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What Miles per Gallon Do You Expect on the RBRR


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Only started this thread because I've just got the Spitfire back from being retuned and was curious what mpg we would achieve running on the RBRR route.

Katy and I did a trial run from Gartcosh down to the Tesco petrol station at Carlisle off the M6 J43 that we intend to use for Momentum petrol on the RBRR.

We brimmed the tank at Tesco Cumbernauld with the intention to brim it again at Carlisle and again back at Cumbernauld.

We kept a steady 65 to 75mph just keeping up with the traffic all the way down the M73, M74 and the M6 and averaged 32mpg, which surprised me how low it was.

On the way back, we avoided the huge tailbacks northbound on the M74, due to bridge works from south of Larkhall to Hamilton and went cross country from Abington, through Lanark, Carluke and Newmains before joining the M8 and M73 back to Gartcosh.

This time, we averaged 39mpg after keeping a steady 50 to 60 mph off the motorway and a lot slower through the towns.

So, if we go with our worse case scenario of 32mpg, with the fuel stops we intend to make, we should have plenty of petrol to get round.

The Spitfire performed faultlessly and we now have the joy of an overdrive that engages when we want it to rather than when it feels like it.

A great day's driving and a useful shakedown for the RBRR.

Jim.

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On this years Coast to Coast event we averaged 33mpg in our Stag over the 870 miles. Obviously the Mpg was much better on the M56, M60, M62 sections getting from Cheshire to the start at Flamborough Head and then back home again than what we got on the roads over the Yorkshire Moors and Cumbrian Fells. 

Based on that route mix I am hoping for 35mpg overall on the RBRR.

Bruce

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I always got around 32mpg on a Triumph 4-pot - 1300 and 1500 varieties. 

 

I get 28-34 mpg out of what's in there now. I've just fitted a new FPR so hope to have a bit of a play with its settings and a tinker with the laptop on the way to the first control stop.

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2 minutes ago, ferny said:

I get 28-34 mpg out of what's in there now. I've just fitted a new FPR so hope to have a bit of a play with its settings and a tinker with the laptop on the way to the first control stop.

FPR? 

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Good topic @McJim! I get a bit obsessed with fuel economy.

On the 2018 RBRR my mk3 Spitfire miraculously averaged over 40 mpg, the best economy figures i've ever had. However it also got through a gallon of oil.

Since then i've messed about with the cylinder head and exhaust so it's a bit perkier performance-wise but noticeably worse on fuel (also had a rebore so hopefully won't need so much oil). So I'm expecting something around 33mpg, but hoping for 35.

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In 2018, we were getting 38 - 40 mpg but we weren't pressing on since the engine sounded really rough.

We were pushing on today but I have my suspicions that the tank wasn't brimmed before we set off.

Still, with our planned fuel stops we won't be running dry (I hope).

Our longest run between stops is 185 miles from Wetherby to Shell Dreghorn at Edinburgh but a good part of that is on roads like today when we averaged 39mpg, so not too bothered.

Jim.

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Not RBRR specific, but my Mk3 with J type overdrive consitently returned 38mpg on along steady crusing runs with over 30mpg on shorter wiggly bits.  It's a standard engine but the carbs were properly rebuilt some years ago.  My Stag struggled has averaged 25mpg on the last few 10CR's that it has done, with the worst section dropping to 21mpg (mountains) and the best coming in at around 27mpg.  It used to do better, but the carbs are now pretty shot and not quite set up for the tubular manifolds it now has fitted.  A rolling road session highlighted this as well as the fact that around 30 of it's original horses were missing!

I need to decide where to invest the money - do I sort out the twin Strombergs, do I fit a Stagweber or similar or do I move to efi?

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I have just done the NC500 in my 1980 Spitfire 1500 with overdrive - 1300 miles door to door, 2 up with luggage.

The roads included 750 miles of dual carriageway and 550 of mountainous roads of which approx 200 miles were winding single track.

Average consumption was 36.4 mpg and used a pint of oil.

Picture was taken on a detour to Skye.

1C7EFD7F-6011-4034-9045-B70CEC988646.jpeg

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I think my Spitfire gave about 39mpg in Yorkshire last month, including the journeys there and back. That was being driven a bit more gently than it sometimes gets (SWMBO was with me and she's not a speed freak). It will be interesting to see what it gives on the Cambridge group's Peaks-Lakes-Dales run next week.

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On 11/09/2021 at 18:49, Rubce said:

On this years Coast to Coast event we averaged 33mpg in our Stag over the 870 miles. Obviously the Mpg was much better on the M56, M60, M62 sections getting from Cheshire to the start at Flamborough Head and then back home again than what we got on the roads over the Yorkshire Moors and Cumbrian Fells. 

Based on that route mix I am hoping for 35mpg overall on the RBRR.

Bruce

I take it you will pushing the car part way Bruce :) 

Tony.

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On 11/09/2021 at 18:49, Rubce said:

On this years Coast to Coast event we averaged 33mpg in our Stag over the 870 miles. Obviously the Mpg was much better on the M56, M60, M62 sections getting from Cheshire to the start at Flamborough Head and then back home again than what we got on the roads over the Yorkshire Moors and Cumbrian Fells. 

Based on that route mix I am hoping for 35mpg overall on the RBRR.

Bruce

Managed 37mpg in the Vitesse on the C2C pushing it fairly hard most of the time though the trip up the A1 to the start and back to Cambridgeshire was at a more steady 65-70 MPH.

Interestingly on the last RBRR the 2500 TC only came in 1 MPG lower than a couple of 2000's I compared it with. 28 and 29 mpg from memory. The thought was the 2000 had to be pushed harder than the 2500 especially on the hills.

At the end of the day its not about MPG its about SPG. ( Smiles Per Gallon)

 

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On 11/09/2021 at 23:07, PeteStupps said:

Good topic @McJim! I get a bit obsessed with fuel economy.

On the 2018 RBRR my mk3 Spitfire miraculously averaged over 40 mpg, the best economy figures i've ever had. However it also got through a gallon of oil.

Since then i've messed about with the cylinder head and exhaust so it's a bit perkier performance-wise but noticeably worse on fuel (also had a rebore so hopefully won't need so much oil). So I'm expecting something around 33mpg, but hoping for 35.

Only 1 gallon of oil, on our first RBRR we used 5 I think it was.

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I'm only getting around 24 mpg on a run in my VItesse ( Round trip to drivers meet) -  running a little rich perhaps but apart from that seems in good tune - I'm happy but would be happier at 28! 🙃  Any thoughts? 

An oil change and a squirt of Penrite Semi Fluid Grease in the Trunnions next weekend and I'm as ready as I'll ever be.  

 

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