overdrive 5th gear

[poindexter]

there's the link to the overdrive 5th gears.
http://www.marks4wd.com/overdrive-ge...an/mfk730.html

[mudski]

At those prices, they can bite my left one. Sheesh. But its good to know about them.

[Drew]

Would NADS & a Chip give a better outcome ?

[poindexter]

I didn't think that the price was that bad, considering its rrp.
Anyhow, my thinking was to get the patrol to cruise at 100kph at its peak torque rpm of 2000, (currently 80kph), this it should do very easily.
My wifes 4X criuses at 100kph doing just 1800rpm, and its a smaller engine and weighs similar.
I'll do a gear chart to see what the rpm drop between ratios will be, this will give me a better idea of which ratio will suit the ZD30.

[threedogs]

still think by reducing your revs by 15% to 25% you will increase your fuel consumption.
It may be ok going across the Nullabor with cruise control on but no good IMO on any hilly terrain

[poindexter]

I'm right with you threedogs on the hilly terrain side if things, this patrol is my daily commute, so I'd be spending alot of time, unloaded on the freeway, hence the overdrive idea.

[nissannewby]

Peak torque means maximum load and fuel so high temps and high fuel usage. It's geared that way from Nissan for a reason. It's the best spot for it to be efficient while pretty close to its peak outputs. It would stupid to want to drop it any lower than what it's set at, unless shorter diff ratios have been fitted. They are set at that speed (no load speed) for a reason.

[mudski]

I knew the man would come along soon and explain it. It make more sense now what matt has just said, the reason you would change 5th gear ratio is if you change the diff ratio. So you have the power you want in all other gears but not screaming your head off at 100k's.

[Winnie]

Peak torque means maximum load and fuel so high temps and high fuel usage.

Really? I find that say if I am going up a steep hill in 3rd gear at 2000rpm, if I speed up so I am doing 2500rpm (around peak torque) my EGTs drop by a fair bit.

[nissannewby]

Really? I find that say if I am going up a steep hill in 3rd gear at 2000rpm, if I speed up so I am doing 2500rpm (around peak torque) my EGTs drop by a fair bit.

Have a look at your power at that stage. I still have your graphs and your peak torque is closer to 2300/2350. It's hard to explain. When your at 2500rpm it's what they refer to as a no load speed hence Egt's will be lower. At 2000rpm you are right in the middle of your torque curve so more load is on the engine so more fuel is required to get you to that no load speed. I find it hard to explain these things sometimes. Basically when your at a set speed in whatever gear you should be able to pull away smoothly when putting your foot down, of it labours your revs are to low. However if the revs are to high you will also use more fuel. It's a fine line and pretty much all the factories engineers know what they are doing when it comes to that.