Mike04

I've read a lot about converter locking at WOT. I've never ran across anyone doing this in a 1/2 race at high hp in 4th so I figured this would be the place to ask for thoughts/ experience. I've read about guys in 1/4 mile drags locking in 3rd and usually they gained some MPH and MPH is the goal in the 1/2 races.

I'm not sure if I should try to lock it in 3rd and in 4th (I'm concerned about how the shift would go or should be tuned in. I'm running a 0.0 shift time) or only locking it in 4th at say 145 ish... I would plan to do this through EFIlive. I also realize it may not lock with the hp levels, never know until you try.

Would having the converter locked possibly help tranny temps stay lower?

I'm running a Vigilante 2600 triple disk converter (recommended by the manufacture to lock) with a brand new RPM Level X 4l65 tranny. The tune I plan to run should be close to the 1000rwhp mark.

Thanks

RHS Block 427, Mast/ PI 275 Heads, A&A YSi SC, 2.7 Pulley , 238/254 LSA116+5, A&A Direct Drive, AR 1 7/8 Headers, Corsa Touring Cat Back, RPM Level X Tranny/ Flexplate/ Drive Plate, Pfadt Carbon Fiber Drive Shaft, RPM rebuilt DTE Stage 4 3.42s, Vigilante 3 Disk 2600 converter, Custom Fuel System with Dual A1000 Pumps, Dual Nozzle Alky Control, 2.5 Bar SD Tune.

Chris Stewart

I've done WOT in OD and got away with it a couple times, but the band took a beating. I took the trans apart shortly after for 3/4 clutches, and the band was smoked. Locking up is gonna throw even more heat at it. Only a $40 part though. Personally I'm thinking of swapping a 2.73 gear for some 1/2 mile racing.

Rkreigh

that's a fantastic setup and I'd lock up in 3rd and 4th in 1/2 mile for sure

you have the right stuff, but as chris mentioned it would be better to go to a taller rear gear and stay in 3rd

Mike04

I'm thinking of run it unlocked to dial in the tune for the elevation/ conditions and lay a solid run down and then lock a run in 4th and then one in 3rd & 4th. That way I should have good data to compare for the future.

Last race I trapping in the low 180s, at about 6000rpm in 4th. No way gears are going to keep me in 3rd. With the above numbers, the tranny was slipping and that was the last run it held any power at all. I wasn't logging tranny stuff so I don't know how bad the slip was but I bounced off the rev limiter each shift when it didn't before. 3.42s seem to be a good gear for the speed the car will do in the 1/2. I'm also running 28" tires.

Unfortunately tearing a tranny down for a rebuild is something I've never done so the $40 sounds good but.... And the PITA of pulling the tranny....

Chris Stewart

Here's some gear calcs I did factoring converter slip on my setup. 2.73 would get me to 200mph about 7500rpm in 3rd. Locking the converter in 3rd would lower that by about 500rpm. Ignore the highlights, those are just some targets for doing things.

Mike04

I think my car would loose power too much revving past 7000 I think my TRQ starts to fall about 6500.
RPM said I need a power glide and a 9" rear along and a big wallet to empty

I'm assuming you have scaled your VE/ injectors in your car to stay under the G/sec limits (or anyone else can jump in on this), did you do anything to adjust for the tranny pressures when you scaled? I know PCM calculated engine torque is used for line pressure calculations and scaling would have some affect on that. My car is scaled 20% so I'm wondering if I should possibly adjust the Force Motor Current Table....

smokinstorm

Doing before/after pulls on the dyno I picked up 24 RWHP peak with the crossover point being just after 100 MPH in 3rd gear. This was on a 459/483 horsepower N/A car. I don't know how much more, if any, power you'd pick up vs what I did but I'm not sure 24 more horsepower would make a huge difference in you 1000 horsepower car vs the damage you might cause by locking the converter. It was a decent % gain for me but it will not be for you.

Chris Stewart

On mine it picked up from 146mph to 150mph by locking in 3rd. That's about 75hp using calculator, could be more or less depending on converter slip.

smokinstorm

I went from 124 n'change to 126.00 locking the converter at the crossover point on the dyno. The MPH gain seemed to align pretty nicely compared to the dyno gain I saw. ~75 horsepower as Chris saw would certainly make a difference at a half mile.

Mike04

I did see what locking the converter in 4th gear did for me at the last 1/2 mile race. I ended up loosing about 4 mph but there were too many other variables to say it was the lock that did that. The knowledge I did gain was that locking it at 150 mph dropped my rpm from 5750 to 4850 in a few tenths. That cost me about 5 lbs of boost... That can't be a good thing. I had limited runs so I didn't try locking it again, maybe next outing.

I did run 180, not my best but the runway elevation is 2700

smokinstorm

You have to be a little scientific about it to see the gains. Get a dyno sheet in MPH with the converter locked and then unlocked. You lock the converter where the two curves cross to get the benefit out of it. If you lock it too soon you lose performance just like you experienced.

Mike04

that does make sense to some extent,

so after the lock rpm should be 5250 ( point torque and hp always cross). I'll try locking it at about 160 mph vice 150 which should give a locked rpm close 5250.

Or are you suggesting using hp or tq lines from a the individual dyno runs one being locked and the othe unlocked? Picking rpm when the torque or hp increase on the locked above the unlocked line.

smokinstorm

Use where the horsepower or torque curves cross on the dyno sheet with one run being locked and the other being unlocked when scaled in MPH to determine the exact locking point. In my Camaro the curves crossed at 102-103 MPH in Drive (3rd) if memory serves. Since I was only racing a 1/4 mile I didn't go into Overdrive (4th) so I had the dyno runs in 3rd gear both locked and unlocked. Now, since you're racing a much longer distance and going through another whole gear you've got something else you can try. You can try locking the converter in Drive and see if the extra acceleration you get through the latter part of Drive will offset positively the lesser acceleration you get at the beginning of 4th because of your RPM drop and therefore boost drop. The turbo guys don't have quite the issue like this vs the centrifugal supercharger guys. After they make the shift they've got 200-300 more lb/ft of torque to help them accelerate through the gear at first vs what we have. Without a dyno run in 4th to check this you're going to just have to play with it but from the RPM drop you described, you're going to have to be going pretty fast in 4th when you lock it so see any gains. I was just about redlining my Camaro in 3rd (7000 RPM) with 26" tall tires when I crossed the 1/4 mile with 3.90 gears so I got to use all of the gear possible while locked. I trapped 101-102 in the 1/8th so I got to use a whole 1/8th mile locked to gain 1.5-2 MPH. It was subtle but it was faster. It's also about the gain one would expect from 24 more peak horsepower and the way I was able to use it. Try it. There are gains to be had, however subtle if you get it just right. Chris's gains are extraordinary because of the massive torque from his turbos at the RPM his drops to when he locks the converter so don't go in expecting to see his gains.

Chris Stewart

That's cool you got to try it, but a bummer it didn't help any. 180mph is hauling some butt though!

smokinstorm

Chris, iIt's going to help him when he finds the proper locking point. Just not as much as it helped you. Your gain was extraordinary.

romandian

"I'm assuming you have scaled your VE/ injectors in your car to stay under the G/sec limits (or anyone else can jump in on this), did you do anything to adjust for the tranny pressures when you scaled? I know PCM calculated engine torque is used for line pressure calculations and scaling would have some affect on that. My car is scaled 20% so I'm wondering if I should possibly adjust the Force Motor Current Table...."

why is your car scaled if your running a speed density tune? what happens to calculated torque when the maf is not there? also interested in what needs to be done to the trans pressures. i have a stock 4l60 thouh.

C5Natie

Ive done it for years and the trans still runs cherry. I have a Circle D triple disk converter though. Ive done the 1/2mi a few times too trapping 170mph (700rwhp). Locking the tc gained me 50rwhp vs unlocked. I lock it up at 80% throttle but mostly because I do a lot of canyon driving and road course stuff.

algZO6

why not just lock it up wherever you shift? would make sense to just treat it like another gear.