???? (KA-T, Auto Vs. Manual transmission)

[pilgrimage]

i recently heard that a KA-T with auto tranny is faster than a KA-T with standard tranny is there any truth to this i searched it in the forums and didnt find anything?:confused:

[huntz0r]

umm, you might try a more descriptive title... anyway, I will try to theorize on this subject.

***uming we are talking about drag racing, any given car can be faster with an automatic versus a regular manual transmission. There are a few basic factors in that like:

-how the auto is set up... upshifts at the optimal rpm? shifts aggressively? usually stock automatics are suck on those two points, and therefore would not be very fast.

-how good the driver is. it's a lot easier to launch an auto consistently than a manual with a clutch, and automatic transmissions don't miss the notches.

-gearing. If you use four gears in a manual car to get to the finish and only two in an auto, then the manual might be allowing you much better use of the power curve than the auto due to the relative closeness of the gears. Of course, the auto will also be shifting fewer times. The benefits here depend on the torque curve, but in the case of a high-power KA-T I would guess the manual setup to be better as a small displacement engine, the power range will most likely be relatively narrow.

So there's not necessarily one answer... now I would guess that in general if set up properly and built well enough to take the power and abuse, an auto may well be faster in a straight line simply by the virtue of being easier to use. I think a "normal" auto would not be a match for a well-driven 5 speed, other things being equal.

And then there's the consideration of how an automatic sucks the fun out of pursuits that involve more than accelerating in a straight line, which is not what a 240 was primarily meant to do... but that's another topic :p

[AKADriver]

One other thing; with the auto you can brake-torque it at the line to load the engine and spool the turbo a bit.

[GlacierFreeze]

You can rev the manual up to any rpm to spool it more and just slowly let off the clutch. Right?

[AKADriver]

No, because it won't be under load.

[GlacierFreeze]

Ahh okay, I see. I can understand that. Newb to manuals btw...

[twitchy]

couldnt you load the tranny kind of like...using the e-brake.. Im thinking like youd have a load and not be pulling forward though you wouldnt have your clutch out all the way or it would stall right...having trouble picturing this... any thoughts?

[huntz0r]

Well in that case you'd be smoking off your clutch.. probably not a real good solution.

[transient]

Ok, think of it this way. When the clutch is engaged (pedal out) then your engine is directly connected to the rear wheels. That means that if you're not moving, neither is your engine.

Auto's are set up differently. Instead of a clutch, there's a torque converter, which uses ATF fluid passing through it to transfer power to the rear wheels. There is no direct connection between the engine and the wheels (until torque converter lockup).

[Jeff240sx]

You'd need a helluva brake setup to brake-boost on our cars.
My car, about 200rwhp, couldn't hold traction at the rear wheels past 2000 rpm, and this is with sticky Z-rated tires. My turbo spools at 3600rpm... so I chucked the auto in favor of a manual.
Also, many people at 5psi run about 14.0... I ran a 14.8 in my auto.
-Jeff

[X3M]

how much hp or psi can the stock auto tranny handle before upgrades are needed

[Jeff240sx]

Around 350rwhp.
-Jeff

[X3M]

koo, and its approx. like 10hp per pound of boost right

[transient]

You can't really figure it that way. There are sooooo many variables to be considered.

[X3M]

yea i was just goin by wat u hear thats usually close to the normal amount
dont know much about cars only hear-say so i love being corrected