Synchro Rev Matching and downshifting... confused.

Alexus

Now I've searched both this forum and the better half of the Internet and unfortunately I still do not understand fully how, exactly, Synchro Rev Matching works. Does it automatically blip the throttle for me in every situation? I mean, if I downshift from fourth to second in order to induce some compression and henceforth slow down the car while, let's say, going down a hill or into a highway off-ramp, will it automatically blip the throttle for me to keep the car from jerking around, like you would? When I downshift from sixth to third in order to accelerate, will me smashing the gas as I let off the clutch override the rev correction the SRM system does?

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spearfish25

The SRM will work in ANY downshift situation to match the revs. You won't 'mash' the accelerator fast enough to throw off SRM. As soon as you bring the gear shifter out of one gear, you get an initial blip to get the revs spinning faster. As you then bring the shifter into the lower gear, the car will immediately match the revs for the lower gear (and hold them if you are slow on releasing the clutch).

I suppose you could theoretically screw up the SRM by never letting off the accelerator when you downshift. You'd just hit the rev limiter as you clutch and declutch...not sure why you would do that though.

Bottom line...go drive the car and it will all make sense.

chubbs

Don't worry about SRM - just turn it off.

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spearfish25

lol

Alexus

Silly-talk.

__________________
"The object of war is not to die for your country but to make the other bastard die for his."
-General George S. Patton Jr., 1885-1945

mcphelps

You cannot engine brake with SRM on.

It actually rev matchs on upshifts as well, if you wait for it. Really not much use though.

spearfish25

Completely false. Engine braking has nothing to do with rev matching. Engine braking simply means downshifting to attain higher RPMs which will slow the car down if you do not apply throttle. Rev matching will make your downshift silky smooth. Then all you have to do is NOT press the accelerator and you're engine braking.

Pushing_Tin

Of course you can. It just makes it smoother. Downshifting from 5 to 2 will induce much higher RPMs that will engine brake you when you let out the clutch.

mcphelps

But downshifting from 5 to 4 or from 4 to 3 without your foot on the accelerator will not result in engine braking, at least at nowhere near the same rate as with SRM dissabled. My experience has been that if I'm trying to slow down, downshifting is not the way to do it. It's like it keeps coasting, just at a higher RPM. I haven't tried 5 to 2, but just moderately downshifting as I'm coming to a stop, or slowing down in town for a corner has not resulted in the engine braking I'd be expecting, causing a bit of an adrenaline rush; kinda like stepping on the brake and there not being any.

Shunya

trust me... if a girl is telling you that you won't need one then it's true

shabarivas

Umm... all the SRM is doing is making you downshift better and quicker... so if you downshift to engine break - then you will do it sooner and smoother w/ SRM... please go drive your car...

armensti

the reason you think that your car is slowing down faster with the SRM off is because you dont rev match when you downshift and thats why it feels like its slowing down faster. but if you rev match like your supposed to when downshifting its going to slow down at the same speed as it would with the srm on

Namir

I think there is some confusion as to what engine braking is.
"Engine braking is the act of using the energy-requiring compression phase of a heat engine to dissipate energy and slow down a vehicle."

No where does it say you have to jerk the car while re-engaging the clutch in a lower gear (from not having the wheel speed match the engine speed for the chosen gear).
Once you are in the lower gear (which you are presumably engaging to 'engine brake') the throttle is not being applied by the SRM system. This means that the turning wheels are responsible for most of the force required to turn the engine at these RPMs.

A low gear means high RPMs which requires more energy, thus engaging this lower gear and opposing the car's momentum with the energy required to turn the engine at this high RPM is what causes the car to slow down ... engine braking.

I hope this clears things up a bit.
And like others have said, drive the car. If you feel like SRM is 'overriding' your inputs and you don't like it, turn it off. I doubt this will be the case though.


Summary:
Jerky downshift /= engine braking.
Jerky downshift = short synchro life.

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mcphelps

This is what I'm talking about:

She's acting up....

At least I'm not the only one...

I have gone out and verified that it will indeed engine brake with SRM engaged, but I had kinda given up on it after having it not work.