Converter too loose?

[TurboBob]

there is an easy way to calculate slip on a stock car.

You need DS or a PowerLogger to do this, but while driving in 3rd, tcc locked, part throttle log some data and then calculate the RPM/MPH ratio at a few spots. On my car its about 47 (stock tire height, axle ratio, speedo gear).

Then, on the log you want to check slippage on, calculate the RPM/MPH ratio in 3rd gear at several points. divide the number above by this and you will have the speed ratio across the converter. So .92 would be 92% coupled, or 8% slip.

Note: the coupling increases with RPM, so quoting X% slippage is meaningless without specifying the RPM or MPH you measured at.

Bob

 

[Lee Thompson]

.

Lee, if you don't mind....how fast are you going at the top of 3rd @ 5800 RPM? Precision gets $225 for a restall (I thought the first one was free, but evidently not) and before I spend that kind 'o money I want to see if mine is really loose. I lock at 90 MPH, which is 5300 RPM. You have a 29" tire, right? I'd have to adjust for that since I have a 28" tire.

Thanks,
Jim

From looking @ my DS files--looks like 97-98 MPH @ 5800. Not sure but I think my convertor has LOOSENED some but it is alos 5 years old.

 

[bison]

From looking @ my DS files--looks like 97-98 MPH @ 5800. Not sure but I think my convertor has LOOSENED some but it is alos 5 years old.

This sounds way too loose for that mph unless you have a high revving engine that couples around 7000.

 

[turbojimmy]

Is the trans that is currently in the car now, the same one that 9-11 converter took a dump? Was any parts re-used in the current trans from the 9-11 trans?

Billy T.
gnxtc2@aol.com

No, the trans that the 9-11 was in was replaced with a new trans - that's when I put the Vigilante in. None of the parts from the failed trans were used in the new trans.

there is an easy way to calculate slip on a stock car.

You need DS or a PowerLogger to do this, but while driving in 3rd, tcc locked, part throttle log some data and then calculate the RPM/MPH ratio at a few spots. On my car its about 47 (stock tire height, axle ratio, speedo gear).

Then, on the log you want to check slippage on, calculate the RPM/MPH ratio in 3rd gear at several points. divide the number above by this and you will have the speed ratio across the converter. So .92 would be 92% coupled, or 8% slip.

Note: the coupling increases with RPM, so quoting X% slippage is meaningless without specifying the RPM or MPH you measured at.

Bob

So is calculating the efficiency unlocked not relevant? Again, at 90 MPH, WOT I'm at 5300 RPM w/ 28" tires (stock trans and rear gear ratios). This is 43.5% slippage. I'm thinking if I have the converter 'tightened' then it will be more efficient at that RPM. Before I plunk down the $225 I want to make sure that this is what I'm going to accomplish by having it re-stalled.

From looking @ my DS files--looks like 97-98 MPH @ 5800. Not sure but I think my convertor has LOOSENED some but it is alos 5 years old.

Thanks for looking that up. At 97-98 MPH I'm at 5200 RPM with the converter 'locked'. Again, I'm at 5300 RPM when I lock at 90 MPH, the RPM drops 100-200 and then the RPM climbs slowly to about 5700 when I cross the line at around 115. So the locking is doing something. Looking at logs from 2004, the non-locking 9x11 was almost exactly the same RPM and MPH-wise though the RPM was a couple hundred lower. The car has definitely slowed down with this Vig converter - about 2-3 MPH in both the 1/8th and the 1/4. It might be too loose, I don't know but it's starting to give me a headache.

EDIT: Here's why I'm reluctant to have the Vig restalled. If you look at the chart in the link, it compares my 9x11 to my Vig. If you ignore the fact that I spun out of the hole on both runs, you can see that the RPM and MPH curve are nearly identical. The car is down on power a little vs. the 9x11 run since the MPH doesn't climb as fast, but the RPMs are within a couple hundred (max) of each other. You can see the 9x11 isn't locking at all while there is a small dip in the RPM when the Vig 'locks'. This makes me think that the converter isn't too loose, but that I just need to get it to lock??

http://www.turbojimmy.com/vig_vs_911.htm


Jim

 

[norbs]

Some more expensive ptc and ati converters, claim efficiency of under 4%, and your getting 43%? Something is wrong bigtime.

 

[Otto J]

I ran a PTC convertor in my car in BG.It resulted in a slip of 3.4%!!
(Thanks BillyT)

Just for arguement sake,I was running an ART CARR 9" and was trapping
147 and change at 7000 crossing the line
changed in the PTC Convertor That Dusty and Chris H spec'd out for Billy T
and immediatly went 151.99 at 6450 on the same tune boost.

The PTC Convertors re awesome.

I am putting one in a SS TrailerBlazer next week that has already gone 12.60
at 109 on a stock convertor with a 1.9 60ft.

 

[turbojimmy]

I ran a PTC convertor in my car in BG.It resulted in a slip of 3.4%!!
(Thanks BillyT)

Just for arguement sake,I was running an ART CARR 9" and was trapping
147 and change at 7000 crossing the line
changed in the PTC Convertor That Dusty and Chris H spec'd out for Billy T
and immediatly went 151.99 at 6450 on the same tune boost.

The PTC Convertors re awesome.

I am putting one in a SS TrailerBlazer next week that has already gone 12.60
at 109 on a stock convertor with a 1.9 60ft.

Wow. Is it the same converter that BillyT now has for sale?

But, I have a lot of $ tied up in this Vigilante converter. Maybe mine is too loose? Like I'm not getting to a high enough RPM for it to couple? My problem is that it's behaving just like the 9x11, which everyone says is a good converter too. That's why I'd like to compare a full 1/4-mile of data from someone who has a good locking converter.

If I have the Vigilante re-stalled ('tightened') this should theoretically fix it right? What is the correlation between stall speed and efficiency (or is there one). If I have it tightened would it couple better at lower RPMs? Is the trade off then less stall?

Thanks,
Jim

 

[turbojimmy]

Because I'm a dork, I plotted slippage vs. RPM and MPH in 3rd gear. Previously, I had not corrected for the MPH due to the 28" tall tires (the MPH readings would be off by .077). So at 90 MPH my slippage is 'only' 38%. The slippage calculation is wacky on the transition between 2nd and 3rd, but you can see the converter couple as RPM climbs. By the time I get to the end of the track the converter gets to 15% slippage. Check it out:
http://www.turbojimmy.com/slippage.htm

Jim

 

[norbs]

That last graph, is that locked up?

 

[TurboBob]

verify the calculations by checking it against some part throttle data (locked) which should be 0% slip

B

 

[turbojimmy]

verify the calculations by checking it against some part throttle data (locked) which should be 0% slip

B

Good idea - I'll have to do that later today (need to steal my Directscan back from my brother).

Jim

 

[turbojimmy]

Here's a file of me locking at light throttle at 60 MPH. The RPM is the primary (left side) Y axis. TPS, MPH/10 and slippage are the secondary (right side) axis. You can see when I increase the throttle (TPS is light blue) it starts to slip a little. You can also see the forumula is correct: it's only about 1% slippage once it locks (until I get on the gas, then it slips).

http://www.turbojimmy.com/lock.htm

Jim

 

[TurboBob]

it might be slipping some, remember that the MPH data in the stock ECM is heavily filtered. so it lags the RPM some. (so its not an exact science)

But its more than good enough to detect a non-locking or badly slipping converter.

Bob

 

[bison]

By the time I get to the end of the track the converter gets to 15% slippage. Check it out:
http://www.turbojimmy.com/slippage.htm

Jim

15% is not good at all up top. You have a lot to be gained with the converter locking or replacing it with a more efficient non locking unit.

 

[turbojimmy]

15% is not good at all up top. You have a lot to be gained with the converter locking or replacing it with a more efficient non locking unit.

I didn't mean to imply that 15% was good, it's just better than before I adjusted the MPH. It still needs to lock.

I'll get it sorted out - I appreciate the help.

Jim

 

[gnxtc2]

Wow. Is it the same converter that BillyT now has for sale?



Thanks,
Jim

No. The converter that Otto was talking about is my PTC converter that is going into the Turbo 400 that I picked from Dusty while in Bowling Green. Otto's converter went bad and I LENT :tongue: him my brand new converter.

The one I have for sale is a non-lock up Pro Torque somewhere around a rated 2800-3000 stall.

Each car is going to make the converter stall different.

Example: The above Pro-Torque converter was installed behind my 109 block and it was rated at 3600 stall. I built a higher HP 109 motor and used the same converter. The when the car was shifting, I was getting no rpm drop. The datalog files showed a 6000 rpm flatline, you heard the car shift but no drop. Removed the converter and freshened the trans. Had the converter re-stalled to 2800-3000rpm and never re-installed the trans/converter.

Then I went to a Turbo 400.

Billy T.
gnxtc2@aol.com

 

[bison]

No. The converter that Otto was talking about is my PTC converter that is going into the Turbo 400 that I picked from Dusty while in Bowling Green. Otto's converter went bad and I LENT :tongue: him my brand new converter.

The one I have for sale is a non-lock up Pro Torque somewhere around a rated 2800-3000 stall.

Each car is going to make the converter stall different.

Example: The above Pro-Torque converter was installed behind my 109 block and it was rated at 3600 stall. I built a higher HP 109 motor and used the same converter. The when the car was shifting, I was getting no rpm drop. The datalog files showed a 6000 rpm flatline, you heard the car shift but no drop. Removed the converter and freshened the trans. Had the converter re-stalled to 2800-3000rpm and never re-installed the trans/converter.

Then I went to a Turbo 400.

Billy T.
gnxtc2@aol.com

The converter you loaned Otto worked so well i almost couldnt believe it. But when i saw the data logs its was very clear. Ive never seen a car that quick pick up that much on a converter change. That thing pulled the engine way down where it needed to be. Ill be buying a PTC converter soon because of this.

 

[turbojimmy]

The converter you loaned Otto worked so well i almost couldnt believe it. But when i saw the data logs its was very clear. Ive never seen a car that quick pick up that much on a converter change. That thing pulled the engine way down where it needed to be. Ill be buying a PTC converter soon because of this.

Where is 'way down where it needed to be'? I don't have a super high-HP car, but I wonder what the best RPM range is for a converter to be efficiently coupled.

I sent an e-mail on this topic to Jack @ Precision, who I have been harassing for the past few weeks about my converter. I'm not blaming anyone for the problem, I'm just looking for the best means of getting it fixed. Assuming the lock-up issue can be easily resolved, I've turned my attention to the data logs and slippage at higher RPMs. Lock-up aside, I've lost 3+ MPH in the 1/8th and the 1/4 with the Vigilante converter versus the 9x11.

If I look at the data and calculate efficiency for both converters in 3rd gear, not locked, I get a lot more slippage from the Vig versus the 9x11. At 5400 RPM, for example, the 9x11 is at 12% and the Vig is at 21%. The Vig starts to couple better at higher RPMs, coming close to the 9x11 by 5700 RPM. Plotting the data, the efficiency curves are pretty much the same, but the Vigilante averages about 5% more slip across the range. I'm thinking that maybe this is where my MPH at the track as gone? Is it better to have the converter coupling more efficiently earlier - like around 5k RPM? If the answer is yes, how do I fix this? Is it a function of stall (i.e., if I pay the $225 re-stall fee can I fix it)? Or is it inherent in the converter design (i.e., there is no fix other than moving to a different converter)? Or can the transmission itself be the cause (I know it's not slipping but is there some other factor)?

Jim

 

[bison]

Where is 'way down where it needed to be'? I don't have a super high-HP car, but I wonder what the best RPM range is for a converter to be efficiently coupled.

I sent an e-mail on this topic to Jack @ Precision, who I have been harassing for the past few weeks about my converter. I'm not blaming anyone for the problem, I'm just looking for the best means of getting it fixed. Assuming the lock-up issue can be easily resolved, I've turned my attention to the data logs and slippage at higher RPMs. Lock-up aside, I've lost 3+ MPH in the 1/8th and the 1/4 with the Vigilante converter versus the 9x11.

If I look at the data and calculate efficiency for both converters in 3rd gear, not locked, I get a lot more slippage from the Vig versus the 9x11. At 5400 RPM, for example, the 9x11 is at 12% and the Vig is at 21%. The Vig starts to couple better at higher RPMs, coming close to the 9x11 by 5700 RPM. Plotting the data, the efficiency curves are pretty much the same, but the Vigilante averages about 5% more slip across the range. I'm thinking that maybe this is where my MPH at the track as gone? Is it better to have the converter coupling more efficiently earlier - like around 5k RPM? If the answer is yes, how do I fix this? Is it a function of stall (i.e., if I pay the $225 re-stall fee can I fix it)? Or is it inherent in the converter design (i.e., there is no fix other than moving to a different converter)? Or can the transmission itself be the cause (I know it's not slipping but is there some other factor)?

Jim

Way down where it should have been in Otto's instance was between 6000 and crossing the line at about 6600 rpm and trapping 151.9mph. Previously it was hitting 7100 crossing the line with 147mph trap speed. His slip was around 4%.

As far as your converter goes it sounds like its giving up too much down low and then to compound the problem its not locking either. The torque of the engine, gearing, road speed and converter design all have an impact on the coupling speed and the efficiency. In a build like the one in my sig the converter needs to be coupling well by 5800. Later is hurting my mph. My slip was around 14% at 6100 so i know i can get a lot more out of it with a better converter. If you cant get your to lock up then you may need another converter. I doubt its the trans because the oil would be toast after one WOT pass with it slipping at the directs.

 

[TurboBob]

Slip calculations

So, how is everyone calculating their converter slip?

If you are using the TCI calculator, be sure to verify it using some highway cruise data, locked. It only works for me with a tire size of 24.45"....

See below for something I have been experimenting with...... CS% is "Converter Slip %"