How certain accessories affect fuel economy and vehicle handling/performance

Hey guys, 

I'm planning on buying a 2021 Suzuki Jimny and getting either an Ironman or ARB bullbar, 80L Long Ranger fuel tank replacement and one of the modern flat-design roof racks installed. However, I'm wondering how much each of those accessories will impact fuel economy and also the handling/performance of the car? For example, does anyone know any details such as what the increase in fuel consumption (as a %) will be if the car is fitted with a bullbar? I'm a bit concerned that when I add these three accessories the car's fuel consumption will significantly increase and the handling and performance will drastically decrease. Any advice is greatly appreciated!

Cheers,
Lachlan

You could find the weight of the items you want to fit and temporarily add that weight to the vehicle to see what impact it has on the MPG for your driving style?
Just a suggestion as MPG comparisons are difficult due to the human factor and differing terrain.
As to the handling, yes adding weight to the front of the vehicle will make if feel different, but its subjective as to if this change is drastic or negligible. Those that have them fitted them report they can feel the added weight, but they simply adapt their driving style to allow for the change.

All of these items increase weight and that increases fuel consumption, partly during acceleration and partly during constant driving.
The bull bar may or may not further increase consumption due to it's design ie is it more or less aerodynamic than the original component. Only ARB will know this.
Your roof rack will increase consumption. Please be aware that the max. load on the roof is 35kg. This is rack plus load.
The extra consumption related to the tank is entirely based on how much fuel is in it at any one time.
The effect on handling will depend mostly on the load on the roof. If you load it to the max. then cornering will suffer. It's not a sports car to start with and a fully loaded roof rack will increase sway and will be unpleasant. The bull bar and tank are low down so will not be anywhere near as bad as a loaded roof rack but the bull bar, being a lot heavier than standard, can induce a degree of understeer.
Performance will suffer because you are lugging extra weight.
Overall it will depend on how you drive. If you are a sedate driver you may not notice a drop in performance and a lose of 5mpg would be near the ball park. A faster driver would notice the difference in performance and an extra 5 seconds from 0-60 mph and a loss of 10 mpg is to be expected.
On my LandCruiser I went from 1760kg to 2010 kg and the 50-70mph dash in 5th increased from 10 to 15 seconds.

Roger

I would hazard a guess that it'd be not much different than having an adult passenger in the car.
Yesterday I did a 46 mile return trip with a 41kg kayak on the roof, on twin roof bars, with all the rest of my kit in the back. A mixture of fast dual carriageways, regular 30 & 40mph local roads and a few miles on single lane country lanes up and down Dorset's coastal hills. Didn't notice any performance or handling issues and still returned 42.4mpg.

I don't think weight makes the biggest difference to mpg if I'm honest. Not for more normal driving and cruising.

Most cars will return similar mpg when they have a couple of passengers on board for example.

Driving in hilly or mountainous areas or just hard will make this weight penalty bigger.

To that end, I don't think a bullbar will impact mpg. Although when I had mine fitted, you could tell it was hanging off the front of the vehicle through the feel in the steering wheel and turn in. But you get used to it very quickly and it becomes normal.

A roof rack on the other hand is likely to cause more body roll and impact drag and aerodynamics. So I'd expect at higher speeds they will impact mpg more so. Personally I'd not bother with a roof rack unless you really need to use one.

More weight will decrease acceleration. But to what extent it is tough to call. However I'd say the biggest impact I've seen/felt to mpg and performance is tyres.

On stock tyres I was getting 39mpg+ (never over 40!) commuting on country roads and some traffic. But I was also driving gentle as the car was new and the engine had done very few miles.

On a long 70mph motorway run to get the bullbar fitted I got 38mpg overall average there and back, with about 1mpg less with the bar fitted. But that could also have been other factors.

Running about locally I was still getting 36 or so mpg. However after fitting some 215/75R15 AT's MPG has dropped to approx 33mpg. And a similar motorway run also only yielded just under 35mpg.

There was also a noticeable drop in acceleration with the AT's. It's not that they are all that much bigger or even all that aggressive. But I suspect they do weigh a fair bit more per corner.

Increasing weight will only add to fuel consumption when accelerating, either increase in speed on the flat, going round a corner or up a hill (going round a corner or up a hill is acceleration).

Once you are no longer accelerating the extra weight will not be noticed and it will just bowl along.

Putting a roof rack on will most likely increase drag and at medium to high speeds will dent performance and therefore increase fuel consumption.

The Jimny has a very low weight limit for the roof, probably so it can pass the 'Moose test' so adding too much weight to the roof might make the car unstable and if you were unluck enough to be in an incident and turned over the police and insurance company might take a dim view of the weight.

I doubt a bull bar would make much difference to fuel or handling, unless it was very heavy or stuck out the front a long way, after all the heaviest part of the car is nearby.

Robin