pneumatic shifters downshifting problem

Hi,

I am using a samsonas sequetial gearbox with MME pneumatic paddle shifter, I noticed that I can't downshift immediately when I step on the brakes, the system only allows downshifting once the RPMs drop. I use Ecumaster pro 8 ECU, but I am not using rev matching function, so can anyone tell me what is wrong?

Thank you.

Most paddle shift controllers have a maximum RPM where downshifting is permitted, since the RPMs will go up on the downshift to the lower gear and you don't want to exceed the engine's redline in that new gear. Proper technique for downshifting near redline -- brake, then downshift.

The M1 GPRP Firmware will reject a downshift request if the calculated Engine Speed after the Shift will exceed the Engine Speed Limit, the ECUMaster ECU may do the same protection (I haven't used paddle shift with one so I don't have hands on experience)

Hi, I have done the max RPM setting right, the problem now is I can only downshift if I step on the clutch, to release engine brake power from transimission? If I don't hit the clutch, I can only feel a blip, the rpm rise, but gear won't come out.（It works sometime, but very rare.） My air tank is set to 900 kpa. What could be the problem? Thanks.

And also, even if I adjust the travel of rod of the shifter to proper length, sometimes it will downshift two gears at a time, like from 1st gear to reverse gear, jump the neutral gear. Do you know why?

This problem is the timing of the RPM blip and the actuator. I would suggest you do take advantage of any rev-matching function. To debug this, you need to log shift related channels at a high sample rate (200hz or more). With a dog-ring box, you want to have the actuator active before the torque is reversed with the blip, that allows the dog to release and head toward the next gear. You need to engine to rev to the ideal RPM (rev-matching) to help the new gear engage. If the actuator is activated too late, sometimes you can't get out of the gear. Or if the actuator doesn't stay active long enough, you fail to get into the next gear, and are stuck in a neutral between gears.

I would log Engine Speed and a driven Wheelspeed at 100hz, but use 200hz for channels like the downshift valve solenoid, gearbox barrel position, gear detected, throttle position. Be sure to log (or at least note) any channels with parameters like shift timings, or delays -- so you can later know what parameters produced what results.

The reason for double shifts could be an issue with the paddles (actually requesting two shifts), but even if only one is requested, some paddle shift controllers offer retry options, where they will re-attempt a shift if the gear is not detected.

Does your gearbox have an option to lock out neutral and/or reverse (so you have to pull a cable, or push a button). I find those handy, so you can't downshift to neutral while on track. Gearboxes that have a half-shift between 1st and Neutral can be really challenging to get the timing right to not overshoot -- sometimes it takes a little help from the driver by not fully disengaging the clutch so it drags a bit.

Hey David, thanks for your reply, really helpful! Things are getting great, however when ECU tries to bilp, DBW needs around 30 ms to react, then lift to requested position, is that normal? My car is 2013 BRZ, I am using OEM throttle body. So in ecumaster's logic, I set 30 ms in pre-load session, to wait throttle body to react. Is that a good way to do it?

And for RPM matching function, I have input gear ratio to ECU, but my wheel speed sensor is not working, this will affect the ECU's abililty to judge what RPM it should let engine run into, is that correct?

For double-shift probem, yes the transmission has a lock between 1st and N gear, and between N and R, but if I hold to release the lock, sometime gear will goes from 1st to R, what could be the problem? Thanks. (this problem seems disappear recently, so let me ask you again if I can't solve this. I have't checked log when this problem happens.)

I see similar slow blip response times for V8 engines, and we just have to tune the knobs we have to get the behavior required. Since I don't know the ECUmaster paddle shifting, I would try a range of pre-loads both positive and negative values and see what seems to work the best. I could imagine that a positive value might delay the blip request by 30 ms, so try 0 (or even -30 if it allows it) to see which is better.

If you are logging gear position sensor voltage, and can see actuator request, you can determine the real actuator response time before the barrel starts to move. I often see values in the 5-10 ms range. So I know whatever value I use for other timing will need that 5-10ms before anything will be moving.

Yes -- you will probably need working wheelspeed data for the rev-matching to work. But go ahead and try anyway, some systems just use the RPM change between gears to set a rev-limit, and don't adjust for the decreasing wheel speeds while braking / downshifting.