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Originally Posted by coalitionSE-L
A couple of guys here locally have sheared 3rd gear multiple times by just rolling on the gas in 3rd. They run smaller turbos (T25's and T28's) and their dyno charts at 10+ psi show BIG TIME spikes in third (like +100-130 hp in the span of about 500 RPM). I've seen dyno charts with larger turbos showing much smoother power increases without spikes and those fellows don't seem to have tranny problems. I want to see if the trend is consistent with more folks to determine if it will be safe to run 12 psi on a small turbo given that I control the boost in 500 RPM increments to hopefully prevent the spiking and thus hopefully prevent the shearing. Thoughts?
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I have a t25 and s3 cam setup. my dyno is just a nice fat torque curve on 12psi. Odd that they're getting spikes. They shouldn't with a small turbo. Only thing I can think of is maybe they're starting their dyno run at around 3.5-4k rpms, then their dyno will look like that I guess.
The spike could also be the wastegate or boost controller acting funky.
And concerning the gears ripping when you just roll on the throttle. Just a matter of fatigue. If you beat on it enough, then it'll break even at a light load. And shock loading has a detremental effect on the fatigue life of a metal. It'll reduce the life exponentially.
Still original tranny with over 120k miles now. Seen probably around 8 hours of road course time. about two dozen auto-x's, and probably at least 200 passes at the drag strip. I just don't use 3rd gear in everyday driving since I've been turbo (about 50k miles).
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Khiem
'96 SE-R.... boost, brakes, suspension, etc... sold
'05 Evo
'05 CBR 600RR
