glass slipper

A new C4 owner came onto the ZR1 board recently and posted info about the ZR1 24 hour endurance record. Of course we already knew and having pride in our cars (like all 'Vette owners should), a discussion began as usual talking about when GM/Corvette is going to take back the record that VW took with a purpose built non-production car in Oct 2001. (The ZR1 was a production car IAW FIA rules and still holds the record for that class.) It usually ends with: "the pushrod engine would not last with the high lift together with the high RPM required for the record". This is the last page of the current discussion:
http://forums.corvetteforum.com/show...1786358&page=3
Which resulted in one member starting this thread in the Z06 section:
http://forums.corvetteforum.com/show...post1561570563
To cut to the chase, with input from that member, the discussion took on a more analytical tone (as opposed to an emotional response) with the following result from my last post:

This is the dyno graph for the LS7 (I'm sure you guys have seen it once or twice already):
http://www.corvettels7.com/2006_LS7.pdf

There's a 7 mile track in Stockton, TX where the ZR1 set the record and LGM is in TX. The ZR1 guys are rightfully proud of the 24 hour record and the ZR1 is known as the "King of the Hill", but that was 17 years ago and we're ready to pass the crown on...we want the record back under the "Corvette" name. With help from GM and other sponsors, I think we can take back the record that rightfully belongs to Corvette with the C6Z06 using the combination outlined above. I stated in the above thread that I'd contribute $100 towards any viable attempt, I challenge all Z06 owners to match or better my contribution. So how about it guys, let's see if we can get LGM and GM onboard for this...March is the best time for this with low temps giving better HP, but it's just around the corner.

PS I'll be the first to volunteer to be one of the drivers for no pay to help reduce costs. I'll even pay for the tank of gas I use...now that's a helluva deal!!!

John Shiels

Call LG and he will tell you what the attempt will cost.

AU N EGL

I would bet this works a like a arrive and drive for a race. Cost is far more then a tank or two of fuel. Car preparation and tires will be a huge part of the budget.

My guess is each driver will pay a hefty sum to be part of this venture.

Good Luck to those who attempt it

glass slipper

That last part was done tongue in cheek...it would be a hellava deal for me. I have very little experience racing at speeds over 100 MPH and zero experience over 150 MPH. Actually, I wouldn't want to do it because I'd be a liability and wouldn't want to be the one to cause the attempt to fail. A man has got to know his limits...as Clint Eastwood would say.

The ZR1 attempt is well documented in a book called "Heart of the Beast" and Tommy Morrison nearly went bankrupt over the attempt. They had to pay for a rescue crew every day they were there at something like $6000/day! I'm well aware of how expensive this would be, but with sponsors, I believe it could be done. Goodyear, Mobil, EDS, and many others helped with the ZR1 attempt. GM had a ZR1 development car they used for their 24 hour durability test that was already prepped and it was given to Tommy as well as a new production engine in a crate. Goodyear developed a 17" racing tire just for this event. I have no illusions about this, it will take $$$ and the logistics will certainly be substantial. But wouldn't it be great to have the "unlimited" record back in the Corvette name with a production car!

Verrückt

You can tell the ZR-1 guys that there isn't a single engine on the modern automotive market (pushrod or not) that isn't validated for hundreds of hours at full speed/rated load.

Of course there could be a failure during the test, just as a car may fail under warranty during normal street duty. Statistically, I wouldn't expect any engine related failures during such a test.

To think that the LS7 couldn't handle 24 hours of WOT because of its high lift pushrod design is nothing short of nonsense. I suspect you knew that though.

4cefed

I think the current record by the W12 VW is ~185mph. I believe it has to be broken by 5% so the new record attempt would be ~194mph. Definately could be done. Race tires, lower rear end gear, remove cats.

John Shiels

see what the sancationing body would want to come to the site, a small fortune.

glass slipper

I wouldn't call 200 hours "hundreds" of hours, but I guess technically you can because it's more than one hundred. I might call the 400 hour test hundreds but even that is a little misleading. Also, the test isn't done at full speed or load continuously. Full speed implies redline and the test gets nowhere close to redline. The actual test has the engine cycling between peak HP RPM and peak torque RPM in a sawtooth pattern at WOT in 5 minute intervals. For the LS7, that means RPM is constantly varying between 4800 RPM and 6300 RPM. (Peak torque isn't full load/505 HP.) The engine sees an average of 5550 RPM, far from its' full speed rating of 7000 RPM.

There are failures during those tests...that's why they do them, to find the weak points/parts prone to fatigue failure. The engine isn't considered to have passed if there are any kind of cracks in any part, and I'm not talking about just visible cracks.

To think an LS7 couldn't experience a valve spring failure during the 24 hour attempt is nothing short of nonsense. People on this forum have had a valve spring failure with the engine just idling...but I'm sure you knew that.
Compare the two valvetrains:
LT5: 1.54" intake valve, .390" lift, peak HP at 5800 RPM
LS7: 2.2" intake valve, .591" lift, peak HP at 6300 RPM
Even with the titanium intake valve, it's obvious to the most casual observer that the LS7 has considerably more valvetrain stress. Maybe a hand picked set of valve springs would guarantee success, but a random LS7 having a small defect undetectable to the naked eye in one valve spring (and one is all it would take) would spell disaster for the attempt. Every engine has strengths and weaknesses...the valvetrain stresses in the LS7 demand 100% perfect valve springs, and we know there's no such thing as that. I'm not saying valve spring failure is a common problem or it happens frequently, but it can and does occur. So why not do every thing possible to minimize/prevent that failure??? Running at as low of an RPM as possible will only increase the chance of success...and that is what we want isn't it???

The weak spot of the ZR1 for the record attempt was the cooling system. Lotus design parameters dictated the water pump for the LT5 engine would be 100 GPM (25 GPM/100 HP) but the L98 radiator wouldn't handle that flow without blowing up like a balloon. So Chevy (in their infinite wisdom) designed a bypass thermostat/external thermostat housing that starts bypass coolant around 5500 RPM with the bypass fully open by ~6000 RPM...that way they could save $2 and use the L98 radiator in the ZR1, utter lunacy. The ZR1 can not withstand extended high RPM operations (above peak HP RPM) without overheating. The Chevy engineers figured you wouldn't be spending much time above that RPM before you shifted to the next gear and it wouldn't matter. That's why the record run was done in March when the temps were near freezing...you gotta play to your strong suit and minimize your weak suit.

Maybe it's me, but I thought there would be a lot of enthusiasm about this...so far it's been tepid at best and negative at worst. Come on guys, let's see some passion for these great cars!!!

Tom400CFI

I'm as enthusiastic about this as GS is. Sponsors are required, and who wouldn't want to be named on a record like that?? Set by a nearly stock car w/a stock engine?? That as good a PR as you can get, IMO. I'm not a rich person at all, but I'd throw down money to see this happen, and I'd drive down to help and watch!

glass slipper

The current record is 183.45 MPH and the ZR1 was 175.885 MPH. 5% over 175.885 would have been 184.679 MPH. Maybe it's a new rule since 2001 when VW set the current record. If so, that means we'd need to average 192.623 MPH meaning it would have to run 197 MPH while on the track. Now things are looking a little more difficult as it would have to be closer to 5500 RPM, but I still think it's doable with the right gearing and aero.

Glad to see a positive post showing support.

Verrückt

You don't need to tell me about engine testing, it's part of what I do for a living.

I don't do much work with GM, but others within the auto industry. 200 hours is actually on the low side of an "average" engine validation test. Many customers validate with more hours, and the tests are often different between manufacturers. Some customers DO validate with constant FLRS (Full Load-Rated Speed) meaning the engine will sit at the horsepower peak for hundreds of hours. Yes, anything more than 100 is hundreds.

200-300 hours is common in the Automotive industry. I have one customer in the heavy-duty market who tests to 2000 hours of constant FLRS. THAT is brutal.

In any case, GM wouldn't (or shouldn't) release a product until they are statistically confident that all the components will pass their validation tests. I feel that any engine in the automotive industry should be able to survive 24 hours of WOT. That's not very challenging compared to most validation tests.

Can a valvespring fail during this test? Sure, but it shouldn't. You mention defects, which is a whole different issue entirely. GM strives for 0 parts per million defects from their suppliers. This usually isn't possible, but the actual detected PPM is usually quite low.

You also mention the cooling issues with the ZR-1 which is, as you mentioned, a design flaw. This is another issue as well. Coolant and oil temps are carefully controlled on the dyno.

I would be more concerned about overheating (engine/driveline) than I would about a valve spring breaking.

glass slipper

The FIA wasn't present for the record run by the ZR1, officials from USAC were there to monitor the event for the FIA...so maybe just a tiny fortune.

jvp

I think it's because, in the grand scheme of things: who cares? Really. The 24-hour record was interesting... in its time. But who really cares anymore? How many extra sales did it bring the ZR-1 during its time? How many extra sales has it brought VW?

...

No one cares. Or, more accurately stated: the number of folks that actually care about this record is a small number approaching a statistical 0.

GM knows where the advertising numbers are. They're centered around a small track, somewhere in the foothills of Germany. Not on an oval track here in the states.

jas

AFVETTE

I agree, what a pity. Why they didn't choose a track like Road America is beyond me. Here almost any one could play, and the results would be just as impressive. Think of the savings and the ability to "test" more cars.

Tom

glass slipper

I know you're involved in the auto industry, but when you say hundreds when you mean 200 is very misleading even if it is technically correct. I don't know what others are, but I know GM does 200 hours on most of their engines and they also have a 300 and 400 hour test. I'm also sure the 2000 hour test you mentioned is a diesel engine (probably for a boat too)...the low RPM and high LB/HP ratio of a diesel makes 2000 hours a walk in the park, not really a high stress or "brutal" event for them. The LT5 was the first GM engine to pass the 400 hour test and the Duramax diesel engine also passed the 400 hour test, and it's all aluminum. You also have to define "rated speed"...I could make an engine with a redline of 7000 RPM but then say its' "rated speed" is 5000 RPM. GM uses peak HP and torque RPM, two easily defined points. Their marine/crate engines are tested to 300 hours.

I agree, any engine should be able to run WOT for 24 hours at peak HP RPM without failure...but we know the LS7 has valve spring failures (however few percentage wise they are) in its' history, so why not do everything possible to minimize the risk? I'm not trying to say the LS7 is spitting valve springs out left and right, but all it takes is for one to let go during the run and the game is over.

If everything is done to reduce the risk of valve spring failure, I agree with the engine/drivetrain overheating being cause for greater concern. But I think the transmission/differential coolers on the Z06 will handle the extra heat load, especially if done in near freezing temps. During testing of the ZR1 for the record run, the front wheel bearings were overheating as the cars came in to pit. Interestingly enough, it wasn't during the actual running at 180 MPH that overheated the bearings although that certainly got the grease temps elevated. It was during the braking for the stop for gas (done about once an hour) that was literally burning the grease off. They switched to synthetic grease at the Delco factory and changed the braking procedure coming into the pits and the problem disappeared.

With your background in autos, I really enjoy discussing these topics with you. But this is kind of getting off topic, I really wanted to see if others have as much enthusiasm for this as me. I really think it can be done, any other people want to cheer this idea/effort on???

Tom400CFI

Man....that's some focked up chit, right there. I care. I've always loved 'Vettes and when the ZR1 busted those records back then, my love grew stronger. It was PROOF that the Corvette was everything I thought it was. Proof that it was the unchallenged dominant alpha of all cars. It definitely helped give validity to the Corvette name, in my mind. In any school-bus car argument, who could argue against THAT achievement? No one. There wasn't a Nissan, Toyota, Mazda, or any other sports car back then that could challenge that feat, for less that $150k, and I don't think that there is today at ANY price, other than the Z06, a Saleen S7, and a Bugatti Veyron. Oh, and maybe an SLR McLaren. Even above that figure I wonder if any could do it back then.

Now I own a Corvette, so who cares? I do. To break that record again, and specifically against a purpose built, one-off VW wienermobile, is undeniable fodder for marketing and "King of the Hill" bragging rights.

jvp

In your opinion. The world begs to differ with you, and would rather point at the Z06's 7:4XX time at the 'Ring. That is one hell of an achievement, right there. And it matters more in today's world than speeding around an oval for 24 hours.

The world has changed, and GM is (slowly) getting it.

jas

bernrex

The C6Z has little chance of taking the highspeed endurance record. Almost certain to break a valve/spring, melt its tranny, or lose a roof.
Its too much a c.i. brute on steroids ... and not aero-shaped.

The record will stand for a while longer ... until a supercar like the Million Dollar Bug decides to step up to the challenge.

But, I don't see anyone putting the luxury bug thru the torture test.

Some records should live on (w/o an asterisk) ... like Hanks H.R. record deserves. And, million $ technology shouldn't be allowed to purchace the record.

Tom400CFI

In my opinion is right. Also I never said anything to down play the Z06's time at the 'Ring. It is FBA. But no more so than the other challenge at hand.

Tom400CFI

What?! The C6Z is more aerodynamic than the last stockish car that set the record (the ZR1).

And the CID "brute" is to the C6Z's favor, allowing the lower RPM discussed above (did you READ and absorb the first post??). You know that the ZR1 was refered to as a "brute" and "on steriods" when it debuted? I'd say that being a "brute" is a requirement for this task.

I can't believe the lack of enthusiasm.