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Fuel Consumption - 420R


Colin Heseltine

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What sort of fuel consumption figures are you guys getting with 420R.  I have new 420R and have followed running in recommendation of 500 miles at max of 4000rpm and am increasing by 1000rpm every 150 miles.  Now up to 850miles. My average appears to be around 28-29mpg.  During the first 500 miles the average was around 30mpg, a bit lower than I would have expected as I was not being stupid as trying to get used to the increase in power over my previous 158bhp 'K' supersport.

Colin

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I'd say that was fairly normal.  Looking at my records, my R400D (with plenum at the time) averaged 27.9 over the first 1100 miles, with a gradual improvement as everything loosened up.. 

Since my roller-barrel upgrade in 2014, I've been getting 28-33, depending on conditions, with the higher figure achieved on quiet and traffic-free French D-roads.

JV 

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  • Area Representative

With RBTB & 'careful' driving one may see 220 miles out of an S3 tank. On track or nailing the car on the road to the legal limit (honestly constable) may only see 180 miles or less from a tank.

Touring ser le continent with the speed limiter in the pax seat will easily see 30 mpg.

Fuel quantity anxiety/management is all part of the 400/420 experience.  Is mpg that important when driving a road weapon like a 400/420 ? Just enjoy.

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Don't get me wrong, I am enjoying the car and the extra performance.  My previous 1600 K series would give me typically 38mpg, sometimes as low as 35mpg, other time low 40's.

Geoff, I like your 'Fuel quantity anxiety/management is all part of the 400/420 experience'.

I think a bit of the problem is the wild swings the gauge makes, up hill and downhill can swing the needle over 1/4 of the gauge,so need a level road and steady driving to get a an accurate reading.

Thanks for all your responses.

Colin

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400/420 fuel anxiety/management does include the fuel gauge. An approximate instrument system if there ever was. My gauge when showing half the tank physically has nearly one quarter more (2 gallons). When showing one quarter physically has again nearly one quarter more.

Eventually I worked this out by being suicidal - on returning from Quay 4 my car a few years ago I thought that I had sufficient fuel to return home (Poole - Swindon). Just after entering the Salisbury plain area SWMBO mentioned the fuel gauge was nearly on zero. With 25 miles to run & foot off the gas a tad she calmly stated that the needle was resting on zero *yikes*

Safely arrived home & next morning topped up tank. The splashing of fuel on bare aluminium told a story! So from there I calibrated fuel state against the gauge.

Now I know that with the gauge needle on zero I have 22 - 25 miles of fuel remaining. My constant mantra is fill up when indicating just below one quarter even though there is more in the tank.

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but does not seem to change much when only on the road!

if you don't drive like the Stig all the time on the road, if you haven't done already I'd take a look at the plugs to see if Sooty has taken up residence due to an underlying over fuelling problem.

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  • 4 weeks later...

After a two day Blat (Friday/Sat) with 6 others round the Scottish Borders with overnight in Dumfries I covered 675 miles.  I averaged 30.5mpg overall, with a low of 26.6mpg and a high of 34.5mpg (return trip down M6 J40 to J15 in howling storm).

My fuel gauge also now appears to behave itself.  I'm wondering if the bush the float arm runs in has been sticking and has now freed off.  As Geoff says above i think when down on the 1/4 mark there is at least a gallon more than one would be led to believe.

Overall a lot happier with the consumption.

Had a couple of minor issues with car.  Indicator switch just puts indicators on and does a continous beep.  The lock on the fuel filler cap gives me no confidence I will be able to either lock or unlock it.  12volt socket also appeared to fail.  Few more jobs to add to the warranty list.

Colin

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Blimey 38mpg out of 1600 k series - My 1400 Supersport is nowhere near that - 200-220miles out of tank and  that's about it (and that's with areoscreens so less wind resistance) - mind you I don't hold back on revving the arse off it (engine sweet spot is 5,300-7,500) and rarely use dual carriageways/motorways and therefore 5th is rarely used

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Maybe - 220 miles is getting seriously squeaky bum time - generally I refuel at around 200 mile mark and around 30 litres, bit under so I reckon 30/31ish - still better than when I had a Mk2 RX7 - 185 miles out a tank if you really went for it - circa 16/17 mpg - even general drving around 23/24m.pg was typical - mind you those were the days when you could fill up a big tank for under £40 - in the days when you mainly had red nozzles on the forecourt

 

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