Number Crunching GM's Performance Update

[Bogie]

Current 0-60: 5.5 seconds.

After GM's performance mod: 4.9 seconds.

********************************************

Assumptions:
Density 1.2 kg/m3
ACd = .9
Rolling Resistance Coefficient: 0.02
Shift time: 500ms
Wheel spin delay: 300ms
WT: 1449 kg (car plus driver)
Current Torque to Wheels: 229 lb-ft
Performance Mod Torque to Wheels: 266 lb-ft
No change to redline RPM

Lots of variables involved here. A good rough estimate is half a second better. And if GM can extend the redline to about 6500 and keep decent torque, we could shave close to a second since a 6500 redline will basically get you to 60 in 2nd, saving shift time.

[LANDSCAPE]

And what about the two pedal stomp & go system, since it originally has a 0-60 of 5.2 would your assumptions mean an even greater improvement?

[TulsaSky]

Still .9 seconds slower then hubby's corvette, maybe he will stall on takeoff
He has more gears to go through 6 instead of my 5 that might help slow him down some
I still look and get more attention in my Sky anyway he can have those .9 seconds
Already told him I wanted the Mod when it was availble, Look Out

TulsaSky

[BSRL]

Originally Posted by TulsaSky

He has more gears to go through 6 instead of my 5 that might help slow him down some
TulsaSky

Correct me if I'm wrong but can't the vette do 0-60 all in 1st gear? o.k. maybe shift once to 2nd?

[Bogie]

Originally Posted by LANDSCAPE

And what about the two pedal stomp & go system, since it originally has a 0-60 of 5.2 would your assumptions mean an even greater improvement?

I ran the numbers for manual.

Based on feeback from GM, the performance upgrade won't deliver as much torque to wheels on the automatics.

Also, stomp & go is probably already at the limit of wheel slip...so that would be a major factor, albeit I often wonder if our slight turbo lag isn't actually a benefit here since it probably helps mitigate wheel slip.

As we begin to deliver more torque to wheels, the long pole is going to become grip. Better tires? Proper inflation? Condition and type of road surface? My models can translate force into acceleration and acceleration to into distance/time. But when it comes to when the wheels break loose and the force isn't producing acceleration, that's all fudge factoring. And the fudge isn't just analytical. Vehicle setup and mother nature can become major factors.

Aside: It is interesting watching the upgrades of not only our SKY, but other production performance cars as well. Take the new ZR1 Vette. 638HP and 604 lb-ft of torque. Insane torque isn't useful without grip. Gotta have more rubber on the road. The Chevy engineers equip the ZR1 with 13 inch WIDE 20inch rear wheels. And even that's not enough, so they have implemented a computer controlled suspension launch control; when you're at the tree picking your launch revs, the computer will drop the rear and stiffen the rebound, essentially pre-loading the entire vehicle for launch and keeping the rear planted when you clutch for the shift.

[Animator]

I think that 1/2 a second is reasonable. Especially if you can get a jump on someone, smoke 'em early and then let off. It's just impressive.

I'll wait a little on the mod after seeing the reports in the field, but will probably do it.
Mike

[Bogie]

Originally Posted by BSRL

Correct me if I'm wrong but can't the vette do 0-60 all in 1st gear? o.k. maybe shift once to 2nd?

I don't know about the C6, but the Z06 and the forthcoming ZR1 can go 0 to 60 all in first gear...no shifting required.

And another tidbit. If the GM Performance upgrade for the SKY can deliver spec'd torque to the drivetrain the actual torque at the wheels in first gear is pretty darn close to what you get at the wheels in a C6, Z06, or even the ZR1. Our first gear is almost twice as strong as a ZR1. The ZR1 delivers a lossless 4680 lb-ft in first. Our SKY delivers about 4300 lb-ft. Of course, the problem is we're shifting at around 34mph and the ZR1 is exploding all the way to 60.

Originally Posted by TulsaSky

Still .9 seconds slower then hubby's corvette,

Which Vette does he have? I'll run the numbers. I think the C6 runs X9 in first, which means our upgraded 310 lb-ft would map equal to a C6 480 lb-ft in first. Unless his C6 generates 480 lb-ft or better, you get bragging rights for more "torque to wheels" in first.


Caveat: The reality is we don't deliver spec'd torque to wheels, and our turbo still has to spool..and by the time it's fully spooled, we're shifting and lose our bragging rights. But hey, it's bragging rights so I'll just list the assumption, and we can still say (based on the assumptions) that our SKY delivers more torque to wheels than a C6 on launch.

[OKC08SKYR/L]

Would you happen to have a link to this GM upgrade or at least more details?

[Ahnuld]

Stomp & Go...

So, are we sure that it is 100% computer driven? Is there a hardware component involved?

If the gradual levels of the clutch being depressed is connected to, and measured in the ECM (one would think), then it seems the Stomp & Go could be a simple reflash (ecm gradually stops gas flow in sync with clutch being depressed... even if pedal remains to the floor).

If the clutch is not connected to ECM.... or only passes only a binary "on/off" state... then prob isnt a simple reflash.


The more I think about it tho... it would be a cool mod. May actually be enough to erase the slight time advantage the auto has.

[Ahnuld]

interesting read.... 2nd post
Cobalt SS no clutch shifts - Ask the Road Test Experts - Road & Track Forums


(hmmm.. did I hi-jack?)

[TulsaSky]

Hubby has the stock C6 06 corvette with the Z51 handling package, manual 6-speed Asian shift. That extra handling package has the crossed drilled rotors on the brakes and oil cooler, plus some type of stiffener on the handling.
I have not driven our Corvette in quite a while, I have more fun in the Sky Redline They both have all that computerized handling so you can only spin the wheels so much with it on. I know that the Sky seems to launch out just as hard as the Corvette but yes you can hit 60 in 2nd or 3rd in the Corvette and it is not even close to the limit or redline, then again if the wheels start slipping that drivers control will reduce the RPM's till the wheels stop slipping. Its the top end that the Corvette has over the Sky that 200 miles per hour ours is not quite that high!
I like to tell people as long as hubby keeps it under 150 I have no trouble keeping up with him

TulsaSky

[Bogie]

Originally Posted by TulsaSky

Hubby has the stock C6 06 corvette with the Z51 handling package

Assume equal drive train losses of...say....30 lb-ft each, we have for first gear:

Z51: 10.15 X 370 lb-ft = 3755 lb-ft

SKY (GM mod): 13.98 X 280 lb-ft = 3914 lb-ft ****SKY WINS!!!!!!

SKY (Current): 13.98 X 230 lb-ft = 3215 lb-ft


You don't have bragging rights now, as the 230 lb-ft is too much of a deficit for our stronger gearing to overcome. However, if the performance mod delivers on the claim, then you get bragging rights that your modified SKY will put more torque to the wheels in first gear than an 06 C6 Z51.

[lorennerol]

Originally Posted by Bogie

Assume equal drive train losses of...say....30 lb-ft each...

Is drivetrain loss a constant or a percentage??

[TulsaSky]

Lets not tell hubby the mod will make the Sky Redline jump harder in 1st gear he may not want me to get the Mod, but it won't stop me from getting it Make sure I don't brag at a car show and let the cat out of the bag before or after the Mod, so you all keep it under your hat, Mums the word on this
Thanks Bogie for crunching the numbers

TulsaSky

[Bogie]

Originally Posted by lorennerol

Is drivetrain loss a constant or a percentage??

It's whatever it is.

Seriously, it will not be a constant because changing the load will inevitably change the factors contributing to losses in the train. It will not be a fixed percentage because that implies the losses in the train vary linearly with load; they don't.

Of course, that doesn't stop anyone from computing torque at the wheels, adjusting for gearing, and dividing by engine output, which will basically provide drive train loss as a percentage of engine output. If the measurements are correct, the loss percentage will be an accurate reflection of the drivetrain losses for that particular test. Also, if the measurements are accurate and several similar drive trains are tested over the operating load range, and the percentages come out close to the same, one could reasonably use that percentage for analyses involving that drive train operated over the load range. The problem with this approach is you need dyno and crank measurements, whereas most percentage losses are used to back out crank power from the dyno. This is only valid if you have baselined the crank power via a measurement to properly establish the percentage train loss.

[lorennerol]

Originally Posted by Bogie

It's whatever it is.

Seriously, it will not be a constant because changing the load will inevitably change the factors contributing to losses in the train. It will not be a fixed percentage because that implies the losses in the train vary linearly with load; they don't.

That's what I figured: There is a part that is mechanical and should be fairly constant, and a part that is related to fluid dynamics (including air friction in the drive train, etc) that is variable based on the velocity of each component. I bet GM knows the magic equation, and I bet they won't share with us.

Regardless, it's not correct to assume that a 29HP gain at the crank from the tune will be wholly translated to the wheels. It's likely to be in the low to mid-20s at the wheels.

[mbeardsley]

I wonder what the BSR and Westers guys are thinking right now. I would assume they are going to lose many potential customers to this.

Personally, if I can get a tune from GM that gives me most of what the others give AND lets me keep my warranty...well, the choice is obvious.

Now maybe they can say, "well, our tune gives you more than the GM one does", but it better be an awful lot to make up for losing the warranty.

(and yes, I know all about the "they can't detect it/they have to prove it" arguement, but that's a pretty weak position in my opinion)

[bones]

4.9 0to 60 doesnt sound that good for a $1000 tune. I'm running 4.9 now with just a magnaflow exhaust. The car dynoed in at 216 h.p.

[mbeardsley]

Originally Posted by bones

4.9 0to 60 doesnt sound that good for a $1000 tune. I'm running 4.9 now with just a magnaflow exhaust. The car dynoed in at 216 h.p.

Wow, I don't think that anyone else is claiming this kind of performance.

This 0-60 time didn't happen to be on the dyno, did it? If so, that doesn't count - you're not fighting the wind resistance, which is a big factor.