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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. :eek:
GT3 Rod Cost Via Pelican |
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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?
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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.
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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? |
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 |
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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. |
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? |
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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. |
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. |
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