930 w/ stock 4 speed, what RPM @ 70 & 80 miles per hour
05-12-2006, 09:56 PM
#1
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930 w/ stock 4 speed, what RPM @ 70 & 80 miles per hour
CIS 930 owners, I would like to know what RPM your car runs at 70 miles per hour and also 80 miles per hour with a stock geared 4 speed transmission. Also, if it's below 3000 RPM at these speeds, how is the cruising and lag factor on the interstate?
05-13-2006, 01:32 PM
#3
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It really depends on the ring and pinion, and tire circumference. I have a low ratio R&P and at 70MPH, my tach reads 3100RPM. I guess 90MPH would equate to around 4500RPM!
Way too low for a street car.
Way too low for a street car.
05-13-2006, 01:45 PM
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3000 @ 90? Wow, how is the drive at 70 & 75 on the interstate? Is the motor chokeing needing to downshift or does it cruise ok? I am gearing to run 2800@ 80 miles per hour. Don't want the motor to LUG @ 70 on the interstate needing to down shift.
05-13-2006, 03:48 PM
#5
Burning Brakes
It's been two years since I've driven my car, but I don't remember any problems cruising in 4th gear with stock gearing. As I recall, even below 3000 rpm in 4th, it would still make boost as soon as you mash the loud pedal.
05-13-2006, 03:50 PM
#6
As per the gearing chart in the manual, with stock gearing and tire size, for a '79 930 in 4th gear:
60 mph = 2200 rpm
70 mph = 2500 rpm
80 mph = 2800 rpm
90 mph = 3100 rpm
100 mph=3500 rpm
My car has an early k27 and B&B headers which greatly reduce lag compared to stock. At 2000 rpm it is kinda sluggish but the engine runs smooth, it starts building boost in a hurry above 3000 rpm. At 70-75 4th gear works great, with good acceleration initially, and GREAT pull shortly thereafter. If I am anticipating a need for max power I grab 3rd gear, such as passing on a 2 lane road. I actually like the tall gearing as the engine doesn't seem to be working very hard at hwy speeds. It is a bit tall for track days - a 5 speed would be great to have, but the $$ doesn't make sense.
These #'s are approximate, as best I can extropolate from the graph in the manual.
60 mph = 2200 rpm
70 mph = 2500 rpm
80 mph = 2800 rpm
90 mph = 3100 rpm
100 mph=3500 rpm
My car has an early k27 and B&B headers which greatly reduce lag compared to stock. At 2000 rpm it is kinda sluggish but the engine runs smooth, it starts building boost in a hurry above 3000 rpm. At 70-75 4th gear works great, with good acceleration initially, and GREAT pull shortly thereafter. If I am anticipating a need for max power I grab 3rd gear, such as passing on a 2 lane road. I actually like the tall gearing as the engine doesn't seem to be working very hard at hwy speeds. It is a bit tall for track days - a 5 speed would be great to have, but the $$ doesn't make sense.
These #'s are approximate, as best I can extropolate from the graph in the manual.
Last edited by Last930; 05-13-2006 at 03:59 PM. Reason: add
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05-14-2006, 10:05 AM
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Last930, that's amazing, I made a trip from Orlando to Melbourne FL yesterday. Most of it on expressways at 90 mph and my tach was indicating exactly 3000RPM. So, they sure seem consistent.
