What RPM is the 1.7L running at 65???
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vwbill
- Posts: 970
- Joined: Sat Feb 15, 2003 12:01 am
What RPM is the 1.7L running at 65???
Anyone know what the RPM's are at 65mph and what is the RPM limit and speed? It seems like the motor is at a high RPM at 65mph?? Does the four speed tranny have a good final ratio or would a overdrive gear help out the final drive and RPM's??? Need to install a RPM gauge!! bill
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raygreenwood
- Posts: 11912
- Joined: Wed Jan 22, 2003 12:01 am
The type 004 four speed has one of the best final drive ratios. It is either 3.79:1 or 3.91:1. It does have a 1:1 fourth gear ratio, so it is not as advantageous a fourth gear as it could be.
With the stock tire....say a 185/75r-15.....you get a circumference of about 79....or 6.6 feet. That means you roll about 6.6 feet per revolution of the final drive.
At 3000 rpm....at 1:1 ratio into the final drive.....gets you 3000 rpm divided by 3.79= 791 wheel rpms.....X 6.6' per rev......=5224 feet per minute......is 59+ miles per hour.
3000 rpm at 60 is really not that bad at all. Bear in mind that this is smack dab at the very lowest end of the torque producing band of the type four . The passing acceleration (from 60 going to 70 mph) of a well tuned, four speed type 4....is just superb. Very very quick. Being that it is in the low range of the peak torque band.....under 3200 rpm, it also gets good gas milage.
It takes just a nudge of the gas pedal to get the rpms into the jammin torque band. But it really is not the exact most efficient spot to be (gas milage wise)....in the torque band. Being somehwat higher with more rotational force and better efficiency works even better. But we all know that having the rpms higher also produces heat...so its worth it to tune well and watch.
Having a better than stock cam and exhaust...and perfect ful injection tuning really helps.
Bear in mind, that with lower profile tires you get slightly higher rpm.
With my 205/60-15's...... the tire circumference is 24.6186 as compared to 25.244 with factory tires. 60 mph gets me 3105 rpm.
60 mph is 5280' per minute.
70 mph is 6160' per minute. At 6.445' per tire rotation.....you get 955.77 rpms at final....X 3.79= 3600 rpm at 70 mph.
I averaged 32 to 34 mpg on my last engine...at 70-75 mph...which was
D-jet.,..highly tuned web #73, 42x 36 valves (unshrouded) , pertronix ignitor, flamethrower coil, and ernst stock exhaust. The heads temps ranged to about 285-325 on average.
The 3.91:1 final was generally found on Variants after 71, and later...like 74 only...was found in all four speed models. So if you have a 71-72 411 or a august 72 to august 73 412 two or four door coupe, you probably have 3.79:1. If you have a late 73 to 74 412...its probably 3.91:1. Ray
With the stock tire....say a 185/75r-15.....you get a circumference of about 79....or 6.6 feet. That means you roll about 6.6 feet per revolution of the final drive.
At 3000 rpm....at 1:1 ratio into the final drive.....gets you 3000 rpm divided by 3.79= 791 wheel rpms.....X 6.6' per rev......=5224 feet per minute......is 59+ miles per hour.
3000 rpm at 60 is really not that bad at all. Bear in mind that this is smack dab at the very lowest end of the torque producing band of the type four . The passing acceleration (from 60 going to 70 mph) of a well tuned, four speed type 4....is just superb. Very very quick. Being that it is in the low range of the peak torque band.....under 3200 rpm, it also gets good gas milage.
It takes just a nudge of the gas pedal to get the rpms into the jammin torque band. But it really is not the exact most efficient spot to be (gas milage wise)....in the torque band. Being somehwat higher with more rotational force and better efficiency works even better. But we all know that having the rpms higher also produces heat...so its worth it to tune well and watch.
Having a better than stock cam and exhaust...and perfect ful injection tuning really helps.
Bear in mind, that with lower profile tires you get slightly higher rpm.
With my 205/60-15's...... the tire circumference is 24.6186 as compared to 25.244 with factory tires. 60 mph gets me 3105 rpm.
60 mph is 5280' per minute.
70 mph is 6160' per minute. At 6.445' per tire rotation.....you get 955.77 rpms at final....X 3.79= 3600 rpm at 70 mph.
I averaged 32 to 34 mpg on my last engine...at 70-75 mph...which was
D-jet.,..highly tuned web #73, 42x 36 valves (unshrouded) , pertronix ignitor, flamethrower coil, and ernst stock exhaust. The heads temps ranged to about 285-325 on average.
The 3.91:1 final was generally found on Variants after 71, and later...like 74 only...was found in all four speed models. So if you have a 71-72 411 or a august 72 to august 73 412 two or four door coupe, you probably have 3.79:1. If you have a late 73 to 74 412...its probably 3.91:1. Ray
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vwbill
- Posts: 970
- Joined: Sat Feb 15, 2003 12:01 am
Great Info!!
Thanks for some great info!! It just sounds like the motor is reving high at 65ish but if its at that rpm then it isn't odd! What is the max RPM of the pancake motor 1.7L?? It does sound sweet in that higher rev zone curve!! So is the sweet spot start at the timing set point?? If you can get in the 30 mpg range I think that the motor is running sweet! Think of the amount per mile is 4 and a quarter oz. per mile or one oz. per cylinder per mile!! What does a over drive change the final drive? THanks again for all your help! bill
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raygreenwood
- Posts: 11912
- Joined: Wed Jan 22, 2003 12:01 am
Bear in mind...the factory timing point is 27 BTDC at 3700 rpm. This is the point wherin they want all of your timing in...so in their mind...that is in the everyday..."acceleration zone". You will find good and reasonable driving with the gears in the 4 speed shifting between 3700 and about 4300-4500 rpm...no problem...when getting on the interstate....and going light to light. The redline is 5500. Mainly....because there is no more ablity for the FI system to add fuel after 5500. Power starts to flatten out around 4800-4900 rpm. Ray