JonsilvZ

I would never trade my Z into a 6mt Z. If I wanted to take that kind of loss, I would get a completely different car like a TT Z putting like 350whp. My point here is the performance #s are too close between the 6mt and auto Z.

julian

So let's compare a locked-out TC and a manual trans, both with the same final drive. Then the two major things that affect acceleration are (rotating) mass and gearing of the actual tranny.

Who knows the weight of the components rotating in the auto vs manual trans?

I haven't looked up the gearing in both trannys but even if the auto and manual have the same gearing in one gear (say third), I'm pretty sure the 6 speed has smaller differences between gears. so even if both trans have the same rotating mass (and assume no missed shifts), the car with the manual trans will out accelerate an auto as you run up through the gears.

capnfrantic

The bioligridal frigritive bangs into the positive dimension causing a disturbance in the state of being which disrupts the biolatic sphere which therefore results in the end equation of peaceful solitude, Assuming proper barometric pressure. Hope I made myself clear. We all drive Z's Let each side think ours(theirs) is better.

JonsilvZ

Now your talking out of your ***. Proven fact when I raced a friend of mine with a 6mt Z(CAI)I was stock from a 65 roll. Both in 3rd gear he started to crawl way later. Hmm the shorter gears in the 6mt? Now if I had the same gearing it would be about even. I know my Z very well and encountered many Zs. So I know the facts. Recently this guy I know has a 6mt Z(CAI,PIA 19s). We did several runs from 65 to 120. I beat him half to more than a car. Since he has 19s that puts the gears closer to mine.

capnfrantic

Ok, so I'm not as good as you guys explaining things.... Now I'm on JonsilvZ side!! 5AT,5AT!!!!! Go Man Go!

Aggro_Al

Go back a few posts and you will see my post on gearing and click on the the bottom link. You'll see in my example of the Enthusiast 350Z what factors affect the dyno.

Yes, the cars do have different gearings but Nissan did a fairly goof job in matching the gearing ratios to each transmission. Plus, gear ratios they use in the spec sheets for the 5AT are when the gears are in the locked position. The locked position is the tallest gear ratio. On the 5AT, 1st-3rd gears have variable gear ratios when the TC is unlocked. So, unless you use the same gear ratio in the 6MT and the 5AT it will be difficult, if not impossible when the TC is unlocked, to measure the difference between the 5AT and 6MT. What really matters is how both cars perform overall. Both the 6MT and the 5AT perform very close, the deciding factor is not the mechanics of the transmission but the skill of the driver.

Now if you are talking weight of the transmissions, the 5AT is about 13lbs heavier than the 6MT and most of that weight are the fluids used in the 5AT. The 5AT in the Z is one of the most compact and lightest autoboxes on the market. If you are talking rotational mass, the 5AT has a low-inertia geartrain. The 5AT uses a two fans and a planetary gearset. The 6MT uses heavy friction and clutch plates, a weighted flywheel and a gear spindle.

Aggro_Al

1sick350

My suggestion would be to go and learn how to drive a manual first. You can probably learn the basics in a few hours and be semi-proficient at it a few days. Once you have the shifting down go test drive the 6MT and the 5AT and just go with which ever one you like better. If you don't want to learn how to drive a standard transmission then your decision is already made. Get the 5AT and be happy with the knowledge that your car performs just as well as the 6MT. The Z is a great car regardless of transmission.

Just my 2 cents.

NismoChic

Uh huh what he said

julian

whatever dude. do even understand my line of reasoning?

by the way, thanks for responding to my a$$ when it speaks to you. it appreciates it.

edit:
aggro_al - it looks like you know a lot about trannies. i don't know the finer details so i was wondering if you knew if the TC locks out at a certain rpm? my understanding was it can be designed in.

case 1: so if 1st through 3rd have variable ratios, what happens when you're in manual mode, 5000 rpm, and got WOT? does the ratio stay the same or does it vary? is the TC locked or is it spinning?

case 2: same questions as (1) except you're in 5th gear (or any non-variable gear).

Aggro_Al

In 1st and 2nd gears, the lock out isn't based on the engine RPM alone. The lock-out is based on the speed difference between the impeller and the turbine. The bigger the difference between speeds, the bigger the torque multiplying effect. If the impeller (engine input side) is spinning faster than the turbine (output side) the torque converter will use what is called a stator to redirect the fluid back to the impeller to re-accelerate the fluid. Since the fluid has now been accelerated muliple times it now carries more force. Simple physics (Force=mass x acceleration) more acceleration will give you more force. This will continue until both the impeller and turbine speeds are matched then it will achieve what is called fluid coupling or fluid lock and stop mulitplying. As you can see because of torque multiplication the gear starts out in a lower gear ratio and gradually adjusts to a higher gear ratio as the torque converter begins to reach fluid coupling. 1st and 2nd gears don't use a physical clutch lock-out so it has the ability to continually adjust torque.

4th and 5th gears are fairly simple because it is a full lock-up. These gears use a clutch to create a physical connection to the engine and driveshaft. They are not variable like the first 3 gears. They can be treated basically like gears on a standard transmission.

3rd gear is a little tricky, this is a partial lock-up gear. It starts out like 1st and 2nd gears but instead of fluid coupling it will use a clutch lock-up like 4th and 5th gear. Is sort of a combo gear.

Case1:
If you were in 1st-3rd gear and went to WOT, the transmission would flash directly to its stall speed if it wasn't already there and it would torque multiply the difference between the impeller and turbine until it achieves fluid coupling or clutch lock-up.

Case 2:
Using your 5k RPM scenario and assuming you didn't downshift, if you were in 4th or 5th gear it would be fully locked and act just like a standard transmission.

julian

ok, did more research through a co-worker and the internet.

and my understanding is the torque converter's lock out/stall speed is based on the torque converter design and engine.

lock-out occurs at the stall speed of the TC, which is the rpm at which the impeller rpm = the turbine rpm. below the stall speed, the impeller and turbine turn at different rates, i'll call it "slip." you can design the ramp-up function of this slip: on one extreme, the turbine gradually catches up to the impeller's turbine, and on the other extreme, the turbine is almost like a step fuction - the impeller spins fast but the turbine remains still. but once you pass the stall speed the turbine and impeller match rotating speeds all of a sudden.

drag racers use TC's with a higher stall speed (to get the engine into its power band) and more aggressive ramp-up characteristics. so if the stall speed is 3200 rpm (engine rpm = impeller rpm), they can sit at the light and engine rev to 3000 rpm with the car in gear but speed = 0 because the TC is slipping. once they push the throttle past 3200 rpm, the TC locks-up and all that power is transferred.

i don't think the auto trans itself does anything besides shift gears through hydraulic fluid. it's just like a manual gearbox; and a TC's function is to act like a clutch from a manual trans. maybe the TC has different calibration for gears 1-2, 3, 4-5?

anyway, this topic is being beaten to death so i'll stop here.

Eastbayz

Unless you drive in traffic all the time... The stick is a lot more fun to drive!

Aggro_Al

Julian

You pretty much got it. Glad to see that someone actually is open to learning. It's great that you just didn't just fall prey to some of the misconceptions but actually went and verified the information. Good job!

The only thing you're missing is that the Z's 5AT uses a stator.

http://www.victrans.com/multiplication.html
Torque Multiplication Explained

JonsilvZ

Aggro-Al you explained the scientific facts between the auto and 6mt Z. I explained the real world facts on the two. Maybe those ignorant people will learn something and not just say things that are not proven facts.

Aggro_Al

We can only hope. It doesn't matter what the topic is, there will always be those who just won't get it no matter how off they are or those that will choose the opposite opinion even though they know it's not right just to provoke a negative response. Not much you can do about it.

Pedal Pusher

The real difference is in the driver. If we are talking a 1/4 mile drag race the A/T will win more often because it will shift at the maxium point every time. You simply floor the throttle and let the computer do the rest. The "person" driving the M/T will not be as consistent, miss a shift or have problems getting off the line. The win light will be in the A/T lane.

1sick350

iTrader: (1)

I no the stick is quicker casue of races ive seen, but i just wanna no if the auto feels just as torquey and pulls u to the seat the same. If it feels just as fast then it would be better becasue i dont no how to drive stick and i dont wanna try to learn on the z and wear the clutch down.

1sick350

iTrader: (1)

THanks for advice, but i have to get my brothere to teach me on his supra and i dont think he will be to thrilled if i do soemthin to mess up his clutch, dam wish there was another manual tranny in the family.

Aggro_Al

Try this. Let the dealer know that you are on the fence regarding which transmission to get and that you are serious about buying a Z. Let him know that you are going to buy a Z no matter what. The salesperson might personally teach you to drive a manual if he knows he'll get a sale either way.

1sick350

iTrader: (1)

I never thought of that. Ill give it a try, thanks. I didnt think that a dealer would ever let someone do that. Hope they do.