Thoughts on the "928GT"
04-19-2017, 09:44 PM
#16
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Ahh ok. Yeah the GT's were all very strong, but I remember years ago someone had put together a spreadsheet with all various member's published chassis dyno results and what if any mods had been performed prior to said run, and the '89 GT seemed to reign in the stock RWHP war even over the '90 and '91 models. Not sure if that still bares true but back around 2005 it was . :-)
04-19-2017, 10:45 PM
#17
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The GT ... Cooling is the same as S4 with 5sp where there is no auto trans cooler, but the GT has a low mounted engine oil cooler. 90 and later have the air flaps to block off rad cooling air. From 90-91 got the digi-dash, airbags, and a few other gewgaws over the 89GT.
'89GT does not have the low-mounted oil cooler. 90+ all models do.
all '87-90 928s had the cooling flaps; factory delete starting '91
'91 gets more noise deadening (along with self-destructing rear liners)
Other diffs:
'91+ gets 'fat and short' shift boot
'89GT had standard forged wheels. only 928 to ship with 8" front and 9" rear.
Fun fact: this coming winter I will have 1.09% of the OC-listed GTs in my garage
04-20-2017, 12:08 AM
#18
Burning Brakes
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04-20-2017, 11:30 AM
#19
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04-20-2017, 12:10 PM
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Based upon the dyno charts I have, I will hazard an educated guess that those are rwhp numbers. 300 rwhp is about 'average' for a healthy GT. I suspect Jarrod's made his GT a bit 'healthier' than average. It's not too hard to do so, especially with a SharkTuner.
Last edited by worf928; 04-20-2017 at 12:14 PM. Reason: spelin bAd
04-20-2017, 12:13 PM
#21
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Although, looking at the A/F ratio chart... it's inverted. An A/F of 20 doesn't combust. GT's - without some help - will typically be in the mid-11s or high 10s after 4k rpm and that's actually too rich and robs power.
04-20-2017, 12:13 PM
#22
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Thanks Dave
04-20-2017, 01:15 PM
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That depends upon the powertrain loss from the crank to the pavement. A rule of thumb is 15% for manual and 20% for automatics. My personal opinion is that a torque tube-based architecture has a lower loss (since that's the primary point of a TT architecture) and I used 12% and 17% respectively. I have no scientific basis for that. I've just looked at lots of dyno charts and operated under the assumption that Porsche's BHP figures are, on average correct and used that to back out those numbers.
Anyway: 352 - 364 bhp.
Anyway: 352 - 364 bhp.
04-20-2017, 01:58 PM
#25
Burning Brakes
Thread Starter
That depends upon the powertrain loss from the crank to the pavement. A rule of thumb is 15% for manual and 20% for automatics. My personal opinion is that a torque tube-based architecture has a lower loss (since that's the primary point of a TT architecture) and I used 12% and 17% respectively. I have no scientific basis for that. I've just looked at lots of dyno charts and operated under the assumption that Porsche's BHP figures are, on average correct and used that to back out those numbers.
Anyway: 352 - 364 bhp.
Anyway: 352 - 364 bhp.
04-20-2017, 02:21 PM
#26
Captain Obvious
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04-20-2017, 02:45 PM
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This is one of the reasons why GTs are prized.
In the quarter mile times, the trap speed would've been much higher with something like 360bhp
928s - even with a 2.73 - are not 0-60 cars.
But, that's it: I'm done. If you want to debate this, call Kibort.
04-20-2017, 03:30 PM
#29
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0-60 is a POOR measure of stoutness. Manual shifting is S L O W. I've gone against 928s with an auto transmission with less power in a (virtual) drag race, and they won all because of the time it take to shift a manual. (look up the G-Tech threads).
Dyno is the way to go! The GT cars are a great car. The 91GT is basically a GTS with a 5.0 and no fender flares. Love it!
Dyno is the way to go! The GT cars are a great car. The 91GT is basically a GTS with a 5.0 and no fender flares. Love it!
04-20-2017, 03:57 PM
#30
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0-60 is a POOR measure of stoutness. Manual shifting is S L O W. I've gone against 928s with an auto transmission with less power in a (virtual) drag race, and they won all because of the time it take to shift a manual. (look up the G-Tech threads).
Dyno is the way to go! The GT cars are a great car. The 91GT is basically a GTS with a 5.0 that doesn't have the oiling problems of the 5.4 and no fender flares. Love it!
Dyno is the way to go! The GT cars are a great car. The 91GT is basically a GTS with a 5.0 that doesn't have the oiling problems of the 5.4 and no fender flares. Love it!