The JATCO 5AT in the G/Z can complete an upshift in about 200 milliseconds assuming you're a WOT. Shift speed is usually based off of line pressure which is based off of engine vacuum, throttle position, load, etc. The higher the line pressure, the quicker the shift. The JATCO 5AT doesn't behave like your Mom's Grand Caravan 4AT. I'll agree that there are many lazy autos out there, but the JATCO isn't one of them.

Here are some of the advantages of an auto:

1) Quick shift speed. Thanks to the design, the next gear is always engaged so the upshift can be completed almost instantly. This is why you don't get the rocking motion/load shift on each shift like you do with a manual. The DSG trannies behave basically the same way. Newer autos are now able to execute upshifts and downshifts as quickly as 50 milliseconds. I imagine the upcoming JATCO 7AT will be able to this because the current 5AT in the 2nd gen G is almost there.

2) Torque converter. A TC is a torque multiplication device and can increase wtq on the initial launch (0 to 5mph) be around 2.5X to 3X. This is what is commonly refered to as stalling up the TC. The TC in the G is very efficent and has a high stall rpm (~2,800rpm). Both of these are good traits for drag racing.

3) TC locking. All TCs will lock at part throttle and will have a direct connection to the engine (like a manual) at cruise. This improves MPG. The JATCO 5AT takes it one step further by locking 2nd (top of 2nd gear only), 3rd, and 4th gears at WOT. This greatly improves acceleration in the upper rpms. This is why the 5ATs typically see similiar traps speeds to the 6MT.

4) Gearing. The 5AT is ideally geared for maximum acceleration. Lots of autos are geared for MPG and cruising. The JATCO 5AT in the G is not.

5) Weight. The compact 5AT weighs about 35lbs less than the 6MT.


Disadvantages:

1) Can be slow to downshift in auto mode. Some people think it's slow to downshift in manual mode too because they expect the shift to occur the second the shifter is moved. The current 5AT isn't that quick to react. Anyways, a manual driver would still be hard pressed to execute the downshift as quickly.

2) MPGs. The 5AT will see about 10% lower mpgs around town.

3) Power. The 5AT sucks out about 10whp/10wtq.

4) Lack of total control. I think this one is silly. I always hear about how with a manual you have total control of the car. I feel no more connected to my 5AT G than I did to my other 4 manual cars I've had in the past. I have total control over what my auto is doing.

 

DaveB u have yet to prove that stock AT tranny traps the same as 6MT, u do realize the difference in acceleration when both trannies engage to 3rd gear. Simple explanation to it is that 3rd gear on the 5AT lands ~500-1000 rpm lower than that of a 6mt, So even if 2 cars make identical numbers on a dyno, the car that lands lower rpm next gear is going to accelerate slower due to making being in lower RPM, than the car that lands in higher RPM in our case being 6MT. U trapping 99mph does not prove anything because dragstrips are like dynoes, every track is going to have completely different numbers. Our cars can go anywhere from 15.5 all the way to 13.7 in stock form and trapping from 93mph all the way to 102 mph. I am talking about first gen sedans. I would love to demonstrate this to u in real life just do a 60-80 roll, me being in a bone stock 6mt.

ONE prime example of my claim is with OCG35 who has one of the fastest N/A G35s right now in socal. Before he did his final drive because of his driving skills beat me by 1/2 a car having much more power than my car back then me. We did had identical ET but i still trapped 1.5 mph more than him. Why, because of AT gearing! When he did his final drive he started trapping higher than me! Why? Because his gears are much shorter than stock 5AT gears there for his RPMs land much higher than before when he shifts no next gear. If u want to see a good automatic tranny drive the 335, GTI with DSG then u will see how POS (first gen) G35's autos are.

STOCK 5AT is ALWAYS going to accelerate slower than 6MT, no point of arguing this.

 

W/e! We dont gulp and burn a quart of oil every thousand miles !!!!!
Lousy clutch at that too!

I still like my auto! even though i wouldnt mind a 6MT.... Even with its minor flaws here and there.

 

Since we're bashing 6MT's.. How do you guys like that 3rd gear grinding all the time? lol

 

I seriously lol'd at how fail this post was...

Please stop fighting for a garbage 5AT system the comes in 1st gen G's...its terrible

and BTW the fastest G35 currently runs the 6MT...I wonder why

 

Like he had a choice? It's not easy swapping back/forth.

Also if manuals are so fast what do the fastest drag cars (not just G35s) run?

 

stock for stock, a G will pull a GT all day, with a tune on both, the GT will romp on a G

 

serious draggers run autos no question. auto's are much better for sub-9 second drag racing.

 

DaveB is not talking about automatic vs manual in general, those points that he brought up were on first gen automatic vs manual.

Fastest drag cars don't have 200-400 hp FYI, hence there is a reason to have an automatic drag car that will put down 500hp and above.

 

And those reasons don't apply to lower hp'd cars also? Why not? There are a ton of muscle cars running turbo 400 automatics at the 400-600hp mark.

 

The reason it doesn't apply to lower HP cars because it is easier to put down power on lower HP cars with manual tranny. Shifting 1st - 2nd in a 800hp car can cause disaster. There was a reason when i was stock, automatic g35 were running 0.5 seconds slower on every track, any day, any weather.

I don't think im the greatest shifter in the world either.

 

Gearing? Did all these autos run the same gear ratios as the MT guys? ie.. at least the rear end ratio?

I'm requesting a specific technical reason why autos are worse for drag at any hp level.

 

Yes, the main reason is the final drive, as i stated in post #32, the secondary reason is the power. Any manual car will generally make more power than its automatic version. 3rd reason, is simply faster shifts with 6mt with a decent driver. The only downpart to it is missing a gear especially in our cars.

 

What it boils down to, is for 'typical' cars, the MT is faster. When you get to the extreme end of drag racing, AT is faster.

 

Okay so if we just assume for the sake of argument, the ratios inside the auto = manual. And it's just the final drive. Well that's not a short coming of the auto, it's just how Infinti decided to option the auto tragic car.

More power is not really the way you want to describe it. Put both engines on an engine dyno and measure it. I think you want to say the manual has less driveline loss. But once the auto locks, there should be no more losses vs the manual.

Faster shifting? You sure you can shift faster than auto? I can stomp on the gas and manu-shift with my foot WOT. No clutch pedal push, not gear shift action and no lifting up on the clutch pedal.

I think you will find that an automatic tranny shifts much faster than a human. And that's the torque convertor types. The twin clutch DSG types are probably 2x faster than that.

It's not a function of a "decent" driver vs auto. It's a function of the mechanical speed vs any human having to perform 3-4 steps. Each one having to be performed one after the other. The more steps you have to perform, the more lag inbetween each one there is.