Engine Refresh

[924Srr27l]

LR told me the 3.0 block has a better (less windage) design which produces more power than the 2.5 block, maybe this also assists the Oil frothing
and the amount that's flung upwards especially with the scrapper?, and then further still for the 968 with squirters..

The 944s2 & 968 3.0 Cranks may also perform differently in the Oil bath compared to the 2.5 ?

I'm using a 3.0 block & Sump but with the shorter stroke 2.5 & 2.7 crank (Knifed with a 3kg reduction) which will have less fling...

R

 

[GPF]

Thanks for the crank scraper link Pete. I'll look into that now.

Bores seem to have no wear and no lip/step. There is also no crank end float.

It's all coming apart anyway though

 

[Mike_Pollock]

Saw your car last week in the workshop George, and had a chat with one of the guys there I know - he was very impressed with it. Dropped in to see Mark just round the corner too
I think like most things in life there is a balance to be struck, lightning the rotating parts a little will improve pick up but possibly not the driveability, the clutch is coming out, so a lightened flywheel is a good choice. Or if you're going to machine the crank to lighten it, you can also fit a scraper, I would suggest either rather than both for a weekend not track car.
The 2.7/3.0 block does use more oil cooling, hence the external oil cooler. The 968 make 12% more power than the S2, which is why the oil sprays are used.
I don't like scrapers, as any small movements, even over time, will mean bits in the oil. (Fine for max power/regular rebulid)

 

[Mike_Pollock]

Saw your car last week in the workshop George, and had a chat with one of the guys there I know - he was very impressed with it. Dropped in to see Mark just round the corner too
I think like most things in life there is a balance to be struck, lightning the rotating parts a little will improve pick up but possibly not the driveability, the clutch is coming out, so a lightened flywheel is a good choice. Or if you're going to machine the crank to lighten it, you can also fit a scraper, I would suggest either rather than both for a weekend not track car.
The 2.7/3.0 block does use more oil cooling, hence the external oil cooler. The 968 make 12% more power than the S2, which is why the oil sprays are used.
I don't like scrapers, as any small movements, even over time, will mean bits in the oil. (Fine for max power/regular rebulid)

 

[blade7]

The 968 make 12% more power than the S2, which is why the oil sprays are used.

I seem to recall Jon Mitchell telling me a different reason for the squirters being there, and it wasn't about power.

 

[924Srr27l]

The 2.7/3.0 block does use more oil cooling, hence the external oil cooler. The 968 make 12% more power than the S2, which is why the oil sprays are used.
I don't like scrapers, as any small movements, even over time, will mean bits in the oil. (Fine for max power/regular rebulid)

+15% (S2 208bhp / 968 239bhp)
Changes: Variable valve timing system, induction, twin exhaust pipes, dual-mass flywheel, engine management revisions etc..

Scrapers: are you saying in time bits come off them if they are positioned to close to the crank as opposed to the OE scrapper / baffled Sump
Pan which is not too close ?

Do all stock S2 motors use an external Oil cooler ? I've not fitted one on mine after advice it's not necessary.

R

 

[944Turbo]

thank's Tony..... how did you do that? I tried a number of times and couldn't get the search engine to go back far enough...

Pete

no worries!
I searched for crank scraper it was near the top of the results - there are 'additional options' (on the right of the search pane) I use that to select 944 only if it is something more common.
Tony

 

[blade7]

Do all stock S2 motors use an external Oil cooler ?

R

Yes.

 

[924Srr27l]

Do all stock S2 motors use an external Oil cooler ?
R

Yes.

Ok thanks,
I went with the Engine builder's advice not to run one, as the Internal water stat was fine for road use unless I was racing it etc...
The Engine (Water temp) runs so cool, I've been thinking of blanking some of the Radiator core off. I fitted a China wider
core Rad listed for the 944 Turbo...

R

 

[blade7]

Water and oil temp although linked with a heat exchanger type cooler are different things. I'd consider fitting an external cooler with the shallower water jackets of the 2.7/3.0 block. Like Porsche did.

 

[924Srr27l]

Water and oil temp although linked with a heat exchanger type cooler are different things. I'd consider fitting an external cooler with the shallower water jackets of the 2.7/3.0 block. Like Porsche did.

Yes, i've no reason to be concerned about (no external cooler fitted) or question the Engineer that recommended it didn't need one, he has built many reliable road and Race (championship winning) Porsche 944 / 968 Engines

It pulls less revs than a 3.0 16V, only has one camshaft to lubricate, and I wonder if the 944 2.7 8v also had a external Cooler or not?
It's only 76 BHP per litre so it's not such a highly stressed lump!

R

 

[blade7]

I wonder if the 944 2.7 8v also had a external Cooler or not?
It's only 76 BHP per litre so it's not such a highly stressed lump!

R

The S2 makes less than 76 bhp per litre.

 

[Eldavo]

Water and oil temp although linked with a heat exchanger type cooler are different things. I'd consider fitting an external cooler with the shallower water jackets of the 2.7/3.0 block. Like Porsche did.

I wonder if the 944 2.7 8v also had a external Cooler or not?

The 2.7 had the same oil/coolant cooler as the 2.5 mounted on the side of the block.

 

[924Srr27l]

Water and oil temp although linked with a heat exchanger type cooler are different things. I'd consider fitting an external cooler with the shallower water jackets of the 2.7/3.0 block. Like Porsche did.

I wonder if the 944 2.7 8v also had a external Cooler or not?

The 2.7 had the same oil/coolant cooler as the 2.5 mounted on the side of the block.

That's good then as that's also what my 2.7 has...

R

 

[blade7]

The 2.7 was a bit of a mystery engine, seeing as Porsche dropped it after a year and only carried forward the block...

 

[924Srr27l]

The 2.7 was a bit of a mystery engine, seeing as Porsche dropped it after a year and only carried forward the block...

It was very odd, more displacement and bigger valved head but 2hp more than the 2.5 ??!
Unless they did something on purpose to restrain it from being as powerful as the 2.5 16V?

R

 

[Eldavo]

I had a 2.7 and drove it back to back with a friend's 2.5. The headline bhp may have been negligible but the overall availability of torque was significantly greater and improved driveability no end.

 

[blade7]

The 2.7 was a bit of a mystery engine, seeing as Porsche dropped it after a year and only carried forward the block...

It was very odd, more displacement and bigger valved head but 2hp more than the 2.5 ??!
Unless they did something on purpose to restrain it from being as powerful as the 2.5 16V?

R

Perhaps it was going to be the next 944 Turbo engine...

 

[GPF]

Bores seem to have no wear and no lip/step. There is also no crank end float.

It's all coming apart anyway though

Hmmm, bit of a less favourable update now it's all in bits.

No2 rod is slightly bent (!!) and they think there may be more cylinder wear than initially thought, and maybe to the piston skirts too.

If that turns out to be the case then I may have more of a decision to make - if it wants rods & pistons, and maybe honing, and crank work then......hmmmm......maybe 2.8 isn't that much more of a step??

Equally though, I can just replace the 1 rod - they are not available from Porsche anymore though so It would have to be a good used one - or an aftermarket forged set.

If the piston skirts are worn then they are VERY expensive from Porsche (>£2k) so probably an aftermarket forged set would be the way to go.

I'm probably going to send the block and pistons away to be properly checked - maybe Serdi as Pete suggested, or maybe to EMC who are closer. Anyone used EMC? I'll give them both a call anyway.

 

[PSH]

Bores seem to have no wear and no lip/step. There is also no crank end float.

It's all coming apart anyway though

Hmmm, bit of a less favourable update now it's all in bits.

No2 rod is slightly bent (!!) and they think there may be more cylinder wear than initially thought, and maybe to the piston skirts too.

That's a surprise Graham? which rods are fitted, cast or forged? Looking at your car's model year I'm suspecting cast which could explain it with the mods listed, I wouldn't expect this with the early forged rods. However, are they sure that it's bent? I ask as I wonder how they are measuring it? If only between centre's then I would expect it to be out especially on No.2, I did post pictures of my rods which clearly showed how the wrist pin centre had moved due to the wear on the brass bushes, a reason why I say to anyone doing a rebuild, don't forget to do these bushes.
If the wear warrants a bebore, then I personally would get Serdi to do it with their good track record on modifying these cars, they can also supply IASA full race spec pistons, these really do make a big difference to the engine's response, IMHO of course. Not sure on cost today but IIRC the cost of my rebore, pistons/rings and crank ground was around £1500, admittedly this was about 5 years ago.

Putting all this aside I hope you get the car back on the road soon, having a newly rebuilt engine under your right foot is an experience that needs to be shared by all...

regards

Pete