engineermike

I've always heard that you want the torque converter to stall to the torque peak of the engine. Makes sense at first glance, but. . .

There's a local guy that's gone 11.4x with a stock cam, head, intake LS1 and a Yank 4500 converter. I'm pretty sure that's higher than the torque peak of the engine and it works outstanding.

My Vigilante "2800" stalls to 5400 when I run 18 - 20 psi boost. I was just about to change it to a "2400", when I realized that it may not be the best thing. My hp peak was at 5800 before I destroked the engine from 383 to 363 cid.

Would you want engine to be at peak hp (looser converter) or peak torque (tighter converter) for the launch? I know they gear race cars so that the engine spends it's time around peak hp, but would that be the case with a torque converter?

Mike

Pro Stock John

iTrader: (34)

You can run a stock engine with a 4500 stall, the car will come out at 4500 and shift at 6000-6400 ie. wherever he is shifting his combo. It's a wee bit too much converter but for a drag oriented combo it's going to run a great et with a slightly low mph.

If you make peak hp at 5800 you probably want to run a converter that stalls in the 3xxx range, otherwise you can run through your powerband too fast.

I'm running a (in my blower setup) a 4500-5000 stall and shift it at 7000.

If I were turbocharged and say my combo peaked at 6400 I would run a 4000 stall probably.

onfire

iTrader: (17)

5400 under footbrake or transbrake? Sounds like that converter is too loose.

engineermike

I have a TH350 with no kickdown and 2.73 gears. I hit the gas from <30 mph in Drive and the engine goes to 5400. Coincidentally, when I put it on a chassis dyno, it doesn't start making power/torque until 5400 even though we start the dyno run from 50 mph.

onfire

iTrader: (17)

Too loose...you're giving up a bunch of turbo torque. Try holding the footbrake at idle and see what it will boost to. I get up to 2100 rpm and no boost on the foot brake. About 3500rpm and 10psi on the transbrake. #4pump Vig 10.5 inch with their "turbo" stator.

engineermike

On the footbrake, I can only get about 2200 rpm and no boost.

I'm also concerned about spool time. Since I don't have a trans-brake, I have to leave on the foot brake and no boost. I would think a looser converter would let the engine go to a higher rpm and spool the turbo quicker.

onfire, how does your car run?

onfire

iTrader: (17)

Like crap . 10.71 at 128mph at 3820lbs with a best 1.72 sixty on ET radials off the footbrake. It blows the tires off with the footbrake and runs a sorry 60ft. I've got to get the suspension figured out and leave off the transbrake to get some decent et's. Transbrake launches are just silly now.

Pro Stock John

iTrader: (34)

Mike do you ever run the car at the track? What does it run? Some longtime racers suggested that I shoot for 2000 rpms worth of power band at the track. Meaning that I try to keep the car in a 2000 rpm band. If you run too much converter you go past your power peak and you run slower because you are out of the best part of your powerband.

engineermike

It definitely won't have a 2000 rpm range. The hp peak occurs at 5800 so I shift at 6200 rpm. Right now, my rpm will stay between 5400 and 6200 for the entire pass. In order to have a 2000 rpm band, my converter would have to flash at only 4200. This would be 1200 rpm less than my Vig 2800 stalls, but the tightest they offer is a 2000 stall. So we can't get there??? Also keep in mind that a higher stall will spool my turbo quicker. Not to mention that I'm running a 2.73 gear expecting to trap 140+ mph on 27" ET Streets, so more converter may help me there(?).

I haven't been to the track yet due to my 7.5" rear end and enough power to run mid 9's at 145 mph. After I get a few leaks taken care of and some more gauges, then I'll start saving for a 12 bolt or 8.8".

onfire

iTrader: (17)

Call Vig and talk to them. There is a big difference between stall and coupling efficiency. You may have to go to a larger diameter converter to get both. Stator and pump makes a big difference.

Sounds like you're blowing through the converter since the footstall is so low and the boost rpm is so high.

What is a Vig 2800....#6 pump? 9.5"? Was it spec'd for boost?

I make 880rwtq and my Vig holds it well.

engineermike

Vig 2800 is the #0 pump 9.5". It's one step (400 rpm) looser than your #4 pump.

Also, found this neat vid of how a converter reacts to turbo boost:

http://home.neo.rr.com/turbo68/brake.wmv

Looks like the boost adds 2000 rpm to his NA stall speed, which is similar to mine.

Mike

Got Me SOM

iTrader: (2)

not to overstate the obvious you are blowing right thru that converter. A tight 36-3800 converter would probably work best for you.

Zombie

iTrader: (2)

I'm running a TH400 with a VIG 3000 stall that was setup for 700 hp on a turbo app. I can foot brake the stall to 2800 no boost. When driving down the street and flooring it, it will go to 3000 and then quickly to 5000 when boost builds. Almost identical to that video. I plan on shifting at 6500-6700 on the new motor.

Not sure if this is good or bad but it's a lot of fun to drive around.

2002 Trans Am

You should tell Ernie to run something like that

Korben

I'm running a Yank ST3500 with a 2.8 STR and it works pretty well......I might send it off to get it loosened up a little bit so I can build some boost off of the line.

cablebandit

iTrader: (37)

i am running a th400 with a vig 2800 stall......this stall and the 3200 multidisc on the 4l60e are the two best stalls i have had. i had a 3400 and 3800...both Precisions but i like this one best. For ME...a bigger stall no change in et but did affect off boost driveability

y2khawk

iTrader: (5)

He'd be changing the converter quickly if he did