f=ma

Hello all,

I am a new RX-8 owner. I have had my RX about a month now and really like it. I have never had a Mazda let alone an RX before and I am really beginning to appreciate the quality and performance of the car. It is a velocity red 2011, sport package, w/6 speed. FYI, my fuel mileage has been from 21-22 mpg so far. That is mostly highway and rural routes with some small town traffic mixed in.

I do have a question about shifting and shift points. For normal driving, what RPM gives the smoothest shift from 1st to 2nd? I have experimented with this a little and am a somewhat vexed. The only time I seem to get a nice smooth shift from 1st to 2nd is when the engine is still a little cold. When the engine is warm, I seem to make the car jerk a little on this shift for any RPM between 3000 - 4500.

It usually doesn't bother me too much but my wife comments that I (it) shift(s) roughly when she rides with me. All other gear transitions are much smoother. Taking off from a stop is fine too.

Any advice?

v/r

John

paimon.soror

iTrader: (15)

I have a notchy 1 - 2 shift as well, mine is only when the car is cold though. I basically shift out of 1st around 4k.

It's unconventional, but I double clutch 1st to second and the shift is smoother.

SayNoToPistons

iTrader: (8)

1st to 2nd shifts must be done quick. If the RPM drops too much, it will jerk upon engagement, unless you feather the clutch.

Dale E'm

I had a notchy/almost not shifting from 1st to 2nd on my 300 hp 88 turbo RX-7 that was cured by changing the transmission lube to a high end racing synthetic gear lube. My car was (miss it badly) an autocross project car with some hard miles on it (w/only 12k on it). The rear differential fluid came out like black goo. I researched synthetic lubes and soon replaced the trans gear lube with the best street trans lube and the 40 degree temperature (in Florida?) 1-2 shift became buttery smooth noticeably better than the RedLine stuff. It really pays to use top notch lubes & filters and have your any maintenance done early if you feel somethings not right. If your problem is happening when it's not cold then I would guess the realtively high RPM 1-2 shift jerk is being caused the car's heavy stock flywheel momentum (ie shift fast so the flywheel speed remains constant)
I normally shifted by 3k rpm for fuel economy & pollution reasons (no cats in city driving) and had no problems with torque or jerking. This was a much lower compression turbo motor compared to the Renesis motors and the power was still good and 20-22 mpg was not uncommon on many tanks (75% hwy driving). Hope this helps!

Jacob6875

1st to 2nd on my car is pretty hard to get right as well. When cold (espically in winter) it will slightly grind unless I am very careful. After it warms up it is fine for me. I usually shift around 15MPH which is around 4k rpm.

f=ma

I think this is a reasonable explanation. Feathering the clutch does seem to help. Will that reduce clutch life?

Shifting below 3k may also help. I'll give that a try and see how she responds.

Does anyone just take off in 2nd?

v/r

John

Chad D.

iTrader: (19)

I just use first gear to get it moving than pop it into 2nd right away and let 'er go. Like the others said, 4k is good.

dynamho

Are you referring to the jerk while shifting and accelerating hard?
If so, it's just physics working against you.

Any car accelerates hardest in the lower gears, especially first. When you step on the clutch to shift, the car isn't accelerating so hard anymore. The car slows down before the passenger due to all the friction (mechanical and aero), so the passenger's upper body "jerks" forward. The driver jerks less forward because he anticipates the shift and compensates body muscles.

So, SayNoToPistons is somewhat right in that if you shift fast enough, you can shorten the interval for "jerking". This is why double clutch transmissions only have an eeny weeny jerk (almost imperceptible). In slushboxes, the fluid torque converter smooths out the edges, but the jerk is still a bit there.

So you can either shift fast or don't accelerate so hard when you have a passenger.

Rev matching is another issue and there is a thread in this forum for that.

ken-x8

I don't find the 1-2 shift in my 8 to be much different from the 1-2 shift in any other car.

Shifting was rather notchy for the first couple of thousand miles, then smoothed out as everything broke in. I've had that happen on other new cars.

Ken

SayNoToPistons

iTrader: (8)

Agreed. Also to mention that the "jerk" that occurs when the rpm is above a perfectly rev-matched shift is seemingly more tame than a jerk that occurs when the rpm is below a perfect rev-matched shift. During a jerk with the RPM higher than perfect, the car will lunge forward, forcing the passenger against the seat. Seemingly less aggressive when the car is engine braked by a below perfect rev-match shift, simply because the human body has no object to stop it other than the seatbelt. OP, since your user name is f=ma, I am sure you are quite familiar with how physics (Newton's laws) applies to this situation.

Now taking that into consideration. Shifting quicker between 1st and 2nd gear leaves you higher RPM's to work with when 2nd is being engaged. Like I said before, feathering the clutch when engaging 2nd helps also. Only do it slightly so you get the feel of how to shift into 2nd smoothly by using timing.

I experimented with my 1-2nd gear shifts when I first my RX-8. I realized that it helps when i make the process quicker. Clutch in with a QUICK left leg motion (quicker than the right foot getting off throttle), flick the shifter into 2nd in a gentle motion, and disengage the clutch according to my feel of the timing. With the right timing, the RPM will be perfectly match with practically no jerk. Not to toot my own horn, but I can engage 2nd gear smoothly without slipping the clutch now.

At the end, I think we are all over analyzing the situation . It all comes down to experimenting and practicing the right formula. Unfortunately the sensitive clutch and low torque doesn't help much.

sh0gunshin

it might be your clutch control. gettin the car moving from neutral to first and then 1st to 2nd might have to do with your feet

jasonrxeight

RX8 clutch is very touchy, and the rpm drops very quickly and the mass of the rotors making the jerking effect very noticeable. best way to do is to lightly press gas pedal before engaging the clutch abit so the the rpm matches perfectly.

f=ma

This technique seems to work well.

I understand the physics behind this. I was just curious what techniques other RX-8 owners are using to mitigate the effect.

All this being said, I really am enjoying the car. The corning is fantastic. Handling is really responsive. Highway exit/entrance ramp curves are really fun to take in it, especially when you push it a little.

v/r

John