overdrive 5th gear

[poindexter]

Hi all,
Has anyone fitted the overdrive 5th gear to their ZD30?
My coil cab (CRD) has the standard tires (265) and would like to know if gearing the ZD30 for 2000rpm @ 100kph is feasible. Currently it is geared to do 2500ish @ 100kph according to the GPS.
I do plan to do the usual mods to the engine to fatten up the torque.
My rationale is for touring and aiming to keep fuel consumption down.
I'm aware that there are 3 ratios available, just wondering if its worth it.

cheers

Ralph

[mudski]

Hi all,
Has anyone fitted the overdrive 5th gear to their ZD30?
My coil cab (CRD) has the standard tires (265) and would like to know if gearing the ZD30 for 2000rpm @ 100kph is feasible. Currently it is geared to do 2500ish @ 100kph according to the GPS.
I do plan to do the usual mods to the engine to fatten up the torque.
My rationale is for touring and aiming to keep fuel consumption down.
I'm aware that there are 3 ratios available, just wondering if its worth it.

cheers

Ralph
There is? Where? I would be keen as I have a box here I want to build soon. But it depends on if you tow too. If you do would keep it the way it is.

Come to think of it. Its a big job to remove the gearbox and strip it down and change the ratio. Would be easier to change the ratios in the diffs I reckon.

[fxst78]

Running at 2000rpm at 100kph will be stressing your motor a lot IMHO, and you may find you actually use more fuel. High rpm does not equate to high fuel use in a diesel. Higher rpm with low EGT versus lower rpm with high EGT, the low rpm is actually burning more fuel and placing more stress on your motor (very simplistic explanation).

[emm]

Running at 2000rpm at 100kph will be stressing your motor a lot IMHO, and you may find you actually use more fuel. High rpm does not equate to high fuel use in a diesel. Higher rpm with low EGT versus lower rpm with high EGT, the low rpm is actually burning more fuel and placing more stress on your motor (very simplistic explanation).

What's an EGT? Sorry got no idea... our patrol is an automatic.

Sent from my GT-I9305 using Tapatalk 2

[megatexture]

What's an EGT? Sorry got no idea... our patrol is an automatic.

Sent from my GT-I9305 using Tapatalk 2


Exhaust gas temperature



There is? Where? I would be keen as I have a box here I want to build soon. But it depends on if you tow too. If you do would keep it the way it is.

Come to think of it. Its a big job to remove the gearbox and strip it down and change the ratio. Would be easier to change the ratios in the diffs I reckon.

I'd love to do my diff ratios to drive 33s like standard but its a bit to much $ for my shallow pockets lol

[Drew]

IMO the egt is more important than saving a few litres of fuel. When they go up you have two options, take the foot off the go juice or drop a gear (higher revs). It's important to remember that in certain circumstances the second option isn't enough so you should take take your foot off the accelerator a little to get the temps down.

There was a great post somewhere that describes how a diesel is different from petrol. The one thing that I think I got right was when you dump more fuel into a diesel it burns hotter (to produce the torque they do), not paying attention can kill your engine.

I get 100kph at around 2250 rpm so I guess that's the difference between chassis.

I'm assuming you're not towing ?

Like it was said before dropping rpm for same speed doesn't always equal better fuel economy (I'm using a scangauge).

[mudski]

What's an EGT? Sorry got no idea... our patrol is an automatic.

Sent from my GT-I9305 using Tapatalk 2

Oh! So there is a mod for auto's to add another gear your saying? I have manual sorry im out of ideas.

[poindexter]

Hi Mudski,
Marks Adaptors have the 5th gears, and, according to them, no need to pull gearbox, just drop the transfer case.

[Drew]

Hi Mudski,
Marks Adaptors have the 5th gears, and, according to them, no need to pull gearbox, just drop the transfer case.
Any chance of a link ? Thanks

[threedogs]

I think you're going the wrong way by dropping revs at hwy speeds, totally agree with fxst78.
You might be better off changing diff ratios to suit the larger tyres we run,
Doing it the other way your peak power will be at 130kph, impractable IMO
I think those reduced 5th gears are better suited to Duramax or 6.5td conversions.
maybe even LS1, Going to be peed off if you fit them and not all cracked up as could be.
Leave the ZD30 alone its fine as it is, no big power machine, As I always say its only 3ltrs
and highly tuned as is, best spend some money on keeping it efficient.
Its never going to win any best motor awards, just NADS it and leave it, gearbox and auto included
unless you want reduction gears

[poindexter]

there's the link to the overdrive 5th gears.
http://www.marks4wd.com/overdrive-gears/nissan/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.

[BigRAWesty]

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.

I agree with above purely due to the fact Nissan (and others) poor thousands into finding the best setup for their cars.
Power, efficiency, pollution.
Why fark with it..

Bit like changing your thermostat for a lower temp. Your engine is made to run at x degrees.. Made like that for a reason.

[boots]

Reckon most peeps would consider changing tyre size first , before extreme mods with gearing . ie - taller tyre = reduces revs .

[poindexter]

Interesting discussion.
Tell you what I'll do: I'll run the numbers through the simulation software at work (I work for a car company) and see what spits out. My gut feeling is that .74 is the right number.
By the way, Nissan would not have spent thousands on finding the best setups, more like millions.
Love to hear the discussions on EGR blanking, big exhaust, let alone chips etc, because Nissan did it for a reason.....

[mudski]

Interesting discussion.
Tell you what I'll do: I'll run the numbers through the simulation software at work (I work for a car company) and see what spits out. My gut feeling is that .74 is the right number.
By the way, Nissan would not have spent thousands on finding the best setups, more like millions.
Love to hear the discussions on EGR blanking, big exhaust, let alone chips etc, because Nissan did it for a reason.....

Well let me start on the egr plate. Its law to have a working egr, regardless of what its doing to your engine. Bigger exhaust, noise pollution. Chips, the way I see it is when the car is stock from the factory the ecu is tuned to the factory items on the car. Probably even under tuned. For fail safe results. Using a chip you will only see the benefits if you have mods already done like the exhaust. Im sure there is other reasons but none that I can think of.