C/D: Two new V6s for Cadillac

[kevm14]

Probably will arrive in the CT6 but find their way to the ATS and CTS. And I'd assume other GM brands, as well.

http://blog.caranddriver.com/cadillacs- ... orsepower/

New N/A 3.6, RPO LGX, has 335hp @ 6800 rpm and 284 lb-ft @ 5300 rpm. 11.5:1 compression. These ratings are with 87 octane.

And the rumored 3.0 twin turbo is finally here. It is a 3.0L V6, RPO LGW, with 400hp @ 5500 rpm and 400 lb-ft @ 2500 rpm.

With a bore of 86 mm, it follows popular world practice, combining 500 cc–per-cylinder displacement, boosted aspiration, and direct fuel injection. While other members of the “500 club” use an under-square bore-stroke ratio, those dimensions are nearly equal in GM’s LGW engine

Of course, I'm more interested in what's happening with the V8s (i.e. turbo or what).

In transmission news, GM has a new 8L45 transmission, which I was kind of waiting for, since the 8L90 is made for big HP applications, not modest V6 applications.

[bill25]

We are in a great time where V6 HP is 335 - 400 HP and that is modest.

[kevm14]

Well, yeah. The 8L90 goes behind the LT4 in the new Z06...and in 6000 lb GMT K2XX SUVs and trucks.

[kevm14]

Slight correction:

Get the CT6 with the twin-turbo 3.0-liter six, and you get the same 8L90 eight-speed automatic that debuted in the Corvette and quickly spread to GM’s truck lineup

So 400 hp/400 lb-ft evidently qualifies for the 8L90.

[bill25]

That makes sense. That seemed like Camaro SS power, and I am pretty sure they came with the 6L80.

[kevm14]

Yeah, that's right.

Historically, a trans with a designation like 8L90 would be reserved for only very high power/weight applications, and would be too inefficient for lighter duty applications. So either A) the mechanical design somehow can accommodate higher and lower output applications without losing efficiency or durability or B) there are different "8L90" branded transmissions.

Thinking about it, I think HP * weight would give you heat-capacity related information and lb-ft * weight would give you mechanical strength related information.

This transmission goes behind the C7 Z06, which is 650 hp * 3524 lbs = 2.29M HP*weight units, or 650 lb-ft * 3524 lbs = 2.29M torque*weight units.
In the Escalade: 420 hp * 5887 lbs = 2.472M, 460 lb-ft @ 5887 lbs = 2.708M

The Escalade can probably tow at least 7,000 lbs, so add a TON there, too.

In the 2016 ATS-V: 455 hp * 3650 (est) = 1.66M , 445 lb-ft * 3650 (est) = 1.624M

Base Corvette: 460 hp * 3298 lbs = 1.517M, 465 lb-ft * 3298 lbs = 1.534M

If the CT6 is 3900 lbs, then 400 hp * 3900 lbs = 1.56M, which is on the low end like the base Corvette.

For the 8L45, if the CT6 that gets the N/A 3.6 weighs 3800 lbs, then 335 hp * 3800 = 1.273M, and 284 lb-ft * 3800 lbs = 1.079M, which clearly is a lower multiple than any 8L90 application.

So, the world makes sense.