How do you calculate slippage?

E

evil666

Active Member
Joined
Dec 4, 2004
How do you calculate slippage on a torque convertor with the torque locked and with the torque unlocked? For example could someone tell me what is the % of slippage of my torque? With 26" tall tires with the torque locked I come in at 5333 rpm and with 28" tall tires and torque not locked I come in at 5371 rpm. I have the stock diff with stock gears?

Thanks,
Marco.

T-Top 86 Grand National (61400km)
stock long block, stock suspension, 12 inch red stripe convertor (2800stall), te44, smc alk injection (95 % etanol), 25.5lbs boost,( boost spike 28 psi in 1st gear), 94 octane, hooker cat back with dyno max ultra flow muffers, 42 ½ lbs 009 injectors, turbotweak alky chip, thdp, mease 24 row IC, Ron Custom max boost brake module, MT drag radials (275/50/15) 3720lbs race weight with driver. (Torque convertor locked only after car shifted in third), rjc power plate, rjc boost controller, zeitronix wideband, HR motor mounts, comp cam 980 valve springs. Weld Drag Lites with skinnies up front, electric exhaust cut-out.
BEST E/T
60FT=1.53
1/8= 7.25
1/4= 11.48
MPH=120.82
BEST 60FT=1.52
 
mikestertwo said:
What was your speed?:confused:
Click to expand...

It was 120.82mph at the end o the 1/4 mile.

T-Top 86 Grand National (61400km)
stock long block, stock suspension, 12 inch red stripe convertor (2800stall), te44, smc alk injection (95 % etanol), 25.5lbs boost,( boost spike 28 psi in 1st gear), 94 octane, hooker cat back with dyno max ultra flow muffers, 42 ½ lbs 009 injectors, turbotweak alky chip, thdp, mease 24 row IC, Ron Custom max boost brake module, MT drag radials (275/50/15) 3720lbs race weight with driver. (Torque convertor locked only after car shifted in third), rjc power plate, rjc boost controller, zeitronix wideband, HR motor mounts, comp cam 980 valve springs. Weld Drag Lites with skinnies up front, electric exhaust cut-out.
BEST E/T
60FT=1.53
1/8= 7.25
1/4= 11.48
MPH=120.82
BEST 60FT=1.52
 
Chuck Leeper said:
TCI - TECHNICAL INFORMATION: Racing Calculators
Click to expand...

Chuck Leeper thanks alot for those tci racing calculators, got the answer I needed. 12.8% slippage when the tranny is not locked and 0% slippage when the tranny is locked.

T-Top 86 Grand National (61400km)
stock long block, stock suspension, 12 inch red stripe convertor (2800stall), te44, smc alk injection (95 % etanol), 25.5lbs boost,( boost spike 28 psi in 1st gear), 94 octane, hooker cat back with dyno max ultra flow muffers, 42 ½ lbs 009 injectors, turbotweak alky chip, thdp, mease 24 row IC, Ron Custom max boost brake module, MT drag radials (275/50/15) 3720lbs race weight with driver. (Torque convertor locked only after car shifted in third), rjc power plate, rjc boost controller, zeitronix wideband, HR motor mounts, comp cam 980 valve springs. Weld Drag Lites with skinnies up front, electric exhaust cut-out.
BEST E/T
60FT=1.53
1/8= 7.25
1/4= 11.48
MPH=120.82
BEST 60FT=1.52
 
Thanx...just added it 2 my favorites

evil666 said:
Chuck Leeper thanks alot for those tci racing calculators, got the answer I needed. 12.8% slippage when the tranny is not locked and 0% slippage when the tranny is locked.
Click to expand...

+1
 
mikestertwo said:
That's the percentage of slippage in your converter at the end of the 1/4. If you had zero slippage your speed would have been 140mph@6200rpm.
Click to expand...

Can you run a car with zero slip? I know that Dick Kereny has a 2,500 stall but he has that fluid dump converter. Hit the trans brake and it sucks all the trans fluid out of the converter for quicker spool let off the trans brake and it sends all the fluid right back in. Who makes that?
 
Underboost said:
Can you run a car with zero slip? I know that Dick Kereny has a 2,500 stall but he has that fluid dump converter. Hit the trans brake and it sucks all the trans fluid out of the converter for quicker spool let off the trans brake and it sends all the fluid right back in. Who makes that?
Click to expand...
That has to do with the vb. He was running a PTC on his record setting pass. Dusty said he didnt need to use the variable stall to spool with the PTC but he used it anyway.
 
turbojimmy said:
Nice numbers!

Jim
Click to expand...

Jim I know you told me that you think these are nice numbers, but don't you find that 12.8% slippage with the tranny not locked is high? I am starting to wonder if this is why I am not running the ETs for the mph I am running on the 1/4 mile. I must be slipping in 1st and 2nd and losing some ETs there and when I lock it in third then the car gets all its power but not the perfect ET. Maybe if I would use race fuel with more timing, things would make more sense. Anyways I don't know if what I am saying makes sense but I am just trying to figure something out. Jim look at your car, you are running a perfect ET for the mph you are running.

Marco.

T-Top 86 Grand National (61400km)
stock long block, stock suspension, 12 inch red stripe convertor (2800stall), te44, smc alk injection (95 % etanol), 25.5lbs boost,( boost spike 28 psi in 1st gear), 94 octane, hooker cat back with dyno max ultra flow muffers, 42 ½ lbs 009 injectors, turbotweak alky chip, thdp, mease 24 row IC, Ron Custom max boost brake module, MT drag radials (275/50/15) 3720lbs race weight with driver. (Torque convertor locked only after car shifted in third), rjc power plate, rjc boost controller, zeitronix wideband, HR motor mounts, comp cam 980 valve springs. Weld Drag Lites with skinnies up front, electric exhaust cut-out.
BEST E/T
60FT=1.53
1/8= 7.25
1/4= 11.48
MPH=120.82
BEST 60FT=1.52
 
Underboost said:
Can you run a car with zero slip? I know that Dick Kereny has a 2,500 stall but he has that fluid dump converter. Hit the trans brake and it sucks all the trans fluid out of the converter for quicker spool let off the trans brake and it sends all the fluid right back in. Who makes that?
Click to expand...

Just to add to what Bison said. You can run with near 0% slip but there are several things to consider. You have to look at rpm drop on the shift. It's tough to have great efficiency yet keep the motor in it's rpm range without excessive rpm drop. And in Dick's case he had been fighting tire spin which was caused by the extemely tight torque converter. When you make a lot of power on a small tire the converter is also key to making it down the track. The VSC enabled him to spool very quickly with a super tight converter but the car would never 60 foot like it should. It was spinning the tires when the fluid filled. With our PTC converter the car started leaving like it should, smashing the oil pan in it's first pass after a wheelstand. So in other words. VSC and a super tight converter is not the best way to try to achieve near 0% slip. I haven't seen the logs but I expect Dick's efficiency to be in the 3-4% range, spool without VSC if he wants and 60 foot well.
 
evil666 said:
Jim I know you told me that you think these are nice numbers, but don't you find that 12.8% slippage with the tranny not locked is high? I am starting to wonder if this is why I am not running the ETs for the mph I am running on the 1/4 mile. I must be slipping in 1st and 2nd and losing some ETs there and when I lock it in third then the car gets all its power but not the perfect ET. Maybe if I would use race fuel with more timing, things would make more sense. Anyways I don't know if what I am saying makes sense but I am just trying to figure something out. Jim look at your car, you are running a perfect ET for the mph you are running.
Click to expand...

On a LU converter I don't think 12.8% is high. That's what you're giving up with a lock-up converter - more slippage but the ability to lock it. When you lock you go to 0% which is good. Your ET is really a function of traction. The 120 MPH shows the car is pulling the whole way down the track. I see you have a 1.53 60' time, which is hard to explain when compared to my 11.3 @ 117 (it was actually closer to 118) with a 1.53 60' time. All I can think of is that maybe you're spinning beyond the 60' mark. My 11.3 was with a 9x11 3500 RPM LU converter. Plot your data so you can compare RPM and MPH as you go down the track. You'll be able to see if you're slipping and when, or if you're getting a big RPM drop on shifts that might slow you down.

Jim
 
turbojimmy said:
On a LU converter I don't think 12.8% is high. That's what you're giving up with a lock-up converter - more slippage but the ability to lock it. When you lock you go to 0% which is good. Your ET is really a function of traction. The 120 MPH shows the car is pulling the whole way down the track. I see you have a 1.53 60' time, which is hard to explain when compared to my 11.3 @ 117 (it was actually closer to 118) with a 1.53 60' time. All I can think of is that maybe you're spinning beyond the 60' mark. My 11.3 was with a 9x11 3500 RPM LU converter. Plot your data so you can compare RPM and MPH as you go down the track. You'll be able to see if you're slipping and when, or if you're getting a big RPM drop on shifts that might slow you down.

Jim
Click to expand...

I ran an 11.34@114mph with a 3,200 "O" stall last year.
 
I just made an excel sheet to calculate the slip % based on some numbers we got in testing at Reynolds. Converter was a "0-pump" Vigilante 5-disk lock-up. We ran it unlocked all Friday and at the beginning of Saturday. I am going off memory on the RPM's.... they may not be exact... but they are real close.

On one of the best runs unlocked.... tranny was shifting around 5600 and recovering to around 4950-5000. Crossed the finish line at 5700 RPM in 3rd. Trap speed was around 117.69 mph.

If my math is correct... assuming 28.5" (which ought to be close on a 275/60 MT drag radial with some tire growth).... I calculated the following:

(1-2 shift)
Converter slippage at the shift recovery point (5000 RPM shift recovery point) 35.8% slippage.

(2-3 shift)
Converter slippage at the shift recovery point (5000 RPM shift recovery point) 28.7% slippage.

These are not exact RPM's... but they are real close.... and because the 2004R's gear spacing... affects the "theoretical" shift recovery point... if both shifts occurred at 5600 RPM.... the calculated slip % is not the same (35.8% vs. 28.7%)

We went through the traps at 5700 RPM.... and the speed on the slip was 117.69 (again...I remember that number... but it could be slightly different (.1-.2 mph different)..... this shows the TC slip percenatage of the vigilante converter (not locked) at 16.7%..... as you go through the traps.

In summary our data shows:

35.8% slip at 3209 RPM (approx theoretical shift recovery point on 1-2)
28.7% slip at 3567 RPM (approx theoretical shift recovery point on 2-3)
16.7% slip at 4747 RPM (approx theoretical engine speed at 1/4 mile with 0 slip)


As you can see this converter is extremely inefficient when not locked IMHO. I am not sure how much ET is being sacrificed... but I know mph is being sacrificed by the inefficiency.

Our speed that we picked up between the 1/8 and the 1/4 (unlocked) was around 21 mph. When we locked up the converter after the 1/8.... we picked up just over 27 mph.....again... in our case... locking the converter was worth around .1 sec in ET reduction.... but worth approx 6 more MPH.

Maybe someone else can benefit from what we learned.
 
turbojimmy said:
On a LU converter I don't think 12.8% is high. That's what you're giving up with a lock-up converter - more slippage but the ability to lock it. When you lock you go to 0% which is good. Your ET is really a function of traction. The 120 MPH shows the car is pulling the whole way down the track. I see you have a 1.53 60' time, which is hard to explain when compared to my 11.3 @ 117 (it was actually closer to 118) with a 1.53 60' time. All I can think of is that maybe you're spinning beyond the 60' mark. My 11.3 was with a 9x11 3500 RPM LU converter. Plot your data so you can compare RPM and MPH as you go down the track. You'll be able to see if you're slipping and when, or if you're getting a big RPM drop on shifts that might slow you down.

Jim
Click to expand...

Jim I can't tell you at what mph the car was shifting but I could tell you at what rpm the car shifts and how much the rpm drops.
1st to 2nd shift 5300rpm drops to 4340rpm in 2nd.
2nd to 3rd shift 5260rpm drops to 4040rpm in 3rd but this is with locking the convertor right after the tranny shifts into 3rd.
Finish the 1/4 at 5333rpm with the tranny locked.

Marco.
T-Top 86 Grand National (61400km)
stock long block, stock suspension, 12 inch red stripe convertor (2800stall), te44, smc alk injection (95 % etanol), 25.5lbs boost,( boost spike 28 psi in 1st gear), 94 octane, hooker cat back with dyno max ultra flow muffers, 42 ½ lbs 009 injectors, turbotweak alky chip, thdp, mease 24 row IC, Ron Custom max boost brake module, MT drag radials (275/50/15) 3720lbs race weight with driver. (Torque convertor locked only after car shifted in third), rjc power plate, rjc boost controller, zeitronix wideband, HR motor mounts, comp cam 980 valve springs. Weld Drag Lites with skinnies up front, electric exhaust cut-out.
BEST E/T
60FT=1.53
1/8= 7.25
1/4= 11.48
MPH=120.82
BEST 60FT=1.52
 
evil666 said:
Jim I can't tell you at what mph the car was shifting but I could tell you at what rpm the car shifts and how much the rpm drops.
1st to 2nd shift 5300rpm drops to 4340rpm in 2nd.
2nd to 3rd shift 5260rpm drops to 4040rpm in 3rd but this is with locking the convertor right after the tranny shifts into 3rd.
Finish the 1/4 at 5333rpm with the tranny locked.

Marco.
Click to expand...

We're venturing way beyond my area of expertise here, but I think your converter might be a little tight. A 1,000 RPM drop on each shift is a lot. Blazer406 is seeing about a 600 RPM drop between shifts and I see about the same.

Here's a chart I put together comparing the 9x11 I had when I ran the 11.3 in my sig vs. the Vigilante I have now. The pink line is the RPM for the 9x11 and the yellow is the RPM for the Vigilante. You can see that the shift points are pretty much the same as is the drop in RPM (around 500). You can also see that neither converter is locking (which is a whole 'nother topic).

http://turbojimmy.4t.com/vig_vs_911.htm

Jim
 
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