I've read this before:

I've never owned an automatic vehicle before, so pardon my ignorance. I noticed my L ran better 2 days ago at the track if I would just stomp it out of the hole at say 1000 (lightly applying brakes just so I could get the revs up ever so slightly) versus brake torquing up to 1500 to 1800 (basically right before the point of spin). My 60's didn't change really, but my e.t. was better as was my mph.

My friends were telling me that I was "shocking" the converter and that I only needed to come out of the hole at idle. Is this the best way?

I could also feel my torque converter locking up going down the track in 2nd. I could tell I was losing power right before it would do it.

On the dyno you can see where my friend's '99 L arcs lower before the converter spike versus after it locks up. Meaning, if if you imagined the spike wasn't there, then there wouldn't be a smooth transitional rise (Picture enclosed in next post). It's apparent it's costing power down low it seems.

Somehow I managed to keep my converter from spiking on the dyno. It did it a couple of times, but I figured out how to stop it by coasting the truck up slowly through the gears to about 3300 rpms and then stomping it (in Drive of course).

Is there a better explanation for all of this?

Thanks for your help in advance!

BfB
'01 Silver Lightning

 

Here's the spike I was referring to. I drew a reference line of how I figured it would look if the converter wasn't locking up like it is. Would this be close to correct then?

 

What did you run at the track?

 

What an excellent post and I get no replies but one from Jeff. Geez, what's this board coming to, LoL! j/k

Jeff, I don't want to break the subject off here in fear no one will reply to my main "?'s", but if you must know I ran at a 600 ft. track and turned an 8.3's and 8.4's @ 76 to 77 w/ a 2.0 '60. Factor in approx. .35 tenths for a true 1/8. It was very humid and foggy on the track. Weather sucked really.

Ivan from this board w/ his black Lightning was on there as were 2 of my other friends w/ their Lightnings. Ivan was running 8.1's and 8.2's @ 78 to 79 I do believe. He's ran 8.0's there so he was off about 1.5 tenths (keep in mind again that this track is only 600'). At Gulfport's 1/4 track he ran 13.1's @ 104 to 105 last week, so I'm guessing I could pull some 13.5's or .6's out of my '01.

Now, will someone please help to answer my post, PWEEZE!

BfB

 

ttt

 

Nice times... As for your theories on torque converter flashing I have never heard of that before. I'm no expert on auto trannys but I have been at the strip allot and NEVER have I heard any of my 25 Lightning buddies talking and NOT breaking torqueing the motor to a certain rpm (track dependent) to maximize 60' times.. Obviousily you don't want to do that for any length of time because of the added heat. Good post and maybe someone else can chime in with their opinion....

 

i would say your doing it right i found the same if you launch at idle your gonna spin like a son of gun. but torquing up to 1000 rpms is what i have heard as the norm so ther is less wheel spin of the line if you look at my signature below those are the times i pulled with launching at 1000 rpms with f1s notice the 60' time.

 

In a way that's what I meant, but basically I'm stating that if we could launch off of dead idle w/ the stock converter I feel this would be a better way of doing it. Maybe I'm wrong.

I could tell the truck launched NO harder at torquing to 1800 (or however high it was I got it. btw, I wasn't spinning at all, as this track was awesome!) and then coming out of the hole vs. coming out at 1000. I never tried it from a dead idle, for reasons I'm not sure why. Next time I will.

It just seemed that the stock torque converter was getting wigged out when you would brake torque it up like I was doing, especially feeling it kick in going down the track like it did (I've never really noticed that on the street).

Trying to powerbrake (do a burnout) on this track was nearly impossible too. It wouldn't give hardly.

BfB

 

BfB,

Well, I'll try to answer your question the best I can. I may be wrong in my statements, I am not an expert when it comes to torque converters, but I do have some understanding in how they work.

To answer the question in your last message, I'd say Yes, Theoretically we should see better times if we launch from an idle. Here is my reason for thinking this. A torque converter transfers torque from the crank to the tranny via Fluid coupling. The Crank Turns the Impeller, the Impeller throws oil at the turbine which causes the turbine to spin, the turbine is connected to the tranny (A crude explanation on how it works). Then comes "Flash Speed" or "Lockup Speed". Flash speed is the speed the Impeller/crank can turn without spinning the turbine/tranny. If you start from an Idle and Gun the throttle, it will cause the Flash Speed to be momentarily higher than if you slowly bring the engine up to speed and hold it with the brake. This should cause more torque multiplication, and will get the engine up into it's power band sooner.

As for the dyno graph showing loss of power before the converter locks up, well, this does make sense to me, an unlocked converter is less efficient than a locked one, which is near 99% vs. unlocked which can usually be from 0-95% efficient. If you left the torque converter unlocked throughout the rpm range, you would see lower horsepower. If you locked to torque converter too soon, you could drop the rpms below the power band.

Hopefully some of this makes sense. Please correct me if I am wrong about any of this....

Dan

 

I REALLY do appreciate you going over all of that with me. It makes clear sense.

Now, how many of you race by brake torqueing these beasts up?

BfB

 

I remember reading/someone telling me that with F1's your best bet is to powerbrake up to about 700-800 rpms to get the best time at the track. I've done this the last few times at the track, and finally got my first 12.9 (@106.5). However, my best 60-foot time to date (even on that run) has never been better than 2.02...so maybe this isn't really the best launching method (since many/most others are getting consistant 1.9x's and even 1.8x's on F1's. I think I'm heading up to the track tonight, so maybe I'll try my own little test and let you know what I find.

Thanks for asking questions like these.

Later...

GK

 

If you have 4# or more of extra boost from pulleys all you're going to flash is your tires on F1's. If you have ET streets it probably works fine.

 

bfb you seem to talking to yourself buddy. I have tried the same thing at the track and I am sure that flashing it from an idle or just slightly above is the best way to leave the hole with the F1's. I have tried it just about every way I can and it works for me. I am however in the middle of building my own traction bars that connect at the axle just under the springs and run forward 6', they are going to have adjustable rod end on them for preload, and will attach with pit pins,(ball locks) so they can be removed and installed quickly. I have already bought them material and should have them done soon for under 100 bucks. I'll let you know how things come out since your just across town.

 

Interesting topic! Assuming your converter/trans/gear ratio/tire is properlly matched to the vehicle, you want to leave the line as close to the torque peak as traction allows. For example, in my race car I use a Hughes 'glide w/ a Hughes 5800 RPM converter. This works well, b/c my torque peak (about 750 ft./lbs) is at 5800 RPM's.

Using a trans brake, I generally leave the line at 5600 RPM's (I don't like being up on the converter to it's stall rating), and my '60 foot is usually around 1.011. The key is a combination where every part is setup to work together.

 

I was afraid somebody was gonna do that. Its probably not a good idea to compare a Lightning with a super comp camaro, for obvious reasons, they have "0" read that zero in common with each other.

If you want to compare the lightning with any kind of race car, your gonna have to go way down the food chain to the stock class cars.

You guys are on the right track about shocking the converter so to speak, but it goes way deeper than that. You are shocking the whole chassis. When you get up on the converter at the starting line it preloads everything and the truck doesn't have time to pitch rotate or weight transfer, its as stiff as a board and will spin the tires.

When you stand on the gas pedal from an idol and if you have enough traction, the truck will weight transfer better.

I know this works on my truck and the cost was zero. There are no down sides to trying this. But if you try it and it doesn't work then its probably because you didn't have enough traction to begin with.
Dale