beepbeep

Hello!

I have a little question:

We are assembling a hot twin-turbo engine based on N/A 3.6 993 engine. As far as I know, crankshaft fitted in 993 N/A and 993 Turbo are the same, or are they?

PET shows only one article number for 993 crank from 95' onwards. Is this crank a good choice compared with 964 item (strength-wise)?

My understanding is that 993 crank has narrower journals but stronger side-bars, which makes it heavier but stiffer. Is this correct?

Also, what is the difference between 94' (993 102 021 01) and 95'> crank (993 102 021 02)?


Thank you for all help!

Red rooster

Not an expert but the choice of 964/993 crank usually comes down to the rods you are using.
The 964 journal is wider so for really big bhp is a better choice.
Have you checked out the GT3 crank ? Thats reckoned to be the best 3.6 crank !

Good luck

Geoff

beepbeep

We used GT3 crank on old 964 3.6L engine before it blew up on Nurburgring. Now we have 993 N/A core to build on. Rods are not purchased yet as we have to decide which crank is best to use.

I got information that 993 crank is actually stiffer even if its journals are not as wide as 964 one, as it has more "meat" between journals. I also heard that stiffer 993 crank allowed Porsche to get rid of harmonic balancer. Is that true?

I don't know much about 993 engines, actually. Right now, we would like to keep 993 crank if possible. If GT3 is much better, we will purchase it. Old one was already polished once and engine spun a bearing afterwards, ruining it.

Geoffrey

The 993 N/A crankshaft is the same as the 993TT engine and the same as the 996TT and GT2 engine. The narrower journals do not handle the loading as well as the wider journals of the 964 or GT3 crankshaft. In addition, Porsche change some of the tolerances which I think was a mistake and we are seeing 993 engines that have been tracked quite a bit begin to show rod bearing failures. I don't think the 993 crankshaft is a good choice for a high HP turbo engine, especially if it is going to see track usage. Neither the 993 nor the 964 crankshaft is fully counterweighted like the older 74.4mm crank in a 3.2 Carrera or 930.

If the engine will see street only, it might work out Ok for you, it just wouldn't be my first choice. My crankshaft of choice is a GT3R crank.

beepbeep

Hmm...interesting findings.

Why did Porsche use narrow-journal crank on GT2 (are we talking both 993 GT2 and 996 GT2?) with its higher power output but opted for wider journals on GT3?

Also, what is the difference between 964, 996 GT3 and 993 GT3R crank?

Regards,
Goran

Jean

beepbeep
sorry to hear that the engine blew, you guys had built a true beast.
The 996 GT3 goes up much higher in revs and therefore has to bear more load. Stress on the engine is exponential not linear with RPMs as you know.

I cannot add anything beyond what has been said by both Geoffs, other than make sure you post more videos of your cars.

For those who have not seen it.
http://www.zatzy.com/if-story/The_IT...ry_trailer.wmv

beepbeep

Jean: yeah, but old engine really had it coming. It was build from second-hand 964 clunker with 170000 miles under it's belt, overreved dozen of times, had oval cylinders, blew one of heds in pieces, recieved "rebuild" that consisted of new piston rings and piston bolts and was ridden hard and put away wet. It run whole summer and finaly gave up it's ghost on a 'ring, just like engines should do (It was actually captured on the video)

http://www.youtube.com/watch?v=BtxBvKW7FA4

Back to crank:
I suppose that higher revs that GT3 expirience require wider journals due to higher loading on rods and thus wider oil film? Loads on jourals are part cylinder pressre and part inertial loads due to revs. On most engines, peak rod loads are lower than inertial loads at highest revs (except for modified SAAB-engines), so I guess they sacrificed rigidity for wider journals? Am I thinking right?

To re-formulate the question:

If you had 1000Nm of torque at roughly 4500 RPM and max power at 7200 RPM, which crank would you use? The sturdy and stiff 993 crank with it's narrower journals or little less stiff (and expensive!) GT3 crank with wide journals?

Those GT3 cranks don't grow on trees, unfortunately.

beepbeep

P.S. Jean: you asked about accelleration figures a long time ago. Now they have been published and logged by a 3:rd party calibrated equipment so I can reveal it.

100-200km/h in 4.96 seconds.
0-200km/h in 8.3 seconds and 0-100km/h in 3.4 seconds.

Measured on ordinary pavement, not strip.

Geoffrey

I don't think the GT2 program was ever a fully developed program with many special racing parts installed. The GT2 race engine was homologated from a GT2 street engine which was largely stock 993tt, all things considered. If Porsche wanted to, it could have installed a better crank, like they did with the 993RSR which has the larger journals of the 964 but they didn't.

The GT3 crank is basically a stroked 930 crank, meaning it is fully counterweighted, the journals are smaller in diameter but the same width. More importantly, they have 180 degree oiling on the rod bearings. The crankshaft is available from the dealer, that is where I got mine and it only took 10 days direct from Germany.

red993tt

Lucky you they do. I have a brand new GT3 R crankshaft and Arrows rods specially designed to go with it. I bought them form Kevin but never had a chance to use them.
Similar to this ones Link

sonny1

I must point out that a GT3 crank is different than a GT3R crank ( a few dollars difference).,.cheers, Sonny.

Kevin

You wrote.... The sturdy and stiff 993 crank with it's narrower journals or little less stiff (and expensive!) GT3 crank with wide journals?

That's not correct. If you trashed a bearing with the GT3 crank then you will trash it with the 993 crank.. The 993 crank and rods are not the correct choice out of the box. You have to spend alot of crankshaft prep.. Like cross drilling the crank..

Buy the GT3R crank and be done with it.. Make sure you get the correct bearings and the GT3 dual pickup oil pump.. 1000NM with a stock 993 crank is asking for another rebuild.. By the time you add up the machine work you could have purchased a GT3R crank..

Tippy

Ah....beautiful reading guys, I love this type of stuff....keep it up so when I get mine I will be better informed

Red rooster

996 based parts like the GT3 crank are usually lower cost than the aircooled versions !
Porsche moving into realistic pricing for the watercooled cars ?

Without being pedantic Jean , the loadings are square law with rpm so a 10% rpm rise is a 20% increase in bearing load . Because of the way it all works the same law does not apply to boost .

Geoff

Jean

beebeep
Thanks for sharing, those are amazing numbers. I think I saw a 10s, 140+mph quartermile run somewhere else too? Obviously traction is a serious issue.

It would be interesting to know the weight of the car , I remember it was quite gutted. Yes it is an "honour" to break an engine on the 'Ring at full blast !

Red993TT
Don;t sell it! I would keep at home in the living room.

Geoff,
Thanks for the info, I just knew it was not linear but never did the effort checking out the correct formula.