WOT Converter Lockup
Thread Starter
Staging Lane
Joined: May 2013
Posts: 77
Likes: 0
From: OKC, OK
WOT Converter Lockup So im still in the debate of swapping to a 4l80 on my build or sticking with the T56. The car is an 06 GTO, planning on making 600-700whp at first then going from there. My question is, if I go 4l80, how much will having a converter that is capable of wot lockup help with roll racing? The price difference is fairly considerable so Im just wondering how much of a difference it makes. As its mainly a street car/roll racer, I plan on going with a fairly low stall anyways. Any opinions?
Teching In
Joined: Jan 2014
Posts: 27
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Not to be a smart@ss, but did it make a good or bad difference? Every trans builder I have spoke to said it is better to leave the converter unlocked when racing...which seems counter intuitive.
I know in the diesel truck world locking the conv would knock a half second or better off my ET.
Apples and oranges...
Paul
I know in the diesel truck world locking the conv would knock a half second or better off my ET.
Apples and oranges...
Paul
Moderator
Joined: Aug 2010
Posts: 7,323
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From: Ann Arbor, MI
You don't want to lock the converter before you reach the stall speed in the final gear (e.g. in 3rd gear); otherwise the RPMs might drop below the power band of the engine or the stall speed of the converter.
You definitely do not want to keep the converter locked during shifts - something has "to give/slip" during a shift - it is better for the converter to slip than for the transmission frictions to slip. Keeping the converter locked during a shift is analogous to side stepping the clutch when shifting a manual; it is extremely hard on the drivetrain.
REMEMBER - Only lockup in WOT if you have a triple-clutch converter, which typically cost $1000+. (If you don't know if you have one, you probably don't.)
I suspect all diesel trucks have a triple-clutch converter and since they likely have very low stall speeds to match high-torque low rpm diesel engines, I would expect that locking the converter in 2nd and up gears would improve ET.
You definitely do not want to keep the converter locked during shifts - something has "to give/slip" during a shift - it is better for the converter to slip than for the transmission frictions to slip. Keeping the converter locked during a shift is analogous to side stepping the clutch when shifting a manual; it is extremely hard on the drivetrain.
REMEMBER - Only lockup in WOT if you have a triple-clutch converter, which typically cost $1000+. (If you don't know if you have one, you probably don't.)
I suspect all diesel trucks have a triple-clutch converter and since they likely have very low stall speeds to match high-torque low rpm diesel engines, I would expect that locking the converter in 2nd and up gears would improve ET.
Thread Starter
Staging Lane
Joined: May 2013
Posts: 77
Likes: 0
From: OKC, OK
Ive heard alot of conflicting opinions on it. Jake (Jakes Perf Trans) told me it was possible to wot lockup shift, however he recommended at least getting the billet input shaft to deal with any shock loads during the shift. Im just curious if all the extra money spent for a multi disk and the trans upgrades are worth it or not. Are guys like FR8TRN or StangKillr using a lockup during wot setup? (I only reference them as I know they both roll race frequently)
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Every trans builder I have spoke to said it is better to leave the converter unlocked when racing...which seems counter intuitive.
Them simply saying to never lockup a converter makes me think they never heard of triple or 5 disk billet converters that are made to lockup at WOT.
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You must not be speaking with the right builders, because any decent transmission guy will be able to tell you that you CAN lockup a converter at WOT given that it's built for that specifically (aka multi-disk).
Them simply saying to never lockup a converter makes me think they never heard of triple or 5 disk billet converters that are made to lockup at WOT.
Them simply saying to never lockup a converter makes me think they never heard of triple or 5 disk billet converters that are made to lockup at WOT.
Locking the converter on a boosted car seems to pick up a few mph, so you will need to decide if that's worth it for you. I would suggest just locking 3rd towards the top of the gear.
Not to be a smart@ss, but did it make a good or bad difference? Every trans builder I have spoke to said it is better to leave the converter unlocked when racing...which seems counter intuitive.
I know in the diesel truck world locking the conv would knock a half second or better off my ET.
Apples and oranges...
Paul
I know in the diesel truck world locking the conv would knock a half second or better off my ET.
Apples and oranges...
Paul
It's a significant pull difference and feel inside the car. Just dial your lockup in to the point where lockup HP at the lower rpm after lock is higher then unlocked HP at the higher rpm before lock in your final gear. (dyno locked and unlocked and layover the graphs) So long as more HP is getting to the tires, it will always net a gain. I only lock in final drive gear, never in early gears as shift extension from the converter outweighs any lockup gain.
If you have a good converter then locking it will hurt
performance every time. Good as in properly matched
to motor powerband. There are rare and special cases
where locking gains you anything at all, but rolling on
the street is certainly not one of them.
The deal is how much of the slip is lost power vs how
much is just the flip side of torque multiplication. You
like torque, right? The only place you gain power to the
wheels is after your torque multiplication has fallen to
1:1. On my oddball converter this is above 5000RPM,
because I've got scans showing acceleration dropping
when I lock it there during an uphill pull.
It's a trick that can be useful when, say, you would
upshift right before the traps, locking can drop your
RPM below rev-limiter just long enough to shave a tenth
and maybe that's more valuable than TCC longevity to
you. On the other hand, locking under power always
is hard on a clutch, even a stout one, and you -will-
shorten its life and put friction material particles in the
soup, hopefully to end up 100% in the filter. Hope is
not the best way to get durability or broad-envelope
performance, though.
performance every time. Good as in properly matched
to motor powerband. There are rare and special cases
where locking gains you anything at all, but rolling on
the street is certainly not one of them.
The deal is how much of the slip is lost power vs how
much is just the flip side of torque multiplication. You
like torque, right? The only place you gain power to the
wheels is after your torque multiplication has fallen to
1:1. On my oddball converter this is above 5000RPM,
because I've got scans showing acceleration dropping
when I lock it there during an uphill pull.
It's a trick that can be useful when, say, you would
upshift right before the traps, locking can drop your
RPM below rev-limiter just long enough to shave a tenth
and maybe that's more valuable than TCC longevity to
you. On the other hand, locking under power always
is hard on a clutch, even a stout one, and you -will-
shorten its life and put friction material particles in the
soup, hopefully to end up 100% in the filter. Hope is
not the best way to get durability or broad-envelope
performance, though.
Last edited by jimmyblue; Mar 11, 2014 at 03:27 PM.
Ah, the infamous question. Is WOT lock up for me. Very deep question and you will get a lot of opinions. We have seen a lot of deferent setups and the general rule we use - NA unlocked - FI locked. But we have seen success with the exact opposite approach. Good example of a car locking up just happens to be the fastest stock bottom end 5th Gen NA Camaro out there, Rhino79. Currently at 10.4 NA, locking in 4th. Having a multi disk adds options for you. You can lock it up on the dyno, freeway pulls, at the track - test it out to see if and where it benefits you. Video link is Rhino79 locking in 4th, you can see the car start to pull away - very impressive.
Chris
Chris
If you have a good converter then locking it will hurt
performance every time. Good as in properly matched
to motor powerband. There are rare and special cases
where locking gains you anything at all, but rolling on
the street is certainly not one of them.
The deal is how much of the slip is lost power vs how
much is just the flip side of torque multiplication. You
like torque, right? The only place you gain power to the
wheels is after your torque multiplication has fallen to
1:1. On my oddball converter this is above 5000RPM,
because I've got scans showing acceleration dropping
when I lock it there during an uphill pull.
It's a trick that can be useful when, say, you would
upshift right before the traps, locking can drop your
RPM below rev-limiter just long enough to shave a tenth
and maybe that's more valuable than TCC longevity to
you. On the other hand, locking under power always
is hard on a clutch, even a stout one, and you -will-
shorten its life and put friction material particles in the
soup, hopefully to end up 100% in the filter. Hope is
not the best way to get durability or broad-envelope
performance, though.
performance every time. Good as in properly matched
to motor powerband. There are rare and special cases
where locking gains you anything at all, but rolling on
the street is certainly not one of them.
The deal is how much of the slip is lost power vs how
much is just the flip side of torque multiplication. You
like torque, right? The only place you gain power to the
wheels is after your torque multiplication has fallen to
1:1. On my oddball converter this is above 5000RPM,
because I've got scans showing acceleration dropping
when I lock it there during an uphill pull.
It's a trick that can be useful when, say, you would
upshift right before the traps, locking can drop your
RPM below rev-limiter just long enough to shave a tenth
and maybe that's more valuable than TCC longevity to
you. On the other hand, locking under power always
is hard on a clutch, even a stout one, and you -will-
shorten its life and put friction material particles in the
soup, hopefully to end up 100% in the filter. Hope is
not the best way to get durability or broad-envelope
performance, though.
A converter cant multiply torque past its true stall rpm. Additionally, so long as locked rpm hp is greater then unlocked rpm hp there is ALWAYS a net increase in acceleration, since HP is a function of torque. Slip is always wasting hp, it's not something that can be convincingly argued.
Your first statement is complete nonsense, as a converter matched to an engine's powerband is going to be larger then 99% of people want to deal with regularly (ergo my 5500 stall), however the smaller the stall rpm, generally the less the lockup benefit is due to the fact that they usually slip less and are thus more efficient. Your "scans" are completely invalid because I'm fairly certain if you attempted to WOT lockup a fuddle converter (yours, in this case), that it would slip and burn up, or end up embedded in your calf or thigh. It's not even remotely comparable to a converter designed to do such a thing.
I should add that a multi disc/steeled clutched used to lockup is no different then the ones used to engage gears and the forward band in the transmission. Just a fluid clutch with hydraulic apply
On a turbo car it's a compromise having the converter loose enough to build boost but tight enough not to have a huge % of slippage when your trying to be as close to direct drive as possible. My last converter was a little to loose and I would pick up 9mph in the 1/4 mile by locking the converter.
On a N/A car you might not benefit but it would be nice to have the option.
On a N/A car you might not benefit but it would be nice to have the option.
A converter cant multiply torque past its true stall rpm. Additionally, so long as locked rpm hp is greater then unlocked rpm hp there is ALWAYS a net increase in acceleration, since HP is a function of torque. Slip is always wasting hp, it's not something that can be convincingly argued.
slip with a portion of slip going to waste. Only when all
multiplication ceases, is slip entirely waste.
How "true stall" relates to advertised, maybe you can
enlighten us all. But I have demonstrated that on my
hardware, there remains torque multiplication past 5000RPM
on a 3500 stall speed rating, 2.0 STR converter.
Your first statement is complete nonsense, as a converter matched to an engine's powerband is going to be larger then 99% of people want to deal with regularly (ergo my 5500 stall), however the smaller the stall rpm, generally the less the lockup benefit is due to the fact that they usually slip less and are thus more efficient. Your "scans" are completely invalid because I'm fairly certain if you attempted to WOT lockup a fuddle converter (yours, in this case), that it would slip and burn up, or end up embedded in your calf or thigh. It's not even remotely comparable to a converter designed to do such a thing.
pulls in and holds at full pedal, without complaint. You speculate;
I have done it. Your imagination invalidates nothing about it.
X2. Torque multiplication is highest at stall, and drops at a linear rate until its nearly coupled (roughly 90% coupled).
No. A torque converter trades torque multiplication for
slip with a portion of slip going to waste. Only when all
multiplication ceases, is slip entirely waste.
How "true stall" relates to advertised, maybe you can
enlighten us all. But I have demonstrated that on my
hardware, there remains torque multiplication past 5000RPM
on a 3500 stall speed rating, 2.0 STR converter.
Your certainty is your business, but wrong. The converter
pulls in and holds at full pedal, without complaint. You speculate;
I have done it. Your imagination invalidates nothing about it.
slip with a portion of slip going to waste. Only when all
multiplication ceases, is slip entirely waste.
How "true stall" relates to advertised, maybe you can
enlighten us all. But I have demonstrated that on my
hardware, there remains torque multiplication past 5000RPM
on a 3500 stall speed rating, 2.0 STR converter.
Your certainty is your business, but wrong. The converter
pulls in and holds at full pedal, without complaint. You speculate;
I have done it. Your imagination invalidates nothing about it.
Last edited by DietCoke; Mar 13, 2014 at 07:45 PM.
TECH Enthusiast
Joined: Mar 2012
Posts: 728
Likes: 3
I decided to go lockup because I would be hitting the rev limit in 3rd gear on the track. I gained 10 mph at the end of 3rd gear by locking.
When you're N/A, locking doesn't seem needed. You need the torque multiplication. When you're pushing 600+ whp boosted, lockup is a god-send. No more falling on your face, it locks and hooks.
When you're N/A, locking doesn't seem needed. You need the torque multiplication. When you're pushing 600+ whp boosted, lockup is a god-send. No more falling on your face, it locks and hooks.
