Speed Buster Box: Inside Look & Alternatives

Hello!

I would like to know the exact meaning of the spindle trimmer settings I, S, and T. It seems reasonable that "I" specifies the maximum value for the absolute power increase. I can also experimentally verify that "T" controls the influence of the mass airflow sensor (MAF) signal, determining when more fuel should be added.

But what the heck does "S" do? In my case, it definitely affects the engine's idle speed, making it unstable and then stable again. However, I can't detect any influence on the power output just by turning "S."

Ulf:
A while ago (as far as I remember), you came into possession of a circuit diagram for the aforementioned device.
Could you please take a look and explain what the basic effect of these spindle trimmers is?

Hello!

I would like to know the exact meaning of the spindle trimmer settings I, S, and T. It seems reasonable that 'I' specifies the maximum value for the absolute power increase. I can also experimentally verify that 'T' controls the influence of the mass airflow sensor (MAF) signal, determining when more fuel should be added.

But what the heck does S do? For me, it definitely makes the engine idle unstable and then stable again. However, I can't detect any influence on the performance just by turning S.


Hi Georg,
According to my installation instructions, the suction area is adjusted using screw S.
I hope I was able to help you a little bit, even though I'm not Ulf.

Best regards,
Steffi H.

Hi everyone,

I have a plan with characters named Potis I, S, and T. I'm wondering if it's a "speedrun build" or something similar...?

Certainly, T regulates the influence of the mass airflow sensor signal, S regulates the influence of the accelerator pedal, and I limits the maximum fuel enrichment – essentially, it's the sum of the mass airflow and the accelerator pedal input.

@Georg:
You'll notice that in my plan, a connection is already provided at the mass airflow sensor and the accelerator pedal . (According to my documentation for AFN engines, cable 1 goes to the pedal, but for ALH engines, it seems cable 4 is used...?).
I wouldn't consider forcing the LMM input onto the pedal as a good practice for regular operation.

Sure.

Ulf:
Thank you for looking into it.
"How does the box determine the position of the accelerator pedal? The signal likely isn't transmitted through the cable running to the pump, as there would be no reason for it to be there. Otherwise, the box would simply be connected to the mass airflow sensor."


Steffi: Thanks for your reply, but I already have the installation instructions myself. Perhaps the term "suction range" meant more to you than it did to me. For me, that refers to the area below the turbocharger boost. And so far, I haven't been able to observe any increased injection volume in that area.

George.

Georg_G wrote:

How does the box determine the position of the accelerator pedal? The signal likely isn't in the cable running to the pump, as there would be no reason for it to be there. Otherwise, the box would simply be connected to the mass airflow sensor (MAF).

Hi Georg,

Of course, the pedal signal only goes from the sensor to the engine control unit.
Therefore, it must be tapped into either at the sender, the engine control unit connector, or somewhere in between.

I vaguely remember a wiring diagram that listed various different pin configurations for motor control units, along with all the important details.
Okay, here's the translation:

"That means opening the large connector, tapping into pump cables 2 and 3, the pedal signal, the mass airflow sensor (MAF) signal, as well as the positive and ground wires, closing the connector, plugging in the device, and you're done."

Do you have a definitive wiring diagram for your device?

Hello Ulf!


Maybe "S" means something different for my box.

I have the correct installation instructions. Furthermore, the box itself was installed by Speed-Buster, so I could see the original wiring. There's definitely only one connection besides the pump wiring harness, and that's to the mass airflow sensor (MAF).

The connectors of the pump cable harness are disconnected, and the electronics are bypassed in between.

Georg_G wrote:

Maybe "S" is something different for my box. I have the correct installation instructions. Furthermore, the box was installed by Speed-Buster themselves, so I could see the original wiring. There is definitely only one connection besides the pump cable harness, and that is to the MAF sensor.

Hi Georg,

That could then be a simplified version...

My schematic diagram shows 7 connection pins, but their numbering ranges from 1 to 9. Pins 4 and 6 are missing or appear to be unused.

Otherwise, they are...
1 = +12V
2 = LMM input.
3 = Accelerator pedal input.
5 = mass
7 = connect to pump cable 3.
8 = connect to pump cable 2.
9 = connect to pump cable 2 with a 470-ohm series resistor.

If your device also has a 9-pin connector and the pin assignments match all the way up to the gas sensor, please compare the resistances between pins 2 and 3 respectively, with respect to pin 5.
In my design, I have a 1 MΩ resistor connected to ground at both pins. Otherwise, the wire connects to a positive op-amp input through a 220 kΩ resistor.

If you measure the same resistance (i.e., 1 MΩ or less) between both pins, there might be a throttle input connected to that pin – it's worth trying.

Otherwise, S could implement a constant baseline power setting, which I don't think makes much sense because it could quickly lead to jerky operation under partial load conditions.