What hp/tq differences would this show on a dyno sheet with the convertor in lockup versus 1 to 1 in 3rd gear? Seems at the track this wouldn't be authentic as you don't run with the convertor locked. :crazy:

 

^

 

There is not a perfect relationship between HP and track times. We all would like to get the highest number on the dyno.
Who says you don't lock the converter at the track. Some do, some don't. :steering:

 

I hear ya on that. Mine locks up at the very top of 3rd. Its not like you run all of 3rd gear in lockup is what i'm getting at. :chevy

 

why would you want to run unlocked anyway? especially if you're producing a lot of power through mods.

 

I will try to post a graph of the locked vs. unlocked curves later tonight or tomorrow. I have them both plotted on one chart from the same dyno session.

 

:cool: :thumbs:

 

When I dynoed with my old PI 2800, the difference b/w locked and unlocked was 3 hp. I expected a larger difference but it did not show on the dyno.

 

OK.. here you go. The graphs here show runs from the same day, same dyno, all within about 30 minutes of each other. The first graph has runs plotted with the TC both locked and unlocked. As you will see the Unlocked runs produce a lower HP# and higher Tq# whereas when the converter is locked, the HP# is higher and the Tq#.

http://ts.cranesystems.com/2002Corvette/Web%20Pages/2003/dyno_sheets/20030912/20030912_DRM_Verification.htm

 

Had this very discussion with Dave @ Cartek yesterday..............
My stroker A4 was run unlocked 448rwhp/504rwtq.
This dyno did not have a manual lock-up switch that should be kicked in at ~110 mph for a more accurate reading..........I was told if mine was run in 3rd locking it up that the #, should be more like 470/480.
Looks good to me either way :D
The track will tell me any way :yesnod:

 

So, since torque peaks before HP, you can get the best of both by locking the converter after the torque peak.

 

Locked will always give BETTER numbers and I am sure someone smart will chime in and tell us all exactly why this is. :D

 

Here is the short & sweet of it:

What is “Lock-Up”?

The term “Lock-Up” refers to a clutch inside the torque converter that , when applied, locks the internal components of the converter together to achieve zero slippage in the converter. These type converters are found almost exclusively in overdrive transmissions but were also incorporated into some 3speed automatics with electronic control.

Why do I need a “Lock-Up” torque converter?

The greatest source of heat in an automatic transmission is the torque converter. This is because there is a constant source of friction within a converter and as we know, friction creates heat. Even the most efficient low stall torque converter will never stop slipping so you will always have that source of heat generation in a non locking converter. When you add stall speed to a converter you are raising the RPM that the converter must attain before it transmits full engine power back to the transmission. While this is great for performance, it creates an even greater heat and efficiency
problem. To make matters worse, in an overdrive transmission, even with steep gears, the engine rpm’s at cruise may be substantially less than the stall speed of the converter, a recipe for disaster. By applying a Converter Clutch you eliminate this slippage and heat source, allowing you to have the benefits of a performance oriented stall speed, plus economy, efficiency and lower operating temperature.

What do you mean by stall speed?

Think of a torque converter as two fans facing each other. The first fan is attached to the engine and as it spins moves air to the second fan which causes it to spin as well. This second fan is attached to the transmission. As the speed of the first fan increases it pushes greater amounts of air to the point where the second fan is turning at nearly the same speed. This would be considered stall speed. In the torque converter these “fans “ are moving oil instead of air and by manipulating the angle of the fins, size of the converter and internal oil flow we can alter the speed at which the converter passes engine speed back to the transmission.

There are a couple of ways converter stall speed is rated, “brake stall” and “flash stall”. Naturally a converter slips the most at idle by design, so when you are stopped at a light it doesn’t drag the engine down like releasing a standard clutch. When the light changes and you ease on the throttle the converter begins passing engine torque to the vehicle gradually as rpm increases giving you a smooth ramp up to acceleration. This holds true for both stock and modified torque converters. If you were to hold the brake on and apply throttle till the engine stopped making rpm this would be “brake stall” speed. This is hard to measure because most performance vehicles will overpower the brakes and begin spinning the wheels before the stall point is reached. If you were to observe the tachometer as you made a full throttle launch with little or no wheel slip the tach would swing up quickly then stop and rise more slowly as the car accelerated down the track. The point to which the tach would quickly swing to would be the “flash stall” speed. You can also measure flash stall by having your transmission in top gear with the kickdown linkage disconnected and floorboarding the throttle, at approximately 45 mph. this will indicate flash stall as well.

There are a great many variables used in rating a converters stall speed including, cam size, engine torque, vehicle weight and gearing to name a few. An 1800lb. t-bucket with a mild small block can use the exact same converter to achieve 2000rpm stall speed as a 3800lb. Chevelle with a warmed up big block would use to obtain a 3000 rpm stall speed. The difference is in the torque converters ability to transfer engine power back to the trans. A heavier vehicle with more torque will need a higher rpm to achieve this transfer. That is why it is important that your converter builder have as much information as possible about your engine and vehicle combination so that he may design a converter to best get the power your engine makes transferred to the trans and rear wheels in the most efficient way possible.

:cheers: