firepinch

Hey guys,

I was not able to find a tread on this for our Cobalt SS/SC.

When we have smaller pulleys with custom tunes, we can set our rev limiter up to 7500 RPM. But really, do we make power up to that point??

When you race, what are the best shift points? For example from first to 2nd, 7200 RPM, from 2nd to 3rd: 7000 RPM etc...

I can't feel if this is better to shift at 7200, 7000, 6800 RPM. Sometimes I shift at 7400 but I don't even know if I'm loosing power by shifting that high with my car. I didn't pay attention to the differences I could see at the track by using different shift points.

Experienced racers, what are the best shift points for our car?? Does shifting passed 7000 RPM really make a difference?

Thanks!

stoon_cobalt_colby

sub for info was wondering same thing about a week ago... let us know guys

Bl4des

iTrader: (4)

you shouldn't be revving you car to 7400 with out valve springs

08slatecobalt

I would be inclined to say that in order to really know the best time to shift your car is to have a dyno sheet on it. That way you can see the powerband and be able to determine the best shifting points. IMO the best shift points vary from car to car. Just my .02

gwatson650

this.
some cars make lower power right before redline.

DSmastery

iTrader: (5)

dyno the car, to see if the car makes power at those rpms ranges and yea 7500 redline is for vtec haha jk

shift at 6800-6900

i have limited boost in 1st redline is 6500.....never is enough haha and the rest is 7k but i shift at 6800-6900

it depends on where power is being made

EDIT: u guys got it out 1st haha

firepinch

But the thing I don't understand in dyno sheets, because I see many, is how to know where to shift??????

For example, if you shift at a higher point, you fall in higher RPM's right? If you shift at 7200-7300 RPM, you may loose a little bit power but ONCE you get into the next gear, you start with higher power right?? So you make more power overall?? I NEED TO MAKE THIS STATEMENT VERIFIED!!!

I don't understand how to evaluate a dyno sheet and to say you have to shift at these points because of the thinking I have just above...

Please tell me the science behind this so I can understand fully how you loose or make power with different shifting points...

08slatecobalt

My understanding is this...


Just using fake numbers here and feel free to correct me please. If you make peak power of 425 at 5800 and by the time you hit 7000 it drops to 300, you need to then look at the power created before 5800. Say you shift at 6000 and the next gear drops to 3400 you then need to look at the power produced between 3400 and your peak of 5800.

Again, this is my understanding and guessing at all of this...and yes going to high in the RPMs without proper work to the motor can be dangerous.

beefbusta

me personally i've found that shifting immediately after hitting the peak of the dyno sheet per gear give me the best times in the 1/4 mile.

rnjmur

This is basically right, but you have to remember that the torque also has to factor into the powerband as well.

terry11

iTrader: (6)

short shift 1-2 if you want better times. helped me alot. 5500-6000

08slatecobalt

Thank you for adding to this...I knew I was forgetting something. Torque does play a big part in it as well.

insylem

After looking at my Dyno data, and useing observations of RPM to MPH in diffrent gears, I created a chart for what RPM at each speedin what gear ect....
Then used the chart to find shift points so that the gear im going into will be just entering my high torque zone. I Determined that I should shift to 2nd at 6,000, then 3rd at 6,000, then 4th at 5,000, and 5th at 5,000 although that would be a long race...

restonSS

idk if id shift at 6k but i found that between 6500 and 6700 is best. ive been on here a while and when i first got on a lot of the knowledgeable guys all said this.

wbrevels

iTrader: (2)

cobalts stop making power between 5.9-6k, clear image said not to lengthen my redline for that reason.

rnjmur

With stock cams the power starts to fall off right around 6.5K on an SS/SC. The TQ peaks at different rpms depending on what pulley you are running.

firepinch

But my understanding is still not clear...

I'm gonna picture bit an example:

Case #1: End of second gear, 7200 RPM, 250 hp.
Third gear, 5500 RPM, 180 hp.

vs

Case #2: End of second gear, 6500 RPM, 255 hp
Second gear, 4800 RPM, 155 hp

In the case #2, you have 25 less hp than the first case once you go in 3rd gear, but you didn't loose 5 hp at the end of the second gear. So you have a 20 hp disadvantage.

Case #1 to me, is better... this is my understanding but I'm not sure that I'm right at all. This is why I want to verify my understanding with other more experienced people...

So heres the thing I think. If you shift at lower rpms then you just gonna hit less power when shift into the next gear. Yeah you gonna lose some power running it to redline, but the next gear that you shift into will be closer to peak power. So why not shifting always at 7000-7200 RPM?? I don't get it... Please explain...

chris88z24

Learn to drive the car by feel/sound. I shift when I hear the blower/engine at the right frequency, which works good considering the tach is rather laggy.

2-3 is fun to look at the gauge and flat foot shift ~7000 with the needle in the red zone, however.

Zach06CobaltSC

Shifting at higher rpm's will leave you with more power when you hit the next gear, you are also staying in your powerband longer. You have more power at 6800-7200rpms then you do at 3-4k so why worry about it? The longer you can stay in your power band the better. The less shifting you can do in a 1/4 mile the better also. This is why some guys rev out to 8grand and trap in 3rd with valve springs obviously.

False statement. A car does not stop making power at a certain rpm. Sure the car can produce LESS power at a certain rpm, but you are still far off. Our cars can produce power all the way to redline. Shifting between 5900 and 6k is a bad idea, especially when our cars are still making power up to 6900 rpms and more.

freakta

iTrader: (1)

you dont lose hp in different gears... your car will make he same chp per rpm through the band in any gear.

if your car makes 200hp at 5k and 180hp at 7k shift at k in first and second then 3,4 shift a bit earlier. too early will drop you out of your tq band when shifted

too many factors in play to know when whos car makes power where.... but as a general rule the m62 cars powerband dies off about 6400 the tvs cars power dies off about 7400... change cams change powerband.

wbrevels

iTrader: (2)

true, i personally and going to ride faily conservative... if it was for best 1/4 mile time i'd rev out but i dont have the money incase anythig goes wrong. i guess by not having my redline extended i wont stress my engine as much, considering its a 2.2

terry11

iTrader: (6)

haha

rnjmur

Case #2 is best. The reason is that you are still forgetting to factor in torque. Once you factor in torque you will see something like this:

Case #1: End of second gear, 7200 RPM, 250 hp/160 tq
Third gear, 5500 RPM, 180 hp/220 tq

vs

Case #2: End of second gear, 6500 RPM, 255 hp/170 tq
Second gear, 4800 RPM, 155 hp/200 tq

In Case #1 you are shifting into peak torque, but torque will be falling off quickly right after. In Case #2 you are shifting into slightly lower torque but you have the rising torque to help accelerate out of the shift change.

Do_WorkSS

i cant believe someone would redline their car at all. I have never red lined my car since the day i bought it. im too afraid of seeing something flying through my hood.

wbrevels

iTrader: (2)

isnt ur sedan automatic? that would be hard to redline wouldnt it?