Weakness Of The New Gtr?

[NISZILA]

Been looking through as many photos and specs as possible. Can't wait to see this beast. When I saw, this photo, however, it got me a bit concerned.

As you can see the gearbox is located at the back, which is great for weight distribution. The concern I have is the shaft that travels from the engine to the gearbox. This shaft will be spinning up to 7-7.5k rpm. For a shaft of this length to be spinning at that speed, it would need to be perfectly balanced. This is very difficult to achieve. That is why formula one have gone to V8's. Because the shorter shaft is easier to balance at those high speeds. If the gearbox was in the front, it wouldn't be a problem as the shaft would be spinning a lot slower due to being geared down. This is how most rear wheel drives operate.

What do you guys think?

[m3gtr]

i disagree im afraid on this point

F1 went to v8's because of the regulations. The FIA wanted to cut costs and thought this could be achieved by dropping 2 cylinders.

It wasnt because of drive shafts.

[funkymonkey]

Aston martin and a couple of other modern supercars use this same technology and they seem to have no problems with the shaft not being balanced properly... also keep in mind that the material the shaft is made of is a lot lighter these days than the oldschool chunk of metal.... lot less forces acting outwards due to weight.

F1 cars are shorter stroke high RPM cars... we're talking about a GTR here which will see half those RPM's in day to day use.

Will be interesting to see what the GT500 platform is, as that's usually what the aftermarket performance world tries to emulate.

[Al]

So you think that the Nissan engineers have over seen this issue

I'm sure they have it under control

[NISZILA]

I'm not doubting the Nissan engineers. I'm sure they have it all figured out. I just know that the longer you make a shaft, the harder it becomes to balance due to more and more harmonic frequencies that come into play. I just find it quite interesting

[NISZILA]

i disagree im afraid on this point

F1 went to v8's because of the regulations. The FIA wanted to cut costs and thought this could be achieved by dropping 2 cylinders.

It wasnt because of drive shafts.

Have you noticed the gain of the redline they are capable of with the shorter shaft. That was more my point. A shorter shaft can be spun a lot faster.

[funkymonkey]

So you think that the Nissan engineers have over seen this issue

I'm sure they have it under control

Nissan engineers make a car for regular use under factory specifications... I think what the OP meant was the suitability of the technolog for high end tunes.

Nissan engineers also spent millions of dollars on oil drainage and recirculation on the RB26DETT, and we all know how well they do on a circuit.

[DRIFTER]

in top gears, wouldn't the shafts spin at the same speed? won't the overall shaft length be similar between them as they both have the same amount of components?

[Lunatikk]

Think about this:

By the time a conventionally-configured car is in either 5th or 6th gear, (considering both are overdrive gears) the tailshaft is actually spinning FASTER at any given engine speed than the new GTR tailshaft which will always be at 1:1 with engine revs. I also think from memory the new GTR has a composite/carbon fibre tailshaft which goes a long way to negating problems with harmonics etc

[NISZILA]

Yea, didn't think of that. Thats a good point. Didn't really think about conventional tail shafts doing that speed, but in top gears they would. Its an interesting configuration none the less. Can't wait to see it in the flesh

[Al]

Nissan engineers make a car for regular use under factory specifications... I think what the OP meant was the suitability of the technolog for high end tunes.

Nissan engineers also spent millions of dollars on oil drainage and recirculation on the RB26DETT, and we all know how well they do on a circuit.

Monkey you funky dummy, the Nurburgring and all the countless other extreme tests are hardly regular use.

[Abo Bob]

[sh@un]

Think about this:

By the time a conventionally-configured car is in either 5th or 6th gear, (considering both are overdrive gears) the tailshaft is actually spinning FASTER at any given engine speed than the new GTR tailshaft which will always be at 1:1 with engine revs. I also think from memory the new GTR has a composite/carbon fibre tailshaft which goes a long way to negating problems with harmonics etc

true, true- but on most old 5-speed gearboxes, 4th gear war direct anyway, so actually only 1st, 2nd and 3rd would have seen prop shaft speeds below engine speed. the thing to consider is, with the current setup, the prop shaft will be under less load at high-speed, due to the fact that while it has to transmit the same huge twisting force required to push the car through the air at speed, it won't have as much centrifugal force acting on it at the same time

the only draw back with this sort of setup with a normal gearbox, is that the synchros essentially have to "brake" the speed of the propshaft as well as the reciprocating mass of the engine before selecting the next higher gear. but due to the fact that it's made from carbon/kevlar and no doubt a lot lighter than steel, and that the DSG gear pre-selection eliminates most of the synchro wear, all is well.

[2rismo]

+1

[djr81]

A few of points.

1. F1 cars do not have tail shafts.

2. Transaxles have been around for longer than carbon fibre has been used in motor cars.

3. All that Nissan have to do is to ensure that the harmonic frequency for the tail shaft is higher than the speed that the tail shaft can reach. Obviously putting the shaft being before the gearbox has a tendency to make the figure a higher number (Assuming you can't hit the redline in top gear - not true in the case of most GT-R's). As an example my old AU Foulcan has a limiter set at 180km/h to prevent this very problem.

[thrtytwo]

lol people are too concerned with finding something wrong with the new GTR. i dont think nissan would be putting anything in this car without millions of R&D and testing.

[djr81]

lol people are too concerned with finding something wrong with the new GTR. i dont think nissan would be putting anything in this car without millions of R&D and testing.

Yeah, strange isn't it. You'd think that the fact that it is both ugly & over weight would be enough for most people.

[sewid]

WAIT WAIT HOLD PRODUCTION. INTERNET FORUM USER FINDS FLAW IN NISSAN DESIGN.

Back to the drawing board everyone...

[thrtytwo]

Yeah, strange isn't it. You'd think that the fact that it is both ugly & over weight would be enough for most people.

thats down to personal opinion. maybe its a bit heavy but u cant argue with the times its putting out, and i rekon its hot as

WAIT WAIT HOLD PRODUCTION. INTERNET FORUM USER FINDS FLAW IN NISSAN DESIGN.

Back to the drawing board everyone... :P

lol

[warps]

Yeah, strange isn't it. You'd think that the fact that it is both ugly & over weight would be enough for most people.

Gold!!

Just a quick comment about the driveshaft. In this design, the driveshaft will see maximum RPM every time you redline the engine, meaning it will see a lot of cycles at maximum load (fatigue and all that). In a "conventional" driveshaft design, the driveshaft will only spin at redline speeds when the car is travelling at approx 200km/h+ (this varies hugely with diff ratio, obviously).

Conversely, a conventional driveshaft will see a lot more torque transmitted through it, as the engine torque is multiplied through the gearbox, whereas the new GTR driveshaft will only ever see the max engine torque (as well as impact loading under clutch dump situations etc.)

Bottom line? Probably nothing to worry about, as the Nissan Engineers would have covered it. If the shaft speeds became an issue, it's nothing to replace the single piece driveshaft with a 2 piece unit. Problem then goes away.