Shift Points

[Goob]

i am confused what does stall speed have to do with shift points?

Nothing, but it does matter what it comes back to after the shift.

If your spread is too wide, the car will be inconsistent, because you are taking the engine in and out of it's preferred power band.

according to what you are saying your engine only has 1000 rpm of useable power band?

Well, more like 1300, but yeah. How much do you need?

With a too tight converter (one that stalls at or near peak torque), it is possible to have a slightly quicker ET, but it will be inconsistent, and you will more likely lose performance from killing the engine on the gear changes.....

Steve is a little behind the times.......HP will accelerate a vehicle more smoothly, quickly, and with better consistency than torque will, even when you consider that torque is the same as HP, just measured differently.
HP is a mathematical calculation of torque over a timed period.

Keeping the launch and shifts at or near torque peak is for STICK cars, NOT automatic trans equipped cars......the torque converter provides all the torque multiplication that you need.

For a light to medium weight (3200#) vehicle, the ideal converter stall will be 300-500 RPM over your dyno torque peak, with a drop of no more than 600-700 RPM's on the shifts.

Light cars that run consistent will have a stall RPM about 400-600 under the shift point......

While not the quickest combination I ever had in my car, I used a borrowed converter that stalled 6000, shifted it at 6400, and collected my checks at the tower.....

Are we cornfused yet?

 

[Anonymous]

"Keeping the launch and shifts at or near torque peak is for STICK cars, NOT automatic trans equipped cars......the torque converter provides all the torque multiplication that you need. "


Lol... Dave, I highly suggest you check around with engine builders and trans companies and see what they tell you as well. I said the shift point should be a couple hundred over the HP peak, not the torque peak. As to stall speed... a Glide car responds well to stall speed 300-500 over the peak torque point. Marv Ripes at A-1 prefers to set stall speed at the point where the engine is 40-50 HP shy of the HP peak. Shift points normally work well just over the HP peak by a couple hundred, but you need to test to find the sweet spot. A 3-speed auto can use a little less stall speed in some cases with its narrower RPM drop between gears vs a Glide. Shift points IMO should still be just over the peak HP. I'm not 'behind the times' here, trust me on that.

 

[GreenDragginBu]

No Goob, not confused yet...I enjoy reading your posts.

But on the narrow powerband thing...There is a video (or was?) of 5doors wagon. and once it launches the rpms dont drop back much at all, at the shifts...

Stays right where it needs to be...

 

[Goob]

A 3-speed auto can use a little less stall speed in some cases with its narrower RPM drop between gears vs a Glide.

Oh, so the 2.48:1 (TH400) or 2.52 (TH350) drop to the 1.48:1 (TH400) in second range is a narrower drop in RPM than it is from 1.76:1 to 1.00:1 (Pukeglitch) ??????

News to me!!! I guess I'M the one behind the times....

I love ya Steve, but I've gathered my information on the track, not talking to everyone and their brother. A-B-A- testing Steve.
Comp Eliminator racers don't count in this discussion.

Ask Edmond Richardson what his stall and shift points are, OR, I can just tell you now.....6400 stall, 6800 shift.
'Nuff said from me.

 

[Anonymous]

Lol Dave. A shining example of wrong stall speed was a local guy's Super Stock style chassised Firebird with a small block and Glide in it. I changed the converter to the proper stall (500 over the torque peak) along with going to a 1.96 low from his 1.76 and he dropped from a 10.72 to a 10.21. A narrower RPM band is fine. But, if you give up usable torque it will run slower. I've seen it many times. The only time when I suggest going every bit of 500 over the peak (and more) is for an 1/8 mile only car. I'm cool with you, you know that! Seriously... check around and see what others say. As to Comp stuff... they run in a narrower RPM band than most, but still subscribe to the same stall speed thoughts. I had a lengthy chat with Darin Morgan a few years ago when a pal was struggling with a B/AA door car. Darin flat out asked if my pal wanted to know the exact engine/converter combo that Slavinski had run and set the record with before getting out of Comp. Darin again told me they generally see engines running the quickest and most consistent with stall 500 over the peak with a Glide. I still love ya man...

 

[Goob]

I agreed that you can leave some ET on the table, but you will suffer in consistency with the stall at closer to peak torque......in my case, it did not work out that way....when I went from 4600 on the stall to 5200, I not only went quicker and faster, it was much more consistent between the 60' and 330' timers, with both the 'glides and the TH-400.

Speaking of Comp Eliminator, I have a little inside with Jaclyn Gebhardt's crew, and she is the only A/ED out there with a 3 speed, and consistently qualifies in the top 3.......hmmmmmm.

Setting up for a difference between 1/8th and 1/4 mile is also a leftover of the stick car days.....400 RPM difference between the 1/8th and 1/4 doesn't warrant a gear change in my book, but I'm a bracket racer. I trap at 6000 in the 1/8th, 6400 at the 1/4, now how does the car gain 23 MPH with only 400 RPM difference?
Modern torque converter technology.

I still can't find the need to call a half dozen people to argue about what I already learned..and comparing S/S and Comp Elim rides to us poor ol' Malibu guys is like setting a table to slop the hogs.

Do what makes ya happy.....

 

[Anonymous]

so maybe this is a dumb question. but the car i have now only has 4 passes on it and that is with 2 different trannys... long story. and the cars i ran before this were slower by about a second and a half.

so you are talking about launching at 6000 shifting at 6500 (what is that like 60 foot mark?) and then running the rest of the 1/4 and not using more that 1300-1500 rpm?

how is that possible?

so yes i am thouroughly confused

BTW: everything I have ever heard and or read said your torque peak has nothing to do with shift points??

 

[Anonymous]

maybe a better question would be:: how much rpm drop between gear changes is acceptable and or wanted?

I am currently building my th350 to go back behind my ride (so it will last longer than 1 run)

My reasoning for this: if you watch the fast successful super stockers and eleminators are starting to make the move to 3 spds.

I assume this is to keep the engine in the useable power range better, which makes all sort of sense to me.

 

[Goob]

so maybe this is a dumb question. but the car i have now only has 4 passes on it and that is with 2 different trannys... long story. and the cars i ran before this were slower by about a second and a half.

so you are talking about launching at 6000 shifting at 6500 (what is that like 60 foot mark?) and then running the rest of the 1/4 and not using more that 1300-1500 rpm?

how is that possible?

so yes i am thouroughly confused

BTW: everything I have ever heard and or read said your torque peak has nothing to do with shift points??

Well, I should have this data ingrained in my head, but It's a little past the 60' timers before any shifts occur, with either the glide or the TH400, seems it was near 2.5 + seconds out with the glide, about 1.7 out with the Turbo, but I'd have to review the last run to verify.....
It's a rather odd feeling as the car is accelerating like a bat outa hades but the tach is rather lazy, the torque converter is doing all the work.

Think of launching at the torque peak as hitting the car with a hammer, it moves real quick, then lays over and re-accelerates, when you get up nearer the HP peak, it's more like a steady pull from a come-a-long, but anyway, yes, I've left at 6000, shifted at 6400, and finished at 6000, couldn't feel a thing, but the time slips and pictures don't lie......it was hauling serious azz, and was very, very consistent over the course of 17 runs down the same track, gagged the 1.82 gear set on the 19th launch.

remember I've only got a 4.11 rear gear and 30" tall slicks too....uh yeah, I have a 2.10 low, 1.40 2nd range gear set in my TH400 too.

Put it up in the HP curve on the converter and let it eat man!


Torque is a physical measurement of the actual force required to rotate a certain load, in timed increments, at 5250 RPM's, the torque measurement becomes a mathematical conversion of the engine ability to continue accelerating that load over a timed period....in theory, a properly programmed dyno sheet should have the torque and HP curve meeting at 5250 RPM, unless the readings or load application were incorrect, or the engine combination is so far out in left field it's out of range.

My rule of thumb for a bracket car is to get your stall at least 600-700 above your peak torque, some folks still say you need at least 1500 to your shift point with a heavy car, but it just ain't true, I'm happy with 500-800 RPM's from stall to shift even in a heavier vehicle, 400 is plenty for a light vehicle like a dragster, all of this ASSuming that your engine combination has about a 1700-2200 RPM power band, or narrower.
I've been told that a 700 RPM drop on the shift is acceptable, I've got 400 drop and I'm real happy with it. If I could up my stall another 300 and still have my 5950 at the shifts, I'd like it better.


I've had everything from a 700R4 with 5.14 rear gears to a 1.76 'glide with 4.11's in this same car, with mostly the same engines, after 2500+ time slips, I'm sticking with my 2.10 low gear TH-400 and Opel style 8" converter, and low RPM flat tappet smallblocks.

But, I'm a bracket racer, and only .12 away from having to add a certified cage and license, and full monkey suit to race, so I'm not looking for any extra performance, I'd trade ET for some MPH right now......

 

[malibuguy]

my car footbrakes 3500rpm, & flashes up to 4300...if i shift lower then 6500, i run a slower ET, seriously


according to desktop dyno, i start losing power at 6000...so it sounds about right then,....