Technical Editor Robert Pepper peels back the metal to take a look at the 2015 Nissan NP300 Navara technical details and explain why Nissan has made some key changes.
Coil suspension – learn to love it
ALL THE OTHER top-selling utes have leaf springs in the rear, and now Nissan has gone and put coils in the back of all dualcab NP300s. At this point, the dinosaurs start whining that coils cannot carry a load. But that’s dead wrong.
Exhibit A is the Land Rover Defender, in 110 and 130 guise. Say what you like about Defenders, everybody in the know agrees they can carry a load (although the 130 uses coils-within-coils). Exhibit B is the Mercedes-Benz Unimog, and Exhibit C is the Hawkei (pictured) which also has, horrors, fully independent suspension. The reason utes have leaves in the rear is because of tax laws in places like Thailand, not because they need it for load carrying.
So, now we’ve established coils can in fact handle a load, let’s look at why they’re better than leaves.
A leaf spring is made up of several thin pieces of metal (leaves) that rub against each other as the spring compresses and extends. This creates a damping effect, which is great news for cheap trailers as it means they need not bother with a shock absorber. Coils on the other hand have none of this problem and so their extension/compression can be entirely controlled by the shocks.
Leaf springs are bad news for vehicles because you want the spring compression/extension controlled by a properly valved shock absorber (damper) which can do a much better job than bits of metal rubbing against each other. That is one reason why leaves don’t handle as well.
The second reason is that leaves do not locate the axle very well in relation to the chassis – how can they, as they are literally a spring which is flexible. In contrast, as coils cannot locate an axle there’s all sorts of other gear to do the job such as Panhard rods. Nissan have gone for a multi-link 5-point rear end which is pretty standard. With the axle placement under control, the handling improves in turn.
Incidentally, if you ever wondered why leaf-sprung utes have the shocks mounted one in front of the axle and one behind it’s to try and combat the inherent problems with a leaf setup caused by torque from the driveshaft twisting the axle. Not a problem with coils. And even better, Nissan tell us there’s a bit more wheel travel with the coil setup. And one more reason to prefer the coils, at least in the case of the NP300, is that Nissan have gone for an underslung setup where the axle sits on top of the leaf, as opposed to under it. Usually 4X4s have the axle under the leaf to improve clearance, and indeed many vehicles have SOA (spring over axle) conversions for that purpose.
So, to recap, coils handle better on and off-road, offer more clearance, and can take a load. What’s not to like?
Stability Control, Traction control and locking differentials – all different kinds of goodness
This is a really difficult subject and to be frank the manufacturers do not help with different names for the same thing. There’s a full explanation in the 4WD Handbook, but in Nissan speak here’s what things mean:
TCS – Traction Control System. Imagine you’re at the lights and it’s wet. You plant the hoof and both rear wheels light up. The computers realise the front wheels are rotating much slower than the rears, and cut the power. Most modern vehicles have a similar system, and it’s great for onroad use as it stops you getting into trouble. The generic name is engine traction control, because it works by cutting engine torque. This is not good offroad, and is disabled or reduced in 4WD modes as often you do want some wheelspin such as when you’re nailing it trying to get through a boghole. But don’t confuse TCS with…
ABLS – Active Brake Limited Slip. Clearly, named by marketing people because the rest of the world knows this simply as electronic traction control (ETC). Take a look at this photo:
This is your classic cross-axle scenario – which is why I’m using this track. What’s happened is that we’ve got very little weight (and therefore traction) on the front left and rear right wheels, which are spinning. ETC (oops, ABLS) detects the fact that those two wheels are spinning quicker than their counterparts on the same axle and briefly applies the brake to those wheels only, which has the effect of increasing torque (turning force) on the other two wheels, and then you can move forwards.
All modern 4X4 have ETC, but I have to say Nissan has done a very good job of the calibration. Specifically, the ABLS kicks in very early, and very effectively, so you can really inch your way up over things. In contrast, the Suzuki Jimny I tested a week earlier had a traction control system that took a long time to kick in, and when it did, wasn’t very effective. It seemed that it applied the brakes harshly on and off, and left long intervals between brake applications, so which resulted in pretty severe vibration that made me fear for the safety of the vehicle’s drivetrain once we got the revs up. No such problem for the NP300.
Rear locking differential – no special name here, maybe the marketing people ran out of imagination. Anyway, the ST and ST-X models have a rear cross-axle differential lock, commonly known as a “rear locker”. This is a mechanical device that entirely locks the rear differential so both wheels have to turn at the same speed. That is excellent for offroading in a mostly straight line, because there’s no wheelspin at all, unless both wheels spin in which case life is not good.
There are a few points to make about rear lockers. First, they are not always better than ETC (or ABLS in Nissan-lingo). This is because rear lockers will increase the turning circle and require more energy to turn, not a good thing in mud or sand. Also, lockers might break traction entirely at the rear, something much less likely with ETC.
The main advantage of a rear locker is that it is pre-emptive, it doesn’t need to wait for wheelspin. This is a huge advantage when climbing rock ledges in a straight line. Basically, you really want both ETC and locking differentials so you can choose the point at which you use one or the other, and as general guidance ETC is better unless you are crawling in a straight line with wheels in the air.
We also have to call out Nissan for special praise, and hold them up as an example to follow because…when you engage the rear locker on the NP300, ABLS keeps working on the front axle.
Most other vehicles – looking at you, Ranger and Triton – disable ETC on the front axle when the rear locker is engaged. Which is kind of hopeless because if you need a rear locker chances are a front wheel is in the air, and then all you’ve really got is the rear axle driving you forwards. Whereas ETC works on all four wheels.
So with Nissan keeping ABLS on the front axle, and locking the rear you can kind of have your cake and eat it, as you get the benefit of the rear locker, and the front axle does something useful with its time as front wheelspin is controlled by ABLS. ABLS never works on the rear axle with the locker engaged as the two rear wheels turn at the same speed all the time.
This rear locker/front ABLS is tremendous news and with the NP300’s effective traction control (and coil suspension) I reckon it’s probably going to be top of the heap or close to it for offroad capability. Also helping are the relatively low weight (below 2000kg for all variants), and a turning circle of 12.4m, better than the D40 of 13.3 and the Ranger at 12.7 and Amarok at 12.95, but nowhere near the new Triton at 11.8m.
A bit of bad news is that the rear locker can only be engaged in low range. This is probably going to be fine as you don’t really want it in high range, but it’d be nice to have the option just in case. Or if you felt like a bit of drifting. Other vehicles such as the Ranger permit the rear locker to be engaged in high range.
By the way, cross-axle rear lockers are great for descending rutted hills as you don’t lose engine braking when one wheel leaves the ground or is unweighted.
BLSD – Brake Limited Slip Differential. Only on 2WDs, and appears to a variant of ABLS.
VDC – Vehicle Dynamic Control or as the rest of the world knows it, ESC or Electronic Stability Control. This is for safety – the system detects understeer (running wide) or oversteer (back end steps out). It will brake indvidual wheels to keep you pointing straight, and where necessary, cut the throttle too. This is excellent for on-road or dirt-road driving, but definitely not what you want for offroading, particuarly sand, mud or snow where the car can slip and you need to keep the power on, not have the car’s momentum chopped. Happily, VDC is either reduced or eliminated when in 4WD, and/or when the button is pressed. Often VDC/ESC is called traction control, but that’s wrong. See above. To be clear, ABLS keeps working in low range which is what you want to happen.
Hill Descent Control and engine braking – kiss the manual goodbye
Time to bust another myth – autos don’t have good engine braking. Well, let’s look at the crawl ratio, which is the lowest possible gear found by mulitplying the first gear ratio by the transfer case ratio by the final drive (differential) ratio.
For the NP300 we have a 1:44.6 crawl ratio for the automatic, even if the manual is an impressive 1:49.8. Remember when Nissans didn’t have good engine braking (GU Patrol!) Those days are gone now. Ranger PX by the way is 1:42.3. Fact is, auto engine braking is very, very good these days, eradicating pretty much the last advantage manual had over auto. Someone asked about the Amarok – the auto only 8-speeder with no low range is 1:17, and the 6-speed manual we can’t calculate because there’s no transfer case ratio in the spec sheets…if I find out what it is this article will be updated.
The Navara has electronic hill descent control, and these systems are now very good indeed. I recently did some work with 4WD instructors and we agreed that in the case of the Ranger and LC200 the electronics do a better job of hill descent than we can. We’ve not yet fully tested the NP300’s system, but one problem is that it is single speed whereas most others can be speed-varied by the driver using the cruise control. It does however work in both high and low range.
Engine size – two is the new four
Dear ute buyers – please get over this obsession with large engines.
As time goes on, engines become more and more efficient so less and less capacity is needed to produce the same power and torque.
Turbochargers become more sophisticated, with seperate turbines for low and high revs. Common-rail injection meters very precise amounts of fuel at several points during the four-stroke cycle. Smart aircon and alternators reduce engine load when not required to operate. The list is endless, and the end result is vastly improved efficiency per cubic centimetre. That’s one reason why a big old 4 or 5 litre engine isn’t needed these days.
The other reason is gearing. No more four-speed autos with their lazy inefficient torque convertors and after-the-corner indifferent shift mechanisms. The Navara has a seven-speed auto, and it’s a smart one that downshifts downhill and adapts to your driving style. Seven speeds means the engine can be always working in or close to its best power or torque band, unlike a four-speeder. By the way, that adaption is only in the short-term for a few minutes, so don’t worry about your partner/wife/mate driving the car and teaching it bad habits. Not going to happen.
Ultimately, just drive the modern utes. They’re more powerful than ever, and engine capacity isn’t relevant any longer.
We’ll shortly cover off the vexed issue of towing, and when a 3500kg tow capacity isn’t really a 3500kg tow capacity. That’s not a problem specific to the Navara though. For the moment, we’ve got an NP300 review here, and a bullbar roundup so far here, and we’ve also offroad-tested a Thai-spec NP300.
Not to doubt you or anything, but if coils handle load just as well, why does the single cab Navara have leaf springs?
Pathetic reasons really.
Half the engine size but efficiency hasn’t doubled.
Leaf springs are favourable for space efficiency, hence utes with good bed sizes. Nothing to do with Thai tax law…
Brake articulated LSD is crap, they use it because its lines of code, doesn’t add to the per unit build cost. It’s already in the blank ecu that Siemens or Bosch have developed.
I wonder why VW just dropped the tD v6 into the amarok. Could be that engine capacity has always and will always be relevant.