Heres my build :

99 corvette
VRX5 camshaft
Ls6 katech heads
78 fast intake
Xspower long tube headers
ls7 water pump
Slp harmonic balancer
Vararam
Trunion upgrade
4000 yank ss converter
3.15 gears

So first of all my torque converter would "lock" at 4800 RPM on the dyno, that is kinda high... Is that normal?

Would also changing gears ratio help torque converter lock sooner or that's not how they work?

Thanks guys.

 

Ok.....the convertor "reacts" to load. So that can be achieved a couple different ways. More engine power or gear would "tighten" up the convertor because of the added load.
And when it's tighten, the convertor can be locked sooner and will flash lower.

When the convertor is locked it falls against the gear (just lIke a clutch being engaged), which in turn will pull the engine down (in rpm). You do not want to pull the engine down, out of it power band (counter productive to making hp). So this is where more gear would be very beneficial, when locked the engine would not be pulled down to low and the added gear helps load the convertor which will tighten it.

Having a "lose" converter allows the motor to get up in the rpm range where the power is being made (thus, this is the quickest way down the track). But remember, "lose" is a relative word.

Lose and tight are just words to describe extreme ends of the spectrum. Ideally you want an efficient converter. One that flashes 300-600 rpm over peak torque, has a slip % ideal for your combo, rpm drops roughly 900rpm and locks up out the back door for that mph charge.

......if this is a car you race, there are several points of data you need to collect to make the best educated decision.
Like... your rear gear ratio, rear tire height, trap RPM, trap MPH and rpm drop at the gear change.


EDIT*****to directly answer your two questions.

4800rpm is relative to your power curve and combo. But I feel 4800 is not "to high", in fact it could possibly be to early depending on what the motor is doing then.

And yes, more gear will help the converter lock earlier. But the gear will help more than that.

 

Thanks a lot! That was a really complete answer. That's why I love this forum.

The title is misleading, I tried editing but could not.

 

No problem, I don't claim to know it all. But if you just wrap your head around what your trying to achieve (engine rpm, most average power, max wheel torque per gear change...etc) it becomes common sense. And will tend to point you in a direction of efficiency.

I have heard this said before......

"For the maximum performance, put the car on a chassis dyno and make a pass it unlocked and one with it locked and lay the graphs on top of eachother. Where the two Torque curves cross is the RPM you want to lock it at."

But I can only assume that this statement holds true once the entire combo (gear, tire..etc) has been dialed in.

 

Well I'm not the hardcore racer guy so dialing the perfect RPM isn't that important. I just always heard about converters "flashing" or locking before the advertised RPM. Mine just does the opposite and is 800 rpm late which makes it a bit too high for my taste

 

So what is your next move ??

I'd suggest a gear but I do not know your driving style or intentions with the car. The gear would help that cam as well as the converter. Which in turn would tie the entire car together.....IMHO.

.

 

My car is a daily driver and I'll try it on the streets for a couple weeks. If it's too sloppy I'll go and switch diff for a 3.73 from RPM next winter.

I'll also check with my tuner what my options are. Nobody seem to change gears in corvette rear end in my area ( quebec,canada )

 

I'm not sure why your torque converter locked on the dyno unless the dyno operator/tuner commanded it to do so. By default, it will not lock at WOT. Also, if you did in fact get it locked on the dyno, then the numbers would actually be higher.

Your tuner can set the lockup to occur whenever you want for street driving (part throttle).

 

The term "locked" was not the good one. I meant when going WOT on the dyno the car would slip to 4800 RPM before making power. I thought it would make power before the 4k advertised

 

10-4. Higher stalled auto's do not dyno well so we just use them as a tool to get the tune dialed in. If you're happy with the track results and/or street manners then that's all that matters! The beauty of a good torque converter is that you really don't need to change rear end gears because the converter keeps you in the power band no matter what rpm or gear you're cruising in.

 

Don't forget what the gear is doing......because there is no substitute....