Reverse rotation engine and porsche 930?

[middy]

Originally Posted by Russ Noble

The OD of the bearing that takes the thrust (i.e. the one in the sideplate) is 90mm, the one on the non thrust side (i.e. in the trans housing) is 80mm and that's the same for both short and long bell. I've got both here.

Thanks. Can't the trans housing be machined to accept the larger 90mm bearing?


Second question - What type of gear is the 930 r&p? Hypoid or Spiral bevel gear?

[Ian K]

The Renault will work fine as is. The DeLorean's apparently flipped the ring gear since
they are rear engine, but the transaxle is situated normally.

The 930 can have its ring gear flipped (as can the G50 series) IIRC, so you could
stick that in there as well. And, of course, all of the Porsche like boxes available.
Or a ZFQ if you're spending that kind of money.

Ian

[Russ Noble]

Originally Posted by croc

Thanks. Can't the trans housing be machined to accept the larger 90mm bearing?


Second question - What type of gear is the 930 r&p? Hypoid or Spiral bevel gear?

I'm sure you would be better off leaving the smaller bearing rather than machining the case. I feel you need to increase rather than reduce the strength in this area of the housing.

930 r & p is spiral bevel. You can't flip a hypoid due to the angle of the teeth. Sorry, no source, just my considered opinion ;-)

[middy]

I recently found out that all tiptronic 911 engines (even 997 turbo!) are running in reverse rotation due to the fact that their transmission side plate are at the other side.

So, there is nothing funny or strange about reversing the rotation of an engine.

All 911 manual gearboxes are fitted with a LH pinion and a RH crown wheel, so if you reverse your engine rotation you need a custom RH pinion and a LH crown wheel.






A right hand spiral bevel gear is one in which the outer half of a tooth is inclined in the clockwise direction from the axial plane through the midpoint of the tooth as viewed by an observer looking at the face of the gear.
A left hand spiral bevel gear is one in which the outer half of a tooth is inclined in the counterclockwise direction from the axial plane through the midpoint of the tooth as viewed by an observer looking at the face of the gear.
A spiral bevel gear and pinion are always of opposite hand.

[Pete T]

That is an incorrect assumption. Just because the cover is on the opposite side does not mean the gears are turning in reverse rotation or the engine is turning in reverse rotation. The gears are cut to run the correct rotation. Take for instance the 915 vs the G31 (924 turbo) The ring and pinions are identical except that one ring gear is on the right side and the other is on the left side. Both are cut to put the drive on the correct side of the teeth and both engines turn the same direction. If you just put a 915 gear set in a G31 or vice versa the output would be backwards. The tiptronic cars have the engine running the same direction as the non tiptronic cars.

There is no OEM that runs the gears backwards.

As for the question about the 930 gears, they are spiral bevel. You can flip the diff. just as in the 915 and 901. You cannot flip a hypoid because the pinion is lower than the ring gear centerline. If you tried to flip it you would need to move the pinion gear up to keep the same relationship with the ring gear. (obviously impossible)

The G50 cannot be flipped because it has hypoid gears just as the 016 and 01E do. Besides being printed in the factory manuals you can see it if you look at a crossectional view.

[middy]

Take for instance the 915 vs the G31 (924 turbo) The ring and pinions are identical except that one ring gear is on the right side and the other is on the left side.

That's because the 924 is front engined and the 911 is not

What matters is which side is the ring gear of the car? Please note I said 'of the car', not 'of the gearbox'.

If the ring gear is on the left side of the car (regardless of whether the gearbox is facing forwards or rearwards, and whether it's sitting upright or inverted) the engine/transaxle must run in standard rotation and use LH pinion and RH ring gear.

If the ring gear is on the right side of the car, the engine/transaxle must run in reverse rotation and use RH pinion and LH ring gear.

[Pete T]

Incorrect. The ring and pinion gears are cut differently so they rotate the same way. It does not matter which side of the car the ring gear is on.

The 915 vs G31 was to show that the ring and pinions are interchangeable except that when you swap them the output will change to the opposite direction.

I have both G31 and 915 ring and pinion gear sets. If i use the 915 set im my G31 the ring gear will be on the left side. If i were to put the G31 gear set in the 915 the ring gear would be on the left side.

The 016 and 01E have the ring gear on the left side. The G31 has the ring gear on the right side. the 924/944/968 all have engines spinning the same direction. These cars had both right and left ring gears and engines that spin the same direction.

There are only a couple of auto engines ever made that spin the opposite direction. One was the Corvair the other I think is an air cooled Fiat. Unless there is some other obscure engine besides these, all automotive engines spin the same direction.

All Porsche engines spin the same direction. What you claim is simply not true. Porsche does not make engines that spin in opposite directions for use with manual vs auto transmissions.

[middy]

Engine
Thanks for correcting me about Porsche engines. You are right. I double checked the parts catalogue last night and found that the manual and tiptronic engines share the same camshafts. So, yes, all P-engines do run in the same direction.

Transmission
I was confused by the following picture of the new 911 (rear-engined) PDK gearbox


because, as you can see, the teeth of the pinion in the pic is a RH. I now realise why- it's because the PDK is a 3-shaft gearbox. The input shaft turns in the same direction as the flywheel (anti clockwise by looking at the flywheel), the secondary shaft turns clockwise, then the pinion shaft, as it meshes with the secondary shaft, turns anti-clockwise hence the RH pinion.
In manual gearboxes, which is a 2 shaft design, the pinion shaft turns clockwise hence LH pinion.

The upcoming mid-engined PDK gearbox for the Boxster and Cayman will also have a RH pinion (I think!) but moved to the other side.

I don't know how a tiptronic works so I can't make comments about that.

Reverse engine rotation
The theory of the reversing the engine/transaxle (manual 2-shaft) rotation is still valid if one wishes to install an upright 915 or 930 in a mid-engined car if he doesn't wish to flip the standard ring gear to the other side.