Lotus Elan

What can I expect?

PostPost by: prezoom » Thu Sep 21, 2017 4:01 pm

As I play with jetting in the 45's on my Zetec Plus2, I am wondering what I could expect in the way of gasoline mileage. My initial shake down spirited drive up through the mountains, resulted in 27.5 mpg. Is it possible to tune for better mileage in an engine with carbs?
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PostPost by: mbell » Thu Sep 21, 2017 5:58 pm

I presume that's a US Gallon (3.78L) not a UK imperial Gallon (4.54L). If so 27.5 MPG sounds pretty decent to me, especially if driving reasonably hard. There always room for improvement thou but it really depends on how much energy effort you want to go to?

Presuming it runs well and no noticeable driving issues then you probably going to need a Air Fuel Gauge and possible data logging to figure out if there much improvements can be made to the AFR and under what circumstances they could be improved. Given the reasonable MPG your getting your probably need to head over SideDraft central to get some good feedback on possible changes once you have some data.
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: MarkDa » Thu Sep 21, 2017 7:55 pm

Let's face it unless we're using our cars as daily runners on commuting the cost of fuel is going to be small beer.
As said 27.5 miles per US gallon is actually pretty respectable. I've a sneaking suspicion that paying for analysis etc won't be cost effective.
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PostPost by: prezoom » Thu Sep 21, 2017 10:19 pm

Started following Keith back in 2006 on this site, when I bought my S2, and continued to his site when he left here. Lurking ever since, picking the things that worked and were not discarded by him. My carbs are 152G's with 5 progression holes, which up until a short time ago, Keith said would not work. He seems to be changing his mind on this though. He also keeps talking about how thirsty the 5 holes make the mixture. I made a SWAG on the jetting, and have been down sizing the idle jets a little bit at a time. So far, all changes have not changed the engine's running noticeably. Having an Elan that has no bog from idle, and will pull away from below 1500 rpm in 4th gear, using 38mm chokes, and equipped with a 3.54 smoothly, is something I have never experienced before. All this has made me believe the engine may be too rich off idle. I realize that most Zetec conversions employ some sort of electronic fuel injection. But, old age has left me mired in yestertech, plus I like the look of the Webers. I also had a complete electronic crank fire ignition system sitting on the shelf, not a combined unit, which included fuel management. My current mileage is actually acceptable, with a 15 US gallon tank. The car will go farther than my bladder will allow on a single fill up. An AFR would be ideal, but if I can achieve current or slightly better mileage by my seat of the pants tuning, and the car continues to perform as well as it does, the cost of a recordable system does not make economic sense to me. I can buy a lot of fuel for the cost of the system. However, I am curious as to what others have achieved from carburetors, or fuel injection for that matter.
Rob Walker
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1964 Sabra GT
1964 Elva Mk4T Coupe (awaiting restoration)
1965 Ford Falcon Ranchero, 302,AOD,9",rack and pinion,disc,etc,etc,etc
1954 Nash Healey LeMans Coupe

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PostPost by: john.p.clegg » Fri Sep 22, 2017 6:15 am

Avg. 29 mpg Dellortos
Avg. 39 mpg Fuel Injection

No loss in performance...

John :wink:
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PostPost by: denicholls2 » Fri Sep 22, 2017 1:53 pm

The purpose of the Weber/Dellorto carburetion system is not to be fuel efficient.

As a somewhat extreme benchmark for Loti, My S2 Europa on stock manifold and 2-barrel Solex yields above 50 mpg U.S. On Hermes kit (single DCOE 45) it gets about 25, maybe 35 on the highway where it isn't happy because it's a 4-speed and geared to get to the redline in top.

But it's a heckuva lot more fun in 25 mpg mode... :wink:

Gary Anderson told me once that if he needed fuel economy, he'd switch to his Ford pickup instead of the Elan. If you've done time in the passenger seat of his Elan you know why.
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PostPost by: prezoom » Fri Sep 22, 2017 3:45 pm

John, envy.......

Will be taking a more relaxed trip tomorrow, up to Cars&Coffee in San Clemente with Holywood and a friend with a 56' AH 100-4, which is completely original. Cruise driving will give another view, along with another jet change.

Thanks everyone for the info.
Rob Walker
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1964 Sabra GT
1964 Elva Mk4T Coupe (awaiting restoration)
1965 Ford Falcon Ranchero, 302,AOD,9",rack and pinion,disc,etc,etc,etc
1954 Nash Healey LeMans Coupe

Owning a Lotus will get you off the couch
prezoom
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