[C7] Interesting reading.....

[Rich Z]

The real reason why Corvette C7 Stingray uses steel torque tube and why this signifies the fundamental failure of the new car

Posted 7th March 2014 by Peter MJ

In a nutshell, the reason for steel torque tube housing is because the AFM was originally designed and tested on vehicles using conventional driveshaft while Corvette uses a torque tube.

The official story, the one that +Tadge Juechter and the rest of the Stingray "design" team continue to spew out goes as follows:

The (unanticipated) vibrations generated by LT1 motor when in 4 cylinder mode exceed the damping characteristics of the relatively light weight original aluminum torque tube housing. Thus, in order to dampen the vibrations more effectively, a heavier steel torque tube had to be used to reduce the aforementioned vibrations. Through use of the heavier housing, the problem with vibrations was eliminated.

So is the chief "engineer" Juechter speaking the truth and more importantly the full truth?

As a matter of fact, assuming he holds the professional license, should have this license revoked due to unprofessional, dishonest and unethical conduct.

So what is happening here? The explanation, the real explanation is not all that complicated. The vibrations related to Active Fuel Management were observed long time ago, in 2007 specifically and in ironically enough, Pratt Miller constructed C6R race car. The problem was so bad at that time that during the corresponding year's Le Mans endurance race, C6R was pulled out of the race and retired. When the car came back for the following season, C6R no longer used the AFM system and did in fact successfully compete in the following seasons.

What was the real reason why +General Motors developed AFM? AFM was developed to increase the fuel efficiency of the GM pick up truck line up, plain and simple. Anything that the system was used on otherwise was done as an afterthought, to recoup the development costs.

The same system is currently used on all new GM pick ups and Camaro, the system (in reality a result of GM's refusal to invest in light weight material technologies like Ford is currently implementing) works as a half ass corporate fuel efficiency measure. The vibrations? They are still there but in neither pick ups or Camaro, they are of real concern beyond drivers feeling the system being activated. The reason why the vibration is not an issue in either pick ups or Camaro? The drivetrain, or more specifically CONVENTIONAL DRIVESHAFT being used. What is special about conventional driveshaft? As inefficient it may be, it is not a structural member of the vehicle's chassis. The shaft simply transfers power at REDUCED rotational velocity from transmission to the differential while using universal joints and rubber isolated supports.

Now, enter Corvette... Ever since 1997, Corvette uses a torque tube system, a layout that is more efficient in power transfer and one that uses a direct power transfer from the engine to the rear mounted transaxle AT ENGINE SPEED. The torque tube housing, in spite of ignorant skeptics is indeed a structural member of the chassis, in spite of rubber isolators and couplers being used.

The fact that twisting moment typically transferred in cars with conventional driveshaft through the engine mounts and onto suspension is eliminated, thus, the energy process is considerably more efficient and does not stress the suspension components.

The actual energy transfer is accomplished through an internally mounted splined shaft, rotating at the engine speed and supported by doughnut shaped carrier bearings.

So what happens when there is a vibration like the one caused by AFM, the vibration is transferred at full magnitude (shaft rotates at engine speed) through the carrier bearings and into the tube housing and finally into the vehicle chassis.

Now, it is pretty clear that the AFM is not suitable for torque tube equipped Corvette. Why? For a simple reason that the vibration is still in the driveshaft and carrier bearings, the only thing that the heavier torque tube can accomplish is to dissipate partially the energy and reduce the vibration transfer to the chassis. However, the stress on the engine crankshaft, main seal and carrier bearings in the tube remain. In the event AFM is used frequently, all of these components plus the transaxle will experience premature and sudden death.

So... If Tadge Juechter had any integrity and honesty, what would be the proper way of dealing with this problem resulting from using unsuitable technology? Occam's Razor would dictate to simply tossing out the AFM and increasing fuel economy through light weight materials and improved aerodynamics, assuring better fuel efficiency at ALL TIMES.

Since Tadge Juechter chose to mask the effects instead of addressing the cause, absolutely nothing was corrected, the unsuitable technology was forcibly made to work and becoming another ticking time bomb setting up the buyers for very high repair costs after the car outlives its warranty period.

If there a glaring example of Juechter's et al. dishonesty and incompetence, AFM gets the top prize. Ironically enough, the same AFM has been forced to work on the upcoming Z06 and once again, Juechter has no intention to correct this fatal flaw of the new Corvette. Shame on this guy and the rest of Corvette "design" team. Why exactly there is even a suggestion of "engineering" element included is a big mystery. Certainly neither Juechter or anyone else is expected to make an honest disclosure here or anywhere else as long as ignorant buyers continue to buy this failure on four wheels.

SOURCE: http://corvettec7fiasco.blogspot.com...rvette-c7.html

[mrr23]

even if i could afford one, it's one generation to skip.

[Rich Z]

Seems to me that the most practical solution would be to just disable AFM completely. Are the minor gains in gas mileage really worth the potential premature failures in the drivetrain?

[Cor66Vette]

This guy speaks gibberish.

I plan to get one as soon as the '17s are available.

Best Vette (technologically) to date.

I freakin can't wait.