sh0gunshin

Every time i downshift to pass a car, my car jerks a tad bit like the engine just finally caught up with a laggy shift or so. This happens when i let the clutch out a little bit faster and whether i Rev match or not it still happens. When i let the clutch out much slower, it doesn't jerk - but if i'm trying to pass someone i need speed asap. is this jerk normal or missing something here?

p.s. tried google searching

-WILL-

yeah dude this is normal.. you would have to rev match perfect (really perfect) to not feel any kind of jerk. i usually just try and get the revs higher so when i dump the clutch the "jerk" is a pull froward instead of it slowing down then jerking back forward when i hit the gas. i hope that made sense

jasonrxeight

revmatch, give it more gas.
rotary engines dont have very good rpm response, just need to give it more gas to get higher rpm.
http://www.youtube.com/watch?v=cPj9XXW25GA

lateralus

iTrader: (1)

Now that you posted it in this section, delete the one in the Multimedia section.... My response to what you said in the other one...

Rev matching isn't just blipping the throttle... You have to get the RPMs to where they are going to be once the shift is done.... If you are going 45mph in 4th gear and are downshifting to 3rd, you punch the RPMs up to about where they would be at 45mph in 3rd gear, then let off the clutch.

Marklar

Whatever you've heard about double-clutching being useless, this is where it shines. To drop three gears smoothly, double-clutching is the way to go, it's easy to get it perfectly smooth that way.

Kick in clucth, shifit to neutral and clutch out, hit throttle to rev high enough for lower gear (don't be afraid to hit it hard, you are going to be shifting down to fairly high revs), then kick the clutch in again, put it in lower gear (should just fall right in if you got revs right), and clutch out while you floor it and zoom-zoom.

jasonrxeight

double clutch has nothing to do with down shifting jerkiness. double clutch is to reduce the wear on the syncros which you cant feel them spinning up the input shaft of the transmission. whats making the jerkiness is when letting out the clutch, engine rpm too low dragging the wheels to slow the car down.
I'm not saying double clutching is useless, if you want to save the syncros then do it. with modern technology, new designs can last very long time unlike the old time.

Marklar

You don't get it, double-clutching makes it much easier to do the downshift without any jerkiness, this has nothing to do with syncho wear. Just because double-clutching is often justified by less syncro wear doesn't mean that's all it's good for.

Double-clutching has everything to do with making large downshifts without jerkiness. It works really well for that.

jasonrxeight

the jerkiness is caused by drive wheels being slowed down by the engine. the benefit of rev matching is to matching the engine speed to reduce the effect of speeding up the engine using the car's momentum.

double clutching is to speed up the input shaft of the transmission with the engine so the syncros can mesh the input and output shaft speed without too much wear. even if you double clutch in to the gear, if your rpm drops too low, you still getting this jerkiness caused by mismatch rpm.

I suggest you read related materials before you say things like this. you gonna confuse the new drivers.
http://en.wikipedia.org/wiki/Double_clutch
"The purpose of the double-clutch technique is to aid in matching the rotational speed of the input shaft being driven by the engine to the rotational speed of the gear you wish to select (directly connected to rotating wheels). When the speeds are matched, the gear will engage smoothly and no clutch is required. If the speeds are not matched, the dog teeth on the collar will "crash" or grate as they attempt to fit into the holes on the desired gear. A modern synchromesh gearbox accomplishes this synchronization more efficiently. However, when the engine speed is significantly different than the transmission speed, the desired gear can often not be engaged even in a fully synchronized gearbox. An example is trying to shift into a gear while travelling outside the gear's speed or directional range, such as accidentally into 1st from near the top of 2nd, or intentionally from reverse to a forward gear whilst still moving at speed."

lateralus

iTrader: (1)

Judging from what his post, it sounds like this part is his main problem. The getting the revs right.

Marklar

You're still not getting it. It's much easier to do the rev-match for a large gear drop if you double-clutch instead of single-clutch. It's very easy to get it buttery-smooth that way.

Have you ever done a good quick double-clutch drop from sixth to third, or are you talking about double-clutching from reading articles about it?

jasonrxeight

actually his problem has nothing to do with transmission but the clutch control. unless hes down shifting from 6th to 2nd, then he will have some trouble with the transmission blocking the gear out because the syncros just cant take that rpm difference. then he needs to double-clutch.

sh0gunshin

god i love heel toe videos. i've been driving stick for about less than 2 weeks now and i attempted my first heel toe going from 4th to 3rd that was actually really smooth. The heel toes after that were pretty terrible tho

edit: yeah when i go from a higher gear to a lower gear i double clutch. but i usually coast in neutral for a bit before hitting a new gear. i'm just trying to figure out 6-5th without the jerk 5-4th etc

DocBeech

iTrader: (1)

Theres a TSB for this. If you downshift to third gear, and have problems its a possible motor mount failure.

Marklar

Oh so you use clutch control for smooth downshifts. Surely you realize the problems with using your clutch for this.

sh0gunshin

actually this kind of reminds me of another problem. sometimes when i'm cruising in 1st gear with my foot off the throttle, the car shakes a bit (i can understand from low rpms) but theres also a weird sound coming from the back wheels. any idea?

jasonrxeight

I think of clutch control includes rev-matching and heel&toe. not just the plain clutch pedal.

jasonrxeight

my R3 has this wining sound in 1st gear if I decelerate in gear. I think its probably the gear is a straight cut gear but idk.
the diff sound I heard some of the S2's have this diff sound, but mine doesnt.

Marklar

OK then, I assumed you were talking about using the friction plate as a rev brake.

sh0gunshin

i have a '10 r3 and it sounds like a whining sound as well. like every tire rotation it sounds like something is powering down

jasonrxeight

yes, its like that. like wee...wee...wee...sound when you decelerating in 1st gear.

sh0gunshin

^haha yeah exactly. a friend of mine told me a good way to get rid of it is to depress the clutch while decelerating/off the throttle. Works kinda good

Marklar

Wasn't there a thread here recently about R3s making a weird noise? I can't remember what the fix was, and I couldn't find the thread in a search. Came up in a "marbles in a can" thread, but it wasn't really that sound.

jasonrxeight

the MIAC sound isnt just R3. its all RX8's its small air bubbles rushing thru the heat core at high speed. this sound usually happens a t 7000rpm+.

sh0gunshin

also, it's ok to rev while clutch is fully disengaged right?

(some mazda sales rep told me to rev the motor to lubricate the seals at stops/intersections lights)

lateralus

iTrader: (1)

I'm not talking about how his transmission is blocking him out of the gear because he isn't getting his revs right... I'm saying that when he blips the throttle, it sounds like (hypothetical example) if he is going to be at 7k rpm when he is done with the downshift, he is only revving it up to 6k... The jerk is probably coming because the RPMs are short of what they need to be at the speed he is going.

Sh0gunshin, when you are driving, try to get a feel for what RPM certain speeds fall at in each gear. That should help out