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Question for: PTC converter users

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With your combo you should be able to pull a 10.9 with a 2.0 60ft without much problem, assuming you feed it a little boost.
 
Not entirely true.

Below the point where the converter 'couples' part of the 'slippage' is generating torque multiplication.

The only way to know the true efficiency is with a torque converter dyno.

You can still get a converter slip number without a converter dyno. You need a driveshaft speed sensor. There is no more accurate way to do so. The slip is likely 40-50% at 5000 rpm then it couples and winds up being around 5% or better up top.
 
Thanks bison, I appreciate your input. Here is the problem IMO, My car makes a ton of power between 4000-5000 rpm. If the converter is not coupled hard to the trans at that point, It just dumping the power off as heat.

The power is most likely not being dumped off as heat. If you had an accelerometer you would see that the g force is usually much higher at the highest slip % on a ratio change as Bob stated because of the torque multiplication in the converter. If your engine is making the most power at 4000-5000 you have way more turbo than you need. The 70GTQ will gain nothing over a 6265 under 5500rpm unless you are running 30+psi boost. As Dusty said you would have a hell of a time getting the 70GTQ to come on with a converter that is dropping to 4000 on shifts at full boost. The turbo needs to see about 3600 just to get going. My old combo dropped off drastically if my engine went below 4800 on a shift with the 212 and 66 s tirm with race ported heads. The closer to 5100 it got at full power on a ratio change the quicker it went. What is your cam?
 
The power is most likely not being dumped off as heat. If you had an accelerometer you would see that the g force is usually much higher at the highest slip %.

Very true. These converters were tested and developed using G-meters in the racepak system. I'm not concerned what the rpm trace is doing, compared to the actual acceleration of the car. Lots of Pro-mods will actually loose rpm from the gear change to the finish line as the converter continually couples the engine and holds it in it's power band.

You can put a loose converter in a car and have the rpm climb quickly but acclerate the car slower. A tighter converter will hold the rpm at a lower level before it starts it's trend upwards.
 
You can still get a converter slip number without a converter dyno. You need a driveshaft speed sensor. There is no more accurate way to do so. The slip is likely 40-50% at 5000 rpm then it couples and winds up being around 5% or better up top.

he has a driveshaft speed sensor...... (the VSS) so the speed differential is easy to see.

But below the coupling point you can't really tell how much of the speed difference is due to efficiency and how much is due to the torque multiplication.

I think we are saying the same thing, but with different words.

Bob
 
I'm not concerned what the rpm trace is doing, compared to the actual acceleration of the car.
Me too. More average g force = a quicker car. Im at about .7 g's@90mph at 750-800hp. Id like to see the data from your 181mph pass Dusty. Id bet its over .8g at the eighth trap:eek:
 
Alrighty fellas, here is what we been waiting for. Things feel a little better tonight. Tell you what, 5800 rpm is the end of the line. :eek:
 

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Alrighty fellas, here is what we been waiting for. Things feel a little better tonight. Tell you what, 5800 rpm is the end of the line. :eek:

Your MAF signal is a little wobbly in spots. You still running that blow-thru setup?

The RPM's drop to 5000 on the shift. Stay flat momentarily, then start rising.

Looks all good to me.

Bob
 
Your MAF signal is a little wobbly in spots. You still running that blow-thru setup?

The RPM's drop to 5000 on the shift. Stay flat momentarily, then start rising.

Looks all good to me.

Bob

I noticed thar too. I am still using ls1 maf blow through. I'm going to hotwire it and see if it helps.
 
The other thing to look at is overall rpm. If it never climbs over 5200, your springs are shot. I never ran less than 981's on a flat tappet cam because the spring pressure after several heat cycles wasn't enough for boost and rpm. I sent 3 boxes of 981's back when I did my last flat tappet motor. Very few of the 3 boxes were close to the advertised spec. Had I not checked the spring pressure myself before putting the engine together, I would have had rpm issues.

I started using a Sealed Power spring from the local parts store. They all checked between 100-110# at 1.7 installed height.

dusty any chance you have that part # on those springs? the sealed power ones. thank you very much
 
Alrighty fellas, here is what we been waiting for. Things feel a little better tonight. Tell you what, 5800 rpm is the end of the line. :eek:

You might want to check your TPS. In that log it never got above 3.66 volts. It should be around 4.7 or so. :eek:
 
The PTC 9.5 is definately a much different converter than anything I have used before. It's the first time I have seen rpm drop 1-2 seconds after the 2nd/3rd shift. Pretty cool! I concur with Bison on the g-force number, at about 20psi I was seeing about .67 G's.
 
The PTC 9.5 is definately a much different converter than anything I have used before. It's the first time I have seen rpm drop 1-2 seconds after the 2nd/3rd shift. Pretty cool! I concur with Bison on the g-force number, at about 20psi I was seeing about .67 G's.

At what speed?
 
Not sure, it (my DPIC gauge) may have only measured maximum at the time. Have to wait for next season to try it again I guess.
 
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