mPG

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JoeLondon
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#1 mPG

Post by JoeLondon » Tue Sep 29, 2020 5:29 pm

Well.. I just filled the tank for the second time and ran my calculation for MPG. I wasn't expecting too much, but I also wasn't expecting so little - a whopping 7.69 MPG! :seeingstars: - Hence the title mPG

All city driving in stinky traffic, and I've been "enjoying" the V12 aplenty, but is there anything other than my right foot that I should be looking at?
Joe
1972 S3 2+2 V12 Manual, FHC, Racing Green

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Heuer
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#2 Re: mPG

Post by Heuer » Tue Sep 29, 2020 5:49 pm

Purchase of an oil refinery?
David Jones
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mgcjag
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#3 Re: mPG

Post by mgcjag » Tue Sep 29, 2020 6:23 pm

Hi Joe...i was drivring from SE london into the city quite a few years ago.......13 miles usually took 1hr 45mins....yes you arnt going to get many mpg...especially in a V12.....Steve
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Gfhug
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#4 Re: mPG

Post by Gfhug » Tue Sep 29, 2020 7:00 pm

Joe, buy an S2 :wink: 29 mpg for Malcom, post no. 15
viewtopic.php?f=13&p=135309&sid=233a4cf ... 54#p135309

Though I reckon he was slipstreaming a pantechnicon :bigrin:

Geoff
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JoeLondon
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#5 Re: mPG

Post by JoeLondon » Tue Sep 29, 2020 7:34 pm

Thankfully oil price is dropping :roll:

Looks like I'll be getting chummy with the guys at the petrol station, I might see if I can open an account.

I wonder how it runs if I unplug half the HT leads
Joe
1972 S3 2+2 V12 Manual, FHC, Racing Green

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PeterCrespin
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#6 Re: mPG

Post by PeterCrespin » Wed Sep 30, 2020 1:09 am

“I wonder how it runs if I unplug half the HT leads?”

Don’t unplug the leads, unhook one of the capstan rods. No bore wash and not unpleasant at slow speeds. I unhooked one side a long time ago before letting a very famous E-type person drive his/her first Series 3.

After 2-3 miles I told him/her to pull over in a country lay-by and popped the bonnet up to reconnect A-Bank so it wasn’t merely idling. “You’ve passed the test!” I joked and she/he availed themselves of all twelve cylinders.
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 2001 Vanden Plas

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AussieEtype
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#7 Re: mPG

Post by AussieEtype » Wed Sep 30, 2020 3:40 am

I kept detailed fuel records for my V12 - worst ever is 12.5mpg and best ever was 17.5mpg - normally around 14 -16mpg.

So at 7.5mpg you have an issue - get the car tuned/looked at.

Garry
1971 Series 3 E-type OTS

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#8 Re: mPG

Post by christopher storey » Wed Sep 30, 2020 9:23 am

Although Garry's advice to have it tuned is sound, London is very very different from Canberra ! I remember when the XJS was brand new, a friend bought one and found even out of town he was getting only 9 mpg, and that sort of figure is quite common on petrol Range Rovers . So, whilst you may be 1 or 2 mpg down on best figures, your result doesn't exactly shock me , particularly if your is automatic

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JoeLondon
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#9 Re: mPG

Post by JoeLondon » Wed Sep 30, 2020 10:21 am

I won't go hunting specifically for missing MPG, I'll get to it along the way -
It's probably prudent for me to go through the carbs now anyway, and/or Im thinking of EFI or similar. What's the current school of thought on electronic ignition for these V12s, I see plenty of discussion on the forum.

I would be interested in any slight improvement in MPG, but also less stinky exhaust and spritely throttle response. But also not looking to get too complicated. Does the 123 thing work for V12's?

Quite happy to stay stock on the carbs if there's no real advantage, my car is driver level finish. I'm not trying to get a show car together.

(maybe i'd be better off disconnecting the throttle altogether, I can then sit in the car making vroom vroom noises)
Joe
1972 S3 2+2 V12 Manual, FHC, Racing Green

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ralphr1780
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#10 Re: mPG

Post by ralphr1780 » Wed Sep 30, 2020 10:35 am

Upgrade to a start-stop engine management 😁
Ralph
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Marcus2571
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#11 Re: mPG

Post by Marcus2571 » Wed Sep 30, 2020 2:07 pm

Sorry being a bit thick but what is a capstan rod and how does one disconnect it? I've got a 4.2 straight 6...


PeterCrespin wrote:
Wed Sep 30, 2020 1:09 am
“I wonder how it runs if I unplug half the HT leads?”

Don’t unplug the leads, unhook one of the capstan rods. No bore wash and not unpleasant at slow speeds. I unhooked one side a long time ago before letting a very famous E-type person drive his/her first Series 3.

After 2-3 miles I told him/her to pull over in a country lay-by and popped the bonnet up to reconnect A-Bank so it wasn’t merely idling. “You’ve passed the test!” I joked and she/he availed themselves of all twelve cylinders.

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AussieEtype
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#12 Re: mPG

Post by AussieEtype » Wed Sep 30, 2020 2:12 pm

christopher storey wrote:
Wed Sep 30, 2020 9:23 am
Although Garry's advice to have it tuned is sound, London is very very different from Canberra !
My figures are from when I lived in Hambledon in Hampshire and the car was used most days - is an auto as well.

Having said that - figures here in Australia are the same.
1971 Series 3 E-type OTS

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#13 Re: mPG

Post by mgcjag » Wed Sep 30, 2020 4:12 pm

Hi Joe.....Mpg figures are all well and good if the car is moveing, so you need to give some context..... as soon as you stop then your on 0 mpg....as i mentioned in a post above regular driving into the city(London) 13 miles took 1hr45 ..if your doing this sort of journey then you will be in the 7mpg area...but not very good for your engine....Take the car out for a good(Italian tune up)..give it a blast....then a long run out off London....fill up to the brim first......then refill and calculate mpg.........you will then find out if you running well or not..........Steve
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1969 S2 2+2 & Building a C type replica

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JoeLondon
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#14 Re: mPG

Post by JoeLondon » Wed Sep 30, 2020 6:05 pm

Thanks Steve.. Good idea. Will do.
Joe
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#15 Re: mPG

Post by PeterCrespin » Wed Sep 30, 2020 10:44 pm

Marcus2571 wrote:
Wed Sep 30, 2020 2:07 pm
Sorry being a bit thick but what is a capstan rod and how does one disconnect it? I've got a 4.2 straight 6...
The thread is about V12s, which use a single cable to operate the throttles on each bank by a system of push/pull rods operated by a single capstan (rotating plate) on a cast bracket in the rear centre of the engine 'valley.

It wasn't a serious fuel saving suggestion but it's a fun party trick and far kinder than cutting off the fuel or sparks to one bank.

The equivalent 4.2 action would be to remove the link between the two carb throttles on a Stromberg car and leave the fron three cylinders idling while the accelerator linkage operates the rear carb only. You can guess how uninspiring the performance would be. If a person were that desperate to save fuel they should get rid of their Jag and buy a Wolseley Hornet or a Vanden Plas 1100.
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 2001 Vanden Plas

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#16 Re: mPG

Post by chrisfell » Thu Oct 01, 2020 5:24 am

“ a Wolseley Hornet or a Vanden Plas 1100.”. What’s wrong with the Riley Kestrel?
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Last edited by chrisfell on Thu Oct 01, 2020 12:26 pm, edited 1 time in total.
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#17 Re: mPG

Post by Neil Duke » Thu Oct 01, 2020 6:36 am

ralphr1780 wrote:
Wed Sep 30, 2020 10:35 am
Upgrade to a start-stop engine management 😁
Spend all your money on starter motors,instead of fuel. :lol:
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He who dies with the most toys wins.

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JoeLondon
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#18 Re: mPG

Post by JoeLondon » Sat Oct 03, 2020 11:46 am

Peter,
Now I get what you're saying, that's actually quite an interesting concept :bigrin:
Joe
1972 S3 2+2 V12 Manual, FHC, Racing Green

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