I was chatting with PSJ about a converter lockup switch, and we came to a disagreement that maybe someone here can settle.

Although I've never tried it myself, I believe that using a lockup switch with 3.23/3.42 gears, on a car with a ~3800rpm stall, at the bottom of 3rd gear, in a mid/high 11 second car, will net you almost no ET. PSJ thinks its worth at least a .1th. I know Patrick and others have tried it, just wondering if there is a general consensus on this and for what applications benefit from a converter lockup switch.

I assume guys with 3.73s/4.10s who spend a lot of time in 3rd gear, and have larger converters, will benefit.

 

From what i have seen on LT1's with big stalls and 3.23-3.73 gears it can be worth a tenth if the car has a nice broad powerband and you can lock up to take advantage of it, but that's about the most I have seen. Generally I saw a little less than a tenth but 1-2mph.


Chris

 

Locally we have seen 4-5 A4, converter cars pick up from the switch. I picked up a solid .1 last year and 2 mph. But it was an art to lock it up. I found that the middle of 3rd was the best place. But my old PI3600 slipped more than my Yank TP4400E currently does.

 

Mine is almost exactly what you are talking about. I only hit the switch one time making a pass and the engine fell on its face reducing my et. How much I don't remember but at the time I decided I would never do that again. The rpm dropped to much with these 26" tall ET streets and my 3.23.

I do have a #7 Vigilante(3600). I need to get John to update my web as it shows a 3200.

[ December 31, 2001: Message edited by: Larry ]</p>

 

My experience was the same as larry's (YTP 4000, 3.23, 26" ET Streets). Locking the verter caused my rpms to drop away from maximum HP.

 

The only way a lockup switch will benefit you in a drag set-up is when you lock-up the converter after its "coupling point". This coupling point varies with each converter. The coupling point is when torque multiplication ends and the turbine starts to catch up with the pump (and efficiency climbs above 90%). Engine torque can move this coupling point up or down and so can converter design. Any time you lock up below the coupling point, you are losing the benefit of torque multiplication...which means you'll go slower with the converter locked.

For my ST3500, the coupling point is around 5200 rpms. On a Vig 3600 and a Yank PT4400, it's around 5600 rpms. The key is to lock up the converter at a point to where it won't lug the motor down below the "coupling point". For example, I would need to wait until 5700 rpms to lock up my converter to keep it from falling below the coupling point. With a Vig 3600, I would need to lock it up about 6100 rpms to keep it from lugging the motor below the coupling point. When you lock the Vig at 6100, the rpms will drop down to 5700-5800 and climb from there.

That said, it is very difficult to orchestrate the locking-up for this to actually benefit you. You could install a window switch that would lock up the converter above certain rpms (like on at 6100 and off at the 6700 shift point), or better yet, have someone like Ed Wright program it in. The biggest problem people have, is locking the converters too early and lugging the motors below the converter coupling points...that's bad.

In my experience with many converters, I have found the lock-up switch to be worth 1 mph and no ET. I also agree with Terry that you'd need to use up all your rpm in high gear for it to really be of a benefit. With a 3.23 gear, you may not ever be above the coupling point of a YPT4400 in 3rd gear unless you have a really stout motor. Now if I could lock it up in 2nd and 3rd above the coupling point, I think it would be worth some additional ET and mph...but not as much as you might think.

 

Patrick said it best IMO...

Too early and it lug the motor down. Car would still pick up a 1mph.

I'll try locking my combo next race season.

I like that idea of a window switch.

 

So what would happen if you always locked the converter at say 6100rpm. Would the tranny blow during the up shift or something?

 

Terry, you would want to unlock the converter at the upshift to keep from bogging the motor down below the coupling point. An upshift at 6500 with a YPT4400 would drop the rpms to only 5600 with the converter unlocked. Locked-up, the rpms would drop to around 4000 rpms! The converter unlocked helps cushion the shifts, preserving the tranny and rear end a bit too.

 

[quote]
Terry, you would want to unlock the converter at the upshift to keep from bogging the motor down below the coupling point. An upshift at 6500 with a YPT4400 would drop the rpms to only 5600 with the converter unlocked. Locked-up, the rpms would drop to around 4000 rpms! The converter unlocked helps cushion the shifts, preserving the tranny and rear end a bit too.
<hr></blockquote>

But as soon as the RPMS went down, the converter would unlock itself if it fell below 6100rpm right? I'm just wondering if I could set up an RPM switch to do this rather than a window switch.

Now that I think about it, if I set a switch at say 6000rpm, whenever the converter hit 6000rpm it would lockup and the rpms would drop below 6000rpm, unlocking the converter. You almost need something that tells it to lock at 6000rpm and unlock at 5500rpm, for example.

 

Terry and Patrick this is good info
Terry is correct,A rpm switch would just go on and off when it hit a certain rpm point everytime the trans shifted.

I will be shifting at 6600 and I have 4.10's w/a 26in tall tire.I feel this is a good combo with a Yank TP 4000/4200.I hope to get into 3rd pretty fast.I was gonna look at a wire diagram and figure a way u could wire a rpm switch into the 3rd gear shift noid.ONLY under current would it engage the LU.This way I can play with pills from say 5900 to 6100 to see where the sweet spot is for locking my TP.

I hope to cross at about 6500
Hopefully the switch locked at 6100 to 6500 will be worth .1 MPH/.05 ET?

Will see?


JS

 

Does anyone have alockup switch diagram. I have been looking into doing this with my 3200 Vigialnte.

 

I would not lock the converter in 2nd. It can burn up the tranny.