Undecided: CX-5 vs Escape/Edge

[CC58]

I question the value of forged this and that, though. Forged pistons vs. hyper pistons are a losing proposition unless you plan on a power adder. They fit sloppier in the bores, and they are often heavier. I simply see zero gain to a forged piston unless it is necessary. It's akin to installing chassis reinforcements on your CX-5. Would it make it more rigid? SURE! But really? Is it necessary? Nah. It would just add weight and cost money.

My 2000 LS1 Camaro had hyper pistons and had notorious piston slap on cold start. The CX-5 has no piston slap.

Mazda didn't just pick a forged piston over cast. Forged pistons are stronger and so can be made thinner. Mazda designed skyactiv engines from the ground up with bleeding edge technology and I believe the entire forged lower end (pistons, rods, crank) are built lightweight. When engine braking going down mountains, I was surprised how little braking occurred due to lightweight reciprocating mass of the engine. The CX-5 engine is; tough, lightweight, and very efficient.

 

[Unobtanium]

My 2000 LS1 Camaro had hyper pistons and had notorious piston slap on cold start. The CX-5 has no piston slap.

Mazda didn't just pick a forged piston over cast. Forged pistons are stronger and so can be made thinner. Mazda designed skyactiv engines from the ground up with bleeding edge technology and I believe the entire forged lower end (pistons, rods, crank) are built lightweight. When engine braking going down mountains, I was surprised how little braking occurred due to lightweight reciprocating mass of the engine. The CX-5 engine is; tough, lightweight, and very efficient.

The ls1 had piston slap because of wrist pin location and piston skirt design.

The cx5 has a great engine. Very solid design. I don't imply otherwise. However, the forged pistons are neither here nor there as far as "advantages". They simply are.

I've found engine braking about what I expected. Its a 4 cylinder in a 3500# vehicle.

 

[MikeM.]

My 2000 LS1 Camaro had hyper pistons and had notorious piston slap on cold start. The CX-5 has no piston slap.

Mazda didn't just pick a forged piston over cast. Forged pistons are stronger and so can be made thinner. Mazda designed skyactiv engines from the ground up with bleeding edge technology and I believe the entire forged lower end (pistons, rods, crank) are built lightweight.

Yep, forged stuff for lighter weight, better city mpg. The big advantage of forged pistons is that they dissipate heat more uniformly and run cooler so much less chance of a hot spot causing detonation.

When engine braking going down mountains, I was surprised how little braking occurred due to lightweight reciprocating mass of the engine. The CX-5 engine is; tough, lightweight, and very efficient.

Engine braking, at least the steady state, continuous type of engine braking, does not depend upon reciprocating mass but on compression and frictional losses in the engine/transmission. Mazda engineers claimed a 30% reduction in internal engine friction in Skyactiv engines.

There is a temporary form of engine braking that lasts as long as the rpm's are increasing. In a manual transmission vehicle this component of engine braking is felt as the clutch is engaged after a downshift and less reciprocating mass will reduce this temporary braking effect. However, an automatic transmission controls the speed of engagement and therefore it's harder to tell whether the perception of this temporary braking effect is actually due to lighter reciprocating mass or the engagement properties of different automatic transmissions on different cars.


Engine braking that exceeds that necessary to maintain a certain speed on a given grade will cause the vehicle to gradually slow down. In this case, more reciprocating engine mass will actually cause less engine braking due to the engine having more momentum which increasing the engines resistance to slowing down via compression/frictional losses.

 

[littlebear]

Mazda used forged for many reasons and one of them was that they didn't want to end up with a bad reliability rating if something did go wrong. Unreliability like the Subaru engines would destroy a small car company like Mazda.

High compression is considered in the same category as turbocharging and supercharging, in that it puts extreme pressure on the piston.

Here is an article that talks about it:
http://www.carsdirect.com/aftermarket-parts/why-install-forged-pistons

 

[CC58]

The cx5 has a great engine. Very solid design. I don't imply otherwise. However, the forged pistons are neither here nor there as far as "advantages". They simply are.

The advantages of having forged bottom end in CX-5 is that it was specifically designed to be reliable with high compression. Comparing reliability of CX-5 to a turbo vehicle for reliability is a losing battle. Turbo vehicles will require new turbos at regular intervals costing at least $1500 per repair.

 

[Rarebit]

The advantages of having forged bottom end in CX-5 is that it was specifically designed to be reliable with high compression. Comparing reliability of CX-5 to a turbo vehicle for reliability is a losing battle. Turbo vehicles will require new turbos at regular intervals costing at least $1500 per repair.

I don't have aggregate repair records for a large number of vehicles, so I can't argue this one way or the other. However, I bought two turbocharged vehicles new and owned one for 9 years, the other for 15, racking up more than 100,000 miles on each. Neither required any repairs to the turbocharger, and both seemed to be running perfectly when I traded them in. That's too small a sample, and probably not enough mileage, to draw any conclusions about other vehicles but I would be interested in what reliable evidence people have that turbochargers require new turbos, and at how many miles.

 

[RG_Flyer]

Littlebear and CC58 are likely spot-on regarding the forged pistons. The SkyActiv engines are cutting-edge and some previous taboos (such as high-compression/low-octane) are being cast aside. While the design was certainly tested, there may be conditions where engineers erred on the side of caution. This is not uncommon or unexpected, much larger and resourceful automakers, such as littlebear mentioned above, have made some costly mistakes when pushing new technology. The EPA mileage mandates have all manufacturers scrambling to increase efficiency. Only time will tell if the radical advancement in engine technology will still yield 200,000+ mile engines.