Jack Olsen are you out there?
02-19-2007, 12:23 AM
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Jack Olsen are you out there?
I have been enjoying your track videos immensely, just a question or observation on your transmission gearing. The shifts sound very close together, are you running stock gears in your transaxle? I've got minimal experience with Porsche to this point, may be changing in the near future. 
Jeff
Jeff
02-19-2007, 12:51 AM
#2
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Jeff, where are Jack's videos located? I would like to have a look...
02-19-2007, 01:09 AM
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02-19-2007, 01:55 AM
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Thanks. You can see everything I've put on YouTube here:
http://www.youtube.com/JackOlsen
Or you can also click on one of the track names in my signature, and then clicking on the "more from this user" link on the subsequent YouTube page.
If you really like in-car footage, I've got a complete session on Google Video. Click HERE for part one and HERE for part two.
But yes, Quikshft, I have shorter (or closer) than stock gearing on my car. It's a 1977 transaxle (the last year of the Magnesium case) with a stock 1st gear, a taller-than-stock 2nd, a stock 3rd, and a shorter than stock 4th and much shorter than stock 5th. It makes for very small rpm changes between gears, which allows you to keep things in your engine's torque sweet spot longer.
The downside is that cruising at 80 mph in 5th means I'm at 4000 rpm. And my top speed is only 135.
http://www.youtube.com/JackOlsen
Or you can also click on one of the track names in my signature, and then clicking on the "more from this user" link on the subsequent YouTube page.
If you really like in-car footage, I've got a complete session on Google Video. Click HERE for part one and HERE for part two.
But yes, Quikshft, I have shorter (or closer) than stock gearing on my car. It's a 1977 transaxle (the last year of the Magnesium case) with a stock 1st gear, a taller-than-stock 2nd, a stock 3rd, and a shorter than stock 4th and much shorter than stock 5th. It makes for very small rpm changes between gears, which allows you to keep things in your engine's torque sweet spot longer.
The downside is that cruising at 80 mph in 5th means I'm at 4000 rpm. And my top speed is only 135.
Last edited by JackOlsen; 02-19-2007 at 10:39 PM.
02-19-2007, 02:25 AM
#5
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Nice driving, Jack. The only thing I would like to see in yours or anyone else's' videos is the tach and speed gauges. That would be neat
02-19-2007, 02:29 AM
#6
Race Car
Thanks.
Frustratingly, I have the software to add that. But for weird technical reasons (the limitations of running Windows on an Intel based Mac), I haven't been able to get the software activated.
This clip of Willow Springs does show a facsimile of that. It shows throttle, brake, gear and occasional speed samples. I added the data in editing, but it's based on data logger info -- so it's fairly accurate.
Frustratingly, I have the software to add that. But for weird technical reasons (the limitations of running Windows on an Intel based Mac), I haven't been able to get the software activated.
This clip of Willow Springs does show a facsimile of that. It shows throttle, brake, gear and occasional speed samples. I added the data in editing, but it's based on data logger info -- so it's fairly accurate.
02-19-2007, 02:31 AM
#7
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A little OT, but someone told me that these stock G-50 transmissions in these 911s don't do well on the track - that they can overheat easily. Is that true? I figured it we're running the right oil, we should be OK.
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02-19-2007, 03:52 AM
#8
Race Car
In track use, transaxles suffer. I put a temp sensor on mine, and was surprised to see temps higher in the transmission than they were in the engine, at times. And gear oil starts to break down at a much lower temperature than engine oils (I've been told anything more than 200 degrees means trouble.)
On the street, it's a total non-issue (maybe autobahn use would be different). I've never been able to get my 915 hot in even spirited street use.
But for track use, I installed a cooler. And I can't imagine why the G50 would have any different temperature characteristics than the 915. But maybe someone here knows.
On the street, it's a total non-issue (maybe autobahn use would be different). I've never been able to get my 915 hot in even spirited street use.
But for track use, I installed a cooler. And I can't imagine why the G50 would have any different temperature characteristics than the 915. But maybe someone here knows.
02-19-2007, 12:35 PM
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What kind of oil are you using, Jack? How hot does it get?
I'm not sure, but isn't a 915 R&P a spiral bevel gearset? And a G50 a hypoid gearset? If so, the G50 will indeed run hotter since there are more losses in a hypoid gearset. The tradeoff is for strength.
The helix angles of the individual gears contribute to heat. If the helix angles are different, that could account for some extra heat. (greater helix angle = more axial thrust = more friction)
I'm not sure, but isn't a 915 R&P a spiral bevel gearset? And a G50 a hypoid gearset? If so, the G50 will indeed run hotter since there are more losses in a hypoid gearset. The tradeoff is for strength.
The helix angles of the individual gears contribute to heat. If the helix angles are different, that could account for some extra heat. (greater helix angle = more axial thrust = more friction)
