Gearboxes for turboed fives
Discussion
I know that the standard engine internals are good for around 250bhp before swapping out pistons and conrods, but how do gearboxes stand?
My car has around 120k miles on it's gearbox, which has had a fluid change but is otherwise standard. How further can the gearbox be pushed? What options are available to replace it? I've seen that Quaife do a box, but they're not exactly cheap.
Cheers,
Chris
My car has around 120k miles on it's gearbox, which has had a fluid change but is otherwise standard. How further can the gearbox be pushed? What options are available to replace it? I've seen that Quaife do a box, but they're not exactly cheap.
Cheers,
Chris
Thanks for the replies so far.
I'm not worried about my clutch as I'm running an updated ACT unit rated at circa 350ft/lbs of torque; the standard clutches will take mild boost (150bhp ish) but don't work with 200bhp applications for very long!
I'm not convinced by the 'don't worry about it till it breaks' approach; doesn't an explosive gearbox take other bits of the car with it?
Since the handling, brakes etc. are all suitable for taking the car much faster, I'm curious what the next bottleneck would likely be. An engine rebuild with uprated pistons and conrods is expensive, but affordable, provided I don't have to replace gearboxes, diffs, clutches etc. after the powerboost. I would love to attempt to break the 300bhp mark, but I'd only got for it fully understanding the costs and risk involved.
Hope this clarifies the question a little!
I'm not worried about my clutch as I'm running an updated ACT unit rated at circa 350ft/lbs of torque; the standard clutches will take mild boost (150bhp ish) but don't work with 200bhp applications for very long!
I'm not convinced by the 'don't worry about it till it breaks' approach; doesn't an explosive gearbox take other bits of the car with it?
Since the handling, brakes etc. are all suitable for taking the car much faster, I'm curious what the next bottleneck would likely be. An engine rebuild with uprated pistons and conrods is expensive, but affordable, provided I don't have to replace gearboxes, diffs, clutches etc. after the powerboost. I would love to attempt to break the 300bhp mark, but I'd only got for it fully understanding the costs and risk involved.
Hope this clarifies the question a little!
piefacemate said:
Good shout on miataturbo, hadn't looked there.
Seems the general consensus is the 5 speed holds till 300ish, the 6 speed after that... Until you get to silly speeds then you're onto Quaife dogboxes!
Still interested in what turbo ph member real world experience looks like?
The problem with the FI MK1 is your run out of gears/diff before your engine will run out of puff Seems the general consensus is the 5 speed holds till 300ish, the 6 speed after that... Until you get to silly speeds then you're onto Quaife dogboxes!
Still interested in what turbo ph member real world experience looks like?
or thats the problem I have at the moment 135mph is the max mine hits,thats running on a standard gearbox but uprated diff and after 3 years its still fine I am not running that high HP about 190/95 though so maybe the extra 100 on top will kill it quicker.
There are a good few in NZ running 250+bhp reliably through standard 5-speed boxes and 1.6 diffs, they're really not as weak as the internet rumour mill would suggest! One bloke gives his absolute death (drags, burnout comps! etc) to see how much it takes to kill the 1.6 diff but hasn't succeeded yet. I wouldn't mind an LSD with a bit more locking action though.
Mine has a low-miles 5-speed from an NB but tbh I preferred the shift action of my old '89 (140k miles) with its original box, this one doesn't seem to like being rushed.
Mine has a low-miles 5-speed from an NB but tbh I preferred the shift action of my old '89 (140k miles) with its original box, this one doesn't seem to like being rushed.
Edited by GravelBen on Monday 17th May 21:02
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