Was thinking about this the other day...

 

All us auto owners will know what happens - you're pootling along at 50 or whatever, see an overtaking opportunity so plant your accelerator down.

 

The revs rise rapidly for half a second or so, the car kicks down a couple of gears, then BAMMMM!! Full boost :mac1: whooooooooooooooosh.

 

I think that short period whilst the revs fly up is something to do with the torque converter, am I right?

 

So the car isnt actually in drive whilst the turbos are winding up right?

 

This probably explains why autoboxs are considered to be weaker - downshift tends to happen under full boost with the the throttle applied, whereas with a manual, you usually shift *then* apply the accelerator.

 

Anyone agree, or care to expand? ;)

 

Pete

good point - I think u may b right. auto gearchange lag is similar to turbo lag.

 

It all points to the blindingly obvious conclusion that autos blow manuals out the water :rofl:

:rofl: Yep they certainly do :dance: http://www.300zx-mods.co.uk/vids/Pete%20v%20300ZX.MPG 12.5psi each - autos wins :bow:

Yeah right then you wake up!!!!!!

Yeah right then you wake up from being knocked unconscious from the sheer acceleration, whilst Mr Manual struggles to find 2nd gear

 

:D:D

 

We still havent had a stock auto v manual 1/4 mile competition have we? How many stock zeds are on here? I think the manual boys are running scared :dance:

Err no......... mines stock and if it's near London would love to know how fast 0-100 is compared with the auto have to say i did love the kick down on my old 4.8 Porsche 928...........from 60 + it beat most things to 130

good point, but in a manual, you just drop a cog or two and you'll have full boost too ;)

and if you are really thinking about it, as you drop the clutch to go down a gear, just plant the throttle, in the time that you have to move to the next low gear, and lift the clutch, the revs are (takes practice mind) just above where you need them, and the turbos get a head start, probably more than half spooled up already, let clutch out, bam, BOOOOOOOOOOSTY BOOOOOOOOOSTY! :)

mines a stock auto...i agree with Pete when flooring @ 50mph its sommit else to behold..throws you back in the seat...it makes my misses go for her brake pedal....:)

My missus just tends to scream "dont kill me" at the top of her lungs... Kind of puts you off keeping your eyes on the road...

My missus promises me she'll give me a treat in bed if I drive nicely. Needless to say I aint seen any action in a while :cry:

My missus just tends to scream "dont kill me" at the top of her lungs... Kind of puts you off keeping your eyes on the road...

 

 

put something in her mouth to keep her quiet :D

i read a stat somewhere saying that the auto beats the manual to 100mph

if you want to change gear wilst on full boost in a manual, with out over reving, it should be easy if you have R.L.T.C. you put in a clutch switch that gives you a second rev limit. you dip the clutch it drops the revs down to a set level whilst still having you foot planted to the floor.full throttle gear change so they say

i read a stat somewhere saying that the auto beats the manual to 100mph

 

I read that too - on a US based 'site. Think it's something to do with the number of gear shifts required with the manual - perhaps loss of revs when coming off accellerator and onto clutch. In the auto, you just keep your foot to the floor, thus maintaining revs (and boost pressure) all the while.

 

But TBH, I drove both versions when looking for my Zed and there was very little in it.

 

I have an auto and for overtaking ability there is a fantastic sense of "urgency" when I press the accellerator to the floor ;)

 

Richard :D

Since I have the afternoon here at work with nothing to do, I'll attempt to explain this according to my understanding.

 

First to clear a few misunderstandings:

 

The revs shouldn't rise (significantly) until after the gearbox has kicked down. If this is happening you probably have a gearbox problem, or are maybe misunderstanding what is happening. The revs will rise because you are in a lower gear than you were previously, the same occurs of course when you change down a gear (or two!) in a manual.

 

You are right in that in a manual you down shift first then accelerate whereas as auto can't read your mind and will only down shift once you've pressed the accelerator. However, a healthy auto should be able to change gear much quicker than the turbos would take to spool.

 

Therefore i would suggest that there is more apparent lag on an automatic because you are waiting first for the gearbox to respond to the throttle input, and then for the turbos to spool before you really start accelerating. A good manual driver will already be in gear so will only have to wait for the turbos. However, if the manual driver is not fully on the ball, then the opposite can be true. An automatic will change gear much quicker than any driver could so if the manual driver also had to allow time to change because he wasn't already in the best gear, then overall, the automatic would be ready to go in less time. To add confusion however, the automatic cars have smaller turbos that have less lag than the manual cars so not only does the manual lose boost when changing gear, it also takes longer to build it back up.

 

Also, the automatics accelerate quicker to 60 mph for various reasons. The easiest to understand is that the automatics although having less power, and more transmission loss, have more under curve area for torque. Secondly, the automatic cars don't lose boost between gearshifts and can also shift more quickly. And finally, and most difficult to understand is that the torque converter acts as a 'slipping clutch' at lower rpms. This allows the engine to spin faster than it really should for the given gear ratio. The higher the engine speed the more power there is and therefore more acceleration. That is why automatic gearboxes typically have fewer gears than a manual. Of course you can achieve the same with a manual car by slipping the clutch, but you will cause damage.

 

Overall, I would suggest that the manual cars have much better 'in-gear' acceleration but lose out when measured 'through the gears'. If you see what i mean!

 

The internal mechanics of automatic and manual gearboxes is very different, and very difficult to explain. Have a look here and search on gearbox for a graphical demonstration of the two:

 

http://www.howstuffworks.com/

 

Hope this helps a little!

the official 300zx brochure says the manual 0-60 is 5.6 (TT) and the auto is, wait for it, 7.4 (TT as well)!!!!! it's true! the test pilot never heard of wide open throttle then obviously...!!?!??

 

the thing that annoyed me at the time was that i had a serious oil leak and ptu problem and my car was only making just over 7 second 0-60s, no matter how perfectly i tried to launch it. almost made me ashamed of the car. then i took it in and the problem got found and sorted, added some mod magic and am pushing about 5.1 :D :D :D :D :D oi lurve moi auto z

Good post Rory!

 

I'd also add that the gears ratios are different - hence shift points in different places. For instance 0-60 is quicker but 30-70 is slower.

 

And you were talking in general terms...

 

On the Z specifically there's another difference - auto cam profile and tubs are tuned a little bit more towards torque and away from peak (and peaky) power. Therefore a stock auto is a bit more responsive than a stock manual - but over a long acceleration run there's more area under the curve in a manual.

 

Which drivetrain is lighter incidentally?

 

Fuserleer - you can manage the lag as you describe - I do it in the Leon all the time (clutch seems way overspecced for the amount of torque so it doesn't do it any harm - still on original at 70k plus)

 

A light flywheel means that engine speed is more directly related to throttle position - which makes it much easier to pick the correct engine speed when engine not connected to wheels. It also means the rev drop between gears happens more quickly which means the clutch can be re-engaged more quicky.

 

Had quite a long conversation about this at Baggins one afternoon and then he took me for a spin in his auto... I don't think you could beat the downshift speed - but on the other hand an alert manual driver will not need to downshift suddenly at any point. Upshifts are about the same if competent. The greater amount of slippage from the torque conv more or less balances out the turbo lag advantage.

 

I suppose the main difference is that the auto is consistently better than a merely average manual shift, so unless every manual shift is spot on the auto will win out over time.

 

Of course a car with linear torque delivery, six ratios, and a 9k rev limit is much better all round. :D