Let me get this straight....LS3 vs. L99 MPG

[JMAN311]

17/29 mpg (city/hwy) – 3.6L DI VVT V6 with manual transmission
18/29 mpg (city/hwy) – 3.6L DI VVT V6 with automatic transmission
16/24 mpg (city/hwy) – 6.2L V8 with manual transmission
16/25 mpg (city/hwy) – 6.2L V8 with automatic transmission


So you have a 426hp 6-spd manual tranny car getting 16/24 mpg
and an active fuel management 6-spd auto car with 26 less hp can only get 1 mpg better?!?!?!?

What's up with that? Guess I didn't realise how much at automatic tranny can rob fuel mileage....


Now let me ask this....How many mpg do you think it would get as an LS3 w/ 6-spd auto tranny (no AFM, just a 426hp LS3 like the manual tranny car uses slapped to the auto tran)?

Also I think it's a testament to how well the LS3 manual can do....It's not much of a trade off over a V6 to only lose 1city and 5 highway mpg and have 122 more hp.

[Muscle Master]

The automatic is to blame

[Kyle2k]

I'm guessing it would have been 23 highway - which gives it the gas guzzler tax I think.

[toehead93]

Doesn't the gearing of the automatic hurt its mpg too? I think the gearing in the A6 is geared more agressively (which means less mpg) in order to accelerate equal to the M6. This steep gearing is needed to overcome the power lost through the torque converter. The A6 could get better mpg with less aggressive gearing but then it would suffer in acceleration.

[JMAN311]

Here's something else.....

Right off the 2009 Corvette pdf spec sheet.



The Vette doesn't need AFM with the auto trans to make up the mpg difference. I figure it's better mpg on the highway compared to the SS is cause it weighs less. Guess I'm just curious why they needed to use AFM with the auto to get the necessary mpg on the Camaro...maybe just cause of the weight?

[cyberbro]

Originally Posted by JMAN311

Here's something else.....

Right off the 2009 Corvette pdf spec sheet.

Attachment 17638

The Vette doesn't need AFM with the auto trans to make up the mpg difference. I figure it's better mpg on the highway compared to the SS is cause it weighs less. Guess I'm just curious why they needed to use AFM with the auto to get the necessary mpg on the Camaro...maybe just cause of the weight?

Absolutely.

[xfiremd]

my 2007 ls2 m6 corvette regularly get 33 Highway MPG, at 65/70, I suspect that a l99 will get much better, I know the car is a bit heaver and less aerodynamic, however some Suv only have a 200 hp four and manage to get 25 Highway. Does anyone know if the test are will regular or premium? Will the ls3 come with Mobil 1 factory fill?

[truth411]

Originally Posted by toehead93

Doesn't the gearing of the automatic hurt its mpg too? I think the gearing in the A6 is geared more agressively (which means less mpg) in order to accelerate equal to the M6. This steep gearing is needed to overcome the power lost through the torque converter. The A6 could get better mpg with less aggressive gearing but then it would suffer in acceleration.

+1

[UsedTaHaveA68]

Originally Posted by JMAN311

17/29 mpg (city/hwy) – 3.6L DI VVT V6 with manual transmission
18/29 mpg (city/hwy) – 3.6L DI VVT V6 with automatic transmission
16/24 mpg (city/hwy) – 6.2L V8 with manual transmission
16/25 mpg (city/hwy) – 6.2L V8 with automatic transmission


So you have a 426hp 6-spd manual tranny car getting 16/24 mpg
and an active fuel management 6-spd auto car with 26 less hp can only get 1 mpg better?!?!?!?

What's up with that? Guess I didn't realise how much at automatic tranny can rob fuel mileage....


Now let me ask this....How many mpg do you think it would get as an LS3 w/ 6-spd auto tranny (no AFM, just a 426hp LS3 like the manual tranny car uses slapped to the auto tran)?

Also I think it's a testament to how well the LS3 manual can do....It's not much of a trade off over a V6 to only lose 1city and 5 highway mpg and have 122 more hp.

You have to realize that even with AFM (which deactivates 4 cylinders in low-load situations), it only cuts fuel to those cylinders. Energy is still required to suck in a dry charge (no fuel, just air), compress it to 1/11th its original volume, let it expand, then blow it out the exhaust. It still takes quite a bit of energy to compress that dry charge. So some of the fuel that you save by not injecting it into the cylinders is used to compress the air in those dead cylinders. That's why you don't get much better mpg with it.

And the automatics have a taller (lower number) rear end than the manuals. 3.23 auto, 3.45 manual. This helps with mpg numbers.

[JMAN311]

Originally Posted by toehead93

Doesn't the gearing of the automatic hurt its mpg too? I think the gearing in the A6 is geared more agressively (which means less mpg) in order to accelerate equal to the M6. This steep gearing is needed to overcome the power lost through the torque converter. The A6 could get better mpg with less aggressive gearing but then it would suffer in acceleration.

If it's just a matter of gearing difference between the A6 and M6, then why doesn't the gearing of the Vette's Auto/Manual matter? It's 1mpg difference between A6 and M6 without AFM....

Originally Posted by UsedTaHaveA68

You have to realize that even with AFM (which deactivates 4 cylinders in low-load situations), it only cuts fuel to those cylinders. Energy is still required to suck in a dry charge (no fuel, just air), compress it to 1/11th its original volume, let it expand, then blow it out the exhaust. It still takes quite a bit of energy to compress that dry charge. So some of the fuel that you save by not injecting it into the cylinders is used to compress the air in those dead cylinders. That's why you don't get much better mpg with it.

And the automatics have a taller (lower number) rear end than the manuals. 3.23 auto, 3.45 manual. This helps with mpg numbers.

I thought the whole point of AFM was to use less fuel and be more efficient....shouldn't that equate into mpg? If what i put in bold is true why bother putting money into developing an AFM engine if it's not helping fuel economy?

[UsedTaHaveA68]

It is. If you'll notice the Corvette ratings, the automatic gets 1mpg LESS than the manual.

The Camaro's automatic gets 1 mpg MORE than the manual.

So overall, it's getting 2mpg better than the automatic in the Corvette.

[69 Hugger]

I'd like to see GM give a motor choice with auto in the near future, I'll settle for a LS3 but LS7/LSA would be the hot lick

[my2010camaross]

Originally Posted by JMAN311

17/29 mpg (city/hwy) – 3.6L DI VVT V6 with manual transmission
18/29 mpg (city/hwy) – 3.6L DI VVT V6 with automatic transmission
16/24 mpg (city/hwy) – 6.2L V8 with manual transmission
16/25 mpg (city/hwy) – 6.2L V8 with automatic transmission


So you have a 426hp 6-spd manual tranny car getting 16/24 mpg
and an active fuel management 6-spd auto car with 26 less hp can only get 1 mpg better?!?!?!?

What's up with that? Guess I didn't realise how much at automatic tranny can rob fuel mileage....


Now let me ask this....How many mpg do you think it would get as an LS3 w/ 6-spd auto tranny (no AFM, just a 426hp LS3 like the manual tranny car uses slapped to the auto tran)?

Also I think it's a testament to how well the LS3 manual can do....It's not much of a trade off over a V6 to only lose 1city and 5 highway mpg and have 122 more hp.

It really not that hard to figure out, I posted a thread about this long time ago. The ls3 in the corvette is rated at 26 on the highway. It is only common since that the camaro would almost have the same rating with the stick.

[JMAN311]

Originally Posted by UsedTaHaveA68

It is. If you'll notice the Corvette ratings, the automatic gets 1mpg LESS than the manual.

The Camaro's automatic gets 1 mpg MORE than the manual.

So overall, it's getting 2mpg better than the automatic in the Corvette.

Right, but taking away 1/2 the cylinders at low rpm cruising speeds and 26hp seems like alot just to squeeze out a 2mpg difference. It must have put it in the gas guzzler tax range without the AFM like Kyle2K was thinking. There wouldn't have been any other reason to use it IMO.

Originally Posted by my2010camaross

It really not that hard to figure out, I posted a thread about this long time ago. The ls3 in the corvette is rated at 26 on the highway. It is only common since that the camaro would almost have the same rating with the stick.

No it's not that hard to figure that the mpg between an LS3 Corvette manual would be close to the LS3 Camaro manual. But that's not what I'm talking about. The info I was talking about was the need for them using AFM at all on the auto in the Camaro.