When a converter locks and unlocks?
When a converter locks and unlocks? Just seeing if someone can explain exactly what happens when a converter locks and unlocks? I've heard of guys having better dynoed when the converters are locked. When do you want it to lock and unlock, better fuel mileage, lower temps, etc.? I'm wanting to step up to around a 4000 stall this winter and am just wondering what to look for.
A locked converter means there isnt any slipping of the converter, it is "locked" to the engine, meaning the tranny is spinning same speed as the engine. When it is unlocked the engine spins faster than the tranny cause the converter slips.
11 Second Club
Joined: Oct 2005
Posts: 1,847
Likes: 1
From: Sandwich, IL
My converter locks at 40 mph. Basically it feels like your entering another gear. I'll be at 2000 rpm's and suddenly the converter locks and I drop to 1200 rpm's which is normal for 40 mph. Then when you give the car some gas the rpm's jump up again as the converter unlocks. Lets say your driving 65 mph in OD. Drop the shifter into 3 and you'll see a sudded jump in rpm's as you leave 4th gear and downshift into 3rd. Then drop the shifter back into OD. That's real close to how it feels when a high stall conveter unlocks and locks.
People will definately dyno better through a locked converter but I heard it's dangerous. New Era Performance did a dyno-tune on my car and advised against it. They would do it but then I would have to sign a waiver first releasing them from any responsibility. That was enough for me to steer clear of dynoing a locked converter. I dynoed 300 rwhp unlocked which should be around 330 rwhp through a locked converter based on what I trap and thier educated guesses.
People will definately dyno better through a locked converter but I heard it's dangerous. New Era Performance did a dyno-tune on my car and advised against it. They would do it but then I would have to sign a waiver first releasing them from any responsibility. That was enough for me to steer clear of dynoing a locked converter. I dynoed 300 rwhp unlocked which should be around 330 rwhp through a locked converter based on what I trap and thier educated guesses.
I see. So how does a higher stall hurt your mileage more. I was thinking of stepping up to a 4000 stall but I've heard some people say they're not real streetable and would hurt my mileage more, why is that? They said it would also keep my tranny temp higher, I figured because it would be spinning higher?
They slip more than a stock stall. When not locked up they are "looser" since they slip more it takes more RPM to get moving or stay up to speed, but once it locks about 40-45mph there is no more loss. Ur gas mileage is affected in the fact that u have to spin higher rpms to get moving.
Originally Posted by darrensls1
People will definately dyno better through a locked converter but I heard it's dangerous. New Era Performance did a dyno-tune on my car and advised against it. They would do it but then I would have to sign a waiver first releasing them from any responsibility. That was enough for me to steer clear of dynoing a locked converter. I dynoed 300 rwhp unlocked which should be around 330 rwhp through a locked converter based on what I trap and thier educated guesses.
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Ok, I'm starting to get the picture. So when people talk about loose stalls and tighening them up they are just talking about when the converter locks and unlocks correct? And is a 4K stall streetable for a DD?
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TECH Senior Member
Joined: Apr 2004
Posts: 6,157
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From: Texas
Originally Posted by MountainMotor
Ok, I'm starting to get the picture. So when people talk about loose stalls and tighening them up they are just talking about when the converter locks and unlocks correct? And is a 4K stall streetable for a DD?
Depends on you and how much you can tolerate. I think a 4k stall is very streetable but someone else may not think so.
Generally the bigger the stall the more the car will rev before taking off. During normal driving, a 4k stall will not rev to 4k every time. Instead it will gradually start moving at around 2XXX rpm. One of the big factors in determining this is the STR.
You really should match your stall with your mods or future mods that you plan on doing. www.converter.cc is a good resource.
Launching!
Joined: Jan 2002
Posts: 224
Likes: 0
From: Monticello, MN
Originally Posted by Ed Blown Vert
I always lock my converter on the dyno. There is no way you can tune correctly unless you do.
I also thought converters were always locked on a dyno run. I guess I don't know how else true rwhp would be measuered.
Ed
Last edited by C5XTASY; Nov 6, 2005 at 08:06 AM.
Launching!
Joined: Jan 2002
Posts: 224
Likes: 0
From: Monticello, MN
Originally Posted by MountainMotor
Ok, I'm starting to get the picture. So when people talk about loose stalls and tighening them up they are just talking about when the converter locks and unlocks correct? And is a 4K stall streetable for a DD?
As mentioned above, my understanding has always been that looseness refers to the amount of slip that a person gets when applying throttle from a stop and/or prior to converter lockup. This can vary dramatically, according to converter rating and design. Differential gear ratios also affect (the feeling of) slip. Higher (numerically) gears will make a converter feel tighter. I have also been told that engine torque output can affect the amount of stall of a converter. The more torque, the higher the converter will stall. I just ordered a Yank SS3200, will be using it with 3.15 gears, and was told it will not seem "loose" as it was designed for the 3.15s. In other words, it will seem responsive to a light throttle input. I hope that's correct as I really don't strip-race the car, and want something that'll give me a good boot in the rear when I hit it, but still drives really nice otherwise. I also am having my throttle-body ported in order to increase responsiveness to throttle input. I have a heads/cam/longtubes, etc., car, but the cam is relatively mild (compared to many on the here anyway
), and still gives me good low-end torque. I tried to score a ride in a car with an SS3200 and was unsuccessful. Most of them appear to be down South and out West. As I'm no expert on converters, and tried to educate myself before I ordered the one, I have my fingers crossed that my understanding is correct and it all works out. I'll find out in the Spring. Last edited by C5XTASY; Nov 6, 2005 at 09:59 AM.
Teching In
Joined: Oct 2004
Posts: 29
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From: Patterson, NY
I would guess that they say to keep it unlocked so you don't overpower the lockup clutch. I wouldn't be surprised if someone had a stock-type lockup clutch in a high stall converter. Too much power and it will slip, the cluthc material that wears off goes through the tranny and eventually it blows, leading to a pissed off customer. Keeping the converter unlocked is just playing it safe.
If they hooked up some kind of sensor to look for a difference between engine and driveshaft speed then they could protect against that.
Anyway, "tightening up" a converter is dropping the stall speed, not using lockup.
The disadvantege to a higher stall is that you lose the low end responsiveness. STR can help, but if you are used to a stock car, that when you let off the brakes will start to move you will have to get used to the fact that a 4000 rpm converter is just going to let the car sit there until the revs come up. You will move before it hits 4000, but you won't move at 1000.
Around town the converter will usually be unlocked and you are going to have the engine spinning faster to do the same speed. This will reduce your mileage and heat up the transmission fluid more. When the converter locks up it will be the same as your stock converter-no slippage.
HTH
If they hooked up some kind of sensor to look for a difference between engine and driveshaft speed then they could protect against that.
Anyway, "tightening up" a converter is dropping the stall speed, not using lockup.
The disadvantege to a higher stall is that you lose the low end responsiveness. STR can help, but if you are used to a stock car, that when you let off the brakes will start to move you will have to get used to the fact that a 4000 rpm converter is just going to let the car sit there until the revs come up. You will move before it hits 4000, but you won't move at 1000.
Around town the converter will usually be unlocked and you are going to have the engine spinning faster to do the same speed. This will reduce your mileage and heat up the transmission fluid more. When the converter locks up it will be the same as your stock converter-no slippage.
HTH
