josh99ta

iTrader: (1)

I had gomer throw a dyno tune on the car this past weekend, and of course with the converter it made a good bit of torque. We didn't have any inflated torque numbers from any spikes. When you go WOT on the street or at the track the converter is unlocked, so why shouldn't they be accepted as the norm when that is how the car runs, and locked numbers thrown out the window? Just curious why more people dont go with their unlocked numbers? If my car did 373tq to the rear wheels on the dyno (only 335hp), thats how much power it's putting to the rear wheels, regardless of whether or not the engine makes that much power or not.

Scotty-Z

iTrader: (5)

I agree with your view, but most people don't see it like that. It's because a converter is enhancing that power without you actually making it at the engine. But you have a good point, because yes the car is actually putting that power down!

I don't know, I can see each view.

Ragtop 99

iTrader: (7)

Only recently did the dynojet software become available to get accurate readings on high stall cars. The reason the high torque numbers are meaningless is because the rpm shown is not the engine rpm, it is the converter output shaft rpm. Think about it. You punch the car to WOT and the converter unlocks and jumps up to 4500 rpm (or higher depending upon your stall). During the time the converter is flashing up on the dyno, it is slipping; just the same way you feel that momentary lag on the street. It is not putting any real power to the ground. Then it catches at 4500+ rpm and stays there for a moment. During this time the car is accelerating the rear wheels on the dyno (you're seeing the shift extension) and then the engine rpms start climbing to redline. At no time was your engine at WOT below 4400 rpms, yet the dyno is giving you a reading starting at say 3500 rpms. This reading is false because the dyno did not factor in the shift extension.

So what good is that torque number? You can't use it to tune very effectively because you don't have a true reading at 3500. The only value is looking at the total torque you have at launch if you start swapping converters around.

The dyno is for tuning. Lock your converter and tune the car on the dyno.
The track is for racing and that is where you can show off the torque converter as you cut a 1.6 60' on a .510 light.

josh99ta

iTrader: (1)

I somewhat see your point Ragtop, but it still doesn't change anything for me. Maybe I dont understand dynos to the fullest extent, but to me, I thought the dyno used the drums to measure hp and tq, figured by rolling resistance obviously. That would mean if the car put down 373tq to the wheels, thats what the car put down to the wheels. Whether on the dyno or on the street, the car would have put that same power through the wheels regardless of whether the converter is slipping or not (because it still did 373tq to the wheels). I would think that is what the STR and stall speed are all about, getting that extra torque to the wheels, as an enhancement to the engine (as thats what the multiplication is all about).

I guess I'm just oversimplifynig it. To me if the dyno read it like that, then thats what the car made at the wheels, and thats what the car has.

Obviously the dyno does a great job in tuning, but short of installing a wideband in your car, there really is no other way to get the same thing on the street as you can get on a dyno, and even then you have to worry about traction. It is a great tuning tool, but it just seems to me that it also doesn't lie and that it would just read the power at the rear wheels, and thats what the car has, regardless of what kind of car it is, what kind of engine it's got, or what kind of torque converter is in it.

critter

iTrader: (9)

Dynojet dynos do not measure torque or HP. They simply measure the acceleration of the drum and compute torque from that and then HP numbers using the drum RPM. Of course a loose or slipping converter destroys the relationship between drum and engine RPM, so you can't really say anything about engine HP since the formula is HP = torque * RPM / 5252. Obviously if RPM is wrong, so is HP. The dynojet can give some approximation of rear wheel HP, but you can't correlate that to engine HP with a slipping converter.

2xLS1

iTrader: (25)

Well the dynojet I use gets a tach signal off the ignition system on the car so how is the rpm it shows not the engine rpm? Also, when you start a pull in 3rd gear, shift extension has nothing to do with the pull.

critter

iTrader: (9)

That RPM is obviously engine RPM, but that is not what is used to calculate torque.