Using a zener diode to defeat the 186 mph limit

[FloydV]

Here are the voltages that I wanted to post earlier and found later after unpacking from a move.

Voltage the ECU sees for each gear in stock configuration:

First: 1.80
Second: 2.26
Third: 2.99
Fourth: 3.68
Fifth: 4.38
Sixth: 4.70

A zener diode with a value of 4.38v should pass all voltages including 4.38v, but clamp the voltage
at 4.38v, so the ECU never sees a value higher than that. Thus, a Busa would see gears 1 through
5, but never see 6th, since the higher 6th gear voltage (4.7v) would not be passed (but 4.38 volts would be passed instead). The bike should see gears 1 through 5 correctly, since the zener diode would pass any voltage at or below 4.38 (1 through 5). It would not see 6th gear, since anything over 4.38 volts would be suppressed. If the ECU does not see 6th gear, it will not limit the RPMs of the engine to 186 MPH.

The point of a zener diode as opposed to a 6.8k resistor, is that gears 1 to 5 would be read correctly, thus not adding any fuel richness or advance in timing. Only the MPH restriction would be removed. No other factors would change, since 5th and 6th gears are identical in ignition advance and A/F mixture. Also, using a zener diode would eliminate the need to go into the clutch and change the resistors running from the GPS (Gear Position Sensor).

The part where I am confused (I have some posts pending) is: Does the zener diode go in line with the wire from the Gear Position Sensor, or does it go to ground from the wire that goes to the Gear Position Sensor. I have seen schematics doing both things (in general, not for a Busa application). Also I am not sure where to find a zener diode that has a value of 4.38 volts. I have found listings close to, but not an exact match.

Zener diodes come in a range of power handling capabilities up to 50 watts. 50 watts should far exceed any gear sensing current, but I'm not sure what value would apply.

I have posted this at SH.org as well.

 

[psycobusa]

way too technical for me

 

[FloydV]

Actually, I think all that is required is to put
a 4.38v zener diode inline with the red wire
to negate the speed limit without
changing anything else. I would guess
about 5 watts would be a good value.

Putting it inline would not endanger any
electronics if my guess is wrong. Running
it to ground could. I'll try and make it a
winter project.

 

[justtight]

I hope you guys work it out. 190mph +

 

[Fugly]

Keep us posted

 

[Professor]

You must be reading my mind. I was thinking the same thing a while back and never went any further with it.

I measured 4.42 on mine in 5th. The ECU will be programmed to a voltage window. Say maybe 4.2 to 4.5. 4.3 volts is a common value in a zener diode that should be the ticket. As far as wattage. I only saw about 3 milliamps or current in my testing which would be in the neighborhood of 6millwatts. About the smallest zener I know of with standard leads (non surface mount) is 500 milliwatts so wattage is not even an issue. Likely less than 50 cents @ digikey.

The correct place to put it would be between the pink wire and the black wire (ground)

 

[cougar694u]

What does Neutral show?

 

[Professor]

Neutral goes to 5 volts as the switch goes to an open state. The blue wire on the GPS switch is the neutral circuit. It closes when the bike is placed in neutral. I'd have to look at the wiring diagram again to verify, but I remember it having a leg going back to the ecu as well. The ECU may use this to realize neutral instead for the pink input.

 

[cougar694u]

If it sends 5v up the pink wire and you have the diode in place, the ECU may think you're in 5th gear when you're in neutral.

Open state would mean 0v, as the circuit is open. If it opens the pink wire and closes the blue wire with 5v, then it shouldn't be an issue.

 

[Professor]

(cougar694u @ Jan. 10 2007,11:37)

If it sends 5v up the pink wire and you have the diode in place, the ECU may think you're in 5th gear when you're in neutral.[/Quote]
You may be correct here.


Open state would mean 0v, as the circuit is open. If it opens the pink wire and closes the blue wire with 5v, then it shouldn't be an issue.[/Quote]

Remember you are measuring at the pink wire with reference to ground. The common black wire (with white strip I think) is ground. Open is 5volts. As the resistance goes down, you go toward 0 volts. 0 ohms or a short ties the wire to ground so you would measure 0 volts.
If you measure the voltage across any working switch, you will have max voltage based on your source because you have infinite resistance when the switch is open. When you close the switch it goes to 0 volts across the switch and the voltage transferred to the load, light, motor, etc.

 

[cougar694u]

I need to just get a picaxe chip and program it to look for the window of 6th gear voltage and supply 5th gear voltage, and include a gear indicator. It would take like 1 if statement to do the voltage, 7 total with the gear indicator.

 

[dadofthree]

waiting for results............................

What's a TRED?

 

[extreemachine]

Sounds like it would work but I don't know where you will find one with that exact voltage. Great idea though. Alot easier than taking the clutch apart etc.. to get at the GPS. Have fun!

 

[FloydV]

(Professor @ Jan. 10 2007,09:18) Neutral goes to 5 volts as the switch goes to an open state. The blue wire on the GPS switch is the neutral circuit. It closes when the bike is placed in neutral. I'd have to look at the wiring diagram again to verify, but I remember it having a leg going back to the ecu as well. The ECU may use this to realize neutral instead for the pink input.

So maybe a 4.3 volt zener diode with a 1 watt range? So, the .7 volts or so would be sent to ground instead of the ECU and you think there wouldn't be enough current going to ground to matter, right?

It's an easy enough thing to do. I just don't want to short the ECU somehow. If I'm understanding you, the diode is passing only voltages above the clamping voltage.

The 5 volt neutral bothers me. If it is being passed by
the blue wire, is it part of the circuit that is being used with the pink wire? What part of Ivan's "Smart" Tre makes the ECU see neutral as neutral and not 5th?

 

[FloydV]

(cougar694u @ Jan. 10 2007,10:12) I need to just get a picaxe chip and program it to look for the window of 6th gear voltage and supply 5th gear voltage, and include a gear indicator. It would take like 1 if statement to do the voltage, 7 total with the gear indicator.

What is a picaxe chip. Something you can
use some kind of programming logic with?

If the 5 volt neutral voltage is going through
the blue wire, does it matter if the voltage on
the pink wire is being clamped at less than 5?
I have read that sticking a 6.8 ohm resistor in
line with the pink wire,to make it see all gears
as 5, screws up idling, which would imply that it
is screwing up the bike sensing neutral when
it is in neutral. What do you think?

 

[dadofthree]

Still waiting on results of the FAT .

 

[FloydV]

OK, I can't find a reference to a "picaxe chip" searching the net. So, I'm guessing what is needed is a chip with programmable instructions. Probably an EPROM.

It would need to be programmable with the following logic:

V = registered voltage from the GPS

If V = 4.70 Then pass 4.38
Else pass V

The above should let the ECU see voltages 1.8, 2.26, 2.99, 3.68, 4.38, and 5.0. It should not pass 4.7 volts which represents 6th.

So, someone point me to a chip and a programmer or a place to purchase these. I can figure out the logic in assembly code.

 

[frisbee]

What ever you guys are saying , Come do it to my bike .

 

[cougar694u]

(FAVahalik @ Jan. 12 2007,23:45) OK, I can't find a reference to a "picaxe chip" searching the net. So, I'm guessing what is needed is a chip with programmable instructions. Probably an EPROM.

It would need to be programmable with the following logic:

V = registered voltage from the GPS

If V = 4.70 Then pass 4.38
Else pass V

The above should let the ECU see voltages 1.8, 2.26, 2.99, 3.68, 4.38, and 5.0. It should not pass 4.7 volts which represents 6th.

So, someone point me to a chip and a programmer or a place to purchase these. I can figure out the logic in assembly code.

Some guys an another forum I'm on use them for boost controllers. I'll get with them and see how exactly they use them.

They're very cheap and easy to program. The hardest part would be building the board itself.

 

[BigGeorge]

(FAVahalik @ Jan. 10 2007,01:21) Here are the voltages that I wanted to post earlier and found later after unpacking from a move.

Voltage the ECU sees for each gear in stock configuration:

First:        1.80
Second:   2.26
Third:      2.99
Fourth:    3.68
Fifth:       4.38
Sixth:       4.70

A zener diode with a value of 4.38v should pass all voltages including 4.38v, but clamp the voltage
at 4.38v, so the ECU never sees a value higher than that.  Thus, a Busa would see gears 1 through
5, but never see 6th, since the higher 6th gear voltage (4.7v) would not be passed (but 4.38 volts would be passed instead).  The bike should see gears 1 through 5 correctly, since the zener diode would pass any voltage at or below 4.38 (1 through 5).  It would not see 6th gear, since anything over 4.38 volts would be suppressed.  If the ECU does not see 6th gear, it will not limit the RPMs of the engine to 186 MPH.

The point of a zener diode as opposed to a 6.8k resistor, is that gears 1 to 5 would be read correctly, thus not adding any fuel richness or advance in timing.  Only the MPH restriction would be removed.  No other factors would change, since 5th and 6th gears are identical in ignition advance and A/F mixture.  Also, using a zener diode would eliminate the need to go into the clutch and change the resistors running from the GPS (Gear Position Sensor).

The part where I am confused (I have some posts pending) is:  Does the zener diode go in line with the wire from the Gear Position Sensor, or does it go to ground from the wire that goes to the Gear Position Sensor.  I have seen schematics doing both things (in general, not for a Busa application).  Also I am not sure where to find a zener diode that has a value of 4.38 volts.  I have found listings close to, but not an exact match.

Zener diodes come in a range of power handling capabilities up to 50 watts. 50 watts should far exceed any gear sensing current, but I'm not sure what value would apply.

I have posted this at SH.org as well.

My head just exploded.