Torque Convertors

[Scoobum]

Just my 2 cents, but I've come to the conclusion that torque convertors are the most important piece of the puzzle with these cars.

LU Convertors. The data I have on the best 3 are as follows. Norbs ran a 2800 Precision multidisc...an d the slip came in at 3 percent. He went 10.3 at 134.

Grumpy went 9.98 at 138 with a 9/11. No slip numbers...but the MPH tells me it was coupling well.

Jasons convertor slip was 7.3 with Jakes convertor.

NL convertors. Our very own Bird...and Rich is one of the nicest guys going went 9.69 at 138 with an AC 19930. Joe went low 10's for years with an AC 19930 in the low 130's. When I ran the 1/4 I'd run 11.5 all day at 120-121 with the slip checking in at 8.9 percent with my 16930. Tons of data out there on the PTC race convertors. They speak for themselves.

Brandon went 11.01 at 123 with an off the shelf 2800 PTC NL on 20 PSI...pump gas...109...wi th a 6131...and TA heads. He's quietly one of our brightest stars.

My own data shows I have to have this convertor flash to 3950-3975 to garner a 1.5 launch. Murph mentioned in his thread that the convertor he was running flashed to 39xx to achieve a 1.5 launch. My theory is the convertor has to flash fairly high to get these car moving...due to the weight. It'd be interesting to get more data to see the RPM and short time from other members.

RPM drop. Steve has mentioned these engines work within a small window in regards to RPM. You need a convertor with enuf RPM drop at the shift points to keep the engine in its 'wheelhouse'. This convertor is giving me a 600 RPM drop...keeping the RPM's between 5200-5800...right where this cam/heads work best. Too much RPM drop...and you'll drag the engine down...too little...and you'll just be buzzing the engine. Norbs lightened this governor...and it shifts at 5800...and I hit the 1/8th mile traps at 5500 and the 1/4 traps at 6000.

In GENERAL...a looser convertor will get you off the line quicker...but will slip more at the top of the track. This AC 16930 is an absolute dog off the line on Erics low gear default fuel and timing defaults. Add low gear timing...and drag the low gear 02's below 800...and it's a whole different animal. I'd rather have a tighter convertor that will couple well at the top of the track...and tune it in to get it to launch.

I see guys complaining of their car not launching well...but the convertor seems well matched for the turbo. Their instant solution is to go with a looser convertor...wh en I'm betting tuning could wake it up.

Once again...just my 2 cents.

[Steve Wood]

I will add another criteria.  If it costs less than $900, it probably is not worth installing....

[TurboCajun]

here is a log from a 10.99 pass, PTC 10" 3000 LU. dropping 400rpm at shift

[reality]

https://www.svtperformance.com/forums/threads/torque-converter-stall-torque-ratio-str-guide.1113661/


Higher stall doesn't have to mean less efficient. Str is only 1 part of the puzzle.


Off the shelf converters are a compromise.

[Steve Wood]

here is a log from a 10.99 pass, PTC 10" 3000 LU. dropping 400rpm at shift

Keith, is the speedometer showing the correct speed?  Or is off about 8% because you have tall tires and did not change the gear in the speedo?  Looks about right to me

[Steve Wood]

hmm, that rpm should be about 146 mph.  Given the time, I am going to guess that the converter was not locked?  And that the speed of 125 is the correct speed ?  Looks like about 14% slip if that is the case which is not bad for a LU converter that is unlocked.

Not enuf info to make a good guess from   I guess that the speed is correct because the car ran 10.99 which would be hard to be that slow if the mph was actually 135 mph after correcting for tire size.

[TurboCajun]

I did change the gear but i still think that it may be about 2 mph off

[Steve Wood]

It may be on top end. It's hard to compare speedometer speed with trap speed.    Was the converter locked?

What was the speed on the slip?

[TurboCajun]

conv was not locked and the speed on the slip was 121.58

[Steve Wood]

That means the speedometer is pretty darned close...You can check it with a gps speedometer on your phone...but, the timing slip time is an average speed over the 66' trap before the line so the actually speed at the moment you cross the line is a bit higher.  I picked 125 which would have been after you crossed the line from the spot immediately before you lifted.  You were probably doing more like 123 at the line, I would guess

[Steve Wood]

Slip is about what I would guess for a good lock up converter that is not locked.  You might gain a couple of tenths if you locked it around 85-90 mph

[good2win22]

My 10.98 pass at 125.96


RPM drop 1-2 shift 6030 to 5066 = 964
RPM drop 2-3 shift 5714 to 4818 = 896
I am locking the converter at 90 mph. RPM drop 5256 to 4818 = 438


I let off and RPM was 5553


I guess I need to lock it just a little bit later in the run. But she is still pulling hard

[Steve Wood]

Converter still looks a bit tight to me.

I forget, are you still spraying alky?

[good2win22]

Converter still looks a bit tight to me.

I forget, are you still spraying alky?

I agree Steve. I would like to have the converter I had in my white T. It was a tad more loose on the bottom end. Of course, I have no specs on it. It was Jake built too.


Yes sir, spraying that alky

[Steve Wood]

That definitely makes the tuning a bit complicated...