GM's next generation small block v8 announced

[Theo]

Originally Posted by FC

Hopefully they will drop it into the ATS-V.

NICE!! and with a manaul of course!!

[FC]

Originally Posted by Theo

NICE!! and with a manaul of course!!

They better.

[lemming]

Originally Posted by FC

They better.

i'm sure they're looking into that (because the pushrod v8 is quite compact) as well as forced induction v6 versions.

[lupinsea]

Remind me again why a lot of the automotive press and a number of enthusiasts poo-poo the "old tech" pushrod V8 and clamor for the overhead cam layouts?

[lemming]

Originally Posted by lupinsea

Remind me again why a lot of the automotive press and a number of enthusiasts poo-poo the "old tech" pushrod V8 and clamor for the overhead cam layouts?

historically, it's been because of low redlines and lower specific output on an HP per litre metric.

if those are the metrics, some of those opinions are valid --on the other side, i've never seen 26mpg in a DOHC V8 in my life, whereas I have with a 427ci OHV one (easily).

[John V]

Originally Posted by lupinsea

Remind me again why a lot of the automotive press and a number of enthusiasts poo-poo the "old tech" pushrod V8 and clamor for the overhead cam layouts?

Because the DOHC layout gives engineers a ton more freedom in creating a broad powerband, meaning more torque at low RPM and more torque at high RPM, as compared to a pushrod layout where there are only two valves per cylinder.

Of course, that comes at a price. Weight, complexity, cost, and size to name a few.

[lemming]

Originally Posted by John V

Because the DOHC layout gives engineers a ton more freedom in creating a broad powerband, meaning more torque at low RPM and more torque at high RPM, as compared to a pushrod layout where there are only two valves per cylinder.

Of course, that comes at a price. Weight, complexity, cost, and size to name a few.

most especially in sports cars where it's advantageous to be able to hold gear longer per shift, the engine that can rev higher wins typically.

while NASCAR powerplants redline at 9000rpms or so, obviously that's not tractable for small block v8s that are in street cars.

so the added weight and complexity is worth it, in that respect.

[JST]

The 26 mpg thing isn't really fair, though--that's in the Corvette, which is small, light, and (most importantly) has an interplanetary overdrive gear.

Put a 4.x liter DOHC V8 in a similar car with a similar OD and I don't know that the mileage would be any worse.

[lemming]

I guess the question is if engines of similar displacement in lightweight cars get ???

The closest would be an F430?

And then the Merc 6.2L in a c class car?

I don't know what those get at cruising speed.

[JST]

There's no direct comparison that I'm aware of. Closest might me something like a GT3, which is obviously a 6 rather than an 8. But no one gears their cars the way that GM gears the Vette, in part because the general bias in European cars seems to be final drives and top gears that put the engine closer to the meat of the powerband at cruising speeds.

The 7 speed in the new Carrera S has a cruising oriented top gear, but I don't have the time right now to look up the gearing and fuel economy numbers for that car (and even that one is down 2 cylinders and 70 hp on the new Corvette).