shift extension?
after you shift into the next gear your rpms stay in the powerband. They wont drop down to 2500. so if you stall has a 4500 rpm shift extension then after the gear change your rpms only drop to 4500 rpms
what rpm the engine drops back to after making a shift. ie...
before my converter my 1-2 shift was like 6,000 to 4,000 or whatever
now it goes from 6,000 to 4,900.
the idea is to keep you in the powerband after shifting.
before my converter my 1-2 shift was like 6,000 to 4,000 or whatever
now it goes from 6,000 to 4,900.
the idea is to keep you in the powerband after shifting.
Thread Starter
TECH Fanatic
iTrader: (7)
Joined: Dec 2004
Posts: 1,555
Likes: 0
From: pensacola, fl.
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
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
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
TECH Resident
Joined: Jan 2002
Posts: 877
Likes: 55
From: Poway, Ca. where GOD and the sun always shines
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
Joined: Nov 2003
Posts: 6,216
Likes: 236
From: Wichita KS / Rancho San Diego
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
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.
Thread Starter
TECH Fanatic
iTrader: (7)
Joined: Dec 2004
Posts: 1,555
Likes: 0
From: pensacola, fl.
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??
