is locking the converter in 3rd worth anything in the 1/4???
my converter is built for WOT locks....
i dont really care about mph, on ET drops.
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is locking the converter in 3rd worth anything in the 1/4???
my converter is built for WOT locks....
i dont really care about mph, on ET drops.
Depending on the (in)efficiency of the converter you
could see 10-30HP from it, but you might benefit more
from torque multiplication and higher RPM, than lower
RPM and efficiency. You'd have to try it both ways and
see what the timeslip says. And of course the timeslip
for most of us ends before 3rd gear does; you might like
top end locked for events greater than 1/4MPH for other
reasons, like heat.
YEs its worth it. I lock em about half way through third. Even better when the juice is added. Try some killer MPH's. I gained 10mph with 100 shot. :)
Rick
For that matter you might also gain by locking 2nd, since
that takes you almost to half track.
Where to put the lockup point, I guess is the interesting
question. You'd want it to be where the locked RPM is
above your shift extension RPM, for sure (presuming you
had that where you wanted, on purpose). Something like
75% of your upshift MPH, maybe?
shift ext. is about 5300 as I shift at 6300. mph after shift ext is 85 or 90 mph. I dont remember which one. that is going into 3rd.Quote:
Originally Posted by jimmyblue
what do you mean 75% of my upshift mph??
Well, obviously locking right at upshift MPH would be no
help at all, and locking at the beginning of gear would
probably lose you some helpful torque multiplication.
If you'd upshift 2-3 at 80MPH and enter 2nd at 40MPH,
75% of 80 would be about 60MPH in your TCC lock MPH
table. But this is just a notion, for discussion.
60 MPH would be between the 2-3 shift... I dont need the trq multiplication on the 2-3 like I do on the 1-2 upshift??Quote:
Originally Posted by jimmyblue
wow, this stuff is confusing :hi: :p
Total newbie here, so apologies in advance for any stupid questions. You said obviously that locking right at upshift would be no help at all...why is this so? I have been thinking about doing just that, to get a little "bump" in the 2-3 shift. Currently, the 2-3 shift at WOT is pretty weak, and the car nose dives ('04 Vette coupe, H/C).Quote:
Originally Posted by jimmyblue
I feel kinda stuck between options here because I was thinking I could either:
- Drop to another gear, 3:42s or 3:73s to try and get a better 2-3 transition. The problem with this idea is that I fear complete loss of traction in 1st and 2nd, as they are already pretty slippery with my 3:15s.
_OR_
- Keep the 3:15s for 1st and 2nd traction, and do something about 3rd gear. It just seems like the 2-3 shift robs me of momentum, which is why I am considering the lockup just shortly after the 2-3 shift, or during the 2-3 shift.
greg
Locking right before upshift might let you stay in gear
through the traps but with 3.15s you're talking, what,
130+ MPH for the 3-4? Congratulations, if that's your
problem :)
What we're talking about is, improving the delivered
HP to move the mass, by changing from high slip to
hard coupled across the mid-high RPM band all down
the track (or some portion).
Now, a well designed converter should deliver you
an efficiency loss that is more than offset by being
at a higher RPM, higher torque position in the power
band. For example, if your converter is 100% efficient
locked up, and you have a flat torque band at 350
lb-ft and you're at 4000RPM in the moment, you
deliver 350lb-ft*4000RPM/5252 = 266HP.
Now let the converter unlock, and slide you up to
5300RPM but at an 85% delivered efficiency. You
get 300HP out the back, a bonus of 34HP. So you
are better off unlocked (presuming your torque is
indeed flat, which in an airflow limited machine is
not to be taken on faith; you have to go by the
results, in acceleration of mass).
At some point in the powerband the converter will
start costing, rather than improving, the delivered
power. I guess this is where you'd like to flip it to
locked. I think you want to see acceleration vs
MPH, rather than acceleration vs RPM, to decide.
And that is why its most important to match a converter to power band of the engine.