shift extension?
01-16-2006, 07:59 PM
#4
TECH Fanatic
Thread Starter
iTrader: (7)
Join Date: Dec 2004
Location: pensacola, fl.
Posts: 1,555
Likes: 0
Received 0 Likes
on
0 Posts
ahh so when i order a converter say i want a 3600 with a 2.5str do they determine the shiftextension or do i? im tryin to learn here. to make a good decision on a converter...thanx
01-16-2006, 08:25 PM
#6
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
Shift extension is where your RPMs actually hang,
when you shift into the next gear up, owing to the
converter's slip / stall characteristics.
If your converter were hard coupled you'd shift from
6000 (2nd) to 3700 (3rd). That might be below the
powerband (or not, depending on the motor, and this
is really a key consideration).
A converter like my old TCI SF3000 would stay up at
4500. That's a little healthier. A 3500 stall, probably
more like 5000RPM.
Now, HP is roughly TQ*RPM (scaled). You have the
converter loss, but you gain power by being higher
up in RPM. If you assume a flat torque profile then
HP at 4500 is 22% more than 3700; HP at 5000 is
35% more. So as long as your converter is more
than 80% efficient your horsepower to the wheels
is increased, in this area, by keeping the RPM up.
My TCI appeared to be maybe 90% efficient at
the shiftpoint-extendd RPM. So maybe a net gain
of 9-10% in delivered RWHP vs the stocker. A TCI
3500 I have data for, suggests 88% at 5000 for a
more substantial 19% increase in the near-shift
RWHP.
when you shift into the next gear up, owing to the
converter's slip / stall characteristics.
If your converter were hard coupled you'd shift from
6000 (2nd) to 3700 (3rd). That might be below the
powerband (or not, depending on the motor, and this
is really a key consideration).
A converter like my old TCI SF3000 would stay up at
4500. That's a little healthier. A 3500 stall, probably
more like 5000RPM.
Now, HP is roughly TQ*RPM (scaled). You have the
converter loss, but you gain power by being higher
up in RPM. If you assume a flat torque profile then
HP at 4500 is 22% more than 3700; HP at 5000 is
35% more. So as long as your converter is more
than 80% efficient your horsepower to the wheels
is increased, in this area, by keeping the RPM up.
My TCI appeared to be maybe 90% efficient at
the shiftpoint-extendd RPM. So maybe a net gain
of 9-10% in delivered RWHP vs the stocker. A TCI
3500 I have data for, suggests 88% at 5000 for a
more substantial 19% increase in the near-shift
RWHP.
Trending Topics
01-19-2006, 09:57 PM
#9
TECH Resident
Remember one thing, what these gentlemen are telling you applies to aggressive throttle, or WOT, when the converter is not achieving lock up.
When driving "normally" less aggressively, the 3000 stall will feel like the stock unit (with some slippage from a dead stop), and once lock up is achieved, the shift extension point is moot.
SteveC
When driving "normally" less aggressively, the 3000 stall will feel like the stock unit (with some slippage from a dead stop), and once lock up is achieved, the shift extension point is moot.
SteveC
01-19-2006, 10:29 PM
#10
Originally Posted by SteveC
Remember one thing, what these gentlemen are telling you applies to aggressive throttle, or WOT, when the converter is not achieving lock up. When driving "normally" less aggressively, the 3000 stall will feel like the stock unit (with some slippage from a dead stop), and once lock up is achieved, the shift extension point is moot. SteveC
01-20-2006, 07:35 AM
#11
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
The shift extension is -more- pronounced at lower
throttle. This is because your shift-from, shift-to
RPM are lower relative to the stall speed and the
coupling is changing more with RPM. down low.
Shift from 3000 to 2000 (by gear ratio), on a 3500
converter and you won't hardly even feel the shift;
the actual RPM will drop from like 3000 to 2800, you
are just paddlewheeling along. But from 6000 you
would see a drop closer to, but not all the way to
the numerical ratio; how "not all the way" is the
WOT shift extension.
throttle. This is because your shift-from, shift-to
RPM are lower relative to the stall speed and the
coupling is changing more with RPM. down low.
Shift from 3000 to 2000 (by gear ratio), on a 3500
converter and you won't hardly even feel the shift;
the actual RPM will drop from like 3000 to 2800, you
are just paddlewheeling along. But from 6000 you
would see a drop closer to, but not all the way to
the numerical ratio; how "not all the way" is the
WOT shift extension.
01-21-2006, 11:43 AM
#12
TECH Fanatic
Thread Starter
iTrader: (7)
Join Date: Dec 2004
Location: pensacola, fl.
Posts: 1,555
Likes: 0
Received 0 Likes
on
0 Posts
ahh ok thanx guys ..ok another question what if i have a bolt on car and say my tranny shifts at 6k but i got a 3800 stall and the shift extensions were at like 5k would that mess anything up having that it only climbs 1k b4 shifts??
