Question does stall convertor rpm happen between shifts ?

[273]

Just wondering eg.. Does say a shift point at 6500 rpm drops to 4000 rpm but your stall is 5000 rpm does it drop the stall 5000 rpm or 4000 rpm or somewhere inbetween ?

 

[B3422w5]

Just wondering eg.. Does say a shift point at 6500 rpm drops to 3000-3500 rpm but your stall is 4500 rpm does it drop the stall 4500 rpm or 3000-3500 rpm or somewhere inbetween ?

rpm isn’t gonna drop remotely that much on shifts.

 

[rumblefish360]

I’d add in a lot smoking hippie but it’s not a available.

 

[fishmens67]

800- 1200 rpm drop from shift is good , so 6500rpm shift and 5000 stall drop to 5300-5500rpm at shift is good.

 

[Bewy]

I think that would be very hard to measure. Stall rpm is based on the tq that the cter sees.
You have two things happening on the shift:
- change in engine rpm due to change in gear ratio
- change in tq that the cter sees due to engine rpm change

 

[Demonx2]

My TC stalls at 5000 (8" ATI Treemaster). I shift between 6100 to 6400. When I play it back on the tach, the rpm drops to right around 5500 on each shift. Between the shift speed and where it drops to, that hugs both side of the assumed power peak pretty well.

 

[fishmens67]

I think that would be very hard to measure. Stall rpm is based on the tq that the cter sees.
You have two things happening on the shift:
- change in engine rpm due to change in gear ratio
- change in tq that the cter sees due to engine rpm change

Yep, convertor should be set for 800-1200rpm drop depending.

 

[GTX JOHN]

Our Converter Shock Stall to 5900 with a few feet of leaving the line given no
tire spin. Shifting @ 7,200 it drops to the same 5,900 on the shifts. Our changes
in ratio thou between gears are more extreme than most people.

We run some ATI convertorsalso but they are custom done for us to our specs. They told us that what we wanted was crazy but they built it and it works in the small block stockers.

I have a good friend locally that rebuildsconvertors primarily for Diesel Trucks and once we know the turbine and stater combos we need = we can duplicate them ourselves and save a ton of money and keep the set up confidential! The pieces are not had to buy.

 

[RustyRatRod]

rpm isn’t gonna drop remotely that much on shifts.

If it does, you gotta BIG problem.

 

[Demonic]

Remenber that stall is not always a hard number - it varies depending on torque input. So it will vary slightly, depending on weather you're racing-full throttle or a leisurely winding out the gears. The efficiency of the converter has a bit to do with this as well.

 

[RustyRatRod]

It can vary more than slightly from engine combo to the next.

 

[Oldmanmopar]

If you are cruising at the stall speed it will drop to the stall RPM on the shift it pulled out at. Under wide open throttle and say you shift at 7500 it will drop to its flash stall ait launched at. My 5000 dropped to 5400 unless there was tire spin. This was my experience with my car. Every engine combination and tire hook up will change the RPM.

 

[12many]

rpm isn’t gonna drop remotely that much on shifts.

Exactly. With the standard TF ratios of 2.45/1.45/1 the rpm drop could only be so much to begin with (%) and then what it actually does will vary as many have mentioned

 

[a-bodyguy]

Exactly. With the standard TF ratios of 2.45/1.45/1 the rpm drop could only be so much to begin with (%) and then what it actually does will vary as many have mentioned

View attachment 1716043528

mine was worse
After 1st Shift: 3,729 RPM. 40.82 % RPM Drop
After 2nd Shift: 4,345 RPM. 31.03 % RPM Drop
1st Gear is 63.95 MPH at 6300 RPM
2nd Gear is 108.05 MPH at 6300 RPM
3rd Gear is 156.68 MPH at 6300 RPM1

 

[12many]

With my setup and shift point of 6200 this is what rpm I roughly see:

I run a 3500 Tight so the converter is not a factor.

But I had a 4000 hard hit FTI that was actually looser with my stroker and my rpm dropped to about 4500 or so at each shift. Lots of slip each shift

 

[a-bodyguy]

With my setup and shift point of 6200 this is what rpm I roughly see:

View attachment 1716043545

I run a 3500 Tight so the converter is not a factor.

But I had a 4000 hard hit FTI that was actually looser with my stroker and my rpm dropped to about 4500 or so at each shift. Lots of slip each shift

you must have 4.10s mine was 3.23s

 

[furrystump]

Right before the shift the converter should have minimal slip %. With some exceptions. Here are my slip % after the 2-3 shift. My converter flashes to 3500.

 

[furrystump]

My motor makes peak torque at 4800 rpm. So after the shift it starts to recover and gain rpm back at 4900. It flashes 3500.

 

[B3422w5]

My motor makes peak torque at 4800 rpm. So after the shift it starts to recover and gain rpm back at 4900. It flashes 3500.

is the lower flash used to help walk it out of the gate on the small tire?

 

[furrystump]

Yes, I bumped it up from 3340 with the 727 to 3500 with the 904. I could probably go 200-300 more, but increase power is in the distant future.

 

[273]

So far it seems like a convertor stalls higher on shifts than out of the hole probably cause the engine making max ish power just before the shifts.

 

[B3422w5]

So far it seems like a convertor stalls higher on shifts than out of the hole probably cause the engine making max ish power just before the shifts.

just remember that torque, more than rpm, effects flash.
more torque higher flash

 

[furrystump]

Plus, the car is moving. My low gear set 904 lowers the flash rpm by its strict definition. Flash rpm is the highest rpm the motor obtains BEFORE the car starts to move. Because it moves easier, it lowers the flash rpm. It doesn’t matter to me, because isn’t one of the reasons to tailor flash rpm is to get the motor into the power band quicker? For me the fact it gets there quicker AND the car is moving helps me.

 

[MinnesotaMopar]

Just wondering eg.. Does say a shift point at 6500 rpm drops to 4000 rpm but your stall is 5000 rpm does it drop the stall 5000 rpm or 4000 rpm or somewhere inbetween ?

I have an 8 in converter that stalls at 5,200 in my drag car. I'll shift at 6,500 and by the math it should drop back to 3,800 from 1st to 2nd shift. But in reality it only drops back to 5,000 or so. 2nd to 3rd shift should drop back to about 4,400, but also only goes back to 5,000.

It sounded kind of weird the first time I used it, because you no longer hear the engine climbing up through the RPM. It simply goes to a high RPM and stays there the whole pass down the track, kind of like a jet engine would even though the transmission is shifting. I think this is a bit hard on the converter and puts a lot of heat into the transmission but keeps the engine higher in its power curve.

FYI I have tried a lot of different shift points from 6,000 to 7,000 and it doesn't change where the RPM drops to after the change. And since my big block has a HP peak at 6,300 it doesn't pay to rev much past that.

I have heard the better/faster racers are now using lockup torque converters to help with this slippage problem. I don't know how those behave during the upshift.

 

[Bewy]

There would be a time lag for the tach needle to register if it is a moving coil analog style tach.
So if some of the above folks are using these tachs & quoting rpm #s, the numbers are probably inaccurate.