One thing leads to another... mean 318?
The only missing info is torque converter slippage. Make it zero for now like a manual, due to newer converters being very very good these days.
All my calcs use 5% for slippage at peak horsepower; I usually state it somewhere.
I think slippage would be foolhardy to incorporate most anywhere else, because it would vary with the ratio of power input, to the resistance to change in acceleration everywhere on the output side, just confusing thechit out of everything....... IMO.
At idle, obviously, the slippage is horrendous cuz the car ain't even moving,lol.
I only use slippage for WOT rpm estimations,
and for cruise rpm estimations where I almost always include the proviso; "@zero-slip". I have to use it in my examples because 5% at 6000 is 300 rpm, an easy to spot fubar if I forget it.
At cruising speed the slip can go either way, so I just say @zero-slip. 5% at 2700 is 135 rpm; so, if the car is geared for 65=2700, and the engine is working hard, the slip might be as high as 2835, whereas if the engine is loafing, it could be less than 2700. Zero-slip just saves me typing all thatchit. Besides; 5% at max-power might not be 5% at cruise. Check your TC; brake stall it at 65mph to see what the tack says. Then lift off at 65 and catch the Rs before the speed drops. Now go compare those to the calculated rpm at 65 using your known tire roll-out and various gears. You might find the slippage is higher than 5%... or perhaps less than 5%..
Part of the TC ratio is due to the rise in rpm, where the engine inputs slightly more torque, than at the non-slipping value. So it's already in the ratio.
I like automatics because, they have the automatically controlled extra "gear", in the TC, which has been reported as up to 2/1. This works out to a split of .50.
But typically I read about 1.8 as the norm or 1/1.8=.56%
The splits in a 727/904 are .59 and .69. If you have a lock up, you can expect 200 to 300 drop there so the equivalent of 7 to 10%, or say .085. when you line those all up I get .56-.59-.69-.085, that's 4 splits so 5 ratios.
Lets assemble that into a working model,with 3.23 rear gears, all at WOT.
At zero mph, the starter gear is 3.23x2.45x1.8=
14.24,
about 60 ft out, the TC ratio has dropped to maybe 1.4, so, 3.23x2.45x1.4=
11.08 .
At the 1-2 shift, the TC might be down to 1.3 so;
3.23x1.45x1.3=
6.09
At the 2-3 shift, the TC might be down to 1.2, so 3.23x1.0x1.2=
3.88
In loc up the TC is bypassed so; 3.23x1.0=
3.23 .
Setting them a-row we get;
14.24-11.08-6.09-3.88-3.23; count them;
I get 5.
Please keep in mind, It is impossible for me to know the actual TC ratios in your combo, so I liberally say; might, maybe, and about. This does not change the fact that the TC is automatically adjusting it's internal hydraulic coupling ratio continuously with power input and roadspeed, the results of which are still 5 ratios!
If you were watching, you have seen the 3.88 to 3.23 transition. The 3.88 is at WOT, don't forget, so the TC is multiplying in there. Whereas the 3.23/loc-up you would not call for at WOT, so is straight thru. Furthermore to be at WOT in Drive,with 3.23s, you are really moving, (I mean 4000 would be ~95mph) and so, as a streeter, you will rarely be seeing that 3.88.
Now if you had a mind to; you could plot your torque or power or popsicle sticks. at say every 4 mph on a graph, running thu those ratios, and see what is getting to the pavement.
Then you could do it over, but with a different gear. See note 1
If you get tirespin, you can't use any of those numbers because the TC automatically readjusts the internal ratio down towards it's smallest ratio. So for instance at zero mph the ratio I used was 14.24. But if she spins, this is automatically gonna drop towards 11.08 or even towards 8.31 (2.45x3.23x1.05), this is why an under-powered combo, stops spinning right away, not enough torque to sustain the spin, with the rapidly dropping internal TC ratio.
I suppose you could think of a TC as a CVT, that continuously varies it's internal ratio somewhere between it's min/max numbers that generally fall between 1.8 and 1.1 at WOT. The ratio is greatest at zero mph and WOT, and least at Part-Throttle and cruise. and falls with decreasing rate of acceleration, and increases with increasing power input. It's a fabulous invention in any case.
Note 1
If you do that often enough, you will see a trend. I discovered that it matters not a hoot from the torque peak in first gear (with no tirespin), to the powerpeak in top gear...... except for two times; namely thru the traps, and from stall to the torque peak in first gear. All of the rest of the time you are just rearranging the numbers. Try it for yourself and see. It is rare that you can optimize both ends, and I wanna say that peak power thru the traps is more important than stall to the torque peak in first,but not being a racer, I don't know that that isn't an over-simplification. What I do know is that the two times I tracked my car it was optimized for neither, and it still trapped really well.
