frito1

iTrader: (12)

http://www.tciauto.com/Products/Tech...culators.asp#4

I decided to do some calculating to see where I'm at. I'm going through the traps at ~6000 rpm according to the log, 26.3in tire height, 3.23 gears, and the time slips show 119 mph. I'm getting a little over 22% slippage with those numbers! I know the car is heavy and the gears don't help, but isn't that terrible? Should I let Yank look it over? The converter is a PT4000 and low mileage with a few track runs.

chrs1313

iTrader: (24)

yeah that is alot of slip i think my dads pt4400 is around 13%

jimmyblue

iTrader: (11)

What you want to know is, how much of that slip is going
to torque multiplication. You could determine that by some
logs of acceleration, locked & unlocked. Not all slip is bad.

My 3500/2.0 is still multiplying past 5000RPM, yours maybe
even further out (depends on STR / construction, where
it lays over into 1:1 coupling @ torque level). By 6000RPM
though I am ~1:1 with 5% slip.

frito1

iTrader: (12)

I might call Yank or they might take a peak at this. They should know at what rpm it quits multiplying the torque and goes 1:1.

I know some 3.73s would help. I just don't want to run out of revs and have to go searching for bigger DRs. I'm not that dedicated to drag racing start changing a bunch of my setup.

MNR-0

If your calculations are correct, that's rubbish for a converter. For NA, the absolute worst I would ever accept is 6% slip. For boosted, that number is dependant on matching the correct stall for your power and weight.

6000rpm isn't that high though, and if you are making 700+rwhp, then likely the converter is too loose and not spec'd properly for your setup.

You could be better served with a tighter converter. Ask the manufacturer for advice and let us know how it goes.

12secSS

iTrader: (30)

The problem with that calculator and the way you are using it is that you are calculating a percentage loss using an absolute value (rpms at unknown point of the track) with an average value (trap speed = average speed over 60'). What you need to do to properly calculate or measure slip % is log Engine RPM and Trans Input RPM, then you will have the true slip %. My B&M unit shows 97% efficiency at 6000 rpms. Try it again before suppling Yank with any data, this is the method I used when developing converters in the past.

ShevrolayZ28

iTrader: (4)

I don't know how one would do this but conceptually....

I think the difference between the input shaft speed and the engine speed will be equal to converter slip.

But it could be that the transmission is slipping. You might be able to determine this, while considering other factors, by calculating the difference between input shaft speed and output shaft speed.

Jimmyblue, can this be done?

Another thought, could it be that the slippage is related to TCC PWM?

Also, aren't these tranis notorious for slipping in third gear?

...Just throwing some ideas out there.

Good luck!

12secSS

iTrader: (30)

Comparing Input and Output Shaft RPMs from the trans will show if the trans is slipping in gear, but not the converter slip. Hence why I posted the Engine RPM versus Input Trans RPM, as the converter sits in between those two sensors. The 4L60E has sesnors for Input Shaft RPM, Output shaft RPM and even slip %.

TCC PWM is only in affect during attempted TCC lock up, which is just a few seconds, but not at WOT. Unless the program is altered, but that will not account for that slip loss.

And no, I have never heardd of the GM 4-speed auto being notorious for slipping in 3rd.

troopercar

iTrader: (6)

engine rpm vs. trans input rpm will show converter slip
a good scanner can do this while scanning trans data

NHRAFORMULA00

iTrader: (2)

Take it somewhere and have it dynoed with trans locked.That way you will have a better idea of your numbers.Do you have any work done to the trans? I see your on drag radials,(no growth).PT series do slip quite a bit( 8-12%) from what ive seen,but either your trans or verter is slipping annother 10% too much.Call and talk to Dave,see what he recomends.

j99fbody

iTrader: (1)

i get a lot of slip out of my yank 4000 to. my car traps 11.6 on motor at 114mph and 11.3 on nitrous at 114mph. Mine also stalls about 5500

ShevrolayZ28

iTrader: (4)

Preliminary feeling on the SS4000 in my 4L80 is that it is quite loose. (I'm new to performance autos so take it with a grain of salt.) I'll see where it stalls once I pass the 150 mile break-in and can check it with the t-brake, but I have a feeling this thing is going to be a little more "track oriented" than I was expecting.

cals400ex

iTrader: (27)

why do the pt series slip more when they are designed to be better from a roll than the ss series?

troopercar

iTrader: (6)

no one builds converters "for a roll" that is ricer bullshit

some are tighter up top ie more efficient, some are looser for harder launch

cals400ex

iTrader: (27)

well i was just curious. yank told me two times that the pt series is better from a roll than their ss series.

w3s1c0a5t

iTrader: (3)

That was a pretty stupid comment.

troopercar

iTrader: (6)

You're right, there is a whole aftermarket of roll racing stuff. And a lot of poeple show up for the NHRA roll racing championships. Racing from a dead stop is on it's way out 'cause racing from a roll is where it's at.

I could go on and on but here is where I leave the thread and let the pimply faced internet morons (who learned about cars from Fast and Furious) take over.

w3s1c0a5t

iTrader: (3)

I would either suggest you stop drinking or start.

All i was saying is that lots of people race from a roll. Some of us believe or not.... even drive domestic... and know a lil about cars. I didnt say anything negative about racing from a dig. And im sure if you race on the street at all you have hit it from a roll. Ever seen the NRRA videos? Ones near the top of the multimedia forum right now. H/C vortech c6z06 sprayed ls1 procharged TA 331 fox, you know ricers.

Sorry for the BS in your thread sir. Good luck getting the verter issue worked out.

Kinda on topic. How many of you guys have manual lockup switches? Im putting one in since im going with a MVB. Wonder how many other people use them. It is very noticeable difference when the switch is flipped.

jimmyblue

iTrader: (11)

You can determine converter slip by motor RPM - input shaft RPM
or just take the existing PID (TCC Slip RPM). Divide the difference
by motor RPM for a precentage (there is a TCC Slip % PID too but
I have seen insane data from that, so roll my own).

But the question still remains, how much of the slip ratio is given
back as torque multiplication. Until you know that, the efficiency
you would calculate is only a lower bound to what's possible.

The attached .png is from an uphill pull where I locked the Fuddle
at frame 1470 (approx 5000RPM). You can see that the slope of
MPH lays over some when the converter locks up and never gets
as high a slope as unlocked; this shows that torque multiplication
is being given even at the higher RPMs. My STR is low so torque
mult does not fade as fast as some of the more normal ones,
but your higher stall RPM pushes out the roll-off even if its slope
(rate of fade in torque mult) is greater. So I suspect you are
still getting some, which is one component of the slip%.

If your converter clutch is up to it, you could determine the
residual torque multiplication at various RPM by a series of
similar pulls. However this is also a good way to find out the
clutch is not up to it (mine was spec'd to be).

chrs1313

iTrader: (24)

my ss4000 is tight as hell on the street, and hits hard as hell at the track...one of the best converter out there right now for a NA car...