Why GM should NOT build a DOHC V8

[Robert Hall]

The OHC vs pushrod argument will be forever arguable, as long as GM and Chrysler stick w/ pushrod. Both designs have their merits.

[ShadowDog]

The 5.5 liter AMG engine makes 660 lb=ft of torque, that is substantially better than the CTS-V's 6.2 liter engine can put out. As far as packaging size, the Merc engine is going to fit under the hood of the E-class, so I don't see how the future GM 5.5 liter pushrod taking up less space matters. And remember this isn't even Mercedes top end engine, they still have the BiTurbo V12.

Stick twin-turbos on the 6.2 Litre and find out what happens. Since that was attempted and the car burned, the LS9-derived engine has been pushed to 717 ft-lbs with a supercharger. Hennessey plans to release two twin-turbo versions, with one producing between 800 and 850 hp and, and the other kicking out 1,000 hp and up to 900 ft-lb of torque.

A powers number pissing match won't work here. Those opportunities are endless. The point is to enable real-world engines for real-world cars for people who care about cars they might also afford.

Edited March 5, 2010 by ShadowDog

[dado]

From this page LINK

Where the C6.R and ZR1 differ significantly are in situations where GT rules actually prohibited the use of the more sophisticated ZR1 components. For example, the ZR1 is equipped with carbon-composite brake rotors, while GT regulations require ferrous (steel) brake discs. And, where the ZR1 utilizes a 6.2L, supercharged V-8, the C6.R will use a naturally aspirated small-block, production-based 5.5L V-8.

The Corvette C6.R race cars' 5.5-liter Chevrolet small-block V8s are developed, built and maintained by GM. The Corvette C6.Rs' LS5.5R is a naturally aspirated race engine, based on the Corvette Z06's 7.0-liter LS7 engine (which in turn was developed with the 7.0L race engine used in the C6.R GT1 cars), built on production cast-aluminum cylinder blocks.

Pending GT2 class regulations specify a maximum displacement of 5.5 liters, the reduction in displacement to meet this requirement was achieved by shortening the crankshaft stroke and reducing the cylinder bore diameter. In accordance with the regulations, the race engines have two 28.8mm diameter intake air restrictors. The LS5.5R engines are equipped with dry-sump oiling systems, CNC-ported aluminum cylinder heads with titanium intake and exhaust valves, and sequential electronic port fuel injection. The race engines use E85R ethanol racing fuel in the ALMS and E10 fuel in Le Mans.

I thought that new GEN V, which this new 5.5 l v8 should be based on, will have new block with cam in higher position, DI etc, not the engine which is basically ls7 engine with smaller bore and stroke.

Dwightlooi any info on this?

[dwightlooi]

From this page LINK

Where the C6.R and ZR1 differ significantly are in situations where GT rules actually prohibited the use of the more sophisticated ZR1 components. For example, the ZR1 is equipped with carbon-composite brake rotors, while GT regulations require ferrous (steel) brake discs. And, where the ZR1 utilizes a 6.2L, supercharged V-8, the C6.R will use a naturally aspirated small-block, production-based 5.5L V-8.

The Corvette C6.R race cars' 5.5-liter Chevrolet small-block V8s are developed, built and maintained by GM. The Corvette C6.Rs' LS5.5R is a naturally aspirated race engine, based on the Corvette Z06's 7.0-liter LS7 engine (which in turn was developed with the 7.0L race engine used in the C6.R GT1 cars), built on production cast-aluminum cylinder blocks.

Pending GT2 class regulations specify a maximum displacement of 5.5 liters, the reduction in displacement to meet this requirement was achieved by shortening the crankshaft stroke and reducing the cylinder bore diameter. In accordance with the regulations, the race engines have two 28.8mm diameter intake air restrictors. The LS5.5R engines are equipped with dry-sump oiling systems, CNC-ported aluminum cylinder heads with titanium intake and exhaust valves, and sequential electronic port fuel injection. The race engines use E85R ethanol racing fuel in the ALMS and E10 fuel in Le Mans.

I thought that new GEN V, which this new 5.5 l v8 should be based on, will have new block with cam in higher position, DI etc, not the engine which is basically ls7 engine with smaller bore and stroke.

Dwightlooi any info on this?

Rule changes dictate a lot of stuff in ALMS. Basically, DI is forbidden for another season, so they had to take it out.

[dwightlooi]

I assume the 5.5 will be in the C-class AMG as well (the current one has the 6.2 V8). Engine packaging is really only an issue with a FWD transverse setup where there are space constraints....if RWD compacts like the BMW 3-series and Merc C-class can fit a DOHC V8, then the space argument is moot..

What's funny is the truck fans always make an argument against OHC V8s, but Ford has built a lot of them for over a decade now...

It matters because space in under the hood not taken up by the engine can be used to house a more efficient intake system, or you can have a lower hood line. Also, if a Pushrod engine is cheaper, lighter and more fuel efficient than a DOHC engine of equivalent power output, why do you want a DOHC engine? The ONLY reasonable justification is the real or perceived civility advantageous, and that has been quite thoroughly discussed elsewhere in this thread.

[smk4565]

It matters because space in under the hood not taken up by the engine can be used to house a more efficient intake system, or you can have a lower hood line. Also, if a Pushrod engine is cheaper, lighter and more fuel efficient than a DOHC engine of equivalent power output, why do you want a DOHC engine? The ONLY reasonable justification is the real or perceived civility advantageous, and that has been quite thoroughly discussed elsewhere in this thread.

A Mercedes or BMW isn't designed to be cheaper, it is made to be excellent. Doing what is "cheap" shouldn't be a primary concern for Cadillac. And the fuel efficiency argument isn't really valid, a CTS-V gets 12/18 mpg, an E63 AMG gets 13/20 and an XFR gets 15/21 mpg. The Corvette gets good mpg (for a V8) because of weight, aerodynamics and gearing.

[Drew Dowdell]

A Mercedes or BMW isn't designed to be cheaper, it is made to be excellent. Doing what is "cheap" shouldn't be a primary concern for Cadillac. And the fuel efficiency argument isn't really valid, a CTS-V gets 12/18 mpg, an E63 AMG gets 13/20 and an XFR gets 15/21 mpg. The Corvette gets good mpg (for a V8) because of weight, aerodynamics and gearing.

A CTS-V can do a lot of things those other cars can't. Where's the benefit to switching it to DOHC?

[balthazar]

If it's heavier, costs more AND returns less MPG, he can bitch about Cadillac all the more.

[smk4565]

A CTS-V can do a lot of things those other cars can't. Where's the benefit to switching it to DOHC?

The M5's 4.4 liter V8 will make 578 hp, Cadillac's 6.2 liter V8 makes 556. DOHC can rev faster and more freely. Some countries tax displacement, even Washington State is considering taxing displacement. The CTS-V has a $2600 gas guzzler tax, Jaguar XFR has $0. A 6.2 liter engine is thirsty, a 4.4 liter that uses less gas and makes the same power is more sensible.

[Drew Dowdell]

The M5's 4.4 liter V8 will make 578 hp, Cadillac's 6.2 liter V8 makes 556. DOHC can rev faster and more freely. Some countries tax displacement, even Washington State is considering taxing displacement. The CTS-V has a $2600 gas guzzler tax, Jaguar XFR has $0. A 6.2 liter engine is thirsty, a 4.4 liter that uses less gas and makes the same power is more sensible.

LOL

Picking and choosing again?

The 6.2 liter LS9 is offered in the Corvette with 638hp. That GM tunes it down for the CTS-V says nothing about the capabilities of the engine. Dwightlooi has already addressed the issues of displacement tax (an idiotic tax) and that the latest GM pushrods lack nothing in the quickness to rev department.

We're not talking about your grandfathers Olds 307 here. This are highly advanced engines.

[smk4565]

I was comparing sedans, but if you want to compare the ZR1 to another sports car, compare it to the 911 Turbo. The Vette gets 13/20 mpg, the 911 gets 15/25. The Vette's 6.2 liter engine gets it from 0-60 in 3.4 seconds, the 911's 3.8 liter engine does 0-60 in 2.9 seconds. The ZR1 is 97 dBa at full throttle and 80 dBa at 70 mph, the 911 is 83, dBa at full throttle, and 72 dBa at 70 mph. The flat six is just more refined, quieter, more fuel efficient and faster.

[dwightlooi]

A Mercedes or BMW isn't designed to be cheaper, it is made to be excellent. Doing what is "cheap" shouldn't be a primary concern for Cadillac. And the fuel efficiency argument isn't really valid, a CTS-V gets 12/18 mpg, an E63 AMG gets 13/20 and an XFR gets 15/21 mpg. The Corvette gets good mpg (for a V8) because of weight, aerodynamics and gearing.

No, a Cadillac should be designed to a standard of excellence, not a cost ceiling. However, designing an engine to be costly and complex for the sake of being being costly and complex achieves nothing.

The CTS-V has a blown V8 of the same approximate displacement as the E63 AMG's (6162 vs 6208cc). A supercharger incurs parasitic losses to drive. More importantly, the E63 has a 7-speed automatic transmission (one speed more than the CTS-V) which has ditched the torque converter in favor of an automated clutch pack. Just think of it as an SMG with planetary gearsets.

If you compare a normally aspirated Pushrod engine with a normally aspirated DOHC powerplant of a similar output with similar transmissions, aerodynamics and vehicular weights, you'll find that the Pushrod engine delivers better fuel economy. A good example will be the Camaro SS vs the C63. The cars are of a similar weights, deliver within 50hp of each other and both pack automatic tranmissions. While the C63 has 7-speeds vs the Camaro's 6-speed, it still has a conventional torque converter unlike the E63 and SLS. In fact, the Camaro beats out the lighter and smaller displacement C55 AMG (which I own).

• Camaro SS -- 6162 cc - 6-speed Auto - 400hp @ 5900 - 410lb-ft @ 4300 - 3860 lbs - 16/25 MPG
  
• C63 AMG ---- 6204 cc - 7-speed Auto - 451hp @ 6800 - 443lb-ft @ 5250 - 3924 lbs - 12/19 MPG
  
• C55 AMG ---- 5439 cc - 5-speed Auto - 362hp @ 5750 - 376lb-ft @ 4000 - 3580 lbs - 16/22 MPG*
  

* (Pre-2008 EPA rating; approx 15/20 under new testing program)

As you can see, the Pushrod powered car not only has a fuel economy advantage, it is a SIGNIFICANT one.

In case you are wondering, the Corvette does a mere 1mpg better than the Camaro when outfitted with the 6.2liter V8 engine (16/26). And, if you up the ante to the Z06 with 7.0 liters, 505hp and more aggressive gearing, the numbers drop to 15/24mpg.

Edited March 7, 2010 by dwightlooi

[regfootball]

I was comparing sedans, but if you want to compare the ZR1 to another sports car, compare it to the 911 Turbo. The Vette gets 13/20 mpg, the 911 gets 15/25. The Vette's 6.2 liter engine gets it from 0-60 in 3.4 seconds, the 911's 3.8 liter engine does 0-60 in 2.9 seconds. The ZR1 is 97 dBa at full throttle and 80 dBa at 70 mph, the 911 is 83, dBa at full throttle, and 72 dBa at 70 mph. The flat six is just more refined, quieter, more fuel efficient and faster.

is the 911 turbo AWD as well?

[Robert Hall]

is the 911 turbo AWD as well?

Yes and no. The regular 911 Turbo is AWD, the GT2 is RWD only.

[Robert Hall]

Bottom line, I don't think we will see future DOHC V8s in GM cars because car V8 development is linked to truck V8 development.

Edited March 8, 2010 by Cubical-aka-Moltar

[regfootball]

Yes and no. The regular 911 Turbo is AWD, the GT2 is RWD only.

next vette needs one AWD version in some way.

and you are correct as long as the vette has to be linked to truck engines then GM is kind of in a box.

[aldw]

A Turbosteamer-electric setup is probably the most favorable setup for a pushrod, as it be very compact and would operate at optimal thermal/fuel use output and thus making irrelevant high-rpm activity, and the power goes straight into an electric motor powering the wheels.

[dwightlooi]

A Turbosteamer-electric setup is probably the most favorable setup for a pushrod, as it be very compact and would operate at optimal thermal/fuel use output and thus making irrelevant high-rpm activity, and the power goes straight into an electric motor powering the wheels.

If you are going turbo-electric you may want to ditch the piston engine completely. A dual spool gas turbine has only two moving parts, no coolant loop, no radiator, no valves, no cams, no rods, no reciprocating parts, no vibrations. A simple cycle 150hp unit is about the size of a 100pcs stack of CDs. Add a recuperator and it's that plus the equivalent of an intercooler. It produces a thermal efficiency between 30~40% at optimal speeds, which is as good as the best diesels. It burns gasoline, ethanol, diesel or all of the above at the flick of a FADEC switch.

A turbine is not without it's problems. It takes almost a minute to start up, it takes about as much time to go from idle to full power as a car typically takes to go from 0-60 mph and efficiency falls off quite dramatically as you deviate from its optimal operating speed. In addition, because the operating speeds are pretty darn high (approximately 60,000~120,000 rpms) the gearbox to take it down to wheel speeds will be extremely challenging.

However, none of that matters, not if your final drive is electric. You'll simply connect it to a high speed generator and run it at optimal speeds or not at all. Excess power is buffered in a battery, ultra capacitors or both. And, you'll simply parcel it out to throttle request via an electric motor. Generation loss is about 5~10%, motor loss is another 10~15%. That's about the same as a typical mechancial transmissions used in today's cars.

[SAmadei]

However, none of that matters, not if your final drive is electric. You'll simply connect it to a high speed generator and run it at optimal speeds or not at all. Excess power is buffered in a battery, ultra capacitors or both. And, you'll simply parcel it out to throttle request via an electric motor. Generation loss is about 5~10%, motor loss is another 10~15%. That's about the same as a typical mechancial transmissions used in today's cars.

After playing with my friend turbine mule, I don't understand why more turbine/electric hybrids have not been considered.

[balthazar]

>>"A turbine is not without it's problems. It takes almost a minute to start up, it takes about as much time to go from idle to full power as a car typically takes to go from 0-60 mph..."<<

Perhaps with a stream-turbine, but these were not characteristics of the now 45-yr old Chrysler (gas) Turbine. Assuredly, tech has progressed since then. 1964 Turbine : "No warmup needed; can operate under full power as soon as fuel is burning."

"Tach needle requires maybe 3 seconds to swing up to idle (22,000 RPM)." 'Redline' is 44,000- but peak TRQ is available at idle... so that's not quite 'what it takes cars to go 0-60'. Again, a steam turbine would be a different story.

Problems w/ the gas turbine even via 1980's standards were cost of manufacturing (much higher cost materials & machining) and an economy about on par with a gas V-8... and at this point ('70-80s), everyone was eyeballing 30-40 MPG. Earlier, there issues with high NOx- but this was later successfully addressed.

I still want one.

[dwightlooi]

>>"A turbine is not without it's problems. It takes almost a minute to start up, it takes about as much time to go from idle to full power as a car typically takes to go from 0-60 mph..."<<

Perhaps with a stream-turbine, but these were not characteristics of the now 45-yr old Chrysler (gas) Turbine. Assuredly, tech has progressed since then. 1964 Turbine : "No warmup needed; can operate under full power as soon as fuel is burning."

"Tach needle requires maybe 3 seconds to swing up to idle (22,000 RPM)." 'Redline' is 44,000- but peak TRQ is available at idle... so that's not quite 'what it takes cars to go 0-60'. Again, a steam turbine would be a different story.

Problems w/ the gas turbine even via 1980's standards were cost of manufacturing (much higher cost materials & machining) and an economy about on par with a gas V-8... and at this point ('70-80s), everyone was eyeballing 30-40 MPG. Earlier, there issues with high NOx- but this was later successfully addressed.

I still want one.

Well, you are talking about a direct drive, simple cycle turbine. Recuperated turbines respond more slowly. The recurperator is a big heat exchanger. The exhaust is used to heat the recuperator before exiting the engine. The recuperator transfer's the heat to the high pressure compressor output before it is introduced to the combustion chamber. This way you recapture a good portion of the heat otherwise wasted in the exhaust. A simple cycle gas turbine with 2 centrifugal stages typically gets to about 25~30% thermal efficiency. Adding a recuperator raises that to the 30~40% range.

Complexities aside, the recuperator is also voluminous device. This means that the compressor has to pressurize a much bigger air volume in the recuperator instead of just the minute little air space between the compressor outlet and the combustor. Imagine inserting an intercooler the size of a room between a turbocharger and the intake manifold and you'll get the idea; the turbo will take a long time to pressurize this volume before the engine sees a boost pressure and subsequent power increase. This reduces throttle response.

That said, throttle response is completely irrelevant however in stationary power generation or in a turbo electric setup since instantaneous power delivery is provided not by the turbine but by a separate electric motor drawing from stored electrical energy in the batteries.

As far as costs are concerned, yes, the materials and high temp alloys used in turbines are more expensive than the metals used in a piston engine. But the turbine is also much less complex, so once the industrial base for volume production develops it is unlikely to be more expensive. Simplicity also means reliability and reduced maintenance. In the aviation world, aircrafts used to be powered by inline and radial piston engines with 4 to 24 cylinders outfitted with a a plethora of overhead or sleeve valves. The advent of jet propulsion dramatically increased dispatch reliability and reduced maintenance requirements. For the most parts, aircrafts now fly 1 hour turn arounds day after day with nearly no maintenance on the engines except for toping off the Mobil Jet Oil II reservoirs. The engines endures daily use for 15000 hours between scheduled overhauls. This is about 3000 cross country flights. And this is because avaiation regulations stipulate rated time between refurbishments. In automotive applications, people usually drive the car until it breaks before doing an engine rebuild.

[balthazar]

No; the Turbine DID have twin heat exchanger/regenerators. The regenerator was actually a Chrysler patent for '49. It's how 1850-degree combustion temps were reduced at the tailpipes so a bare hand could be held in the exhaust stream.

More Turbine copy : >>"A gas-turbine develops maximum torque at stall. So if you want flashy acceleration from a turbine car, you drive it the way you would an auto-trans dragster. You sit with your left foot on the brake and your right holding the accelerator to the floor. Within a second the tach needls touches 52,000 RPM & you slip your foot off the brake. There is no lag. The rear wheels start squealing, the car flies forward and you're off. 0-60 is about 5.5 sec, 1/4-mile in the 13s."<<

[dwightlooi]

No; the Turbine DID have twin heat exchanger/regenerators. The regenerator was actually a Chrysler patent for '49. It's how 1850-degree combustion temps were reduced at the tailpipes so a bare hand could be held in the exhaust stream.

More Turbine copy : >>"A gas-turbine develops maximum torque at stall. So if you want flashy acceleration from a turbine car, you drive it the way you would an auto-trans dragster. You sit with your left foot on the brake and your right holding the accelerator to the floor. Within a second the tach needls touches 52,000 RPM & you slip your foot off the brake. There is no lag. The rear wheels start squealing, the car flies forward and you're off. 0-60 is about 5.5 sec, 1/4-mile in the 13s."<<

Depends on how the power outtake is done. This would be true if it is a thrust generator + power turbine setup. That is the gas turbine provides jet exhaust thrust against a separate power turbine connected to the output shaft. The turbine can operate at maximum power and speed, while the power turbine is stalled and stationary. This also allows the output shaft speed to be decoupled from the turbine's operating speed. However, it will not be true if the power outtake is directly from the main spool or low pressure spool. In the former instance, if you stall the output shaft the turbine stops and you make no power. In the latter case, you stall the low pressure compressor and it greatly diminishes the output and efficiency of the turbine.

Using a power turbine is more flexible, but using a direct drive setup can be more efficient. In large marine engines for instance, the General Electric LM2500 is a power turbine setup. Their larger (57,600hp) LM6000 is direct drive.

[dado]

On March 5th Peter de lorenzo said, on "Autoline After hours" (LINK ) at about 1h 2 min, that there is small block v8 prototype with 3.0 l, and it looks like V8 from oldsmobile and REPCO from the sixties. Wasn't that SOHC engine when Repco finish with it?

[CanadianBacon94]

next vette needs one AWD version in some way.

and you are correct as long as the vette has to be linked to truck engines then GM is kind of in a box.

Maybe the XLR should have been AWD

Edit: and competitive within the class

Edited March 14, 2010 by CanadianBacon94

[Ls7tt]

I was comparing sedans, but if you want to compare the ZR1 to another sports car, compare it to the 911 Turbo. The Vette gets 13/20 mpg, the 911 gets 15/25. The Vette's 6.2 liter engine gets it from 0-60 in 3.4 seconds, the 911's 3.8 liter engine does 0-60 in 2.9 seconds. The ZR1 is 97 dBa at full throttle and 80 dBa at 70 mph, the 911 is 83, dBa at full throttle, and 72 dBa at 70 mph. The flat six is just more refined, quieter, more fuel efficient and faster.

I always love 911 fanboys. 0-60 2.9 really? that's only with launch control ON without it slower than 3.4 0-60 second. Also have fun with those 0-60 in 2.9 when you blow your tranny and it's not under warranty since you used launch control too much

What's MSRP on a 911 turbo again yup 140k+, 4-5k of bolt-ons on that Zr1 you are blowing the 911 turbo out of the water with an extra 35k+ in your pocket.

Really a flat 6 TT is more efficient than a LS9/LS7 lol obviously not to mention all MPG tests the turbo is out of boost pretty simple to get MPG ratings low.

Edited March 19, 2011 by Ls7tt

[Mike The Canadian]

No offense but who brags about the decibel level a sports car being lower?

Have you heard either the 911 or ZR1? I certainly LOVE hearing them, and the more I hear, the happier I am.

[Robert Hall]

No offense but who brags about the decibel level a sports car being lower?

Have you heard either the 911 or ZR1? I certainly LOVE hearing them, and the more I hear, the happier I am.

A quieter sports car makes a better commuter car and long distance road trip car. The horrific seats (or so I've heard) probably limit the ZR-1s daily driver usability. Both are interesting cars, though..wouldn't kick either out of my garage..

Edited March 19, 2011 by Cubical-aka-Moltar

[Mike The Canadian]

No offense but who brags about the decibel level a sports car being lower?

Have you heard either the 911 or ZR1? I certainly LOVE hearing them, and the more I hear, the happier I am.

A quieter sports car makes a better commuter car and long distance road trip car. The horrific seats (or so I've heard) probably limit the ZR-1s daily driver usability. Both are interesting cars, though..wouldn't kick either out of my garage..

I would certainly never own any of these for the purpose of being commuter cars. Nor would I take it on long distance road trips where I get to crap my pants at rock chips beating away at my hood and bumper.

I personally can't afford either, one can dream

[Robert Hall]

No offense but who brags about the decibel level a sports car being lower?

Have you heard either the 911 or ZR1? I certainly LOVE hearing them, and the more I hear, the happier I am.

A quieter sports car makes a better commuter car and long distance road trip car. The horrific seats (or so I've heard) probably limit the ZR-1s daily driver usability. Both are interesting cars, though..wouldn't kick either out of my garage..

I would certainly never own any of these for the purpose of being commuter cars. Nor would I take it on long distance road trips where I get to crap my pants at rock chips beating away at my hood and bumper.

I personally can't afford either, one can dream

That's the beauty of the 911, it makes a great daily driver and road trip car..reliable, solid and drivable (though I would think a GT3 or a GT3 RS would be too hardcore for that).. I know people that drive 'em day in, day out in any kind of weather...(a buddy in Denver has a Boxster S as his commuter car..if it snows too much, he works from home).

If I had a sports car, I'd drive it as much as possible..esp. on road trips, avoiding the interstates and seeking out twisty back roads.

Edited March 19, 2011 by Cubical-aka-Moltar

[SAmadei]

No offense but who brags about the decibel level a sports car being lower?

Have you heard either the 911 or ZR1? I certainly LOVE hearing them, and the more I hear, the happier I am.

A quieter sports car makes a better commuter car and long distance road trip car. The horrific seats (or so I've heard) probably limit the ZR-1s daily driver usability. Both are interesting cars, though..wouldn't kick either out of my garage..

I sure hope that Sat-Nav is top rate. Then you can quiet the engine by turning it off and just sit there and play with the Sat-Nav all day.

[dwightlooi]

I was comparing sedans, but if you want to compare the ZR1 to another sports car, compare it to the 911 Turbo. The Vette gets 13/20 mpg, the 911 gets 15/25. The Vette's 6.2 liter engine gets it from 0-60 in 3.4 seconds, the 911's 3.8 liter engine does 0-60 in 2.9 seconds. The ZR1 is 97 dBa at full throttle and 80 dBa at 70 mph, the 911 is 83, dBa at full throttle, and 72 dBa at 70 mph. The flat six is just more refined, quieter, more fuel efficient and faster.

I always love 911 fanboys. 0-60 2.9 really? that's only with launch control ON without it slower than 3.4 0-60 second. Also have fun with those 0-60 in 2.9 when you blow your tranny and it's not under warranty since you used launch control too much

What's MSRP on a 911 turbo again yup 140k+, 4-5k of bolt-ons on that Zr1 you are blowing the 911 turbo out of the water with an extra 35k+ in your pocket.

Really a flat 6 TT is more efficient than a LS9/LS7 lol obviously not to mention all MPG tests the turbo is out of boost pretty simple to get MPG ratings low.

First of all, comparing engines to engines, the 3.8 Turbo Flat Six in the 911 Turbo is not in the same class as the ZR1’s LS9. It is 138 hp and 104 lb-ft short. Secondly, the 911’s acceleration advantage is not due to its power-to-weight ratio (it’s inferior), it is due to the traction advantages of AWD and shifting speed of the dual clutch transmission.

A better comparison is between the 505 hp / 470 lb-ft LS7 engine in the Z06 and the 500 hp / 480 lb-ft 3.8TT engine in the 911 Turbo. The LS7 is the lighter, smaller, less complex and less costly engine. Fuel Economy wise, the Z06 posts 15/24 mpg to the 911 Turbo’s 16/24 (manual transmission on both). IT also goes to show that displacement is pretty low on the list of characteristics that determine fuel economy. That's a 1 mpg difference between a 7.0 liter engine and a 3.8 liter mill (almost half its swept volume).

Edited March 21, 2011 by dwightlooi

[dado]

A better comparison is between the 505 hp / 470 lb-ft LS7 engine in the Z06 and the 500 hp / 480 lb-ft 3.8TT engine in the 911 Turbo. The LS7 is the lighter, smaller, less complex and less costly engine. Fuel Economy wise, the Z06 posts 15/24 mpg to the 911 Turbo’s 16/24 (manual transmission on both). IT also goes to show that displacement is pretty low on the list of characteristics that determine fuel economy. That's a 1 mpg difference between a 7.0 liter engine and a 3.8 liter mill (almost half its swept volume).

All of this is true..

But buyers of luxurie cars (and luxurie performance cars) don't really care about price of the engine, weight of the engine, complexity of the engine. Do you think owner of Ferrari , Aston Martin go and change oil or tune their car by themselves?? No..they can pay others people to do that. Yes small block are lighter but by how much?? Also engine (small block) is lighter but cars with that engine(camaro, CTS-V) doesn't seems to be much lighter or much more nimble then their competition. If GM can't use lightness of small block what is the point..

Like i sad before if GM are serious about Cadillac they should offer special engine especially for future flagship. LSA engine is an excellent engine..but it can be found in Camaro which cost about 50 000$. Imagine 120 000$ Cadillac with same engine. Yes you know, and i know, and some car enthusiasts knows it is an excellent engine. But large number of people will see expensive car(cadillac rwd flagship) with engine from cheaper and less exclusive brand (Chevrolet)

And reading different forums, car magazines i'm not sure people would not realize

-it is not the same engine from truck

-it is not the same engine as it was before 60 years

-because it has big displacement it doesn't have to weight 1 tone etc.

Outside USA small block are not favorite luxurie cars engine and it is not first thing people will think when they think about luxurie. And it seems there are very large number of people inside USA that thinks the same way.

IF GM is serious about Cadillac as luxurie car maker,and offer small block in real luxurie flagship (i'm not talking about CTS-V here or some SUV) GM should prove to buyers of Mercedes S , BMW 7. Jaguar XJ etc that small block are excellent engine for luxurie cars, that it is not same engine as the one in 50 000 $ car. You think they can do it? I'm not sure GM is determine to do so.

Through the last few decades GM builded nortshtar V8, presented concept of XV12 engine (DOHC design and it could easily be an ohv engine and i bet ohv v12 would be lighter and smaller than DOHC V12), started building ultra v8, builded northstar supercharger just for Cadillac STS-V and XLR-V, than when bankrupcy came along they've cancelled all of it. There was talk about buying v8 from other engine manufacturer... and now there are rumors that they are thinking again about it if they go with real Cadillac flagship. IF it so easy to dismiss need for DOHC v8 GM wouldn't think much about it ..or would they?

What is good for Cahevrolet doen't alway have to be good for Cadillac? Maybe in luxurie class being good enough isn't enough

[Guest Grant]

This thread shows exactly why gm will ultimately fail. Failure to innovate and persistence with trying to force old technology to keep up with the competition. GM will bomb for the same reasons the UK motorcycle industry bombed. The more revs you do in a pushrod, the more inefficient it becomes and any semblance of competitiveness with a DOHC v8 goes out the window.

[dwightlooi]

A better comparison is between the 505 hp / 470 lb-ft LS7 engine in the Z06 and the 500 hp / 480 lb-ft 3.8TT engine in the 911 Turbo. The LS7 is the lighter, smaller, less complex and less costly engine. Fuel Economy wise, the Z06 posts 15/24 mpg to the 911 Turbo's 16/24 (manual transmission on both). IT also goes to show that displacement is pretty low on the list of characteristics that determine fuel economy. That's a 1 mpg difference between a 7.0 liter engine and a 3.8 liter mill (almost half its swept volume).

All of this is true..

But buyers of luxurie cars (and luxurie performance cars) don't really care about price of the engine, weight of the engine, complexity of the engine. Do you think owner of Ferrari , Aston Martin go and change oil or tune their car by themselves?? No..they can pay others people to do that. Yes small block are lighter but by how much?? Also engine (small block) is lighter but cars with that engine(camaro, CTS-V) doesn't seems to be much lighter or much more nimble then their competition. If GM can't use lightness of small block what is the point..

Like i sad before if GM are serious about Cadillac they should offer special engine especially for future flagship. LSA engine is an excellent engine..but it can be found in Camaro which cost about 50 000$. Imagine 120 000$ Cadillac with same engine. Yes you know, and i know, and some car enthusiasts knows it is an excellent engine. But large number of people will see expensive car(cadillac rwd flagship) with engine from cheaper and less exclusive brand (Chevrolet)

And reading different forums, car magazines i'm not sure people would not realize

-it is not the same engine from truck

-it is not the same engine as it was before 60 years

-because it has big displacement it doesn't have to weight 1 tone etc.

Outside USA small block are not favorite luxurie cars engine and it is not first thing people will think when they think about luxurie. And it seems there are very large number of people inside USA that thinks the same way.

IF GM is serious about Cadillac as luxurie car maker,and offer small block in real luxurie flagship (i'm not talking about CTS-V here or some SUV) GM should prove to buyers of Mercedes S , BMW 7. Jaguar XJ etc that small block are excellent engine for luxurie cars, that it is not same engine as the one in 50 000 $ car. You think they can do it? I'm not sure GM is determine to do so.

Through the last few decades GM builded nortshtar V8, presented concept of XV12 engine (DOHC design and it could easily be an ohv engine and i bet ohv v12 would be lighter and smaller than DOHC V12), started building ultra v8, builded northstar supercharger just for Cadillac STS-V and XLR-V, than when bankrupcy came along they've cancelled all of it. There was talk about buying v8 from other engine manufacturer... and now there are rumors that they are thinking again about it if they go with real Cadillac flagship. IF it so easy to dismiss need for DOHC v8 GM wouldn't think much about it ..or would they?

What is good for Cahevrolet doen't alway have to be good for Cadillac? Maybe in luxurie class being good enough isn't enough

That a unique engine or a dedicated variant of an engine for Cadillac will help with exclusivity and perception is definitely valid. However, that such a move will also incur $1~2K in additional costs per caddy from a small volume engine line is also a reality. The question then is how much that perception benefit weighs against the price tag hit. This however has nothing to do with Pushrod vs DOHC; a Toyota Tundra and a Lexus LS460 both us a Toyota UR-series DOHC V8 that is no more or less a problem than using an LS3 in a Camaro and an LSA in a CTS-V.

One thing that I have always been critical of GM on is the way they dress up their engines. I mean GM's current dress covers are better off left on the factory floor. I say that for two reasons. Firstly they look no better than Rubbermaid Trash Bin covers and really have no aesthetic value. In fact, if you remove the LFX dress cover the fancy resonance intake manifold makes the engine look better. Secondly, they can call it an acoustic cover or whatever they want. Fact is, I have deliberately test driven a LaCrosse and a CTS (previous gen) with and without the cover on an it makes absolutely no difference in the noise signature inside the vehicle. I am actually a fan of engine dress covers when they are well done and I seriously hope that GM will emulate the efforts of turn of the Millenium Volkswagen efforts in this regard. The previous gen passat's underhood dressings are exemplary and a Caddy or a Buick deserves at least as much. This will cost not more than $100 or 200 per vehicle and it possibly will have a bigger perception impact that giving the engine a caddy specific tune, displacement or compression.

[aldw]

Cadillac would be penalized for engine sharing much more than Toyota with, especially since there's a greater perceived difference between a Chevy and Caddy than there is between Toyota and Lexus, and the market acts accordingly. That's one reason why having an extra $1000 charge for engine exclusivity may be necessary to win over the target customers.

On the engine cover thing, definitely agree 100% that GM needs to do much better.

[riviera74]

This thread shows exactly why gm will ultimately fail. Failure to innovate and persistence with trying to force old technology to keep up with the competition. GM will bomb for the same reasons the UK motorcycle industry bombed. The more revs you do in a pushrod, the more inefficient it becomes and any semblance of competitiveness with a DOHC v8 goes out the window.

Do you have any proof of that? I call BS on this idea.

[Drew Dowdell]

This thread shows exactly why gm will ultimately fail. Failure to innovate and persistence with trying to force old technology to keep up with the competition. GM will bomb for the same reasons the UK motorcycle industry bombed. The more revs you do in a pushrod, the more inefficient it becomes and any semblance of competitiveness with a DOHC v8 goes out the window.

DOHC is older technology than OHV pushrod, so your theory fails. Furthermore, by being able to have larger displacement due to the packaging of the engine, pushrod engines can give you more torque at lower RPM, meaning they don't need to rev to 7,000rpm to move the car. The Buick Roadmaster V8 and Honda S2000 both have 240 horsepower, but in the same car, the LT-1 V8 would kick the Honda's ass because it also had 360 ft-lbs of torque while the Honda can barely manage 180 ft-lb.

[Drew Dowdell]

Why not a set of DOHC heads that fit on a pushrod block? I know the idea gets a bad rap from the 3.4 Twincam, but the problem there was in the execution, not the theory. Had they not cheaped out on timing belt idler pulleys, the basic engine would have been sound. The other problems with that engine were the accessories that hang off the accessory belt.

[Robert Hall]

Why not a set of DOHC heads that fit on a pushrod block? I know the idea gets a bad rap from the 3.4 Twincam, but the problem there was in the execution, not the theory. Had they not cheaped out on timing belt idler pulleys, the basic engine would have been sound. The other problems with that engine were the accessories that hang off the accessory belt.

Or how about an engine cover that gives the appearance of DOHC...that would work w/ most consumers..

[smk4565]

At the way the market is moving away from V8s, there might not be much need for one anyway. The Corvette loyalists will buy it whatever the engine is, although Corvette sales are shrinking and the fan base getting older and older. Pick-ups will sell with anything due to so few brand options, and the V6 will become more common there anyway. And the Cadillac flagship will be DOA anyway, and that is the only car that really needs a DOHC V8. The CTS could use one since the E-class and 5-series have one, but they will sell the CTS at a discount to compensate for lack of a V8, much like Audi and Lexus do. And that is why the E and 5 combine to sell 9,000 a month and the A6 and GS sell 2,000, with a smaller profit margin to boot.

[G. David Felt]

This thread shows exactly why gm will ultimately fail. Failure to innovate and persistence with trying to force old technology to keep up with the competition. GM will bomb for the same reasons the UK motorcycle industry bombed. The more revs you do in a pushrod, the more inefficient it becomes and any semblance of competitiveness with a DOHC v8 goes out the window.

DOHC is older technology than OHV pushrod, so your theory fails. Furthermore, by being able to have larger displacement due to the packaging of the engine, pushrod engines can give you more torque at lower RPM, meaning they don't need to rev to 7,000rpm to move the car. The Buick Roadmaster V8 and Honda S2000 both have 240 horsepower, but in the same car, the LT-1 V8 would kick the Honda's ass because it also had 360 ft-lbs of torque while the Honda can barely manage 180 ft-lb.

I agree that due to Marketing, people are all caught up in the DOHC V8, V6 or 4 bangers and yet other than horsepower, they suck always on the torque front and that is what is really needed in efficient small auto's. You need a car that can be moved around really well, not a rocket from red light to red light.

I can see GM winning with a 140hp/250lbs of torque 4 banger push rod engine. I truly believe they can build a more efficient version than depending on the DOHC crud.

[dwightlooi]

I agree that due to Marketing, people are all caught up in the DOHC V8, V6 or 4 bangers and yet other than horsepower, they suck always on the torque front and that is what is really needed in efficient small auto's. You need a car that can be moved around really well, not a rocket from red light to red light.

I can see GM winning with a 140hp/250lbs of torque 4 banger push rod engine. I truly believe they can build a more efficient version than depending on the DOHC crud.

The one thing that most people do not realize is that having more cams and more valves actually hurt fuel economy at cruise. The reason is simple. Having more cams and more valves incur more frictional losses -- wasted power from each drop of fuel burned. Their advantage having mulitple valves and a direct acting DOHC head is that it permits higher engine rpm limits and higher airflow potential which translates to higher specific output. However, none of that has ANY value at cruise or when accelerating moderately around the city. The reason being that any airflow advantage is negated by the fact that the throttle is not fully open. In otherwords, the valvetrain and the airflow capacity of the head is not choking the engine -- the throttle plate is. If it isn't you'll have unintended acceleration! So at cruise and with moderate acceleration, all the multi-cam and valves do is increase friction with no benefit whatsoever.

Having said that, I don't see the Pushrod arrangement as being particularly beneficial in an Inline-4. The packaging benefits apply primarily to Vee-type engines, especially wide 90-deg V arrangements where the heads add significantly to engine width and bulk. The frictional benefits of having one camshaft and a minimum number of valves can be had in an Inline-4 by simply using an SOHC head and 2-valves per cylinder -- this is in fact arrangement currently being used in Honda's Insight Hybrid for its fuel economy over DOHC 4-valve setups.

[Drew Dowdell]

This thread shows exactly why gm will ultimately fail. Failure to innovate and persistence with trying to force old technology to keep up with the competition. GM will bomb for the same reasons the UK motorcycle industry bombed. The more revs you do in a pushrod, the more inefficient it becomes and any semblance of competitiveness with a DOHC v8 goes out the window.

DOHC is older technology than OHV pushrod, so your theory fails. Furthermore, by being able to have larger displacement due to the packaging of the engine, pushrod engines can give you more torque at lower RPM, meaning they don't need to rev to 7,000rpm to move the car. The Buick Roadmaster V8 and Honda S2000 both have 240 horsepower, but in the same car, the LT-1 V8 would kick the Honda's ass because it also had 360 ft-lbs of torque while the Honda can barely manage 180 ft-lb.

I agree that due to Marketing, people are all caught up in the DOHC V8, V6 or 4 bangers and yet other than horsepower, they suck always on the torque front and that is what is really needed in efficient small auto's. You need a car that can be moved around really well, not a rocket from red light to red light.

I can see GM winning with a 140hp/250lbs of torque 4 banger push rod engine. I truly believe they can build a more efficient version than depending on the DOHC crud.

lol, I drive with 140hp/255lbs now... but I use 8 bangs to get it.

[G. David Felt]

This thread shows exactly why gm will ultimately fail. Failure to innovate and persistence with trying to force old technology to keep up with the competition. GM will bomb for the same reasons the UK motorcycle industry bombed. The more revs you do in a pushrod, the more inefficient it becomes and any semblance of competitiveness with a DOHC v8 goes out the window.

DOHC is older technology than OHV pushrod, so your theory fails. Furthermore, by being able to have larger displacement due to the packaging of the engine, pushrod engines can give you more torque at lower RPM, meaning they don't need to rev to 7,000rpm to move the car. The Buick Roadmaster V8 and Honda S2000 both have 240 horsepower, but in the same car, the LT-1 V8 would kick the Honda's ass because it also had 360 ft-lbs of torque while the Honda can barely manage 180 ft-lb.

I agree that due to Marketing, people are all caught up in the DOHC V8, V6 or 4 bangers and yet other than horsepower, they suck always on the torque front and that is what is really needed in efficient small auto's. You need a car that can be moved around really well, not a rocket from red light to red light.

I can see GM winning with a 140hp/250lbs of torque 4 banger push rod engine. I truly believe they can build a more efficient version than depending on the DOHC crud.

lol, I drive with 140hp/255lbs now... but I use 8 bangs to get it.

Those are 8 very respectable Bangs!

[riviera74]

I have never understood the perception of DOHC is better than pushrod. What gives people that perception? I ask why for this reason: my Park Avenue Ultra has a SC3800, and the 3800 is easily the best v6 GM has ever put into a production car (prior to the 3.6v6, maybe). Why would a DOHC v8 be so much better when that may not be the case? Engine design and execution and performance, not whether you have OHC or not, should determine what is best for your car.

If I have one complaint about the v6 engines that GM has now in its cars, it is lack of torque compared to the 3800. Can GM fix that please?

[Drew Dowdell]

It's all about HP/L yo! that's what Honda ricer boys told me is best!

[smk4565]

All of you that think you don't need a DOHC V8 don't own one. Once you get used to having a DOHC V8 it is hard to go to anything else. The only thing I have driven that is better is the BMW straight six, that is the smoothest engine out there. Fuel economy concerns though will push the DOHC V8 crowd like myself to DOHC V6s, possibly with turbo or supercharger.

[Z-06]

All of you that think you don't need a DOHC V8 don't own one. Once you get used to having a DOHC V8 it is hard to go to anything else. The only thing I have driven that is better is the BMW straight six, that is the smoothest engine out there. Fuel economy concerns though will push the DOHC V8 crowd like myself to DOHC V6s, possibly with turbo or supercharger.

Define smooth.

[Drew Dowdell]

Smoother then the Rolls 6.7?