One reason why GT3 engine makes power

[Bill Verburg]

Originally Posted by Cupcar

My factory book says the GT3 oil pressure relief valve opens at 5.3 bar or 77 PSI, not 90, so I was wrong in memory here, and the safety valve opens at 7 Bar or 102 PSI .

That jibes w/ Geoffrey's info 80-85lb from 3k up at B which is before the top case oil galley

[lupin..the..3rd]

Originally Posted by Cupcar

Ti 130 mm GT3 rods

What's the ballpark price for a set of these rods? Carillo and Pauter are "reasonably" priced but if these can be had for just a few bucks more... Mmmmm titanium!

[Cupcar]

Originally Posted by lupin..the..3rd

What's the ballpark price for a set of these rods? Carillo and Pauter are "reasonably" priced but if these can be had for just a few bucks more... Mmmmm titanium!

Check with Porsche dealer, they used to be around $5000 a set a couple of years ago. Probably more now.

[lupin..the..3rd]

Originally Posted by Cupcar

Check with Porsche dealer, they used to be around $5000 a set a couple of years ago. Probably more now.

Yikes, that's triple the price of the others. It seems the old saying is true, "if you have to ask how much".....

[Cupcar]

Originally Posted by lupin..the..3rd

Yikes, that's triple the price of the others. It seems the old saying is true, "if you have to ask how much".....

I thought Pauter Ti rods were around $5000.

[KTL]

996.103.012.93 is only $1700 per rod. OUCH. A complete set of chromoly Pauters for our old cars is the cost of one GT3 rod.

GT3 Rod Cost Via Pelican

[cstreit]

Originally Posted by Cupcar

My factory book says the GT3 oil pressure relief valve opens at 5.3 bar or 77 PSI, not 90, so I was wrong in memory here, and the safety valve opens at 7 Bar or 102 PSI .

What book has that level of data. The owner/tech manual is pretty basic?

[brp914]

Can a Ti rod be run 150k miles, resized, and run another 150k miles? Or does Ti fatigue more rapidly than a steel rod making it one-use-only?

[GrantG]

Originally Posted by Bill Verburg

another is the crank shown above here(964 on bottom), can you say 8800+rpm?

Are the GT3 cranks much lighter? Do they have better oiling? Are all 3.6L cranks way heavier than say a 3.0SC crank?

[Flieger]

Originally Posted by brp914

Can a Ti rod be run 150k miles, resized, and run another 150k miles? Or does Ti fatigue more rapidly than a steel rod making it one-use-only?

Ti rods are made to higher quality now than the first ones and can be designed to have a fatigue life long enough for a street car, but Ti alloys do not exhibit a fatigue endurance limit like Ferrous alloys do. Steel rods can still be made light enough that they fatigue due to being stressed beyond the "infinite life" fatigue endurance limit, however.

[KTL]

I've heard that the GT3 rods can be reconditioned. But most who race the GT3 engine really hard (endurance races) choose to junk them and replace.

[KTL]

Notice how the GT3 crank isn't even knife-edged? That in my mind demonstrates that the 911 engine doesn't benefit a whole lot from that racer's trick. That said, knife edging reduces weight, aside from typical windage losses in wet sump engines. So i'm not saying that knifing doesn't have it's benefits.

Also looks like the counterweights on the GT3 crank are smaller (thinner?) than the 964.

The GT3 crank is lighter than the 964 crank. It's rod journals are smaller (SC size). Oilling is basically the same- no cross-drilling on the GT3 crank from factory.

The 3.0 crank is lighter than the 964 crank because it has smaller journals and the stroke is shorter- 70.4mm stroke for SC, 76.4mm stroke for 964.

That 964 crank pictured looks like it had a rod bearing problem on #6?

[Spenny_b]

Over on 911uk.com, I remember reading a couple of articles on the GT3 engine when I had my 996 GT3 Mk2

https://techinfo.porsche.com/techinfo/sit/en/996Carrera/2004/1_2004_996_gt3.pdf

And one on the RS variant:
https://techinfo.porsche.com/techinfo/sit/en/996Carrera/2004/1_2004_911gt3rs.pdf

[500_19B]

Originally Posted by Flieger

Ti rods are made to higher quality now than the first ones and can be designed to have a fatigue life long enough for a street car, but Ti alloys do not exhibit a fatigue endurance limit like Ferrous alloys do. Steel rods can still be made light enough that they fatigue due to being stressed beyond the "infinite life" fatigue endurance limit, however.

That is opposite to what I have long understood (and what is printed in one of my university textbooks). A quick Google calls up numerous sources that confirm that titanium and ferrous alloys both have distinct fatigue limits.

[Flieger]

Originally Posted by KTL

Notice how the GT3 crank isn't even knife-edged? That in my mind demonstrates that the 911 engine doesn't benefit a whole lot from that racer's trick. That said, knife edging reduces weight, aside from typical windage losses in wet sump engines. So i'm not saying that knifing doesn't have it's benefits.

Also looks like the counterweights on the GT3 crank are smaller (thinner?) than the 964.

The GT3 crank is lighter than the 964 crank. It's rod journals are smaller (SC size). Oilling is basically the same- no cross-drilling on the GT3 crank from factory.

The 3.0 crank is lighter than the 964 crank because it has smaller journals and the stroke is shorter- 70.4mm stroke for SC, 76.4mm stroke for 964.

That 964 crank pictured looks like it had a rod bearing problem on #6?

GT3s use a mondo oil pump to partially evacuate the crankcase of air, using a special main seal to hold it. No air means that windage mods are completely unneccessary.

Originally Posted by 500_19B

That is opposite to what I have long understood (and what is printed in one of my university textbooks). A quick Google calls up numerous sources that confirm that titanium and ferrous alloys both have distinct fatigue limits.

I was told differently, but I could be wrong. I am not a materials engineer, just mechanical.

I was under the impression that the mechanism of the fatigue endurance limit had to do with interstitial alloy atoms such as carbon in iron arresting crack growth. With Aluminum alloys it is usually a substitutional alloy since the Al ions are smaller than the Fe ones and therefore there is no endurance limit.

[KTL]

I don't believe the intent of the oil pump is also to expel air from the case.... Isn't the case breather housing there to address the air/positive crankcase pressure issue? Air-entrained oil is the enemy to oil cooling. So I can't imagine the intent is to use the pump to evac air and introduce it into the scavenged oil?

Typical windage loss in wet sump engines is related to the crank counterweights slinging through the oil. I'm not saying there is not a loss caused by the crank parting the air in the case. Just saying that the viscosity of oil is much higher than air (both are considered fluids) and the air effect is much less of a concern than oil. So what you're saying is in the dry sump condition, there's no worry about oil losses and therefore the next loss to tackle is the air effect on the crank?

[Bill Verburg]

Originally Posted by KTL

I don't believe the intent of the oil pump is also to expel air from the case.... Isn't the case breather housing there to address the air/positive crankcase pressure issue? Air-entrained oil is the enemy to oil cooling. So I can't imagine the intent is to use the pump to evac air and introduce it into the scavenged oil?

Typical windage loss in wet sump engines is related to the crank counterweights slinging through the oil. I'm not saying there is not a loss caused by the crank parting the air in the case. Just saying that the viscosity of oil is much higher than air (both are considered fluids) and the air effect is much less of a concern than oil. So what you're saying is in the dry sump condition, there's no worry about oil losses and therefore the next loss to tackle is the air effect on the crank?

All Porsche dry sump engines run a partial vacuum in the crankcase, the GT3 just enhanced it w/ special crank seals and and breather valves. It's speculated that this contributes to the rear main leaks that these cars are notorious for. The seals work fine dynamically but tend to leak when they sit, causing no end of consternation in the owners minds.

[Flieger]

Yes, the pumping of the piston pushing air more than the crank I believe.

Air in oil is common in high rpm dry sump engines from what I read. That is what the air-oil separator (baffles in a 911 oil tank) is for. I can't remember where I read about the oil pump being used for crankase vacuum. I think it might have actually been a Toyota F1 engine. They had to open a tiny hole in the case however. I guess to prevent cavitation or something? Anyway, they had to have some small amount of airflow. But the benefits of lower pressure drop off like most everything as the pressure becomes closer and closer to a vacuum. So that last little bit of air did not matter.

Take a look at the new Suzuki GSX-R engines. The engineers even designed an optimal shape for the holes connecting the crankcase sections (holes through the main bearing saddles). This allowed the air to be pushed around rather than compressed and expanded which would normally also happen on a boxer engine. They made pentagons for some reason. I guess resonance.

[Bill Verburg]

While it's true that the bigger the piston the more air it pushes around, the source of the cc vac is the oil pump, more specifically the scavenge section.
the scavenge side of a 993 pump moves 120l/min
scavenge side of a GT3 pump moves 135 l/min
the competition pumps used in LeMans GT1 move 160 l/min on the scavenge side

these pumps leave the cc under vacuum, increasingly so as the revs go up.

[Flieger]

Originally Posted by Bill Verburg

While it's true that the bigger the piston the more air it pushes around, the source of the cc vac is the oil pump, more specifically the scavenge section.
the scavenge side of a 993 pump moves 120l/min
scavenge side of a GT3 pump moves 135 l/min
the competition pumps used in LeMans GT1 move 160 l/min on the scavenge side

these pumps leave the cc under vacuum, increasingly so as the revs go up.

Yes, I was talking about the bike engine because it still has some meaningful air pressure in the crank case and so they put the ports in the bearing webs. I was just giving evidence that the air pumping losses are significant enough for KTL.