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MG MGF Technical - Accelerating info required
I am searching for info 'bout the best rpm and time to shift up when accelerating hard with the F (1.8MPi or 1.8VVC). Being a not-really-technical guy, I am wondering how everyone is going through the gears.
- at wich number of rpm do you switch to a higher gear ?
- Is it the same for all gears ?
- After shifting to a higher gear, how much has the neelde dropped ?
Off course it all has to do with the number of revs when the highest torque and power is reached, but how do you shift gears ?
I have a standard 1.8i and find that the best time to change gear is at about 5,500rpm. I also have added a small round steel gear knob which has reduced the gear stick height by about 2 inches - which seems to make the gear changes quicker
Also, if the car has been driven for about half an hour, and warmed up, my MG accelerates a lot quicker!
I know you'd expect it too a little, but not this much!
Don't know if this is exactly the same with all F's
Hope this helps
we've had this discussion a while ago here in Germany and I've worked out that at least with a VVC it's best to change up at the highest possible rev i.e. just before the cut-out.
This is the equation for the theoretical acceleration of a vehicle on an even road, where P is the power, k is a constant mass factor, m the mass of the vehicle and v its current speed. You can see from this that the higher the momentary power output of the engine the higher the acceleration. Thus you have to keep the engine as close as possible to its point of peak-power at all times. Now if you look at a power diagram of the VVC engine you'll easily see that in order to do this you have to keep the revs as high as possible meaning change up as late as possible. With the MPI this might actually be different because peak power is achieved earlier in the rev range. You should be able to work this out for yourself having a look at a power diagram for the MPI engine. The difference in revs from one gear to another is typically about 3000 from first to second and roughly 1500 to 2000 for the rest.
Hope this helps a bit,
|Whoww, I see Erik in clouds of rubber steam, ... burning out.|
|I did the calculations (albeit different a method) for my 1.6 K Series engine and, like Nikolaj, found each gear change was best made on the rev-limiter. It is often surprising how far over peak power it is best to go ....|
For a good read on these matters see
This thread was discussed between 16/02/2001 and 19/02/2001
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