I've tried searching the YANK page, and some on here, but still don't really understand the concept of lockup.

I know that a car will make more power on the dyno with the converter locked, but I'm not real sure what being "locked" means.

will the converter lock and unlock by itself during normal driving situations?

anyway, sorry if it's a stupid question...thanks in advance for any advice.

-Alex

 

Lockup converters have a clutch that the PCM (your car's computer) commands to engage under cruise conditions. This clutch physically lockes the two sides of the converter together. Your converter has an input shaft (the engine side) and an output shaft (the transmission side). When the converter is unlocked the input side will turn faster than the output side. This is called slippage. To understand this, realize that the converter is a viscious, or fluid, coupling between the engine and the transmission rather than a mechanical coupling. This allows the car to sit still with the transmission in gear. It also allows for TQ multiplication but that's another subject in itself. With the converter locked, the input and output shafts will turn the same speed.

Example, with my 3500 converter locked and running 75 MPH in OD I am turning 2250 RPM with the converter locked V/S about 3000 RPM (not exactly sure on this figure but you get the point) with the converter unlocked. Obviously, having the converter locked is better for gas mileage.

 

So am I correct in saying that the PCM can lock and unlock the converter? it does not need to be done manually?

if that is so, is/are there any particular times when this happens? will it happen during normal driving? during WOT?

last, is there any advantage between locked and unlocked when at the track?

thanks again for the info! <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

 

You are correct but the PCM will only lock the converter during normal cruise conditions (not to confused with cruise control. I just mean that the speed and throttle position have to be within a certain range for the PCM to engage lockup.) I will not lock it at WOT. It can be programmed differently with LS1Edit, however.

Some folks find they can get a just a little higher trap speed by locking the converter during high RPMs in 3rd gear. Of course, you gotta be geared so that you actually SEE those higher RPMs in 3rd before this could benefit you. With an efficient converter, the gains from doing this are very small...some find none at all.