Simple Gear Calc program - Fuelly Forums

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Old 04-03-2008, 01:26 PM   #1
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Simple Gear Calc program

I love playing with these to find the best gearing solution for better mileage.
I found this on a F-body web site. Any car will work. It asks for your tire size, final ratio, Max RPM, and transmission gear ratios.
Then shows you the rpms in 100's what speed you would be running in each gear. I was comteplating doing a gear change for better highway mileage in my Volvo 960. Stock the car came with 3.73 rear gears. When I played with 3.54 and 3.31 rear gear sets I found that the 3.54's were the best option of the two. The 3.54 would drop the rpms by about 100 rpms at 65 mph. The 3.31's would drop the rpms by 200. Two hundred rpms brings the rpms down too far to be a benefit.

BTW every time you click calculate it opens up a new spread sheet below the one before it. So if you change something and hit calculate you can compare the changes with the previous calculation by scrolling up or down on the page.

Gear Calculator/
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Old 04-03-2008, 09:05 PM   #2
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ALS -

Thanks for the URL, another tool in my toolbelt. Now I have to hunt up my gear ratios for my Saturn and plug them in. I am not sure where I can get my axle ratio. Gotta look around.

Does the spreadsheet remind you of the numbers you might plug into a BSFC (Brake Specific Fuel Consumption) map?

CarloSW2
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Old 04-04-2008, 08:30 AM   #3
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Here you go I'll save you some time.
1999SaturnSW specs
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Old 04-04-2008, 12:13 PM   #4
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ALS -

Thanks! I just plugged in the numbers. I used the "6th Gear"
column to plug in my SOHC "economy" 5th gear, and I input my
one-size-larger-than-stock 195-65/15 tires.

What's really fun is that now I will be able to reference the
chart when I am driving.

Code:
1999 SATURN SW1 / SW2  (Station Wagons)

TRANSMISSIONS  5-Speed Manual          4-Speed Automatic
               L4 SOHC      L4 DOHC    L4 SOHC     L4 DOHC
Gear Ratios    1st 3.25     3.25       2.53        2.53
               2nd 1.95     1.95       1.27        1.56
               3rd 1.17     1.42       0.81        1.03
               4th 0.81     1.03       0.60        0.70
               5th 0.61     0.73       ----        ----
           Reverse 2.92     2.92       1.91        1.91
Final Drive Ratios 4.06     4.06       4.06        4.06


RPM     1st     2nd     3rd     4th     5th     5th
                                       (DOHC)  (SOHC)
500	3	5	6	9	13	15
600	3	6	8	11	15	18
700	4	7	9	12	18	21
800	5	8	10	14	20	24
900	5	8	12	16	23	27
1000	6	9	13	18	25	30
1100	6	10	14	20	28	33
1200	7	11	15	21	30	36
1300	7	12	17	23	33	39
1400	8	13	18	25	35	42
1500	8	14	19	27	38	45
1600	9	15	21	28	40	48
1700	10	16	22	30	43	51
1800	10	17	23	32	45	54
1900	11	18	24	34	48	57
2000	11	19	26	36	50	60
2100	12	20	27	37	53	63
2200	12	21	28	39	55	66
2300	13	22	30	41	58	69
2400	14	23	31	43	60	72
2500	14	23	32	44	63	75
2600	15	24	34	46	65	78
2700	15	25	35	48	68	81
2800	16	26	36	50	70	84
2900	16	27	37	52	73	87
3000	17	28	39	53	75	90
3100	17	29	40	55	78	93
3200	18	30	41	57	80	96
3300	19	31	43	59	83	99
3400	19	32	44	60	85	102
3500	20	33	45	62	88	105
3600	20	34	46	64	90	108
3700	21	35	48	66	93	111
3800	21	36	49	68	95	114
3900	22	37	50	69	98	117
4000	23	38	52	71	100	120
4100	23	38	53	73	103	123
4200	24	39	54	75	105	126
4300	24	40	55	76	108	129
4400	25	41	57	78	110	132
4500	25	42	58	80	113	135
4600	26	43	59	82	115	138
4700	26	44	61	84	118	141
4800	27	45	62	85	120	144
4900	28	46	63	87	123	147
5000	28	47	64	89	125	150
5100	29	48	66	91	128	153
5200	29	49	67	92	130	156
5300	30	50	68	94	133	159
5400	30	51	70	96	135	162
5500	31	52	71	98	138	165
5600	32	53	72	100	140	168
5700	32	54	73	101	143	171
5800	33	54	75	103	145	174
5900	33	55	76	105	148	177
6000	34	56	77	107	150	180
CarloSW2
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