Shift Point Calculations and Speed in Gears

The shift point calculations are based on the dynamometer run for my car. The chart shows the torque to the rear wheels as the engine torque is multiplied by the gear ratios. (I did not use the final drive gear ratio to calculate the real torque at the rear wheels. The number is a constant so the relative magnitude is correct. My thanks to Ben Colley for noticing the error.) The number at the top of the torque in each gear is the ratio of the gear being calculated.

For example, at 2000 rpm, the torque generated at the engine is 96 foot - pounds, and this gets multiplied by first gear's ratio of 3.116 : 1 to get 299 foot - pounds of torque. This should be multiplied by the final drive ratio to get the torque at the rear wheels. The result is a speed of 11 mph.

Assumptions include drive tire size of 225 x 45 x 17 and a circumfrence of 78.45 inches, resulting in 807.61 revs per mile. The final drive ratio is 4.529 : 1.

rpm	torque	3.116	1st mph	2.05	2nd mph	1.481	3rd mph	1.166	4th mph	0.916	5th mph	0.815	6th mph

2000	96	299	11	197	16	142	22	112	28	88	36	78	40
2500	103	321	13	211	20	153	28	120	35	94	45	84	50
3000	107	333	16	219	24	158	33	125	42	98	54	87	60
3500	110	343	18	226	28	163	39	128	49	101	63	90	70
4000	112	349	21	230	32	166	44	131	56	103	72	91	81
4500	112	349	24	230	36	166	50	131	63	103	81	91	91
5000	107	333	26	219	40	158	55	125	70	98	90	87	101
5500	105	327	29	215	44	156	61	122	77	96	98	86	111
6000	107	333	32	219	48	158	66	125	84	98	107	87	121
6500	114	355	34	234	52	169	72	133	91	104	116	93	131
7000	118	368	37	242	56	175	78	138	98	108	125	96	141
7500	115	358	39	236	60	170	83	134	106	105	134	94	151
8000	108	337	42	221	64	160	89	126	113	99	143	88	161
8500	91	284	45	187	68	135	94	106	120	83	152	74	171
9000	80	249	47	164	72	118	100	93	127	73	161	65	181