Fletch F. Fletch

10-4, good point, I guess I was thinking too simply, as I've always thought/been taught to be sure to fully depress the clutch so as to not wear it out. I'm probably overthinking it!

David Lively

This is an old thread, but:

I just finished installing an Autoblip on my 2011. Once the thing was all wired up and powered on, my car wouldn't start. I figured I'd tapped the wrong wires on the clutch sensor (disconnecting the taps going to the clutch sensor wires allowed the car to start), but everything looked good. Finally, I went ahead with the calibration procedure and everything started working. As an EE, I'm still scratching my head over how a device that's passively reading voltage could keep the BCM from knowing that the clutch is down, BUT such is life.

harrydirty

It is not totally passive......I tried to run the car with the unit switched off but some of the circuits may have some open loop voltage that confused my car. I finally resorted to switching off the clutch sensor wire to totally disable the unit for street driving.

David Lively

The switch isn't a terrible idea. I find it interesting that they're tapping the OBD-2 port for +12V but using the clutch for ground (in the '08+ instructions). Potential ground loop? Seems unlikely, but so does having this problem to start with. I'm not sure if the clutch signal goes to the BCM or the ECM, pretty sure the ECM is on the other end of the OBD2 port. Tempted to go measure the voltage between the clutch sensor ground and the OBD2 port ground.

Where'd you put the switch?

I considered just building this thing out of an Arduino, but the time it would take is more valuable than the $400 for the Autoblip. Now, I'm tempted to crack it open and see what sort of questionable design decisions have been made.

NSFW

I had the same thoughts about Arduino rev matching, but it seems to me that it couldn't be that much more work to get it to literally match revs, rather than than using a fixed time/amount of throttle blip. Tap into the speedo and tach signals, figure out the ratios for each gear, figure out how much throttle it takes to achieve 1000-6000 RPM, and have the thing actually match revs. And have it watch the throttle pedal position to know when to kick in - so you'd do the same thing with your feet but you'd get precise rev matching every time. And you could use it to downshift without braking for the occasional freeway pass.

But now I'm hoping I can do it by patching the code in the PCM. My car is on jack stands right now waiting for a new motor, but I'm going to be trying a few things when it's back on the road.

harrydirty

I put the switch on the tombstone, where I already have two other switches (one to switch my AMB transponder on/off, one to control my exhaust flaps). Space is at a premium there, so I used mini toggles with the bat handles.

David Lively

I'd thought about that as well. It'd make the interface a bit more complicated: you'd need vehicle speed as well as knowing which gear you're going into, and a real (fast) tach signal, preferably straight from a coil, rather than what you get over OBD / CAN. Having it work only under braking and assuming that you're going into the next lower gear solves that problem. The biggest challenge I see there is knowing which gear is being selected. You can calculate which gear you are *in* based on the tach and speedo, but for your example of downshifting on the highway, there's no obvious (to me) way to know that you're downshifting rather than upshifting until the shift is complete. There are ways to address that, but it's not something that's going to be simple to wire up or code. (Crazy idea: do it optically. Mount a camera above the shifter, pointed straight down, or two small ones (one on the right of the shifter, one behind or in front of it) and use those to figure out which gear is being selected.) (Or some magnets and Hall effect sensors.)

In any case, it'd be an interesting project.

NSFW

Clutch + 5% throttle = downshift
Clutch + 0% throttle = do nothing
Clutch + 100% throttle = rev match for an upshift

And just assume every shift is one gear.

I my Subaru's ECU to match revs on downshifts just looking at clutch+brake, and upshifts using clutch+fullthrottle, and it works pretty well. The biggest issue is that it sometimes kicks in when I don't want it to. For example if I put the clutch in and brake while approaching a stop - it will rev up momentarily, but it also returns to idle pretty quickly so it's no big deal. Disabling it under 20 mph almost got rid of that. I'm pretty sure that a "5% throttle" condition for downshift rev matching would get it right every time, but I haven't tried that yet. It works pretty well as-is so I haven't been motivated enough to keep tinkering with it.