DOHC or SIBC for Corvette C7

[dwightlooi]

Which engine Corvette fans will like to see in the next corvette...

GM's next generation 5.5 liter Small Block push-rod V8 with DI and AFM,

or a 60 degree V8 derived from the high specific output 3.0 liter DOHC V6 engine?

[gm4life]

The OHV motor simple. No OHC motor belongs in a Corvette.

[ocnblu]

There is no better V8 made than Chevy's smallblock. Best to keep it.

[Satty]

The OHV motor simple. No OHC motor belongs in a Corvette.

Fail

Edited November 15, 2009 by Satty

[Drew Dowdell]

Fail

And it's not offered anymore... replaced with a pushrod.

[Drew Dowdell]

The torque numbers answer this question.

[Satty]

And it's not offered anymore... replaced with a pushrod.

The fact remains that one of the fastest, most exclusive naturally-aspirated Corvettes in the history of the name was DOHC.

[hyperv6]

Well it being 2009 and the C7 is still a few years off. Here is my out look.

The Vette is expected to be smaller and lighter. This is a known. Also known GM will have to go to smaller V8 engines for the trucks. That means the Vette will have to use these said engines or at least be baised on them. Also add in the fact the entire industry is not going OHC and DI.

A smaller displacment engine with VVT, DI and Turbo could deliver punch most engines in the past never could think of. The VVT give the low end torque and keeps it flat all the way up the RPM range.

Turbo's thrive on DI. GM and Fod have proven this already.

IF GM can get 290 HP out of 2.0 liters with 315 ft lbs and 325 HP out of a 2.8 V6 Imagine what they could do with a V8. The Leno Camaro also shows 3.6 DI Turbo can put out the same numbers as a LS engine.

So a small Turbo V8 DOHC I feel would keep the Vette up to date and give it a power plant GM could still use in other heavier vehicles. Cost is everything and the Vette will still be expected to share parts with other cars to live on and still pay the rent.

Also some still have to get over the illusion the present LS engine is a small block Chevy. Other than some odd bore center spacing and a lot of marketing the present engine has as much to do with the old one as the original Dodge Hemi has to do with todays Chrysler Hemi.

The fact is GM and Chrysler both did these engine to contain cost and save money they did not have. If GM has not has money issues they would have been gone long ago. The whole saving grace here is Ford Screwed up on the 4.6 mod engine and never really got it right. The new Eco engines they have are right this time and they will have a V8 to go with it. So GM and Chrysler both need to stop the BS on the 2 valve and move into the best DOHC V8 they can now before it is too late.

The original ZR1 was a over piced chunk of aluminum. They tried to do too much with too little elctonic technology. The computer technolgy just was not there to support what they really wanted to do. Today they can do it in a smaller packackage and make it work.

You can either just have another evolution and get left behind or create a new revolution like the original small block did in 1955. GM has the best powertrain engineers in the world and it is time they are left to do what they can with all the technology available not just what is on hand and affordable.

If you want a V8 in the future you will need to use all things available to keep it on the road unless the CAFE comes down. GM needs to get more from less and DOHC is the way to the future. Everyone else has figured it out.

Not the two companies that still use the 2 valve V8 are the ones that filed chaper 11.

I remember back in WW2 that some pilots fought to keep the piston engine too. At first it looked like the right idea till they did get the jets rigt.

Right or wrong like it or not this is just my 2 cents. Some of the best engines I have ever driven has more than two valves and no GM name on them. It is time the best in the world should again come from GM.

Edited November 15, 2009 by hyperv6

[Camino LS6]

The LS engines are still the best performing, most-efficient,most cost-effective V8s in the non-exotic realm today. I'd look for evolution, not revolution here. Not to mention the fact that they are far easier to package and maintain than DOHC V8s.

One point Hyper makes is certain, what goes into the trucks will find its way into the Vette in some form.

[Drew Dowdell]

The fact remains that one of the fastest, most exclusive naturally-aspirated Corvettes in the history of the name was DOHC.

"most exclusive" = "hardest to find parts for"

It was fastest for it's generation, but it's not the fastest of the naturally aspirated ones.....

[Chevy Nick]

I thought we already did this thread. There are 2 members on here (smk4565 and hyperv6) that think the Corvette needs a bunch of un-necessary tech, expense, and weight, while everybody else loves the small block architecture.

Dwightlooi: Why have you started a new thread about the same topic? http://www.cheersandgears.com/index.php/topic/40869-which-engine-for-the-c7-corvette/

Edited November 16, 2009 by Chevy Nick

[hyperv6]

I thought we already did this thread. There are 2 members on here (smk4565 and hyperv6) that think the Corvette needs a bunch of un-necessary tech, expense, and weight, while everybody else loves the small block architecture.

Dwightlooi: Why have you started a new thread about the same topic? http://www.cheersandgears.com/index.php/topic/40869-which-engine-for-the-c7-corvette/

If you put my post name with that one I may have to change my mind just because of that. LOL!

[z28luvr01]

The torque numbers answer this question.

That, along with the RPMs at which they're achieved.

Again, the C7 is going on a huge diet. Even if the current LS engines are used, if the Corvette slims down to the weights that Dwight is proposing, the performance gains will be significant. Just go with the SIBC and be done with it.

[Camino LS6]

The vette has always been an over-achiever doing more with less.

I expect the same from the C-7.

[ocnblu]

"Also some still have to get over the illusion the present LS engine is a small block Chevy. Other than some odd bore center spacing and a lot of marketing the present engine has as much to do with the old one as the original Dodge Hemi has to do with todays Chrysler Hemi."

Excuse me? Let's get one thing straight. With the smallblock, the line of evolution has never stopped since 1955. Chrysler's "Hemi" descriptor, which I respect, has been on many different architectures... even a four cylinder, with many stops and starts since what, the early 50's?

I will take the straightforward, reliable, easy-to-modify pushrod V8 any time over a DOHC.

[hyperv6]

The LS engines are still the best performing, most-efficient,most cost-effective V8s in the non-exotic realm today. I'd look for evolution, not revolution here. Not to mention the fact that they are far easier to package and maintain than DOHC V8s.

One point Hyper makes is certain, what goes into the trucks will find its way into the Vette in some form.

The truck key is the big one. the truck engine will have to get more MPG and better emissions. I get the feeling we will see more composites on the truck to cut weight but that is not going to be enough.

Just a gut feeling we will see a DI engine with less displacement in the truck and we will see a Turbo package option of some kind. The other factor is Cadillac will share in this engine too. GM will not do more than one V8 and it have to be adaptable from a Truck to a Vette and even the top line Cadillac. Unless they make some changes to the Alpha I expect a twin turbo V6 for the future Camaro.

As for Exotic DOHC is no longer Exotic. It has become the norm. It is what the buyers want and expect from other brands. If you want to win any over you have to give them what they want. The GM fans will buy it no matter what.

[Camino LS6]

DOHC is beyond the automotive vocabulary of most buyers - the demand argument is bunk.

[ocnblu]

"Give them what they want" <--- WTF? All other vehicles in the Corvette's class are looking at its four round taillights on the race track... we don't need to prove a THING.

[hyperv6]

"Also some still have to get over the illusion the present LS engine is a small block Chevy. Other than some odd bore center spacing and a lot of marketing the present engine has as much to do with the old one as the original Dodge Hemi has to do with todays Chrysler Hemi."

Excuse me? Let's get one thing straight. With the smallblock, the line of evolution has never stopped since 1955. Chrysler's "Hemi" descriptor, which I respect, has been on many different architectures... even a four cylinder, with many stops and starts since what, the early 50's?

I will take the straightforward, reliable, easy-to-modify pushrod V8 any time over a DOHC.

The 1955 Small Block you speak of stopped many years ago. That engine shares nothing with todays engine. I would expect a fan of the present LS engine to give it more credit for being a all new modern 2 valve engine that relied on nothing of the original engine. The last LS engine I was in has nothing shared with anything on my last 1970 350 engines I had. To compare a original SBC and to a LS is selling the LS short.

The 2 valve LS is a great engine but GM kept it because at the time it was much cheaper to build. Less parts less cost more profit for a cash starved company. Also without VVT less low end torque with the 4 vlaves. Today the computers can handle it.

As for the Hemi... You know what I mean. Chrysler has tried to convince many this was the second coming of the 426 HEMI. It was all marketing. The new Hemi in fact shares more similarities with the LS engine than any other.

All I can say is I was able to spend time with John Lingenfelter several a few visits and just sit and talk to him. He by far was one of the best builders of the SBC, LT and LS engines there has been. At the time of his death he was well into the Ecotech and the DOHC V6. He was seeing numbers that as strong or stronger than some of his best LS engines. He was sitting on 2,000 HP with the DOHC V6 Turbo with not many aftermarket parts. None were avaiable and he often had to mod stock parts. In fact it was this car that took his life. If he had lived I could only imagine where this would have gone. He loved these kinds of challanges and was making great head way.

But I do have to admit his Twin Turbo LS Vette and LS Sonoma would even make a ZR1 blush.

On last thing to consider. If GM has had to use displacemnt on demand to improve fuel economy just as Chrysler. That should tell you smaller and more efficent is needed. Ford OHC engine have not needed it.

I guess it comes down not so much to what we want but GM needs to survive the regs for the long term future. The next engine needs to last more than 8 years and were all this is going.

[smk4565]

420 hp from a 4.0 liter is like an M3 engine, it would have to be really high revving. How did you come up with the gas mileage estimates and give the pushrod 2 more mpg than it gets now?

How about an apples to apples comparison. 6.2 liter pushrod with 420 hp like the Vette has now, or 6.2 liter DOHC V8 with 518 hp like the Mercedes E63 has. If you want power, DOHC makes more. If you want economy, use a Nissan GT-R type engine.

[ocnblu]

You ignore my "line of evolution" caveat. And simplicity trumps complexity, even with computers.

[Drew Dowdell]

420 hp from a 4.0 liter is like an M3 engine, it would have to be really high revving. How did you come up with the gas mileage estimates and give the pushrod 2 more mpg than it gets now?

you don't think adding direct injection, an 8-speed DSG, and VVT would add a bit of fuel economy....

[Camino LS6]

You ignore my "line of evolution" caveat. And simplicity trumps complexity, even with computers.

Absolutely right, an unbroken lineage.

The original smallblock was such an amazing design that the basic architecture ran all the way from '55 to the nineties.

The LT1 and LT4 were a bridge to the truly all-new LS series, when even 1-8-4-3-6-5-7-2 no longer applied.

Despite the wholesale design differences, application and envelope of the LS series make them a direct descendent of the original

[dwightlooi]

Q&A

Q: Why did I start this thread instead of continuing a previous thread also on C7 engine options?

A: Because this is about which V8 for the C7 assuming we are set on a V8, that was about whether the Vette should get a V12.

Q: Why did I compare a 4.0 liter DOHC with a 5.5 Pushrod?

A: The idea is to get to ~420hp. Also, a 4.0 liter DOHC will weigh about the same and take up about as much space as a 5.5 Pushrod.

Q: Why a 60 deg DOHC V8?

A: Because the idea is to minimize R&D, as well as share most components and the manufacturing line with the existing 90hp/liter liter LF1 60 deg V6 (3.0 270hp). Besides, a more compact 60 degree V8 is required if the engine is to fit in the same width as a 5.5 liter pushrod V8. A 60 degree engine won't be even fire, but neither is a flat crank V8. In a sports car, that slightly off-beat pulse is perhaps even a plus. 60 deg V8s are not horrible or all that rare... the Taurus SHO 3.4 V8 and the Volvo 4.4 V8 are both 60 degree designs.

Q: Where did the fuel economy estimates come from?

A: The 5.5 pushrod's estimates come from assuming a slight improvement over the current 6.2 liter LS3 engine. This assumption is based on incorporation of an 8-speed dual clutch transmission, taller cruising gear ratio, higher compression, Direct Injection, Cylinder deactivation and a lower displacement. This accompanied by about 10% lower weight and slightly smaller size projected for the C7 led me to estimate a 1 mpg improvement in city driving and a 2 mpg improvement in highway cruising. I don't think they are unreasonable estimates. If anything they are a bit conservative.

Q: Why did I assign lower fuel economy numbers to the DOHC engine?

A: Because DOHC V8s of today have worse economy numbers than pushrod V8s today. The reasons are mainly that they have higher internal friction due to having twice as many valves & guides, four times as many cams and a much longer serpertine cam drive chain. In addition, because DOHC engines make a given horsepower with less displacement, less torque, but at higher revs, they also tend to be geared to keep revolutions higher. This often increases pumping losses more than the reduced displacement saves. For example... The 6.2 liter Camaro SS posts 16/25 with an automatic, the 6.3 liter C63 AMG posts 13/20 mpg, the 4.0 liter M3 posts 13/20mpg. The Camaro weighs 3859 lbs, the C63 logs 3924 lbs whereas the M3 tips scale at 3726 lbs.

Edited November 16, 2009 by dwightlooi

[Drew Dowdell]

As always, dwightloo puts them succinctly in their place.

[loki]

sibc. torque and cause it can keep a huge range with one tank the others can't. oh and was it the 0-60 ...faster than the ohc.

[dwightlooi]

sibc. torque and cause it can keep a huge range with one tank the others can't. oh and was it the 0-60 ...faster than the ohc.

Actually, a SIBC (Pushrod) engine does not have higher torque than an DOHC engine of equal displacement. The DOHC engine usually makes more torque as well as power. About 8~12% more torque and 10~40% more power.

But, that's besides the point. The point is that while a pushrod engine needs to be bigger in displacement to match the output of a DOHC powerplant, in can do so without being physically bigger or heavier than the smaller displacement DOHC engine because it has much smaller, simpler and lighter heads as well as much simplified valve train parts. The simplicity, of course, makes it cheaper to manufacture or service as well. In addition, because of the lower level of internal friction and increased low rpm torque from the increased displacement affording taller overall gearing, it is usually also lower in fuel consumption. These are the reasons the pushrod design was invented in the first place -- it actually came after the advent of SOHC and DOHC designs in the 1930s.

The problem with SIBC engines are two fold. The first is the heavier actuated mass of each individual valve -- due to the long pushrod and larger valve diameter -- limits civility at higher rpms and ultimately forces a lower ceiling on revs before valve float and other issues become insurmountable. In passenger cars this translates into a lower level of perceived refinement. In race cars, it limits ultimately permissible revolutions and reduces durability. The second being that in many countries, tax on a vehicle is based on its displacement not fuel economy or anything else. Hence, using a larger displacement engine makes the car more expensive regardless of whether it uses more or less fuel.

Edited November 16, 2009 by dwightlooi

[hyperv6]

You ignore my "line of evolution" caveat. And simplicity trumps complexity, even with computers.

It is nice to see the GM marketing worked well!

As for the future Complexity is what will permit you to still buy the V8 power you want. Again you do not give the LS enough credit. While it may only have two valves it is far from the simple small block that GM used to make years ago. Displacment on Demand, VVT, DI and dry sump systems are not all that simple and are just the same as they are on the DOHC engine. Oh ya all of this is run by very advance computers. To call the LS simple is very short sighted. If you really love this engine give it the credit it deserves. Even with one came it is a very advance well worked out design.

[hyperv6]

Actually, a SIBC (Pushrod) engine does not have higher torque than an DOHC engine of equal displacement. The DOHC engine usually makes more torque as well as power. About 8~12% more torque and 10~40% more power.

But, that's besides the point. The point is that while a pushrod engine needs to be bigger in displacement to match the output of a DOHC powerplant, in can do so without being physically bigger or heavier than the smaller displacement DOHC engine because it has much smaller, simpler and lighter heads as well as much simplified valve train parts. The simplicity, of course, makes it cheaper to manufacture or service as well. In addition, because of the lower level of internal friction and increased low rpm torque from the increased displacement affording taller overall gearing, it is usually also lower in fuel consumption. These are the reasons the pushrod design was invented in the first place -- it actually came after the advent of SOHC and DOHC designs in the 1930s.

The problem with SIBC engines are two fold. The first is the heavier actuated mass of each individual valve -- due to the long pushrod and larger valve diameter -- limits civility at higher rpms and ultimately forces a lower ceiling on revs before valve float and other issues become insurmountable. In passenger cars this translates into a lower level of perceived refinement. In race cars, it limits ultimately permissible revolutions and reduces durability. The second being that in many countries, tax on a vehicle is based on its displacement not fuel economy or anything else. Hence, using a larger displacement engine makes the car more expensive regardless of whether it uses more or less fuel.

Have you considered the factors of adding a power adder like a twin turbo and what the gains would be as in the Ecoboost engines? This would add to cost and weight but vs the power and economy gains?

On the gearing I have found on many of the smaller cars the gearing is rather conservitive. For example the Ecotech LNF in a Solstice has a very flat torque curve. It can and will pull 260 lb-ft from 2500-5300 RPM on 2.0 liters. HP peaks at 260 HP at 5300 RPM. VVT is a very valuable tool.

Edited November 16, 2009 by hyperv6

[loki]

Actually, a SIBC (Pushrod) engine does not have higher torque than an DOHC engine of equal displacement. The DOHC engine usually makes more torque as well as power. About 8~12% more torque and 10~40% more power.

i was just talking about the 2 engines you spec'd out. i was in favor of the sibc.

until NG engines have HCCI down, stick with tech that they have more than limited experience with.

as in, i could see GM going to a ~5.0L ohc engine when they get hcci in more than one engine, prolly be another 6-7 years?

[CaddyXLR-V]

Actually, a SIBC (Pushrod) engine does not have higher torque than an DOHC engine of equal displacement. The DOHC engine usually makes more torque as well as power. About 8~12% more torque and 10~40% more power.

But, that's besides the point. The point is that while a pushrod engine needs to be bigger in displacement to match the output of a DOHC powerplant, in can do so without being physically bigger or heavier than the smaller displacement DOHC engine because it has much smaller, simpler and lighter heads as well as much simplified valve train parts. The simplicity, of course, makes it cheaper to manufacture or service as well. In addition, because of the lower level of internal friction and increased low rpm torque from the increased displacement affording taller overall gearing, it is usually also lower in fuel consumption. These are the reasons the pushrod design was invented in the first place -- it actually came after the advent of SOHC and DOHC designs in the 1930s.

The problem with SIBC engines are two fold. The first is the heavier actuated mass of each individual valve -- due to the long pushrod and larger valve diameter -- limits civility at higher rpms and ultimately forces a lower ceiling on revs before valve float and other issues become insurmountable. In passenger cars this translates into a lower level of perceived refinement. In race cars, it limits ultimately permissible revolutions and reduces durability. The second being that in many countries, tax on a vehicle is based on its displacement not fuel economy or anything else. Hence, using a larger displacement engine makes the car more expensive regardless of whether it uses more or less fuel.

And since the Corvette is a lightweight sports car, it would benefit more from more top end power, than more torque. Torque is great if you want to shred the tires from a stoplight, but on a track when RPMs aren't going to drop to 2k-3k, more power in that range is useless.

[dwightlooi]

Have you considered the factors of adding a power adder like a twin turbo and what the gains would be as in the Ecoboost engines? This would add to cost and weight but vs the power and economy gains?

On the gearing I have found on many of the smaller cars the gearing is rather conservitive. For example the Ecotech LNF in a Solstice has a very flat torque curve. It can and will pull 260 lb-ft from 2500-5300 RPM on 2.0 liters. HP peaks at 260 HP at 5300 RPM. VVT is a very valuable tool.

A turbo setup presents a myraid of issues.

(1) Firstly, a turbocharger introduces turbo lag. On WOT it may not be bad especially if you use small turbochargers and modest boost levels. However, part throttle lag is quite pronounced even in such designs.

(2) Secondly, the turbo extracts energy out of the exhaust which means it takes heat out of it. A catalytic converter downstream of a turbo takes a longer while to light making it harder to meet emission regulations. This is worse on twin sequential turbo setups which is why the 4.4 liter twinturbo V8s BMW just recently introduced are ditching their twin turbos for a single larger turbo. One way around the problem is to insert a pre-catalyst ahead of the turbo. Subaru does this on the turbo H4s, but this reduces turbo efficiency and performance (in the Subarus it meant the torque peak coming in at 4000 rpm instead of 2800 rpm).

(3) Thirdly, with a turbocharger comes a whole spaghetti of pressurized plumbing to take air to the turbos, from the turbos to intercoolers in the front on the radiator and finally from the IC back to the intake. These take up a bunch of space, is often a source of leaks in older cars. They also contribute the turbolag almost as much as the inertia of the turbine and compressor wheels. This is due to the lag time attributable to bringing the pressurized volume up to the desired pressure. The bigger the volume, the worse the problem. Imagine pressurizing a basket ball and pressurizing a room, and you'll get the picture. The alternative is to use an air-to-water system which minimizes the pressurized volume and saves on all those big hoses. However, it also introduces a second water loop with its own pumps, radiators, heat exchangers, etc.

(4) Lastly, while GM is certainly going to a 1.4 turbo for the Cruze for efficiency reasons, the economy advantages of a turbocharged engine is traditionally not very well established. For instance, an VW/Audi 1.8T engine making 150~170hp was not more more miserly on fuel than a typical 2.2~2.4 liter engine of a similar output. Their 2.7T with 250hp was not more economical than a 3.2~3.5 liter engine with 250hp either. The 300hp twin turbo I6 from the BMW 335 is not more economical than a 3.6 liter DI V6 from GM or a 3.5 DI V6 from Toyota also making about 300hp. One can make a reasonable argument that 140hp with 40~42 mpg which the Cruze is shooting for can be had with a 1.4 turbo or with a 1.8 liter NA engine with DI and part time Atkinson cycle (ala the Civic's R18A). This is mainly due to the reduced compression ratio and the inability to utilize resonance charging with the (by now) well honed art of tuning intake runner lengths and plenum volumes. The biggest advantage really is that for a given hp, these turbo engine tend to have better low end torque. The disadvantage is that the cost more than an NA engine with similar output and/or economy.

As far as a twin turbo V8 goes, you can probably go down to about 3 liters and still make 420hp. It'll not cost less than a high reving 4.0 NA and certainly not less than a 5.5 liter Pushrod. It may not be any lighter or take up any less space. It may not be as reliable or as responsive off boost. Finally, it may not be more economical on fuel. If you really want a turbocharged engine in the Vette, it'll make more sense to drop two cylinders and go to a turbo six. The new V6 S4 picked up fuel economy not because it went to a smaller displacement and a supercharger, but because it went from a V8 to a V6 reducing a bunch of frictional loss by eliminating two cylinders, two journals and 8 valves. I had once suggested that... a turbocharged version of the 4.2 liter DOHC Inline-6 making about 420hp using one turbo (about 10 psi of boost and 10.5:1 compression). Afterall, the Vette started life with a six. But, I didn't recall many liking the idea of an six cylinder Vette.

[Justin Bimmer]

I know I may be hijacking this thread but I am interested now in some expert information from dwightlooi. So with the disadvantages to a gasoline turbo. What makes a diesel turbo better? If it is better?

[Camino LS6]

And since the Corvette is a lightweight sports car, it would benefit more from more top end power, than more torque. Torque is great if you want to shred the tires from a stoplight, but on a track when RPMs aren't going to drop to 2k-3k, more power in that range is useless.

Backwards for any street-driven Vette.

Down low is where buyers will feel the power, top-end screamers are for the track.

[hyperv6]

Backwards for any street-driven Vette.

Down low is where buyers will feel the power, top-end screamers are for the track.

That is the sweet part of VVT. You can now carry a flat torque cure from low down to the top. My Turbo 4 as state goes from just over 2000 RPM to 5300 RPM and holds the torque. The same could be sone with about any other engine. Today the cams can be held in the sweet spot even as it changes with RPM.

The days of peak levels are becoming a thing of the past with the new Tech.

[CaddyXLR-V]

Backwards for any street-driven Vette.

Down low is where buyers will feel the power, top-end screamers are for the track.

But it is really not necessary to have more power lower in the RPMs on a 3000lb car. All it will do is make it easier to break the tires loose, with no benefit to performance.

[Camino LS6]

But it is really not necessary to have more power lower in the RPMs on a 3000lb car. All it will do is make it easier to break the tires loose, with no benefit to performance.

A bit of a blanket statement, don't you think? Getting the power to the ground has always been a separate challenge from creating it in the first place. That challenge would remain no matter the configuration of the powerplant used.

The bottom line here is that it would be illogical for GM to develop an engine such as Dwight has described, and I would say that it would be highly unlikely that they would do so. The "advantages" are ephemeral, while the disadvantages are obvious and concrete.

Won't happen.

[CaddyXLR-V]

A bit of a blanket statement, don't you think? Getting the power to the ground has always been a separate challenge from creating it in the first place. That challenge would remain no matter the configuration of the powerplant used.

The bottom line here is that it would be illogical for GM to develop an engine such as Dwight has described, and I would say that it would be highly unlikely that they would do so. The "advantages" are ephemeral, while the disadvantages are obvious and concrete.

Won't happen.

There are advantages to both. In block cam engines could be shared with the trucks, while DOHC engines could be shared with Cadillac. Cadillac could really use a new V8.

And about the tires, there are limits to street tires, and their limits are lower than either engine would put out at low RPMs. The difference is the DOHC engine would have more power where it could be used.

[CaddyXLR-V]

The problem with SIBC engines are two fold. The first is the heavier actuated mass of each individual valve -- due to the long pushrod and larger valve diameter -- limits civility at higher rpms and ultimately forces a lower ceiling on revs before valve float and other issues become insurmountable. In passenger cars this translates into a lower level of perceived refinement. In race cars, it limits ultimately permissible revolutions and reduces durability. The second being that in many countries, tax on a vehicle is based on its displacement not fuel economy or anything else. Hence, using a larger displacement engine makes the car more expensive regardless of whether it uses more or less fuel.

This part shouldn't be ignored. The Corvette should be a race car for the street, something that can be raced on weekends, but still driven daily. With IBC you lose power on the top end, unless they use bigger cams and bigger valves, which require stiffer valve springs, but that decreases reliability.

[hyperv6]

There are advantages to both. In block cam engines could be shared with the trucks, while DOHC engines could be shared with Cadillac. Cadillac could really use a new V8.

And about the tires, there are limits to street tires, and their limits are lower than either engine would put out at low RPMs. The difference is the DOHC engine would have more power where it could be used.

Seeing most trucks other than Chevy and Dodge now have DOHC a new engine with this feature would work well in a Vette, Truck and Cadillac. If Cadillac comes thorugh with a AWD Zeta based car a new V8 will be needed and it needs to be more advance for the class and price it will be. The Northstar is as little old to carry on.

I just find it sad when the Ford Taurus SHO will have more technology than the Vette if nothing changes. It will see harder and harder for Chevy to ask the prices for the Vette in the future and not even come close to the technology offered in a Ford Taurus. The Vette in the past used to lead with Fuel injection, 4 wheel disc brakes and IRS. Today it really leads in Heads Up Displays and Carbon fenders, that's is about it.

Edited November 17, 2009 by hyperv6

[Camino LS6]

No.

The Vette leads in performance, you know, where it actually matters.

And, you can't tell me that the ZR-1 isn't chock full of tech!

[hyperv6]

No.

The Vette leads in performance, you know, where it actually matters.

And, you can't tell me that the ZR-1 isn't chock full of tech!

I am speaking of the regular Vette most people buy. And the little Ecoboost engine as 365 HP out of only 3.5 liters. What is going to happen when this technology is applied to a V8 at Ford?

The ZR-1 is advanced but is it as advanced as the current crop of sports cars on the market. In time that kind of thinking will get you behind. Imagine if someone back in the 80's said the carberator was good enough Or we don't need a computer?

Yes the old ways still work for now but what will you do when you need to go to the next level and the jump will be great as you did not advance when you could. I think with the work Zora did in the 60's that if here were around today he would be pushing the limits and using the best technology avaiable.

The the ZR1 and GS are fine but the point is the biggest seller the base Vette is getting stale. I know platform changes bring the buyers back. But if GM can do what they have on limited technology just think what they could do with more. Then spread it thorugh the entire Chevy line. Use the Vette to intro new tech to the Chevy line.

[Drew Dowdell]

Let's not pretend that Ecoboost is anything more than a nice turbo setup. GM is getting 300hp out of it's 2.8 liter "ecoboost" engine in the Cadillac SRX. Some quick math tells me that Cadillac is getting 107hp/liter while Ford is getting 104hp/liter.

What would happen if a turbo were put on the 'Vette? More power of course.

[Justin Bimmer]

Pushrod engines have lots of technology. NASCAR engines are pushrod with carbs and they can turn 9000+ RPMs for extended periods of time. NASCAR is talking about going with fuel injectors.

[Z-06]

Let's not pretend that Ecoboost is anything more than a nice turbo setup. GM is getting 300hp out of it's 2.8 liter "ecoboost" engine in the Cadillac SRX. Some quick math tells me that Cadillac is getting 107hp/liter while Ford is getting 104hp/liter.

What would happen if a turbo were put on the 'Vette? More power of course.

325 bhp in Opel Insignia VXR, i.e. 116 bhp per liter.

[smk4565]

Pushrod is old fashioned with a negative connotation because if it was well regarded, people wouldn't want to rename it cam in block or SIBC. There is no need to give DOHC a new name, people like it.

Pushrods are gone from 4-cyldiners, the Impala and Lucerne are the last pushrod V6s and look how dated they are. DOHC has taken over, why should the Corvette, GM's halo car use the old, dying engine technology, while the Cruze and Malibu get DOHC.

There is a reason BMW, Ferrari, Mercedes, Audi, Lamborghini, Aston Martin, Rolls-Royce, Lexus, Jaguar, Pagani (AMG engine), Porsche, and Koenigsegg use DOHC, while Chevrolet, Buick Lucerne, and Dodge use pushrods. I'd rather have what the first group has than the second group.

[Justin Bimmer]

The Corvette is an industry leader in performance, price, and fuel economy all with a pushrod engine. I think people in the market for a Corvette understand the engine technology and do not think of it as lacking from that of a Ferrari or Porsche.

The interior is the main problem with the corvette, but that's for another thread.

[Z-06]

Pushrod is old fashioned with a negative connotation because if it was well regarded, people wouldn't want to rename it cam in block or SIBC. There is no need to give DOHC a new name, people like it.

Pushrods are gone from 4-cyldiners, the Impala and Lucerne are the last pushrod V6s and look how dated they are. DOHC has taken over, why should the Corvette, GM's halo car use the old, dying engine technology, while the Cruze and Malibu get DOHC.

There is a reason BMW, Ferrari, Mercedes, Audi, Lamborghini, Aston Martin, Rolls-Royce, Lexus, Jaguar, Pagani (AMG engine), Porsche, and Koenigsegg use DOHC, while Chevrolet, Buick Lucerne, and Dodge use pushrods. I'd rather have what the first group has than the second group.

Listen from a previous Corvette Owner - There is NOTHING wrong and shameful about the Corvette Push Rod. Direct Injection and VVT will make pushrods even better.

The reasons for failure of pushrods in 4/6 cylinder engines are:

• No significant research and development went into them compared to V8
• Benefits are minimal compared to comparable DOHC

[Drew Dowdell]

Pushrod is old fashioned with a negative connotation because if it was well regarded, people wouldn't want to rename it cam in block or SIBC. There is no need to give DOHC a new name, people like it.

Pushrods are gone from 4-cyldiners, the Impala and Lucerne are the last pushrod V6s and look how dated they are. DOHC has taken over, why should the Corvette, GM's halo car use the old, dying engine technology, while the Cruze and Malibu get DOHC.

There is a reason BMW, Ferrari, Mercedes, Audi, Lamborghini, Aston Martin, Rolls-Royce, Lexus, Jaguar, Pagani (AMG engine), Porsche, and Koenigsegg use DOHC, while Chevrolet, Buick Lucerne, and Dodge use pushrods. I'd rather have what the first group has than the second group.

You've been told time and time again. DOHC is actually older than pushrod.

You've also been told time and time again that the reason pushrods are gone from 4-cylinders (or any inline arrangement) is because there are zero packaging advantages.

The V6 pushrods are dying because they've gotten zero investment dollars because even the best DOHC beating pushrod would never satisfy the import humpers like you. You'd find some assinine reason to hate it like "doesn't rev to 8,000 rpm".

You've already been shown that blindly choosing a DOHC engine over a pushrod engine will have you looking at Chevy or Cadillac taillights growing smaller in the distance.

99% of non-gearheads don't have a CLUE what the acronym DOHC even stands for let alone means. They only like it "better" because Consumer Reports told them to.

The Buick Lucerne I rented had the 3.9 liter pushrod. I drove for 20 miles in 3rd gear at 75mph and the only reason I eventually noticed is because the instant MPG reading seemed a bit low. There is no audible or even visceral difference in the Lucerne at 75mph in 4 or 75mph in 3.

66Stang can back me up on this one, I took him out for a ride in it.

[Chevy Nick]

What would happen if a turbo were put on the 'Vette? More power of course.

And awesomeness.

I will gladly take technology when it makes things better. I'm all for direct injection for the gen IV small blocks, but I'm not sold with what I've seen so far with VVT. If it makes things better then let's do it, but some people in this thread want technology for technology's sake.