My Vtec Gives Hugs mmmbah
Join Date: 2007-12-13
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Posts: 4,537
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I would say p10/b13/b14 good to about 300 depending on use, abuse, fluid, clutch etc.
The B15 and P11 70v boxes are good to over 400whp, after that you will probably break them. I broke many.
The 50 series also good to 400whp or so. I should state that hp ratings are pointless, it is really all about the torque. anything more than 400wtq on any gearbox will make relatively short life of it, unfortunately.
So I decided to lower the torque output of the engine, and put in a RS6 transmission from the spec V. It is a very expensive swap, and not for the average guy. But it does have much thicker teeth on the gears, and thicker shafts... but the case is not bullet-proof. Keep that in mind.
If you can get all the parts for a 6 speed swap, it swaps a lot easier into the p11/p10 chassis than the B14 chassis. I'd say the B14 and B13 are the harder swaps to do.
Or just make sure you use a sprung clutch, and LSD P11 gearbox with heavy shockproof gear oil or something else really thick. It should hold up to 400whp for a while, perhaps even a few years....depending on how you drive.