Converter too loose?

[turbojimmy]

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 %"

I am using the formula provided on the TCI page under the calculator itself. By 'only works', do you mean that you're getting a number other than 0% when you calculate the slippage when locked? It seemed to work okay for me with both 26" and 28" tire heights (after correcting the MPH values to account for the taller tire).

Jim

 

[TurboBob]

I am using the formula provided on the TCI page under the calculator itself. By 'only works', do you mean that you're getting a number other than 0% when you calculate the slippage when locked? It seemed to work okay for me with both 26" and 28" tire heights (after correcting the MPH values to account for the taller tire).

Jim

If you enter cruise data with the converter locked it should read very close to 0%, right? The TCI page works fine, but if we all want to compare slip data, we should make sure our data is accurate.

The stuff I am playing with in PLC reads <1% or so cruising. Limited by the MPH resolution in the stock ECM. Also, the MPH calculation in the stock ECM is heavily filtered (laggy) which contributes to error.

The bottom line is there are several threads/post stating converter slip for xxx converter. I want to make sure we are all using valid data......

Converter slip is highly dependent on RPM and torque as well. at 4500 RPM mine is slipping 26%..... (tight Yank 10")

Bob

 

[turbojimmy]

If you enter cruise data with the converter locked it should read very close to 0%, right? The TCI page works fine, but if we all want to compare slip data, we should make sure our data is accurate.

The stuff I am playing with in PLC reads <1% or so cruising. Limited by the MPH resolution in the stock ECM. Also, the MPH calculation in the stock ECM is heavily filtered (laggy) which contributes to error.

The bottom line is there are several threads/post stating converter slip for xxx converter. I want to make sure we are all using valid data......

Converter slip is highly dependent on RPM and torque as well. at 4500 RPM mine is slipping 26%..... (tight Yank 10")

Bob

Yes, it should read very close to 0% locked. I just wanted to make sure that's what you meant when you said it only 'works' with a tire height of 24.45". I haven't used the calculator, I just stole the formula

The formula seems to work in that I get close to 0% slip when the converter is locked. There might be something wacky with their tool, but the formula works okay in Excel. Here is a part-throttle lock file:

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

If you're getting 26% slip @ 4500 on a tight converter, then maybe my 25% @ 5100 isn't so bad with a loose converter?

Jim

 

[norbs]

If you are getting 26%, something is wrong or you are well below your stall ratingof that converter? Whats the rpm@traps with that tight yank 10"? I am picking up a ptc converter and don;t want to see anything over 5% through the traps. The Art carr 9" converteri heard slip 8-10% at the top. I will have some datalogs for you to look over in the future.

 

[bison]

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"....

In the instance i referred to in OTTO J's car he used the driveshaft rpm vs engine rpm. He had a reluctor that indicated ds rpm for easy comparisons which eliminated any error due to tire growth etc. All info was taken from a data log on the XFI. I have not had a problem calculating slip on TCI's site. Mine came out to 13-14% at 132 mph with the build in my sig at 27 psi.

 

[TurboBob]

When you use DS or PL data to calculate slip it is based on the transmission output shaft, and as such does not suffer from tire growth problems. Once its checked against locked-up data its pretty much right on. (bouncy speedo cables can mess with it...)

 

[lazaris]

The formula for slip cannot take into account for tire growth. Also what you enter for your tire size. Make sure you actually measure the circumfrance.

 

[bison]

When you use DS or PL data to calculate slip it is based on the transmission output shaft, and as such does not suffer from tire growth problems. Once its checked against locked-up data its pretty much right on. (bouncy speedo cables can mess with it...)

Thats a shorter version of what i typed.

 

[bison]

The formula for slip cannot take into account for tire growth. Also what you enter for your tire size. Make sure you actually measure the circumfrance.

You have to estimate the growth if you use slicks.

 

[TurboBob]

You have to estimate the growth if you use slicks.

only if you are using trap/radar/GPS speed. ECM speed doesn't care what the tire size actually is.

B

 

[norbs]

If the tire grows the faster you go, that means less gear. That means your slippage numbers actually indicate higher than they actually are in the real world, maybe 1 or 2%?

 

[TurboBob]

If the tire grows the faster you go, that means less gear. That means your slippage numbers actually indicate higher than they actually are in the real world, maybe 1 or 2%?

But the speedo is measuring the tailshaft speed, which can't tell if the tire is changing size.....

Bob

 

[lazaris]

Bob,

The larger tire acts like taking gear out of the car. This will show on the tail shaft speed the same way gear ratio will.

 

[ijames]

Bob,

The larger tire acts like taking gear out of the car. This will show on the tail shaft speed the same way gear ratio will.

In terms of ecm speed vs true road speed, yes. In terms of theoretical engine rpm calculated from tailshaft speed, which is what is needed for converter slippage, no, the tire size change doesn't matter when you use the ecm speed. It does matter, as Bob said, if you are using GPS or radar gun or timed-distance measures to get true road speed because you then have to know the tire size to calculate the theoretical engine rpm for that speed. You guys are both right, you are just talking about different things .

 

[norbs]

Your speedometer is calibrated based on the speedo gear in the trans. If your tires are growing at top end, you speedo will be out, because the speedo is based on gear ratio and a fixed tire diameter. COrrect?

 

[lazaris]

Correct.

 

[bison]

Your speedometer is calibrated based on the speedo gear in the trans. If your tires are growing at top end, you speedo will be out, because the speedo is based on gear ratio and a fixed tire diameter. COrrect?

Correct but were trying to calculate slip %. Knowing the slip % and the indicated mph and actual mph are usually 2 different things. The slip changes quite a bit throughout the run so its useful to know the mph and the slip % at that mph throughout the run.The formulas those calcs use are assuming a constant tire height which will create a small error in calculating the actual slip. Knowing the ds speed eliminates the error in slip % but there is no way to get actual mph unless you use something to measure it like TurboBob stated. The trap method is an average over a distance. The GPS/radar are actual numbers.

 

[turbojimmy]

The formulas those calcs use are assuming a constant tire height which will create a small error in calculating the actual slip. Knowing the ds speed eliminates the error in slip % but there is no way to get actual mph unless you use something to measure it like TurboBob stated. The trap method is an average over a distance. The GPS/radar are actual numbers.

Right - you need something external to the drivetrain to measure MPH. But since typically we don't have that we need to live with the slight error from tire growth.

People also need to make sure that if they are using the TCI web tool or using TCI's formula they need to adjust the MPH part of the equation to account for tire height. Because the formula uses both tire height and MPH you need to make sure they are accurately correlated. The VSS is reporting your MPH assuming you have a 26" tall tire. If you're using a tire taller than 26" you're slip %age is going to come out higher than actual because with a taller tire the VSS is reporting an erroneous lower speed. You can apply a factor to the MPH to correct it (it gets you close enough for government work, as my old boss used to say).

Jim

 

[norbs]

Going back to the original point of this thread, your tranny or converter is slipping, what do you intend to do? I'd like to see you get the slippage down to 5% unlocked and maybe 1% locked, possible maybe ?

 

[turbojimmy]

Going back to the original point of this thread, your tranny or converter is slipping, what do you intend to do? I'd like to see you get the slippage down to 5% unlocked and maybe 1% locked, possible maybe ?

I'm going to take the trans out (using my new trans jack adaptor that no one thinks will work) and bring it to CK to see what's what. At the same time I'm going to send the converter back to Vigilante for a look see. It's gotta be one or the other, either way I'll get to the bottom of it.

Jim