Benjamin Choi

i guess we're splittin hairs about the definition of "rev match"

you don't have to manipulate the throttle to rev match to me and to others i've spoken with in the past (guys who drive sports cars, track cars blah blah).

you're still matching the revs on an upshift "rev match" because if you do it too soon or too early, you feel it and it's not so smooth.

P.S. you certainly wouldn't want to "double clutch" on an upshift

TD in DC

Still not getting your drift. When you upshift, whether you are high enough in the rev band that you need/want to upshift, or whether you are rapidly accelerating, there really shouldn't be any "timing" problems that would require explicit rev matching on the way up. Rev matching on the way down is important to prevent, primarily, the tires from chirping and destabilizing the car. Revs on the way up are, largely I would think, irrevelvant because you could not chirp the tires. At most, you would just lug the engine. However, you would have to be a real dolt, or just not know how to drive a standard, to shift your car on the way up in a way that would lug the engine.

You make it sound like there is some specific technique required to "rev match" on the way up. I don't know it. Fill me in.

vrinner

Here is what I have noticed since I got my Porsche...which I drive mostly in heavy OC to LA traffice...

If I'm rolling along in 1st and let the RPM's "slowly" get up to say 4K then decide it's time to upshift to 2nd, if I...

push in on the clutch/let off the gas (RPM's drop)
shift to second/let out the clutch

It's jerky and I slow down because at 4K in 1st is about 2.5K in second (roughly) but the engine is at 1K.

I THINK that is what Ben is talking about in his upshift rev matching. Of course this has nothing to do with actually shifting from gear to gear issues that I think this thread started off about.

Benjamin Choi

i mean the author isn't clear about "shifting smooth" on his 1-2 shift. it's def going to be diff in the 911 than the saab, but again, it's so basic shifting behavior no one thinks that it is a technique or way of doing things to rev match on the upshift. you are doing it. not all people do it. believe me. they let the clutch do the work and to me that's not good technique.

so to avoid the jerkiness that you so well described, vrinner, is what i'm talking about avoiding by rev matching on the upshift. you are matching the revs to make sure you're smooth on that 1-2 shift by timing it right via experience/feel/technique however u want to call it.

rev matching occurs on both the upshift and downshift. the downshift requires an extra step (throttle blip).

TD in DC

OK, ben, to me, that is NOT rev matching on the way up. That is just shifting at a high enough RPM with proper technique. That's it.

To me, rev matching means doing something specific to manipulate the rpms during shifting. On the way down, for every shift, I am decelerating (usually under braking, but not necessarily), I disengage the clutch, shift to neutral before shifting to new gear (this happens so fast the passenger wouldn't notice it -- it just means shifting like you have a shift gate), blipping the throttle, and then engaging the clutch rapidly imediately thereafter. Since I do this for every downshift on street or track, it has become second nature and I rarely, if ever, chirp the tires.

Fast00

I kind of do exactly what Ben is talking about. I shift wicked fast. When I am upshifting, my RPMs drop at a very quick speed, if I don't shift wicked fast the RPMs will be too low for the next highest gear.

(Granted I am very precise in where I put the stick so there are no shifting problems. I never ever ever go to neutral first for an upshift. If I wasn't exactly precise with my shifting, all would go wrong.)

It is rev matching in the sense that I have to shift at a certain speed to match the RPMs of the engine to the gear, otherwise it is not smooth with dropping the clutch. If I drop the clutch after the RPMs have gone below the speed of the gears it is not smooth.

End of story.

Fast00

And nothing is sweater then a nice double clutched downshift. Somehow I think my pedals are off for the imfamous heal toe delivery.

AndyK

I find this is WAY more necessary when the A/C is compressor is on! Try doing the 1-2 shift with the climate control in the oFF mode. Much smoother! The compressor drags the engine speed down, so when you let of the gas, it goes all the way down to zero quickly, as opposed to slow and steady when the A/C is off.

Jake Ok

Yes...its more complex when the AC is on. I find it shifts much smoother when you do it fast....gas and clutch combo.

TD in DC

I experience NONE of these "issues." Do you guys have lightweight flywheels? Sounds like something is wrong with your car or your shift technique (meant as a serious comment not an insult).

AndyK

For me, there is just a slightly different technique needed when the a/c is on. Stock flywheel and clutch.

TD in DC

Strange. I can't even notice any difference between when the a/c is on or off, and I certainly don't vary techinque. I was thinking about this last night and wondering whether maybe I just wait longer to shift, but I don't even experience the problem when I am warming the car up, at which point I shift at 4K (the only time I shift at 4K).

Benjamin Choi

not sure why others are picking up what i'm laying down yet TD you're not... i think we could be in the clear if we drove in a car together to explain to each other what we're talking about. haha like that'll ever happen.

i know what andy's saying about it being more "complex" when the ac is on since you're not getting as much power than with the ac off since the ac unit is puttin more drag as they say on the engine. the revs do fall quicker and you simply compensate for it by shifting faster to rev match on the upshift. on the downshift, i rarely outright WOT when i have the ac on anyways since i'm probably just cruising and not intersted in any fancy driving. i don't like driving spiritedly with the ac on. just habit/pref.

but honestly, it's much less noticeable in the 911 than any other car i've owned which isn't too long of a list (S2000, E46 M3). the S2000 was very noticeable. M3, slightly less. 911, even additionally slightly less. sometimes, my 911 feels stronger with the ac on so i know my **** dyno is a bit off kilter.

1999Porsche911

I suspect that if you are having problems it is because you either are shift at too low of an engine speed or taking your sweet time completing the shift. The proper way to upshift is at a speed that meets the proper engine speed of the next gear. So if you shift at 4000 rpm from 1st into second, the shift should be completed by the time the engine speed drops to 2200 rpm.

AndyK

Exactly, and since the engine speed falls faster with the a/c on, you have to compensate by giving it a little more gas to keep the engine speed at 2200 rpm, for example.