Auto Blip

Hello Everyone,

MoTeC M130 GPRP - What is the best way to approach configuration of the auto blip feature for rev-matching upon downshifts? I would like to ensure that I am implementing this safely and keeping my gearbox healthy. This is for an FSAE 4 cylinder platform. Thank you for all your help recently!

Is your engine setup using Drive-by-Wire? GPRP throttle blipping only works with DBW setups. If you don't have DBW, you can still do rev-matched shifts, but the driver needs to still mash the throttle pedal.

First think to focus on is to make sure the wheelspeeds inputs are working, and the gear ratios defined correctly. Log the channels "Gear Ratio" and "Gear Estimate Ratio" and verify that those numbers match (or are very close (say within .05 to .10).

Make sure your detection (gear lever, or paddles) are correctly identifying upshift and downshift. The channel "Gear Shift Request" should reflect the proper state, "Gear Shift Request Diagnostic" is useful for figuring out what might be missing.

Read the help for "Gear Shift State" -- this describes exactly what happens when. The "Gear Shift Throttle Aim Main" is where your blip amount is requested, the duration is specified by the various "Gear Shift Throttle Aim xxx" parameters (see the help for each one).

You will need to tune the "Gear Shift Timing" table -- concentrate on each of the up/down power on/off cases separately.

I suggest enabling "Gear Shift Engine Speed Limit Mode" and setting the "Gear Shift Engine Speed Match" table to 102% for Power On cases, and 98% for Power Off cases.

Best driver advice -- use the clutch on the downshifts.

Okay thank you! I should have mentioned this is a DBW setup with clutch-less shifting via fuel/ignition cuts (motorcycle engine). I guess this may counteract auto-blip on downshifts? Any further input with this in mind? Gear shifts are dialed in but adding this function would be a great advancement.

What is the value of "Gear Shift Throttle Aim Main"? -- this is what causes the blip on downshifts. Do you have a data log with all the gear shift channels logged to share?

I suspect your FSAE restrictor just makes the blips so slow you aren't noticing them.

In addition to what David mentioned, the timing of the downshift actuation may need delayed to allow the engine to generate some torque.

I also suggest taking a look at fueling on tip in to make sure enrichment and throttle response is really crisp. This can be rough checked quickly simply by revving the engine from various speeds and making sure response is almost immediate, very crisp, and adjust fuel functions as needed until it's working really well.

Here is the GPRP Configuration Manual. Take a look at this to understand how to setup GPRP to handle your shifting.

Have you fitted a true rotary pot for your gear position, or are you using the stock gear position resistor switch? GPRP will work best with a rotary pot for the gear position.

If you do not have an actuator changing the gears, but just a linkage from the driver (cable or mechanical activation), you still need some way to detect up / down shifts (i.e. strain gage, potentiometer, switches). Tell us more about this.

Thank you for all your help David! We are currently tracking shifts through paddles as a driver switch, and the shifter is actuated pneumatically with an compressed air tank. Attached are some screenshots of what i got going on. I think you got me on the right track?

I would suggest you read and process the help under the help for 'Gear Shift State'. This tells you which gear shift timings are operational for the different shift types.

I would also suggest a non zero value for your gear shift actuator preload values. Pneumatic shift systems don't have enough force behind them to pull a gearbox out of gear and naturally have a delay from actuation to full torque or 20-50ms depending on system configuration and operational pressure. Typically a starting value of 15-30ms works well in the gear shift actuator timing for preload.

You will also want some pre shift time in your downshift gear shift timings. The pre shift is the area where you reduce engine torque output with ignition retard and/or ignition cut and start the throttle blip. As a typical DBW motor will achieve a controlled 0-100% opening in 70-100ms, you are likely looking at 30ms or more to achieve your 50% aim from your minimum throttle aim/idle pedal offset value. The idea in the pre shift is to maintain engine speed, charge the intake with sufficient fuel and get the throttle open for a crisp blip. Any filtering on your intake manifold pressure sensor will hinder the performance of the blip, although you can assist this a little bit with a well tuned inlet manifold pressure estimate table and the inlet manifold pressure decay and blend values.

In your engine speed match, you have no range or margin values set - this needs correcting.

Final item is you have your blip duration set to 0ms and I cannot see the minimum blip duration, however this value should also be a non 0 value.

Nate's advice is spot on... Listen to his experience.