Any possibility of introducing DOHC as against push rod technology in C6 ???

[jon69]

Re: The Focus

Second, the 12.9 1/4mile that the Acura NSX, 3.2L @ 270hp pulled was the absolute best of the day, done by pros who drive test cars for a living, under a system that was originally created in a parking lot. This figure was published in Car & Driver in 1998. The average for this car is around a 13.3 in the 1/4 mile. You're talking about a mid-engine design that incorporates an aluminum body with a weight in the low 3,000s. If I'm not mistaken the 3.2L version comes in around 3100 lbs. in manual transmission form. In '97 the NSX received more weight cutting measures in stronger aluminum panels that also increased rigidity, as well as emission reduction practices. It's a car that comes standard with traction control. It also received updates in cylinder liner materials in reinforced fiber (FRM). The throttle computer software has been updated, including different software and acheived LEV staus in 2000.

Here are some facts:
1991-1995 3.0 liter 270hp 210 torque and approx 2980 lbs weight. NSX type R was introduced during this time period, with a blueprinted engine, more aggresive suspension and gearing, and minus 265 lbs of weight.
1995 - 1996 NSX-T was introduced, 100lbs heavier than earlier cars due to reinforcements made for structural integrity as well as the addition of power steering
1997 - 1999 introduction of the 3.2 liter 290hp 224 torque motor, basically the 3.0 liter bored and stroked with frm cylinder liners, bigger intake valves, larger head gasket, new headers, improved emissions, larger con rods, 6 speed tranny (vs. 5 speed), among other minor revisions here and there. These are the years that the NSX type S Zero was introduced, similiar in theory as the Type R, it was capable of 0-60 in 4.5 sec flat.
2000 - 2001 - meets LEV standards
2002 - fixed headlights, new wheels and rear end treatment, but essentially the same car from 1991.
As for 0-60 and 1/4 mile times, well there are many variances that account for this, model year, transmision (automatics are only 252hp) conditions, driver, etc, etc.
But the fact is that published numbers (there as so many) vary between 4.5 to 5.9 for 0-60 and 12.7 to 14.1 in the 1/4 mile. The slower times are automatics. Granted most NSX are low 13 second cars as are most C5's (Z06 not included).

Sorry I know it's not Corvette info, but hey there is nothing wrong about knowing what's going on with other cars too.

 

[Bullitt]

Refocus

I did not want to give the NSX's history, as it does not pertain heavily concerning the C6 Corvette. It does show however, that there are significant changes in the internal specifcations of the Acura's motor, from an evolutionary standpoint. Titanium connecting rods are quite important. Implemented to find more horsepower, improve performance and decrease rotational weight to improve rev-up. I don't think there is a contention of facts in my previous post, with the exception of the horsepower figure that was given at 270hp instead of the 290hp figure for the model tested by Car & Driver. We can sit here and discuss coeffecient of drag and total air drag numbers of say, the Porsche 911, but where does this further the discussion prompted by the questions of the C6? There is a sub-forum for "Other Cars" here at the CACC, where this topic would be more appriopiate. The discussion is concerning the C6 and improvements that would hopefully be made. --Bullitt

 

[Edmond]

Rob,
The 3.85 was a figure that was written by Hib in an article when he first test drove the 02' Z06. He specifically stated that it was quite POSSIBLE that the Z06 could do that. He didn't say that he did it. It was an internet site that he wrote this on, but I forgot which one.

Well, I for one do not want to sacrifice my creature comforts. I enjoy air conditioning and like listening to my Pink Floyd when I'm driving. It would be stupid for someone to buy a car in excess of $50,000 without creature comforts. I consider myself working class and always want value.

I read somewhere that if Zora Arkus-Duntov totally had his way, the Corvette would've been a mid engine car. Can someone please confirm that?

And did anyone check out the other cars on that website? The 2003 Viper is estimated at $100,000:cry

So will Chevrolet re-introduce the DOHC to the Corvette? No way in hell I think. With their current success of the C5 using a OHV, they'd be absolutely crazy to try something like that. I like ZR-1's, but I'm sure many people have been turned away from purchasing one because they're so expensive. If the C6 Corvette turned out to be a $80,000 car, Chevy would've just sold out on 50+ years of touting themselves as the affordable sports car. That's my theory if the C6 ever did go DOHC, the price would just skyrocket.

 

[Bullitt]

...the price would just skyrocket.

This of course was shown with the ZR1 project before, so as Bullwinkle suggests, we have to learn by what hasn't worked in the past. When talking about creature comforts, I think that the consensus points to really dumb stuff, like standardizing options that only increase the cost of the car. Surely a/c and a stereo should be standard in this day and age, we're not dealing with a Toyota Corolla here. However, how important is a heads-up display, internet connections, or some radio that is usually outdone by the aftermarket? Costlier cars do incorporate brands like Alpine, Pioneer and Kenwood, because they don't need to spend money re-inventing the wheel, so to speak. A replacement GM Bose is not cheap at all, as some of you may know.

Another question that is brought up, and rightly so, is price. Will Vipers sell at $100,000? Perhaps, but will it sustain it for a similar amount of time as the previous generation? Not likely. The Corvette cannot afford to put out a version that will be in the same price range, only to fail and set back the cause once again. How severe the economic downturn will get and how long it will last, is anyone's guess, but history has shown us that a Super Corvette will not last in this enviroment. Again, it goes down to the well being of the dollar, so to gamble on that is a bit foolish. This is why, in my opinion, OHC or DOHC is a mistake when you look at the bigger picture. My hope is that more of the C5R racing technology would find it's way into the Corvette and that perhaps, a larger displacement engine could be an option, as the next step in the Z06 evolution.

So how about this, everyone type in their platform goals for the next Corvette. Weight, hp, interior options, etc., etc. If you want, include a description as to why something should be ignored or included. Then, put it into a price range that you would think will be effective. There's no right or wrong answer, there's no grades to be given, or test to fail. This is just thinking out loud and seeing what will fly and what won't. This is a performance minded discussion, so I don't think we will dwindle down to how many cup holders are important. --Bullitt

 

[Tom73]

Another way to look at this issue is to define the direction you want the Corvette to take for the future. Is it to be a Sports Car or a Grand Touring (GT) car? Right now it is a GT car and looks to be that in the future.

If it is to be a sports car then it must go low weight and smaller size. Reduce the cars overall size, drop weight by doing away with A/C, power windows/locks, radio (we don't need no stinking radio in a true sports car). Forget 1/4 mile and top speed, that does not make a sports car. Handing, handling, and more handling is what it is all about. It does not matter how quick you get to that corner, all that matters is how quick you get around that corner. That is a sports car. That is what, I feel, most Corvette fans do not what.

To me the Corvette is a GT car. A car that can cover huge distances at a very rapid speed with two passangers in comfort.

For the Corvette type of GT car a push rod V8 is great. Nothing wrong with a DOHC engine but the old style V8 does just fine for the American style of driving and roads thank you. DOHC would just add cost of complexity to a great car.

tom...

 

[mz0dxc]

DOHC vs Pushrod motor

Putting the cams on top of the heads makes the engine taller and wider. Thsi means a whole lot of "stuff" has to move to make room for a motor that makes the same horsepower

 

[jon69]

Well the subject at hand is should the C6 be available with a DOHC motor or not? Seems that many people here seem to think that this is not the way to go becouse of price alone, that it would "skyrocket" the price of the car as one person mentioned.

No offense to anybody here but that is totally and completely uneducated nonsense. Just called the local dealer and it goes like this:
new LS1 motor - $12813.00 retail (Canadian)
new DOHC Northstar - $12024.00 retail (also in Canadian funds)
Well that basically kills cost as an arguement. DOHC motor is cheaper than the pushrod small block chevy V8. Granted the Northstar is of smaller displacement (also much lighter and smaller) and of less hp and torque, but how much more could it cost to give it bigger displacement and higher output? Remember the Northstar was the "other" option GM contemplated for the C5 and all the while during development they wanted to stay in at a certain price range so this motor would not have raised the price of the C5 then and most likey would not be a factor in a C6 now.

ZR1 was a completely different story, designed by Lotus, made by Mercury and sold by GM. If you consider all the development dollars put into that car and you consider the the small amount of cars produced then the high price makes sense. As LS1 and Northstar development dollars can be spread over a much more greater number of vehicles (camaro/firebird use vette motors too) they can spread the cost around better = cheaper vette. These last comments are not from GM, but I think it makes common sense.

So cost is obviously not a question, then what is. I think it all falls down to what type of consumer GM wants to target. I think it is fairly obvious that the average vette fan is set on a small or even big block pushrod V8, becouse that is what is familiar and it is what has worked for them in the past. Why change a good thing that has the power characteristics that vette fans like and admire. I'm sure this is the reason the LS1 is in the vette today, GM was about focus groups and what the customer wanted, todays vette is exactly that, what the consumer wanted. You want a pushrod V8 you got it.

What happens to the vette in the C6 has probably been set in stone for a while now, from what we hear the next generation small block has been testing already (400-500hp depending on trim level) this would be logical. However, will the pushrod V8 be around in 10 years? If GM will market their car as a technology leader then I think pushrod has its days numbered, will it be replaced by a DOHC at that time, who knows, with other hybrid technology coming upon us we'll see.

 

[Rob]

I would agree that cost of a DOHC motor is not really the issue. One of the reasons why the LT5 engine was so expensive was because it was the first of its kind for GM. The Northstar engine is actually a direct descendent of the LT5 engine and is used in the Cadillac platform, hence the reason why the engine is about the same cost as a pushroad motor.

However, I would have to argue that the DOHC motor is not as torque happy as a regular pushrod motor. I also think that the additional weight over a pushrod motor is something that can't be overcome without heavy use of exotic materials. However, the more exotic materials used, the more expensive the engine may be.

Also, I would have to argue that the DOHC motor would pose possible packaging problems. Just my opinion.

For the record....the LT5 engine was a joint development project between General Motors and Lotus. At the time, Lotus was owned by General Motors and GM Powertrain engineers spent just as much time in England as Lotus engineers spent in Detroit. The engine was not designed and engineered by Lotus alone for GM. I just wanted to clarify that.

 

[Tom73]

Just called the local dealer and it goes like this:
new LS1 motor - $12813.00 retail (Canadian)
new DOHC Northstar - $12024.00 retail (also in Canadian funds)

What?? :Silly That may be Canadian dollars but it does not translate given any reasonable rate. Just checked the Sallee Chevy site and the LS1 is $4,895 in US dollars. Your price has that doubled. :crazy

tom...

 

[Edmond]

Yes, the cost of the DOHC motor could be spread out over other cars as well such as the Camaro and Firebird. But, by the time that motor would become reality, those F-bodies will be long gone so therefore the DOHC would probably be a 'Vette exclusive.

But Americans want bone jarring torque. I'm sure the brilliant engineers could get more torque out of the DOHC. I don't think there's too much those guys can't do!

If it ain't broke, don't fix it!

 

[Bullitt]

Rob, I've done some looking into the dimensions of the LS1 and the Northstar. Though I've only looked into it for a few days, I haven't been able to get solid information on the Northstar engine. The usual hp numbers and such, but only a few clear items. The engine block and cylinder heads are all aluminum, like the LS1. I have figures on the LS1 at 107.1lbs. (block) and 20.3 (cylinder heads). I haven't found any for the Northstar. The one figure I found for the Caddy engine is 500lbs. How complete the motor is at this weight, is a subject I am still unsure of. The Northstar utilizes magnesium parts, like the cam covers and other parts, to keep the weight in check. I'm not clear if this applies to all Northstar equipped cars, but it also uses four catalytic convertors. I haven't found any exterior dimensions at all.

Another concern of the Northstar is the high water pump placement. Until recently, a engine torque arm was located to the water pump, which caused a considerable amount of stress to the area. It would cause water pump failures, because of rotational forces inverted from the engine under high loads. It was addressed recently, with a different configuration. The extremely limited access to the starter, which is placed in the middle of the engine, is also a concern. There are other issues with the cylinder head bolts becoming loose. The same thing that affects C3 brake calipers (different metal compatibilities) may be partly to blame. A common solution was to Helicoil the threads, but this was a questionable practice because of the "softness" of the aluminum. Cadillac is addressing this issue with steel thread inserts, but from what I have found, the fix is month-long wait. Cost is around $3,000 for the repair.

I will continue my search for more information, but this is what I found so far. I would like to point out something I sarcastically mentioned earlier, but this time with more seriousness. The Northstar motor is by no means a drop in deal for the Corvette, at it's evolution configuration for the C6. Second, R&D time for the Northstar in the Corvette does necessiate a considerable amount of money. There are no quick and simple ideas. The Northstar was developed with the Cadillacs in mind. The LS1/LS6 for the Corvette. Two different cars and engines with two different goals trying to satisfy different customers. --Bullitt

 

[FatherLarry]

LT5

The concept of the LT5 was a great idea. The car is a classic in it's own era, and was designed to hold top speed of 175 mph for 24 hours. I don't care what any engineer says. The basic pushrod engine that's out now could not hold that speed for that long without the bottom end falling out. There's heat factors involved, floating factors and a lot more to take under consideration. GM got scared because it wasn't selling, so they bailed out. Only to reinforce the creation of a classic within its own era. The cost factor is much greater on the LT5. You're pushing four cams, eight more injectors, timing gears, independent piston sleeves. It was a car to keep up with the exotics, and they were very impressed with it overseas. Don't get me wrong, the pushrod is a good engine, which gives you a good bang for the buck, but it's not an LT5.

The future holds for new technology, no cams, no pushrods, no starter. They'll have cervos pounding on those valves instead of rocker arms.

The life span of the LT5, if treated right and not beat, will outlast the pushrod. Long live the King!

 

[XHitman396]

HOLY CRAP!! i know bout as much as most of my friends about vettes, but all this stuff is goin right over the head. for one thing, i have never heard anything about the "revolutionary" ZR-1/LT5. could someone explain?? and a '92 ZR-1 costing $50 G's?? whoa!! ive never heard of the performance (0-60 time, 1/4 mile time, top speed, hp, torque, etc) either. i dunno, i was only like 7 back then, but i guess ive had my head in a box or sumpin, thanx


Thankfully,
Brett

 

[Edmond]

Well, let me put it like this. The ZR-1 is a pretty rare Corvette that was from 1990-1995 and, ahem, is the most bada$$ C4 Corvette ever made! It was to the C4 Corvette as what the current Z06 is to the current C5 Corvette. I guess you could call it the "extreme" version of the generation.

To everyone, aren't the ZR-1's still costing so much because so many people bought them and put them in their garages hoping that they would appreciate in value after a few years? I mean, I've seen a ZR-1 with 17!!!! miles on it advertised in the paper. I think they wanted something like $64,000 for it.

 

[taegdh]

I figured that I'd just add a few more thoughts about both applications:
The DOHC has many fine attributes, and as previously expounded, was built to the GM specs by Mercury Marine. The very close tolerances, and relatively low volume, dictated that these engines be basically hand built. You must remember that GM has produced OHC engines as far back as the 1960's with Pontiac's OHC6, so the idea of mass production of OHC engines wasn't something first done by Toyota or Datsun. But these engines were for THE ZR1 Corvette, not for use in Trucks, Vans, or Sedans, but THE CHEVROLET FLAGSHIP! Yes they rev very freely but that is the nature of the beasts, they have less static resistance in the in interior workings of the engine with this setup. But the old saw of you get what you pay for, the "bean counters" apparently didn't see the ZR1 engine as an economically viable option when you think of what has happened in the following years as in the next paragraph.

Simultaneously, (actually a few years before) GM started the change all their V8 and V6 engines over to roller lifters and later roller rocker arms. What has this done? This has caused the "push rod" engine to have considerabley less static resistance due to the interior workings of the valvetrain. While not as low as the DOHC ZR1 engine, and with only half the valves, the power bands (HP / Torque) while not identical, are comparable and a far site better than the older pushrod engines.

So we don't compare apples and oranges, the end result is what matters. The ZR1/DOHC engine and pushrod engines aren't even in the class. Why was the ZR1 built and marketed? To make the requisite number of models that would make the option classified as a "stock" engine and hence eligible for competition. (Race on Sunday sell on Monday).

As far as applications in the C-6 or even later C-5's there are a few things which enter into the equasion. The DOHC engine has a bigger "footprint" (is wider and maybe needs a bigger engine compartment vertically unless they invest in using "dry sump" technology for the Corvette of the future. But in the end the "bean counters" will look at cost per unit, and that is where the bottom line will come in. Can we sell X units to recoup the cost of tooling and redesign. That is their question, and we will have to live with it.

 

[Edmond]

Yes, I think that they can make money even if they sell it at an extremely high price. People will pay for performance! Look at how the ZR-1's were snatched up back in the day. It's really now that we're starting to see more people selling them, at least to me it is. No matter how expensive you make a product, I'll always believe that there are some people out there that want to be different/unique and will buy it.

Some people I know just want that "status symbol" thing. They don't really care about performance. "Oh look, I have the first DOHC Corvette since the ZR-1."

And wouldn't GM have to develop a new engine since the last one was a partnership between them and Lotus? I'm sure they couldn't just rip off the LT5 because woulnd't Lotus have some kind of rights to that? It would cost millions to design and perfect that engine, and that would take years to make that money back through sales, etc...

 

[XHitman396]

one more question, what does "DOHC" stand for?

 

[Edmond]

DOHC=double over head cam

Aren't the DOHC's mostly used in Japanese cars?

 

[XHitman396]

thanks, ya i normally see them rice burners braggin (TWIN CAM) on the back right of the car, whether they are overhead, i dunno how to tell

 

[Bullitt]

99% of the time, if it says twin cam it's OHV (overhead valve) design or DOHC. It can be one cam for each bank of cylinders, two cams for one bank (in-lines) or two cams for two banks (V- style configuration). Though there have been some motors with two cams in the block, chances are very slim that you'll ever run into this configuration. Pull off the oil filter fill cap and you'll see the cam, easily. On some BMWs where the cap is near the front of the cam cover, you can see each cam, their sprockets and both timing chains, which are usually double-rollers. --Bullitt