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getting better mpg

  • Lambert
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  • The quickest Jimny in Harrogate...(that I own)
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28 Jul 2022 09:14 #244257 by Lambert
Replied by Lambert on topic getting better mpg

Driving down hill in neutral that is coasting is not good. First it reduces your control of the vehicle as you have no engine braking effect which in turn increases reliance on the wheel brakes which can cause them to overheat. Secondly the engine will revert to idle in neutral which requires it to burn fuel, when going down hill in gear the ECU detects this and virtually stops fuel supply, the effect may be small but it does increase mpg.

Great theory, but in practice coasting in neutral uses less fuel.


Maybe on a carburettor motor but it's one of the ways modern European compliant engines meet emissions.

Temeraire (2018 quasar grey automatic)
One of the last 200ish of the gen3s, probably.

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28 Jul 2022 12:04 #244258 by danielbz
Replied by danielbz on topic getting better mpg
so, does going on D shuts down fuel injection? where can i see that??
and going on N does not stops fuel injection? i didnt know about that, is there somewhere i can check this?

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28 Jul 2022 12:12 #244259 by RumbleAndSway
Replied by RumbleAndSway on topic getting better mpg
37.8 mpg from SZ5, running BFG AT, roof bars, bike carrier, awning and occasionally a roof load [bike, ladder, canoe etc.]

Never seen 40mpg but no grounds for complaint.

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28 Jul 2022 13:32 #244261 by DrRobin
Replied by DrRobin on topic getting better mpg
An imperial gallon is 20% bigger, so that takes your 29 to almost 35mpg.

I don't have any figures for 91 octane rating vs 95 we get in the UK, but would expect another increase in mpg, possibly as much as 5%. So that takes you up to about 36.5mpg.

The ECU needs to be able to adjust to the different octane ratings, but I assume they do this, or the ECU is 'tuned' for the market the vehicle is going in to.

Several years ago I hired a Jimny on holiday in the Caribbean, it seemed to drink fuel and it wasn't cheap, so I worked out the mpg, it wasn't very good, I put it down to the state of the roads. Only later did I realise that although the island used to be under British rule, pertrol was sold in US gallons.

I think you are not that far away. You might check the air filter or the CAT might have disintegrated, then again check the plugs and everything else, depending on how many miles your vehicle has done.

Robin

2011 Blue Jimny SZ3, Hankook Dynapro ATm, Radius Arm protectors, Xtrons Head Unit, DAB, 360 degree Camera, TPMS, K&N, Bosch Aerotwin blades, LED lights, boot light, parcel shelf, boot box, dash box. Osram Nightbreakers, CTEK Battery Sense, Front & Rear Recovery points, CB Radio.

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28 Jul 2022 14:37 #244263 by saxj
Replied by saxj on topic getting better mpg

so, does going on D shuts down fuel injection? where can i see that??
and going on N does not stops fuel injection? i didnt know about that, is there somewhere i can check this?

Yes it does. You can see it on the instant consumption gauge on the Gen 4.

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28 Jul 2022 14:42 - 28 Jul 2022 14:45 #244264 by saxj
Replied by saxj on topic getting better mpg

Driving down hill in neutral that is coasting is not good. First it reduces your control of the vehicle as you have no engine braking effect which in turn increases reliance on the wheel brakes which can cause them to overheat. Secondly the engine will revert to idle in neutral which requires it to burn fuel, when going down hill in gear the ECU detects this and virtually stops fuel supply, the effect may be small but it does increase mpg.

Great theory, but in practice coasting in neutral uses less fuel.


Maybe on a carburettor motor but it's one of the ways modern European compliant engines meet emissions.

It's all about friction and momentum, you go further in neutral than you will with your foot off the throttle, so it uses less fuel. I used to live in a hilly area, and it used to make quite a difference to my consumption - Gen 3 manual and Gen 4 Auto. Now I live in a very flat area, so I don't get the advantage any more.
Last edit: 28 Jul 2022 14:45 by saxj.

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28 Jul 2022 15:10 #244265 by 300bhpton
Replied by 300bhpton on topic getting better mpg

im using a non traffic road, i drive 50 mph when going uphill and i go downhill in N, im not in the UK, what mods do you have?

ATs, winch bumper and some other bits.
​​​​​​​
Is your vehicle standard?

I assume if putting it in N it is a manual not an automatic.

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28 Jul 2022 15:11 #244266 by 300bhpton
Replied by 300bhpton on topic getting better mpg

US gallon
91 octane, no ethanol

Curious, where are you?

Do you know what Octane scale you use?

91 octane in the USA at least, would be about the same as 95RON here in the UK.

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28 Jul 2022 15:14 #244267 by 300bhpton
Replied by 300bhpton on topic Re:getting better mpg

Can you use 91 in a series 4 my series 3 staits minimum 95 ?

Sent from my SM-A336E using Tapatalk

Depends where in the world they are. Octane is rated in different ways.

en.wikipedia.org/wiki/Octane_rating

The following user(s) said Thank You: Old Neil

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28 Jul 2022 15:15 #244268 by 300bhpton
Replied by 300bhpton on topic getting better mpg

My very standard gen 4 still achieving a lifetime average of over 42mpg (UK). No motorways near me but otherwise regular A & B road driving. I rarely cane it though. 

I'd suggest over 40mpg is not the norm for most Jimny's. You really do need to drive it very gently to attain that (never managed it in mine, even when 100% stock).

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28 Jul 2022 15:16 #244269 by 300bhpton
Replied by 300bhpton on topic getting better mpg

Driving down hill in neutral that is coasting is not good. First it reduces your control of the vehicle as you have no engine braking effect which in turn increases reliance on the wheel brakes which can cause them to overheat. Secondly the engine will revert to idle in neutral which requires it to burn fuel, when going down hill in gear the ECU detects this and virtually stops fuel supply, the effect may be small but it does increase mpg.

Great theory, but in practice coasting in neutral uses less fuel.

No, neutral will be at idle and still pumping fuel in. Using engine braking will be no fuel and potentially more economical.

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28 Jul 2022 16:16 #244271 by danielbz
Replied by danielbz on topic getting better mpg
i was going down in N, my car is automatic, i will take into consideration what you told me, knowing that modern cars have more stuff included it may be true that going down in D stops fuel injection, i just had not thought about that before, thanks

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