GM's next generation small block v8 announced
 

6.2L, 26mpg

11.5:1 compression

>450hp, >450ft-lbs torque

the LT1 is the powerplant for the C7.

Sounds like impressive tech, but that autoblog post is weirdly breathless. Up at least 20 hp over the outgoing engine? That's 5 percent. I'm not sure I'd call that "a far higher specific output" than the outgoing engine.

direct injection, cylinder deactivation and regular unleaded fuel are the major things.

same torque numbers as LS7 (Z06 motor) is impressive.

this engine obviously will see broad application in GM's portfolio, so the torque is actually more important than the peak HP number (GMT900s).

I'm also pleased they kept the push rod format. It's "old tech" but it seems to have worked quite well for GM. Their pushrod V8s also (I think) are smaller physically, lighter, less mechanically complicated, yet still deliver pretty good MPG number (in the Corvette at least) than the newer overhead cam V8 engines that you see in other sports cars.

an appealing aspect is compactness and low CG. they are able to keep hood height down.

direct injection and cylinder shutoff (as on the new viper) are nothing to sneeze at, though.

They named it the LT1? Interesting.

Being the owner of a 6.2L small-block that gets a little less than 450 hp and, er, MUCH less than 26 mpg, I'm intrigued. I was not really into cylinder deactivation, but I wonder if it'll be smoothed out a bit in the gen5 engines.

Speaking of this I wonder how the new vettes front end is going to look with the new pedestrian safety standards that have ruined the looks of almost all front engined cars out there.

I don't think it'll be too bad.

From what I understand there needs to be a certain clearance between the hood surface and hard points under the hood (notably the engine). But in a Corvette the engines are stuffed so far back in the chassis, well behind the front axle line. By the time the hood covers them I think it'll be high enough over the engine due to other design parameters that it won't be a concern. For instance, there will be some height stack for the foot well, plus room for the steering column and then the dash so that the base of the windshield will be reasonably high enough. Draw a line (more or less) from the base of the windshield out to the front of the long nose on the car and I think the engine block and intakes will easily fit under that.

Hopefully they will drop it into the ATS-V.

NICE!! and with a manaul of course!!

They better.

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

:dunno:

;)

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).

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.

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.

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.

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).

I would guess the new 911 S models could get 26mpg cruising at 75 --which shows how disproportionate the value of displacement would be in this discussion.

3.8L DOHC engine with amazing HP/L and any 6.2L or 7.0L v8.

Very different power deliveries, which speaks to the differences in how the engines breathe. But torque is always a function of physical engine size --so the DOHC engine's point in life is to bring the torque to higher in the rev band. But fuel efficiency (which itself is secondary in a sports car) suffers a lot.

You get away with a massive overdrive when you have big displacement. BMW can't do that in the m3 because the v8 isn't nearly as torquey.

Engines run most efficiently at low rpm but high load and wide throttle openings. So a BMW 4 liter v8 turning lots of revs at freeway speeds gets worse mileage than a corvette 7 liter turning just above idle.

The CTS V was big, heavy and fast. It got 25 on the highway always and sometimes more.