The new ZR1 is a C6 and the engines in both the C5 and C6 are lower than in the C4. This was accomplished due to engine cradle and frame design in both as well as the use of the dry sump oiling system in the C6 Z06 and ZR1. The latter eliminated the larger wet sump oil pan allowing the engine to sit lower in the engine cradle. In turn, that lowers the center of gravity (CG), which is a good thing. In addition, the C5 and C6 Z06, as well as the ZR1, use die cast magnesium engine cradles vs. aluminum in the base model or the original ZR-1. Raising or lowering a mass without changing its longitudinal (fore/aft) location has minimal effect on weight transfer. However, since the engine is also placed further back than it was in the C4 the static weight is more optimally distributed.
"ZR-1" and now ZR1 were and are Regular Production Option (RPO) codes with neither having any official meaning other than that.
Well, this isn't a test or anything, but from the historical Corvette folklore I've read or heard about over the years, "ZR" stood for Zora's Racer.
Remember, the very first instance where ZR-1 appeared in the history of our favorite sports car, was way back in 1970, on what I seem to recall was a 370hp LT1 model Coupe. I think it was an RPO code at the time for a special performance package. Zora was the Chief Engineer from 1955 to 1978(?), so who knows if there is a connection. However, I think Dave McLellan wanted to pay homage to his former boss, when the 1990 ZR-1 came out.
The new "ZR1" (without the hypen) of today may have nothing to do with any of this, and as has been pointed out, no longer refers to an "optional" performance package, but a brand new model Corvette. Just as in the case of the late model Z06, I'm not sure ZR1 refers to an RPO code.
P.S. I tend to agree with No Doubt that lower prices on this car will not be likely year to year. UNLESS GM produces too many cars, contributing to excess dealer inventory and/or the market completely dries up for six figure supercar two seaters. With the economy in such dire straights, who knows anything could happen.
For that matter, I never thought Z06 prices would drop as much as they have in just 3 model years either, but they most certainly have dropped. With exception of the ZR1, dealers are practically giving all their new Corvettes away right now. It is more likely that if ZR1s don't sell well, GM will kill future production, and God Forbid, the same may be true for the Z06.
Well, this isn't a test or anything, but from the historical Corvette folklore I've read or heard about over the years, "ZR" stood for Zora's Racer.
That is a myth. I KNEW you were going to say that.
In fact, I was going to tell you to call Betty at the NCM if you didn't believe me. So go ahead, call her and ask.
Here's the number...
1-800-53VETTE or 1-270-781-7973
Regular Production Option (RPO) codes beginning with the letter "Z" usually indicate a performance option package on all GM vehicles. The same is true for the ZR-1 and the new ZR1, just as it is for the Z71 off-road package on some GM light trucks. "Z" does not nor ever has stood for Zora Arcus Duntov (or anything else), but remains a popular myth in Corvette folklore.
That's why I called it "folklore" (and so did you, ". . . but remains a popular myth in Corvette folklore.") So, we're both right.
Don't EVER try to say that No Doubt isn't 100% correct. The sky will fall, there will be dogs and cats living together and the world would stop spinning on it's axis.
If I didn't know better I'd say that was an insult. Therefore, I won't insult your intelligence by suggesting that you really believe what you just said.
You see Mike, knowledge is like quarters at an arcade: the more one has the longer they can play. And I'm afraid you're out of quarters.
?Seems to me lowering the CG which was said to be a good thing is the same thing as effecting weight transfer. IE Snap oversteer which can occur when the front weight travels diagonally across to the rear.
But, I didn't know my C5 Z had a magnesium engine cradle like the C6 Z, hope thats true?
Also, your cracking me up here "No Doubt"!
Furthermore, I still remember 50/50 and 52/48? weight stuff 15+ years later, and I may have read that "ZR1"&"ZR-1" stuff, but, I'm sure I wouldn't remember that the next day.
Once again, lowering a given mass does virtually nothing as far as weight transfer is concerned because the mass (weight being the measurement of gravities effect on a given mass) remains in the same longitudinal (fore/aft) location.
If, however, one were to physically move a mass forward or backward it would have a direct effect on weight transfer. The same is true as the vehicle consumes fuel. As fuel is burned, the C.G. shifts.
Also, don't confuse static weight with weight transfer. Weight transfer in this case is not the movement of a mass from one physical location to another, including fuel consumption, but rather the shift in C.G. due to the effects of acceleration and deceleration.
That also occurs with lateral acceleration as when cornering for example. Physically speaking, no weight has changed location yet more weight has been transferred to the outside of the turn and thus the outside tires have more 'weight' on them. The same is true when you accelerate or decelerate. As you accelerate weight transfers to the rear. The front tires, having less weight on them, may lack sufficient grip and thus not have enough traction which in turn causes the vehicle to understeer or 'push'. Conversely, as you brake, weight transfers forward.
If one is familiar with the concept of the traction circle, you can see that weight transfer has a direct effect on how the tires react. Given tires, taking into account things like tire width, tread design (or the lack thereof), and rubber compound all determine how much traction (grip) a given tire has.
Simply speaking, the more weight a tire or tires have to bear, the more traction (grip) they require. That means the more weight transfers the more traction the tires will need. In addition, the rate at which weight is transferred also affects how the tire/s will react. A faster rate of weight transfer requires the tires being able to accept that weight transfer at the faster rate. This is where sidewall construction is a key factor, along with all the other factors.
Rate of weight transfer is one of those seemingly mysterious and voodoo like aspects of handling, but is key to understanding how to set up a suspension. The rate at which weight transfers is determined by many things with roll bars for instance being one of them. Too torsionally rigid and weight will transfer laterally at a greater rate than the tires may be able to handle, and if so they will lose traction and the vehicle will lack lateral grip. But hey, it corners flat! That is, when it's not in the ditch.
I'd love to be able to show math and diagrams in order to help clarify these concepts (or confuse the hell out of a lot of people ) But unfortunately, one is limited by the capability of the forum software to text and only very simple math, drawings and images.
That may be a good thing lest Mike's head explode.
Bottom line a Z06 with a supercharger and its extra power is going to loose some its other functionality without additional modifications. Hence, the ZR1.
We're, myself included, are perhaps getting a bit too in depth because the original point was moving a weight UP or DOWN in the car has no significant and discernible effect on weight transfer. It does, however, move the C.G. UP which is indeed a bad thing.
As I mentioned in another post you might want to search for the expression "polar moment of inertia". Usually it deals with weight on the longitudinal plane (fore/aft) and how it effects a cars handling, However, and not to confuse the matter further, it also has an effect on the vertical axis as well. But that is beyond the scope of this debate as it gets into 3-axis planes of movement which an automobile is incapable of, other than suspension travel.
If anyone would like to discuss this in depth we can move on to aircraft weight & balance where things get only a wee bit more complicated. Seriously, it would help in explaining terms such as moment, arm, weight, mass, C.G., station (location of a given weight), total moment, total weight, etc, and would give one a much better idea of how all of this works in concert.
And believe it or not, all of this does have an effect on how I (or anyone else for that matter) should feel about the new ZR1. Thn again, I could make a case for how relativistic quantum field theory applies to the new ZR1 as well. Just in case anyone thinks this is all off topic.
In automobiles, weight transfer (often confused with load transfer) refers to the redistribution of weight supported by each tire during acceleration (both longitudinal and lateral). This includes braking, or deceleration (which can be viewed as acceleration at a negative rate). Weight transfer is a crucial concept in understanding vehicle dynamics.
Weight transfer occurs as the vehicle's center of gravity (CoG) shifts during automotive maneuvers. Acceleration causes the sprung mass to rotate about a geometric axis resulting in relocation of the CoG. Front-back weight transfer is proportional to the ratio of the center of gravity height to the vehicle's wheelbase, and side-to-side weight transfer (summed over front and rear) is proportional to the ratio of the center of gravity height to the vehicle's track.
Liquids, such as fuel, readily flow within their containers, causing changes in the vehicle's CoG. As fuel is consumed, not only does the position of the CoG change, but the total weight of the vehicle is also reduced.
By way of example, when a car accelerates, a weight transfer toward the rear wheels is said to occur. An outside observer can witness this as the car visibly leans to the back, or "squats". Conversely, under braking, weight transfer toward the front of the car will occur. Under hard braking it is clearly visible even from inside the car as the nose "dives" toward the ground. Similarly, during changes in direction (lateral acceleration), weight transfer to the outside of the direction of the turn occurs.
Weight transfer causes the available traction at all four wheels to vary as the car brakes, accelerates, or turns. For example, because of the forward weight transfer under braking, the front wheels do most of the braking. This bias to one pair of tires doing more `work' than the other pair results in a net loss of total available traction. The net loss can be attributed to the phenomenon known as tire load sensitivity.
An exception is during positive acceleration when the engine power is driving two or fewer wheels. In this situation where all the tires are not being utilized weight transfer can be advantageous. As such, the most powerful cars are almost never front wheel drive, as the acceleration itself causes the front wheels' traction to decrease. This is why sports cars always have either rear wheel drive or all wheel drive (and in the all wheel drive case, the power tends to be biased toward the rear wheels under normal conditions).
If (lateral) weight transfer reaches the tire loading on one end of a vehicle, the inside wheel on that end will lift, causing a change in handling characteristic. If it reaches half the weight of the vehicle it will start to roll over. Some large trucks will roll over before skidding, while passenger vehicles and small trucks usually roll over only when they leave the road. Fitting racing tires to a tall or narrow vehicle and then driving it hard may lead to rollover.
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If the center of gravity is moved up statically, the relatively same weight transfer is going to introduce error, everything else being equal. They are directly related!
Again, that is absolutely true. It's becoming repetitious.
This is why the 911 series Porsche with its rear engine design is considered by many to be better under braking and during power on corner exit. Under braking the weight transfer is forward, thereby distributing the weight more equally among the four tires. Furthermore, the weight is baised toward the rear when accelerating which aids in traction over the rear (driven) wheels. In addition, the engines weight is already over the driven wheels which further aids traction.
Conversely, a front engine car under braking also transfers weight forward, but unlike the rear engined Porsche there isn't much car forward of the front mounted engine.
Anyway, aren't late model Corvette's considered front mid-engined since the motor is set back?
And thanks for bouncing this stuff around with me others would have long since burned out, or said something really stupid!
Polar Moment of Inertia indicates a cars willingness to change direction. "Poles of Inertia" is another way of saying centers of weight concentration. A car turns about its center of gravity, so the further away weight concentrations (engine and tranny, etc.) are from the center of gravity the larger their moments. Specifically: the distance from the CG to a given weight is known as the arm, and weight X arm (the distance from the CG) = its moment. The total of the moments divided by the total weight equals the CG.
A high polar moment of inertia is when the weight concentrations are both heavy and far apart. A low polar moment of inertia is when the weight concentrations are both light and close together. In other words, it is easier to steer a vehicle with a low polar moment of inertia.
For example, a car with a high polar moment of inertia has greater directional stability. That is, it resists changes in direction. Whereas a mid engine configuration provides a low polar moment of inertia, which helps with left/right transitions.
Weight distribution numbers describe how much weight is carried by the front and rear tires by using a scale. Given this, the crossweights can be calculated as well. More importantly the static polar moment of intertia can be calculated. Why static? When you scale the car with the driver or their equivelant weight in it plus a given fuel load (and weight) you will obtain the front weight, rear weight and cross weights. From that data you can approximate the CG. However, the CG changes as the fuel is burned off and is only a static CG at the time of the calculation.
The weights are the only variables with the arms being fixed. So, as the weight of the fuel, which is at a given arm length, is used its moment changes. As the moments change so does the CG. However, since the only weight variable for all practical purposes being fuel the CG will have a range that it will be within depending on the current fuel load at any given time. Given this you can see that a cars polar moment of inertia is dynamic, although within a given range. In aircraft we refer to this as the CG range and there is a front and rearward CG limit which cannot be exceeded.
As I said above, vertical weight distribution also effects polar moment of inertia in the vertical plane. However, an automobile is limited in its vertical motion by the surface in rests on. Therefore, raising the height of the C.G. has little significant effect on longitudinal weight transfer.
Both myself and the article referenced above describe how weight transfers longitudinally. And yes, this results in the vehicle appearing to 'squat' under acceleration and 'nose dive' under braking. But again, this is mainly as a result of longitudinal weight transfer. However, although an increase in a masses height will result in a somewhat greater effect on weight transfer it is not as appreciable as the longitudial weight transfer.
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