Best RPM to shift?
 

I have heard a lot about 5spd cars....but what about autos? This is the first auto I have ever ran....it is mostly stock except mods listed below....

Just let it shift itself. Launch off idle, dont rev it up.

Really? I have never raced this car yet...I have raced only 5spd's, so I am not new to racing...but I am new to Autos...

I thought it would be better to stall the stock converter up...and shift manually.....but again, I have no clue on the autos!

Thanks!

stall it up. its always faster this way. my truck got a tenth better 60' when it had the stock when i stalled it up as high as it could go ( which was like 1,800rpms lol).

Just try both ways, see what works better for you.

WTF is stalling up?

With an auto and in drive, you push down on the brakes and rev up as high as you can (before the tires spin) and launch off that. Everyone Ive talked to has recommended launching off idle. When you launch off idle and floor it, I think your rpms will jump up higher then they will if you try to stall it up. But like I said try it both ways, itll be interesting to see the difference you get between the two methods.

Yep what he said. Launching from idle is called flashing the converter, and yes you will get higher in the rpms this way. I can foot brake to about 2500 but I can flash into 3500ish ( not really looking in that direction at that time :)) An auto without cams should be shifted pretty much right before rev limiter (6050rpm). Don't try to manually shift it...the PCM is more consistent and precise than ANY person is.

Adam

Awesome..thanks!

This car should be a killer braket racer...if I can launch at the same RPM every time...

Yep, thats the good thing about autos. Same lanuch and same shift every time. :thumbsup:

Yes, even with a lot of miles they are. My tranny is 128,000 old and at the NMRA Bowling Green event I ran 13.23, 13.21 and 13.19 in my 3 rounds. :toothy5:


Adam

I'd stall it up JMO but hey either way let us know your results

you have a cobra, you dont know what your talking about. :nono:

Ha ha..no sh#t. The only advantage to stalling up the car is when you need to cut a good light. I stalled my car up in BG, hence the slower times ( but R/T's were .023,.017,.123. If you shallow stage and flash the converter you will cut your best ET's. The biggest problem is when you have a loose converter...mashing it on the 3rd yellow cuts you about a .200 light. I have cut an .006 stalling it up and deep staging.


Adam

yeah if i had better tires i would floor it off the start but i always spun and cut a bad light. im more consistant stalling it at a lil pass the 1500 mark and i get 1.8 1.9 60 ft and always cut a 13.5 et. now that i have 3.73 off the line traction is a real issue got new tires to help remedy this problem.

It depends, I shift my stang at 6k but I have my redline set at 6500 so I just depends on your set up! If youre an auto get a good stall and a shift kit and you'll be good to go!

If you have stock cams, anything over 6k is too much. There are no good shift kits for the 4R70W except the J-mod. I shift 1-2@6400, 2-3@6350 and I have set the 3-4 to 7000, that way it will never shift into OD at WOT, which is an excellent way to destroy a tranny.

Why are you shifting that high? Even with VT stage 2 cams I dont THINK you should be shifting over 6k. Instead of making the 3-4 shift at 7k, why dont you just turn OD off?

how bout you just get a manual...

7K..damn...I don't even go that high..I'm guessing you have aftermarket cams!!

My little brother took an entire second off his quarter mile time shifting his automatic manually at his redline. :) But his car is old and doesnt have a computer.

You are better off getting an SCT chip with a track profile in one of the banks with the automatic shift points adjusted to where you want them.

As for "warming up the torque converter" with your foot on the brake, you will get much quicker launches and ETs that way then if you wait until the light turns green to give it some gas.

When your car is faster than mine I will shift where you want me to, or where you "think" I should, hows that sound?:) You set the 3-4shift at 7k because you will never get there. Believe it or not, my car can bury 3rd gear (D) pretty quickly on the street, so on a long deserted road, its very possible for me to have a WOT 3-4 shift which is why its set at 7000rpm. I shut off my OD off when I race. These shift points are WOT only.


Adam

Are you talking about bringing the rpms up a bit on the line by holding on the footbrake? If you are then that is completely untrue. Flashing the converter from idle....will ALWAYS yield the best 60's and ET's....FACT. Where do you guys get your tech from?

Adam

Where exactly do you get this "FACT" from? Because that "FACT" goes against the basic principles of how a torque converter works. Torque converters multiply the torque of your engine when the motor is spinning faster then your transmission. Like when your car is at a complete stop. By bringing up the RPMs at a stop, the fluid begins to flow in the pump, and you are kind of virtually raising your gear ratio until the turbine blades begin to catch up with the blades of the pump when you are moving. This can get your car off the line much faster then starting off from idle. That is, if you don't go crazy and give it too much gas and just spin your tires.

Hahahah alright man, I didnt mean anything by what I said so chill out, but Ill let you know next time I hit the track. For everyone else, just go out and try different ways, this thread is getting stupid.

5300 is where i saw my power drop off on the dyno

OK....lets take traction out of the equation and lets operate on fact. Take your car out and stand on the brake and then begin giving it gas until the tires start to spin and make note of the rpm's that this occurs. Now, do the same thing and stomp the gas from idle, your rpms will be much HIGHER when the car moves...this is FLASHING THE CONVERTER.....which allows a higher launch rpm than bringing up the rpm's gradually.
Now...there are blades in the converter, an impeller and a turbine, of these two the impeller blades are attached to the cover and spin at engine speed, the turbine blades however spin at the input shaft speed (which is what make the car move) The fluid coming off the impeller blades is pushed into the turbine blades, the amount of torque multiplication is based on fin angle. When the input shaft starts spinning, there is now a difference in input shaft speed and engine speed. This ratio is called the speed ratio. When the speed ratio is 1 the engine and input shaft are turning at the same speed. The ideal speed ratio is about 0.8, anything above that is just slipping and creating heat. Now that we know this, lets use some simple common sense.
I bring my car up onto the converter with the brake and gas...it brakes the tires loose at 2300rpm. Now how much torque multiplication do you think you have at 2300rpm?
On the other hand, you flash the converter and your rpms reach 3500 before your car moves...how much torque mulitplication do you have now?
You launch at 2300, I'll launch at 3500 and let's see who is faster?

The rate that the converter rushes the fluid from the impeller to the turbine isn't being debated and has no direct corrolation with what we are talking about. The amount of torque multiplication is whats being discussed, and you must flash the converter to get the most torque multiplication out of it period....this is not debatable. The only downside to flashing...is the fill rate( the time at which the fluid moves in the converter), it will be much shorter stalling the converter up. That is why people use transbrakes, they have all the benefits of flashing the converter and they also have the fluid pressure built up for instant release. Now for a person to say that the fill time by flashing the converter is slowiing them down, that is simply untrue, it will affect your reaction times but not your ETs(except in a positive way). I hope this has cleared some things up.

Adam

:sign5: Nice explanation Adam. As for Fox Body Authority, just stop arguing because you are wrong.

Thanks...everyone is entitled to their own opinion, but when you substitute opinion for fact, then you are steering people down the wrong road. I have made tons of mistakes when it comes to racing, performance mods, etc. there is no reason for anyone else to make the same mistakes I have, thats why I like to see good tech given out, not opinion. All of this aside, I have never cut better than a 1.89 60' stalling my converter up, and have cut consistent 1.77 60's flashing the converter.

Adam

If you want to be a serious "bracket" racer, install a manual valve body with transbrake in the transmission. Then get the car on a Dyno, and find out where the car makes peak power and peak torque. Always launch 3-400 RPM short of peak torque (let it flash) and shift 200 RPM past peak power. Also install a rev limiter that holds the car at that RPM before you launch. If using a shift light, make sure you compensate for the delay in time, from the time you see the light, to when you react to the light, and when the car actually makes the shift, and set the light accordingly. At 5 or 6000 RPM you can be 500 RPM past your shift point during that time.

Ron