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2009 G8 GXP
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446 Posts
Discussion Starter #1 (Edited)
It would be cool if somebody with the knowledge and equipment can make a video like this....


how to downshift (speed , rpm range for each gear) for the street, driving in mexico, road course, autocross etc.

how to quickshift for the street, drag strip, road course, autocross

how to burnout at the track etc.
 

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GWS Pontiac
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634 Posts
your linky be wrong:

Wheel center cap for V6 rims
 

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Grand Poobah
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294 Posts
your linky be wrong:

Wheel center cap for V6 rims
Excellent. Thanks for the free bump on my wheel cap for sale ad!:)
 

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Moddin' and Roddin'
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793 Posts
6th to 5th is about 500 RPM's difference I want to say. 5th to 4th definitely is. 4th to 3rd is 1000 RPM higher, so it takes a pretty good pop of the throttle to match that shift. 3rd to 2nd is another ~500, maybe a little more.
 

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2009 G8 GXP
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446 Posts
Discussion Starter #7
What are the rpm and speed ranges for each gear. I assume it is different when you upshift (1-2-3-4-5-6) vs downshift (6-5-4-3-2)?
 

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Moddin' and Roddin'
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793 Posts
What are the rpm and speed ranges for each gear. I assume it is different when you upshift (1-2-3-4-5-6) vs downshift (6-5-4-3-2)?
Not at all. Depends on the setting (street vs track), what you need, etc. The RPM and speed ranges per gear for your car are mechanically fixed points. RPM ranges, of course, are 0 - 6600 (redline) for each. Speed range varies per gear.

But between all that, where and when you shift is entirely up to you and what you're feeling and needing at the moment. Generally you want to keep the RPM's up such that your engine is always running close to peak power. So if you're in fourth and your revs are sinking below three grand, downshift to third. If you're still braking and your revs are sinking below three grand again, downshift again. That kinda thing. But there is no hard-and-fast rule.

For instance, there's nothing to keep you from downshifting to 3rd when you're already turning 4000 RPM's. It'll just put you up to 5000 RPM's and you won't have that much left on the tach before you have to shift back to 4th. But if it helps you get out of the hole and you gain more time with the acceleration than you lose by the brief shift, then... do it!

Generally, when on track, upshifts happen at redline. When you're on the street... Again, whenever. It doesn't really matter.

Just for the heckuvit, some gear/speed calculations for the M6 GXP...

Gear ratios are:
1st: 3.01
2nd: 2.07
3rd: 1.43
4th: 1.00
5th: 0.84
6th: 0.57
R: 3.28

Final drive is 3.70:1 for GXP M6.

That gives us final gear ratios of...
1st: 11.137
2nd: 7.659
3rd: 5.291
4th: 3.70
5th: 3.108
6th: 2.109
R: 12.136

So if you peg your engine at 6600 RPM's, then in each gear at the wheels you'll get (in RPM's)...
1st: 592.6
2nd: 861.73
3rd: 1247.4
4th: 1783.78
5th: 2123.5
6th: 3129.44
R: 543.84

Radius of wheel + tire for 19" wheel and 245/40R19 tire = 13.358 inches.
That nets a circumference of 83.93 inches.

So to get the MPH from the RPM's above, multiply them by the inches above and then multiply by 60 (for 60 minutes in an hour). Then finally, divide by 12 (to convert to feet) and then by 5280 (to convert to miles).

That gives us our theoretical maximum speed in each gear:
1st: 47.1 MPH
2nd: 68.49 MPH
3rd: 99.14 MPH
4th: 141.77 MPH
5th: 168.77 MPH
6th: 248.73 MPH (yay overdrive gear!)
R: 43.22 MPH

Anyone, feel free to correct me if these seem off.

But basically, once your speed falls into a range that's accessible to the next gear, if downshifting would put you back into the power band... downshift!
 

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2009 G8 GXP
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446 Posts
Discussion Starter #9
Eidolon, thanks for the great info. This should be a sticky.

But for example I am driving on a highway in mexico. Cruisin 60-65 in 6th gear. All of a sudden another car pulls up in the next lane and wants to play. He honks off .....
do i downshift to 5th (Tried not effective) ?
do i then go the 4th (Tried not effective) ?
Go directly to 4th (Tried effective some times but not really)?
Go directly to 3rd (too chicken **** to try....)

Since you refered to power band. maybe I will refrace the questions....
what gear should I be in to make most effective use if the power band of the engine ? then what speed it would be ok to downshift to that gear and be safe?

For ref. I uploaded a dyno graph of the LS3 that I found on the web. This may not be the extact one for a stock GXP M6..
 

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Moddin' and Roddin'
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793 Posts
Taking your post in pieces and out of order...

Eidolon, thanks for the great info. This should be a sticky.
Absolutely. Hopefully a few others, such as MFE or toedrag will also chip in on this, just to make sure my info is correct.

For ref. I uploaded a dyno graph of the LS3 that I found on the web. This may not be the extact one for a stock GXP M6..
The graph is informative because torque remains relatively level, but power continues to build even after the torque peak. In short, there's no reason to cut a gear short until you get north of 6000 RPM's. But even then, as power begins to fall off after the peak, it falls off less than the reduction you'd get by shifting (because shifting drastically drops your RPM's). In short, if you're going for maximum acceleration, wind it up to redline.

But for example I am driving on a highway in mexico. Cruisin 60-65 in 6th gear. All of a sudden another car pulls up in the next lane and wants to play. He honks off .....
do i downshift to 5th (Tried not effective) ?
do i then go the 4th (Tried not effective) ?
Go directly to 4th (Tried effective some times but not really)?
Go directly to 3rd (too chicken **** to try....)
If you're cruising at straight highway speed, you likely want to get to 3rd.

To get RPM's in a given gear at a given speed, do the following:

Wheel RPM = (MPH x 5280 X 12)/(83.93 x 60)

(Simplifies to MPH X 12.582, by the way.)

Engine RPM = Wheel RPM x Final Gear Ratio

(Verified: I'm usually turning just a tick under 2000 RPM at 75 MPH in 6th. Run the numbers through the formula above and 75MPH in 6th = 1990 RPM's)

So at 65 MPH, your engine will be turning approximately the following RPM's:
1st: 9108
2nd: 6264
3rd: 4327
4th: 3026
5th: 2542
6th: 1725

First is obviously right out. But this list does let us answer your next question...

What gear should I be in to make most effective use if the power band of the engine ? then what speed it would be ok to downshift to that gear and be safe?
As noted above, you want to shift into the "power band". In this case, that means close to your engine's torque peak. That's where you'll get the most acceleration in any given gear. For us, that's right around 4600 RPM's, as noted on the dyno graph.

So based on the numbers I gave you right above, you want to be in third gear to get the most thrust from a roll race at 65 MPH. Shifting straight to third is a bit much just because your engine has to climb 3000 RPM's in one shift. You can do it, but that's quite a hold on the throttle. But you're definitely not going to over-rev the engine, not even if you managed to shift to second. So if you get any staging time whatsoever, perform a few throttle-blip downshifts, THEN hit it.
 

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Moddin' and Roddin'
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793 Posts
By the way, if you're looking for quicker upshifts, then you can use a technique a co-worker taught me. When you're in a gear and on the power, the gears inside your transmission are machined such that they lock together. But when you clutch in, the fact that the engine is no longer applying torque to them lets them slide apart.

So what you can do is apply pressure to the gearshift while your car is still in gear so that as soon as you clutch in, it pops out and you're already shifting to the next gear. It's just a hair quicker than letting the gearshift sit, clutch in, THEN apply pressure to move it.

Again, don't apply a LOT of pressure. It only needs to be the same amount of pressure you'd apply to the gearshift if your car were sitting with the engine off in your garage.
 

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2009 G8 GXP
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446 Posts
Discussion Starter #12
1st: 9108
2nd: 6264
3rd: 4327
4th: 3026
5th: 2542
6th: 1725

By the way, if you're looking for quicker upshifts, you can do is apply pressure to the gearshift while your car is still in gear so that as soon as you clutch in, it pops out and you're already shifting to the next gear.
everything you posted makes sense, but wish i could see it in person or a video....

but I am going to note these rpm's down on a post it note and your technique and try it on the way home.

How do you roll race from 30mph ? slowdown the car enough to put in 2nd gear at about 4500rpm and then punch it?
 

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I rev match if Im going from one extreme gear to another, like 5th to 2nd. Normal daily driving around town (less than 55 mph) I see not much more than a 500 rpm difference when shifting down just 1 gear.
 

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Moddin' and Roddin'
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793 Posts
everything you posted makes sense, but wish i could see it in person or a video....

but I am going to note these rpm's down on a post it note and your technique and try it on the way home.
I'll see if I can't rig something up. I have an ancient point-and-shoot sitting around somewhere that does do video.

How do you roll race from 30mph ? slowdown the car enough to put in 2nd gear at about 4500rpm and then punch it?
That I honestly don't know. I've never roll raced anybody in any setting. So I can tell you what engine RPM 30 MPH will get you to (4200 RPM in first!), but for technique and the like for THAT particular setting... No clue.
 

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Moddin' and Roddin'
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793 Posts
I rev match if Im going from one extreme gear to another, like 5th to 2nd. Normal daily driving around town (less than 55 mph) I see not much more than a 500 rpm difference when shifting down just 1 gear.
True. I usually try to rev-match even at that point just for the heck of it. It's good practice.

I'll see if I can't get a graph up of the speed ranges and the like of each gear. You know, in all my free time. :)
 

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Not at all. Depends on the setting (street vs track), what you need, etc. The RPM and speed ranges per gear for your car are mechanically fixed points. RPM ranges, of course, are 0 - 6600 (redline) for each. Speed range varies per gear.
Just curious to know why our tachs don't actually have a redline indication?
You say it's 6600 RPM's, but how would I know for sure?
 

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Not sure why there isn't a redline indicator or at least a shift light, it is a huge oversight in my opinion.

As to you how to find out where the rev limiter kicks in, you can either accelerate in gear until it cuts fuel/spark and check the tach or better yet ask someone to post the rev limiter tables from their stock computer tune - I am sure this info is floating around here somewhere.

The tach does not keep up with acceleration in 1st gear so you have to anticipate it. Not sure about 2nd gear and up. Also, I feel like the rev limiter is slightly different (100-200 rpm) depending on which gear you are in, but someone with the downloaded stock tune can confirm this.
 

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A red line or shift light would have been awesome. Good thread!
 

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Moddin' and Roddin'
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793 Posts
L76 redlines at 6000 RPM in stock form. Due to AFM hardware and heavier valves (solid intake as opposed to the hollow-stem intake in the LS3), its peak is lower than the LS3. LS3 redlines at 6600 RPM.

Just curious to know why our tachs don't actually have a redline indication?
You say it's 6600 RPM's, but how would I know for sure?
You'd have to ask your tuner, read around the 'Net - because a LOT of journalists complained about the lack of a redline - etc.

But my redline was bumped up to 6700, if memory serves, to provide a bit more room to shift.

As to you how to find out where the rev limiter kicks in, you can either accelerate in gear until it cuts fuel/spark and check the tach or better yet ask someone to post the rev limiter tables from their stock computer tune - I am sure this info is floating around here somewhere.
There's also those methods. :)

The tach does not keep up with acceleration in 1st gear so you have to anticipate it. Not sure about 2nd gear and up. Also, I feel like the rev limiter is slightly different (100-200 rpm) depending on which gear you are in, but someone with the downloaded stock tune can confirm this.
Yeeeeah. It's annoying.
 

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Taking your post in pieces and out of order...

So at 65 MPH, your engine will be turning approximately the following RPM's:
1st: 9108
2nd: 6264
3rd: 4327
4th: 3026
5th: 2542
6th: 1725

So based on the numbers I gave you right above, you want to be in third gear to get the most thrust from a roll race at 65 MPH. Shifting straight to third is a bit much just because your engine has to climb 3000 RPM's in one shift. You can do it, but that's quite a hold on the throttle. But you're definitely not going to over-rev the engine, not even if you managed to shift to second. So if you get any staging time whatsoever, perform a few throttle-blip downshifts, THEN hit it.
I believe when the journalists tested the M6 GXP they said that for their 0-60 times they would just wind out 2nd gear to save a tenth of a second or two that would have been lost on the upshift to 3rd. I use that as a quick reference point when I'm choosing which gear to drop into.
 
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