[HEMI V8]

Hello folks,

I have the predator, with CAI if that makes any difference in my question..

What is the best rpm to shift?

the stock 5500 or 6000 or 6250?

or maybe 5700 or 5800?


Which is better for acceleration?

is 6000 and 6250 safe?

some people do not recommed shifting at 6250 as it is not good for the engine? why is that?

I usually shift at 6000 rpm..

If you can please explain to me why either of these rpm's is better than the other or safer...

 

[wickedchargerrt]

Each car is different and you need to dyno it to find the answer to your question. Ideally you want to shift where you will drop into the next gear prior to hitting the powerband in that next gear.

you have no need to raise shift points on your current mods. thats dangerous and worthless. You need no higher than the stock 5750ish until you get a cam and heads.

Remember the power band starts falling off prior to redline on this car. Going 6k rpm isnt anymore power than 5k perse.

 

[gcarrick]

My 3.5L has always shifted @ 6250 with the stock tune, and with predator tune...is this normal?

 

[soxfan4eva]

I don't think it's good to shift that high of an RPM, when I had a standard I would shift between 3000-4000. Any more than that the engine would rev higher but no gain in power. I can't imagine it's a good thing for the engine & tranny to be in the 6,000 rpm range on a regular basis.

 

[Gladiator]

I usually shift between 3-4k when in autostick.

 

[gcarrick]

yes, manually i shift @ 3-4.5k, just to keep the load down. or less depending on traffic....i miss my clutch. but stomp and let it shift itself, it is @ 6250

 

[Junior]

Raising the shift points is about the torque you make after the shift, not the power you make before the shift. A stock 5.7 stops gaining power at something like 5600 rpm - it's not that it stops making power, it's just that it stops gaining power. In other words, the power curve flattens out.

But the ideal shift point is the one that drops you into the next gear at the top of the torque curve. Without putting it on a Dyno, you won't really know what peak torque is, but on a stock 5.7, it's something like 4400 rpm.

So the idea is that you want to watch what RPM you arrive at AFTER the shift, and adjust your shift points so that the RPM you arrive at is near that 4400 mark.

Couple things to watch out for: unless you have upgraded your valve springs, you don't want to be shifting above 6250 or so. What'll happen is the speed of the motor is faster than the stock springs can keep up with, and you can end up with a piston coming up before the valve has fully retracted. That's called valve float, when the valvetrain is moving faster than the springs can keep up with.

Short answer, though, on a stockish motor is that the raised shift points on the Predator are OK, and will probably help a bit, but don't put them up at 6400 without upgraded springs.

 

[Repth]

Raising the shift points is about the torque you make after the shift, not the power you make before the shift. A stock 5.7 stops gaining power at something like 5600 rpm - it's not that it stops making power, it's just that it stops gaining power. In other words, the power curve flattens out.

But the ideal shift point is the one that drops you into the next gear at the top of the torque curve. Without putting it on a Dyno, you won't really know what peak torque is, but on a stock 5.7, it's something like 4400 rpm.

So the idea is that you want to watch what RPM you arrive at AFTER the shift, and adjust your shift points so that the RPM you arrive at is near that 4400 mark.

Couple things to watch out for: unless you have upgraded your valve springs, you don't want to be shifting above 6250 or so. What'll happen is the speed of the motor is faster than the stock springs can keep up with, and you can end up with a piston coming up before the valve has fully retracted. That's called valve float, when the valvetrain is moving faster than the springs can keep up with.

Short answer, though, on a stockish motor is that the raised shift points on the Predator are OK, and will probably help a bit, but don't put them up at 6400 without upgraded springs.

Good man! Thanks for going in-depth about why it is that certain things make the car faster rather than just throwing out a number. Makes it easier for less car-literate people like me to start to catch on.

 

[Junior]

Good man! Thanks for going in-depth about why it is that certain things make the car faster rather than just throwing out a number. Makes it easier for less car-literate people like me to start to catch on.

No worries - just trying to help out like I was helped...

Also, I forgot that the V6's do shift higher than V8's from the factory. The 3.5L shifts at 6400 stock (except for the 1-2 shift, which is always a bit lower than the rest of the shifts - true on the V6's as well as the V8's). So all the stuff I mentioned in the prior post applies to the 5.7L.

The theory is the same for the V6's but I don't know the target numbers...

 

[HEMI V8]

I was talking about shifting at full throttle

thank you guy and thank you junior, great information... it really helped...

 

[aliveguy5]

Here is a little more... Typically you want to set your wot shift about 400 rpm past your peak power. The reason why is you're power hasn't fallen of the board yet, and when you shift you will shift right in the meat of the power band. Meaning none of that second or two bog until the engine winds back up. It's just shift and go. However with you mods... leave it stock.