[Stan Weiss]

I have always run a manual trans.

Elsewhere someone had posted some information about their combination. The finish line (1/4 mile) RPM seemed high to me. So I calculated convertor slippage. I got 11%. What are others see from their combination?

Stan

[Formulajones]

One car in particular is on it's 5th converter for this very reason. It's been a struggle to get a converter snug enough. Long story, but right now it's got one that is finally tight enough, and it picked up over 3 mph from it's best. from 125 to 128 mph, with 28" tire and 3.42's. It's around 3% now.
It's had converters in it that would barely clip 120 mph at 6000-6100 rpm. Major slippage!! I think that calculates to over 21%

What Steve told me at Hughes is that they try to build a converter that provides about a 700 rpm drop at the gear changes, that's ideal. Doing that without affecting other areas of the converter is the trick.

Right now that combo I mentioned has a 1400 rpm drop between gear changes, but the driveability on the street is so good that I hate to mess with it too much. On a real street car there is a fine line and I tend to favor drivability over track times for a car that only sees the track once or twice a year.

To add to that, right now I'm playing with 2 of them with 4L80E's and lockup converters, that have the ability to lock the converter solid anywhere from 2nd gear onward if I wish. So now converter slippage doesn't play much of a roll. Launch the car and once moving lock the converter in 2nd or 3rd. The car I mention above doesn't need to do that because the converter is already pretty efficient, but the other car could certainly see some improvement from it.

[AG]

My car goes across the line at 6700 rpm with a 28" tire and 3.90 gear for a theoretical 143.2 mph. Actual mph is 134.3, slip = (143.2-134.3)/134.3x100=7%. This can be checked with my in car videos.

[Stan Weiss]

Originally Posted by Formulajones

One car in particular is on it's 5th converter for this very reason. It's been a struggle to get a converter snug enough. Long story, but right now it's got one that is finally tight enough, and it picked up over 3 mph from it's best. from 125 to 128 mph, with 28" tire and 3.42's. It's around 3% now.
It's had converters in it that would barely clip 120 mph at 6000-6100 rpm. Major slippage!! I think that calculates to over 21%

What Steve told me at Hughes is that they try to build a converter that provides about a 700 rpm drop at the gear changes, that's ideal. Doing that without affecting other areas of the converter is the trick.

Right now that combo I mentioned has a 1400 rpm drop between gear changes, but the driveability on the street is so good that I hate to mess with it too much. On a real street car there is a fine line and I tend to favor drivability over track times for a car that only sees the track once or twice a year.

To add to that, right now I'm playing with 2 of them with 4L80E's and lockup converters, that have the ability to lock the converter solid anywhere from 2nd gear onward if I wish. So now converter slippage doesn't play much of a roll. Launch the car and once moving lock the converter in 2nd or 3rd. The car I mention above doesn't need to do that because the converter is already pretty efficient, but the other car could certainly see some improvement from it.

Thanks,
Stan

[Stan Weiss]

Originally Posted by AG

My car goes across the line at 6700 rpm with a 28" tire and 3.90 gear for a theoretical 143.2 mph. Actual mph is 134.3, slip = (143.2-134.3)/134.3x100=7%. This can be checked with my in car videos.

Thanks. Remember you will never see 0% slippage. Even if the converter is locked up the calculation will show a small amount of slippage. Why is that? The MPH shown on the time slip is not the finish line MPH be an average over the last x number of feet.

Stan

[Formulajones]

Originally Posted by Stan Weiss

Thanks. Remember you will never see 0% slippage. Even if the converter is locked up the calculation will show a small amount of slippage. Why is that? The MPH shown on the time slip is not the finish line MPH be an average over the last x number of feet.

Stan

I used the datalog on the car to see specifically finish line rpm at exactly the ET the car ran. I can move frame by frame to match the ET slip. That may or may not be more accurate but it's a neat tool to have.
I also use it to log rpm drop on gear changes and a bunch of other things. I can also see when dad isn't going full throttle for 2.1 seconds into the run, lol.

I have yet to play with locking up the converter solid at the dragstrip so I can't answer the other question. I find it interesting you're finding that it still calculates some slippage though.

[Stan Weiss]

Originally Posted by Formulajones

I used the datalog on the car to see specifically finish line rpm at exactly the ET the car ran. I can move frame by frame to match the ET slip. That may or may not be more accurate but it's a neat tool to have.
I also use it to log rpm drop on gear changes and a bunch of other things. I can also see when dad isn't going full throttle for 2.1 seconds into the run, lol.

I have yet to play with locking up the converter solid at the dragstrip so I can't answer the other question. I find it interesting you're finding that it still calculates some slippage though.

I clearly talked about time slip MPH. Data logging is a different animal. How does you data logged MPH @ 1320 feet compare to the time slip MPH?

Stan

[Formulajones]

Originally Posted by Stan Weiss

I clearly talked about time slip MPH. Data logging is a different animal. How does you data logged MPH @ 1320 feet compare to the time slip MPH?

Stan

It's doesn't data log mph currently, unless I put a speed sensor on it and add a PDF.

I use it to capture the rpm at the finish line at the exact moment the ET on the slip matched a datalog point, and then use that rpm to calculate converter slippage. The track itself uses a given distance between two points to calculate your mph.

Sorry if I didn't explain that correctly

In other words, I can't just look at the datalog to find finish line rpm at the moment dad lets off the throttle, because he is already well beyond the finish line so that wouldn't be an accurate rpm data point.

[Formulajones]

Actually now that I think of it, I can datalog on the 4L80E as well which does give me MPH and will calculate converter slippage vs driveshaft speed with the input and output shaft sensors.

I don't think it would get any more accurate than that.

Now I have something else to try at the track

[Stan Weiss]

Originally Posted by Formulajones

Actually now that I think of it, I can datalog on the 4L80E as well which does give me MPH and will calculate converter slippage vs driveshaft speed with the input and output shaft sensors.

I don't think it would get any more accurate than that.

Now I have something else to try at the track

That would be great. If you could capture that data for the full 1/4 mile. You could then see how slippage changes during the run.

Stan

[blueghoast]

I had a slippery converter and use number 46 hydralic fluid in it
to tighten it up works great now.

GT

[mchell]

Originally Posted by Stan Weiss

I have always run a manual trans.

Elsewhere someone had posted some information about their combination. The finish line (1/4 mile) RPM seemed high to me. So I calculated convertor slippage. I got 11%. What are others see from their combination?

Stan

Mine runs right at 11 percent

[Jay S]

The actual distance traveled by the tires revolution is some place between the tires diameter and the tires rolling radius. That changes the slippage a few percent too, especially on a heavy car. Most guys don’t account for that. That even shows up quite a bit on my manual tranny cars. Might be part of the 11 % loss. My car was about 9% by the tire diameter, calculating out by the rolling radius is drops about 3-4%, the actual % slippage is somewhere in between. 11% is a lot.

[Half-Inch Stud]

What i see:

At WOT, the Dry clutch always transfers TQ at </= 100% of engine TQ. Slippage means unapplied hp, lost or at best dissipated as heat.

At WOT, the Wet Converter always transfers TQ at >/= 100%of the engine TQ. Slippage typically mean 2.2 down to 1.1 times the engine TQ. Slippage has a hp loss mostly dissipated into heat. Much heat to the touch, but in terms of hp, not much heat using 745 W/hp and the timespan considered.

Converter Slippage can be the "wet gear" ratio which is load-dependent, that which helps the engine stay in the power band. In fact the car MPH may increase while the Tach RPM sits, showing the "wet gear" ratio changing, while the engine sits at a desired HP window.

And yet; Dry clutch cars can feel aweful quick. Converter cars can go aweful quick.
And you know it takes cubic dollars to get thr dry clutch to equal a converter.

[AG]

Originally Posted by Stan Weiss

Thanks. Remember you will never see 0% slippage. Even if the converter is locked up the calculation will show a small amount of slippage. Why is that? The MPH shown on the time slip is not the finish line MPH be an average over the last x number of feet.

Stan

You'll never see 0% slip from wind friction also.

[mchell]

Originally Posted by Jay S

The actual distance traveled by the tires revolution is some place between the tires diameter and the tires rolling radius. That changes the slippage a few percent too, especially on a heavy car. Most guys don’t account for that. That even shows up quite a bit on my manual tranny cars. Might be part of the 11 % loss. My car was about 9% by the tire diameter, calculating out by the rolling radius is drops about 3-4%, the actual % slippage is somewhere in between. 11% is a lot.

Yeah…that’s from a slip calculator. lots of things can add or subtract slip. I don’t worry about it much. I run what seems to work on MY combo. The slip number really doesn’t mean squat to me. The et and drivability does. Probably never had a “ perfect” converter and I’ve tried my share of them.

[slowbird]

I have never calculated it but my data logger shows 4-5%

[Formulajones]

Originally Posted by Jay S

The actual distance traveled by the tires revolution is some place between the tires diameter and the tires rolling radius. That changes the slippage a few percent too, especially on a heavy car. Most guys don’t account for that. That even shows up quite a bit on my manual tranny cars. Might be part of the 11 % loss. My car was about 9% by the tire diameter, calculating out by the rolling radius is drops about 3-4%, the actual % slippage is somewhere in between. 11% is a lot.

And that rolling radius, or roll out as I call it, changes with tire pressure too. So if you're at the track playing with tire pressure, you're changing the roll out, which affects the math.

[Cliff R]

Converter slippage can vary considerably based on vehicle weight, engine power, and most important gear ratio.

The higher you spin the converter the tighter it will couple.

With the same converter a heavy vehicle and lower (numerically) rear gear will show a LOT more slippage in the lights as a lighter vehicle with the exact same engine but much taller gearing..

There is no "perfect" converter either. For the Ventura the Continental 10" came close showing less than 150rpm slip on top end but flashed to 3500rpms on the starting line for 1.59-1.61 60' times. You got a nice solid engagement and slight RPM drop when the trans was placed in gear, slightest pressure on the throttle and the vehicle would move out right off idle without any "flash" whatsoever, couldn't get past 1900rpm's standing on the brakes as hard as you can and applying throttle before the tires started spinning, and you'd never even know it was in there for "normal" driving.

Even with that said I've sold the exact same converter to a few folks with slightly different set-ups that didn't like anything about them.

Generally speaking I'll also say this about converters, good ones thrive on high input torque to work well. Whimpy engines favor "loose" converter or those with a lot of torque multiplication. Stout engines will like a converter that couples harder both above and below the stall speed.

If you want to know the true stall speed of your converter (TH350 and TH400 transmission cars) disconnect the downshift feature. Accelerate to about 25-30mph and reach high gear, then coast for a few seconds. As hard and quickly as you can "stab" the throttle all the way to the floor and watch the tach. Provided the tires don't slip, and most woln't in that scenario you can watch the tach and get a really good idea of what the converter will do hit with full power in low gear on the starting line with traction..........

[Tim Corcoran]

If you really want to know the stall of a converter get a trans brake that will tell you. Push the button and put it to the floor and look at your tach. Anyhow Chris at Continental really knew how to make a converter work. When my 65 LeMans was a low 12 second street car I had a 10 inch Continental TH-400 3.73 gears and the thing felt like a stock converter in normal driving but when you hammered it, it would flash up and all hell would break loose, never could hook that car up on the street even with slicks. When I upgraded the engine I had Chris freshen it up and loosen up the converter some and it now stalls at 4400 on the trans brake. Really love that converter it's no longer a street car strictly a bracket car running very low 10's and 1.42-1.46 60's 3550 race weight. Been running that same converter since 1996 and it's still going strong. I don't use the T-brake when I race because I could ever stop red lighting so I went back to foot braking but the 60's were no better launching on the brake of hammering it from 1100 RPM which is how I race it.