This will help keep the delicate connections from braking, it will also keep them from shorting out, or from corroding from moisture.
If you hard wire it, take the loose wires from the GPS and tape them off, then tape or tie-wrap them back on the wire bundle so they don't flop around.

Resistance values
GEAR RESISTANCE (Ohms)
1 567
2 827
3 1500
4 2700
5 6800
6 15000