What revs= what speed? 2000sc auto owners!
- Thread starter Pilkie
- Start date
Demetris
Well-Known Member
According to a 1966 Autocar road test of a 2000 auto, in top gear it gives 19,5 mph per 1000 rpm, so 4000 rpm corresponds to 78 mph and 5000 rpm to 97,5 mph.
On the test car the speedo was showing 3 mph more than the actual speed.
On normally brisk acceleration from rest (whatever this means for an SC auto) it changed into the 2nd gear at about 25 mph and into the top gear at 55 mph.
With the accelerator to the floor these change points were raised to 38 and 68 mph respectively. (It seems that the testers were brave enough, after all it wasn't their own car...
)
They do mention the two yellow dots in the speedo at the 47 and 78 mph as the maximum permissible speeds in low and intermediate gear.
I suppose that they correspond to the red line in the tacho, which begins at 6000 rpm in a 4 cyl.
Top speed was 94 mph.
So, there you go, you know how a new car was. Obviously these figures will have to be adjusted for a worn out or tired car.
On the test car the speedo was showing 3 mph more than the actual speed.
On normally brisk acceleration from rest (whatever this means for an SC auto) it changed into the 2nd gear at about 25 mph and into the top gear at 55 mph.
With the accelerator to the floor these change points were raised to 38 and 68 mph respectively. (It seems that the testers were brave enough, after all it wasn't their own car...
) They do mention the two yellow dots in the speedo at the 47 and 78 mph as the maximum permissible speeds in low and intermediate gear.
I suppose that they correspond to the red line in the tacho, which begins at 6000 rpm in a 4 cyl.
Top speed was 94 mph.
So, there you go, you know how a new car was. Obviously these figures will have to be adjusted for a worn out or tired car.
To be fair, I think they must have had a very good one. 94mph is only fractionally less than the manual car! But the achieved change up points are instructive.
There has been discussion a few years ago that the early SC's were much swifter than later ones and why that should be. I think this test highlights the point. Nobody really came up with a convincing answer as to why later cars should be so much slower. My own contribution was to wonder about the accuracy of cam timing on later cars.
If you're having a go at the tappet clearances, Dave, perhaps that's a good opportunity to check the actual cam timing. Ie to find the top point of a cam lobe and work back from there, rather than acepting the cam locking points as gospel. On the same lines as actions when you think the timing pointer has had a knock! That ought to keep your grey matter active!
Chris
There has been discussion a few years ago that the early SC's were much swifter than later ones and why that should be. I think this test highlights the point. Nobody really came up with a convincing answer as to why later cars should be so much slower. My own contribution was to wonder about the accuracy of cam timing on later cars.
If you're having a go at the tappet clearances, Dave, perhaps that's a good opportunity to check the actual cam timing. Ie to find the top point of a cam lobe and work back from there, rather than acepting the cam locking points as gospel. On the same lines as actions when you think the timing pointer has had a knock! That ought to keep your grey matter active!
Chris
NickDunning
Active Member
chrisyork said:
Absolutely. Early cars do not have the recirculating breathers of the later cars, but there may well be something more to this than just that.
My 1964 2000 is very fast and I've had it up to an indicated 95-98mph quite easily, I know it would do well, well over an indicated 100mph if I really let it go.
I doubt a 1973 2000SC would manage that, and certainly not have the acceleration.
Pilkie
Active Member
Well wadya know!
The rev counter is faulty!
I wired up a 2000tc round dial one and it shows that it easily revs to the redline as it should,so the one I fitted sticks at about 5krpm,and doesnt read true!
?? Could I have wired it up wrong ??
I though the engine was still revving as it stayed at 5krpm!
Now I wonder if the speedo is actually showing true speed or it is getting sticky at 60+mph??
I am going to have to do a sat nav speed test,when I find a mate with one that can do that.
Still gonna do the tappets and also check cam timing is ok before I take it apart.
According to the 19.5mph per 1000rpm.it isnt showing true at all!!
With 4000rpm showing is 45mph!! :roll:
The rev counter is faulty!
I wired up a 2000tc round dial one and it shows that it easily revs to the redline as it should,so the one I fitted sticks at about 5krpm,and doesnt read true!
?? Could I have wired it up wrong ??
I though the engine was still revving as it stayed at 5krpm!
Now I wonder if the speedo is actually showing true speed or it is getting sticky at 60+mph??
I am going to have to do a sat nav speed test,when I find a mate with one that can do that.
Still gonna do the tappets and also check cam timing is ok before I take it apart.
According to the 19.5mph per 1000rpm.it isnt showing true at all!!
With 4000rpm showing is 45mph!! :roll:
darth sidious
New Member
Just my thoughts...
Automatics get driven via the torque converter, am I right in assuming there is a certain amount of slip (being that the engine is driving the transmission input shaft via the transmission fluid), and maybe later cars are heavier(?) and so might suffer from a greater degree of slippage?
If that's the case, surely there will be more engines revs per mph, due to the slippage being higher?
Automatics get driven via the torque converter, am I right in assuming there is a certain amount of slip (being that the engine is driving the transmission input shaft via the transmission fluid), and maybe later cars are heavier(?) and so might suffer from a greater degree of slippage?
If that's the case, surely there will be more engines revs per mph, due to the slippage being higher?
Pilkie
Active Member
What a plonker I am! :roll: :roll:
When wiring up the tacho,I used the ign pulse wire as a 12v feed!!DOH!!
This of course is not a constant feed so it affected the tacho reading.
Now I have wired it to a switched 12v feed it works as it should according to the figures Demetris gave of 19.5mph per 1000rpm.
Still wont go above 65 without a long downhill run and a stong wind behind me,but am sure that when I eventually sort the valve clearances it will cure that.
When wiring up the tacho,I used the ign pulse wire as a 12v feed!!DOH!!
This of course is not a constant feed so it affected the tacho reading.
Now I have wired it to a switched 12v feed it works as it should according to the figures Demetris gave of 19.5mph per 1000rpm.
Still wont go above 65 without a long downhill run and a stong wind behind me,but am sure that when I eventually sort the valve clearances it will cure that.