Cupcar

I'm confused a bit, isn't this your engine pictured below? If so, it is without a Varioram intake and should be an M64.05/06, or is that some other engine?

01coccobet

I wish I had this engine and gears
This should be the famous M64/05 R
299cv from a 3.8 non VR.
I always wondered how it feels to drive one
Anyway I tried the M64/05 X51
and it is a little different from the /21.
The latter pulling a little more from low medium rpm and having al little more high end force.
The top in my opinion is to have a /21 and G50/21 (short gear) or a regeared-one....basically going toward the RS specs.
The /05 has more "delta" torque from around 3000 to 4500, this, added to the short gear, make it feel as powerful as the /21

Jasvorken

I have an 95mod C4 with X51. This car was delivered to Japan and later exported to Norway.
How many with this cofiguration were built?

993.NINJA

I have a 1995 Carrera 4 X51 3.8 I bought a few years ago. Non Varioram which is the best. Tougher Engine.
Revs are constant through every gear at the same pace with no flat spots at all.
0-60 3.4 mph.

I noticed a few X51 C2, C4s, Targa for sale 2 years ago in a Toyota dealership, I think was in Norway,
Also France at the same time for sale that have mostly been snapped up now.

It's a riot of a car. Mad as a monkey on crack tickling a box of frogs.

908/3fan

Thanks for sharing.

schmidtwerk

Bill, where did you find the information on the fact the factory built X51 in the V Ram had the 964 crank and balancer? I have the info on the retro and factory non V Ram X51 and the retro R Vam X51 but, not the factory X51 V Ram specs. I own a 97 factory X51 and was shocked to see the tapered snout on the crank with the 964 balancer. Not sure why the factory wanted a balancer type pulley on these 3.8 liter engines but not on the RS version and further more they instruct the retrofit 3.8 folks to install a lighter pulley with single or dual belts and changing to an RS fixated alternator fan duplicating the RS.

Thanks Bill

Bill Verburg

It was in the published specs

I don't know why either. These 993.102.021.70 cranks and damper 993.102.050.70 were also used on the 993Cup. The Cup also had better rods but the street X51 used the same rods as all the other 993s

The 993 RSR used actual 964 cranks, 964.102.021.04

schmidtwerk

Bill,
I see that in the specs but, thats for the M64/05 and doesn't reference the later Vram. Your earlier comment

"the production line engines used a different crankshaft which has a harmonic balancer ala 964. All other 993 engines including RS and turbo used the same crank except Cup & RSR & GT2evo which used a 964 crank and(usually) a harmonic balancer"

According to this the Cup used the 964 type crank along with RSR, and late GT2. The 964 crank has wide rod journals and thick rods and the 993 narrow with the thin (weaker) rods. So, don't think you can have a "993" crank and use the better 964 rods. Are you thinking there was a tapered snout 993 crank that allowed the use of the 964 type balancer that was a narrow rod journal version for 993 rods that was used in the Cup and factory X51? Sorry, confused at your old comment in quotes that stated Cup used 964 type crank thus the wider 964 rods.

*I did notice the factory spec sheets does not mention rods for the factory build X51, thus making me think there is a unique crank that is 993 with tapered snout thus with small journal rods from 993.

Thanks always for your advice Bill.

Bill Verburg

993.102.021.70 X51 crank(all factory production line) and 993Cup, these have the narrow 993 rods and cone nose for harmonic balancer, the 964 balancer is not the same as the 993 balancer
993.102.021.01 or .02 all street 993 have narrow rods and rod bearings, has circular nose for simple pulley.
964.102.021.04 used in 964 and 993RSR, cone front and use 964 harmonic balancer, these have the wider 964/930 rods and rod bearings.

schmidtwerk

Ok, so three cranks. Just looked at the pulley off of my M64/21 X51 and compared to a 964 pulley....they appear the same but perhaps there is a change to the rubber dampening on the updated 993 balancer thus a new part number, otherwise looks identical front and back.

Now why on earth did Porsche use a balancer on the 964, then delete it on the 993? Maybe with new revisions to the crank and rods.....perhaps they determined the balancer was no longer needed with the revisions would be the best reason. However, then they machine a crank with a tapered nose and install the balancer back on the 993 CUP. Perhaps makes sense since they use a balancer on the RSR but with the 964 crank that always used a balancer. Porsche must feel the balancer prevents possible crank failures.....the 964 crank with bigger rods and wide journals adds another layer of strength.

Why then didn't they use the tapered nose balancer set up in the 993RS since the balancer seems to be a component used in racing applications like the CUP, but then use it on the 993 X51 that is not intended to be a track car like the RS? Then if you buy a retrofit kit they want you to simplify the pulley set up to the RS with the fixed alternator and pulley?

My conclusion:
The 964 crank, rods, and balancer pulley are obviously the toughest set up and used in the RSR.

The new 993 crank, thin rods, allowed Porsche to eliminate the previously required balancer in the 3.6 and at least in the 3.8RS. There was certainly additional cost to adding a crank with additional machining and a more complex and expensive balancer over the simple stamped pulley. Also with the single belt (or double with AC) and fixed alternator fan set up the RS engine would have less drag when you eliminate the heavy balancer, extra belt, and slow the alternator speed down.

The 993CUP added a balancer back to the mix, perhaps the thought is the balancer adds extra insurance against crank failure.

The assembly line X51 engine would go into cars with AC exclusively and generally with more options and electronics with more alternator load a consideration. Porsche may have figured the balancer on the street 3.8 X51 was a good idea from an addition load perspective and offer additional longevity. On the retrofit they figured since there is no way to add a balancer due to the retro kit going on a crank without a tapered nose thus a balancer cannot be added, going to the lower drag RS option was best. So either make the drag lower (ala the retro kit) perhaps causing less strain on the crank, or add a balancer. In any case Porsche did not like the triple pulley three belt non balancer set up on the 3.8 that was standard on the 993 3.6.

Cupcar

The 993 style and 964 style cranks are torsionally different so have different dampening requirements.

schmidtwerk

Right, and on the 3.8 version Porsche preferred either a low load RS set up with fewer belts and a fixed alternator fan set up or if used with a triple belt which would allow for higher alternator speeds thus accommodate more electrical load they wanted a balancer type pulley. They really went out of their way to not allow for the standard 993 triple belt set up with no balancer and a non fixed alternator fan.

Cupcar

The race cars use a single Gilmer belt drive, not a V belt.

schmidtwerk

Correct, but I'm trying to stay on the street applications overall. The race car mention was in reference to the use of a balancer.

Bill Verburg

The 993 crank is the heaviest and stiffest of the bunch, the 964/930 has the biggest rod bearing area
part 993 964
flange thickness 9.4mm 7.9mm
crankpin width 19mm 22mm
mains 55 &60 55 & 60mm
weight 15.4kg 14.4kg
pulley -732g base
rods 520g 632g
100mm pistons 602g 657g
weight of the entire crank + rod assembly -.818kg base

Only the RSR used the serpentine belt

the GT2 Evo used the 993.102.021.02 crank and reinforced 993 rods 993.103.020.06 they also use special con rod bearings

just FYI the heat out let covers
holey ones 964.106.409.80
twin out ones 993.332.271.80