Nissan 2.8 SAFARI met patol ratkas

[Tinus lotz]

Thanks gerrit it helps a lot

[David]

Tinus - with the info Gerrit supplied it looks like a match made in heaven
The lower first gear will be nice for those difficult parts when you are heavily laden and on the open road the longer 5th gear will be good for fuel consumption. Best part is that the dead spot between 3rd and 4th of the old box will be gone!

[Tinus lotz]

Yes man I do agree with you I will keep you posted I found one box in pta and the guys from jap auto is also looking for me now to find 2 weeks when the test rig is not working...........

[Gerrit Loubser]

Best part is that the dead spot between 3rd and 4th of the old box will be gone!

I don't think there will be a discernible difference in the ratio step from 3rd to 4th on the new compared to the old setup. On the old the 3rd gear ratio is 1.45 times lower than the 4th and on the new it is 1.49 times lower.

Basically the new setup has a very similar 3rd gear ratio and of course an identical direct drive 4th. The difference is that the new setup has lower first and second gears and an additional fifth gear, so it covers a much wider range of ratios (On the new setup 5th is 5 times higher than first, while on the original setup 4th is only 3.5 times higher than 1st. The new setup has a similar mid range spread, but with 40% more total range width.

If I can get hold of an engine torque curve for the L28 motor, I could put together a cascade diagram to graphically show how the new and old setups would be matched to the vehicle.

[Tinus lotz]

Hi Gerrit
i will try and find one I had a paper copy but kind find it
regards

[Gerrit Loubser]

I found a small little power curve on a Spanish spec sheet that I have. It lists the power and torque of the L28 motor:

97 kW @ 5200 rpm
213 Nm @ 3600 rpm

Does that sound right for the SA Safaris? If it is, I can use it and create the cascade curves.

[Gerrit Loubser]

If my assumptions regarding the torque curve and gear ratios of the Safari are correct, this is how the cascade curves of the four speed and five speed will compare:




The blue lines are for the four speed and the red ones are for the five speed. The dotted black line is a constant power curve and is the type of characteristic that one might achieve with a CVT. Note that the geared speeds will not necessarily be achieved due to air and rolling resistance.

[Gerrit Loubser]

I am, however doubting the gear ratio data that I quoted before. My Spanish spec sheet seems to indicate that the pick-up had the following gear ratios:

1st: 4.222:1
2nd: 2.370:1
3rd: 1.440:1
4th: 1:1
Reverse: 4.622:1

If the SA Safari pick-up had these ratios, then fitting the five speed setup won't really change anything much other than providing an extra, overdrive ratio. This is what the cascade diagram would look like:

[Peter Connan]

Hello Gerrit

These cascade curves of yours are the bee's knees. What program do you do these on?

Thanks
Peter

[Gerrit Loubser]

Peter, nothing fancy, I am afraid: those were done in Excel. It is all simple math if you have an engine torque curve, gear ratios, axle ratio and the tyre size.