3.8 vs 3.6
11-20-2018, 09:24 AM
#1
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3.8 vs 3.6
If you left all pretty much the same but only increased the engine size from 3.6 to 3.8 what would be the HP/torque gain. Given piston/cylinder change and machine work for heads. Just wondering what the HP to $$ ratio is and if the change is worth the move??
11-20-2018, 10:32 AM
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11-20-2018, 10:40 AM
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Know slip fit is not the route to take, definitely bore. Guessing that new pistons would probably increase compression ratio. Have already up graded to 993 valves, and had heads polished and machine for top gaskets.
But, just doing a rough calculation figure it would cost between $500 to $600 per extra HP.
But, just doing a rough calculation figure it would cost between $500 to $600 per extra HP.
11-20-2018, 12:07 PM
#5
Is the argument against slip fit, that it will not be as strong? I've seen people say "slip fit because I'm just going to street drive it".
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11-20-2018, 02:07 PM
#8
Edit: The above boxes are 993 six speed ones but maybe Mr Weiner can answer the question regardless of that? 😀
Last edited by Railmaster.; 11-20-2018 at 02:09 PM. Reason: Wrong forum!
11-20-2018, 03:18 PM
#9
Three Wheelin'
Why consider the 102mm p&c (3746cc) when 104mm (3894cc) and 106mm (4045cc) are available? Though nobody seems to actually be using any of these bores.
11-20-2018, 03:49 PM
#10
Going from stock 3.6 100 to Mahle 3.8 103 w/ a little more compression is worth about 25 lb-ft the flywheel @~5200rpm, a little less at other rpms but nevertheless something that is palpable there at all rpm.
closerer gearing keeps the engine in it's best power range for more of the time but doesn't really change the acceleration positively unless it is also lower(higher numerically)
here is an illustration of the thrust available in a stock 964 w/ 3 different transmissions, g50/03, g50/05 these are stock 964 transmissions and a g50/30 used in 993 Cuop & RSR, Only where the /30 is lower does it improve acceleration, but the extra gear does close the gaps
What would 25 lb-ft extra flywheel torque do to the above curves, well just multiply the overall gear ratio by 25 and add it to the existing curve, of course that is only applicable at 5250rpm, you get less at other rpms
closerer gearing keeps the engine in it's best power range for more of the time but doesn't really change the acceleration positively unless it is also lower(higher numerically)
here is an illustration of the thrust available in a stock 964 w/ 3 different transmissions, g50/03, g50/05 these are stock 964 transmissions and a g50/30 used in 993 Cuop & RSR, Only where the /30 is lower does it improve acceleration, but the extra gear does close the gaps
What would 25 lb-ft extra flywheel torque do to the above curves, well just multiply the overall gear ratio by 25 and add it to the existing curve, of course that is only applicable at 5250rpm, you get less at other rpms
11-20-2018, 04:00 PM
#11
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11-20-2018, 04:07 PM
#12
Here are some rear wheel torque curves for the various 3.6 & 3.8 engines, the 964 ssi is there only to show what a poor choice of exhaust can do
11-21-2018, 09:08 AM
#13
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11-21-2018, 10:15 AM
#14
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Every builder ive talked to said just doing 3.8 is not worth the cost as described here. Other things need to be done to make it worth it.
Is your motor a 3.6 and stockish? What ratios did you go with?
Do you have a suggested ratio set for a 5spd strong 3.6?
Im way over analyzing the gear set ratios. Right now I’m considering a slight deviation to the rs set and going with a set Matt has been selling for these that changes 1-4
Im way over analyzing the gear set ratios. Right now I’m considering a slight deviation to the rs set and going with a set Matt has been selling for these that changes 1-4
11-21-2018, 03:20 PM
#15
