Lotus Elan

Jenvey Heritage TB kit

PostPost by: davidc » Wed May 02, 2018 11:53 am

I'm pretty much finished with the resto of my plus 2.

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now I have a dilemma to sort in my head. :roll:

I doubt very much its going to be an every day car, weekend toy is more how I see it and similarly doubtful it will see daylight through the winter with the exception of the odd cool dry day.

I'm concerned about carburetor and traditional ignition troubles making me loose faith in it. i had intermittent issues with a classic mini years ago where pretty much every time i went to use it is would play up and could not trace fault so started to resent it!.

I've not actually had any issues yet as its not been on the road but i do know in the time since i fully stripped and reconditioned the carbs last year and flushed the tank through with new fuel this will probably need doing again and a good clean of the carbs due to stale fuel.

combine that with stories i read on here about flat spots and stuttering and hot start problems along with carbs being difficult to tune to get most out of engine across the rev range i'm wondering if i should just bit the bullet and go down TB route.

i'm keen to keep originality look so for the bit extra i'll probably go with the kit from QED and use the jenvey heritage system. i'll also keep the webbers and points etc... so can be put back to original if ever required.

is my thinking that TB route is the panacea to all poor running and not getting the most out of a twin cam way off mark?

those who have a form of TB seem to rave about it and laugh off the lack of originality.

finally i consider myself to be pretty good on spanners having done everything to mine except the respray, how difficult would the kit be to fit and am i missing anything that could catch me out like for example needing bigger fuel line from tank to engine bay of needing a return loop or different breather system? don't want to start undoing stuff that's finished!

thanks in advance for any input.

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PostPost by: jono » Wed May 02, 2018 2:58 pm


this is something I planned from the outset of my restoratation 10 years ago yet, still, I have not yet got around to it!

I understand that it does make a huge difference to starting, running, torque and economy and it still appeals very much to me. But, don't under estimate the cost - to do it properly including mapping you are looking at around ?3,000.

I ended up going half way with 3D wasted spark ignition and that does make a big difference. When I built the car I had an FI tank made by Andy Wiltshire and ran in the flow and return lines through my chassis. The wasted spark requires a crank trigger and toothed wheel anyway and I also have a TPS on the carbs as part of the system and I had an oxygen sensor boss built into the my exhaust manifold at the time as it was custom made.

In theory to go the whole way I need a high pressure fuel circuit, DTA or similar ECU, loom, throttle bodies, various other sensors and probably a host of other stuff. Oh, and mapping /RR time.

I reckon I'm still a good 2k away from it and everytime I feel ready to do it something else calls on my money!

I still want to do it and think it will make a big difference to drivability and getting rid of flat spots and the rich running at idle. Its got to be good for longevity as well what with bore wash and all that from the crude carbs?

Personally, setting aside the cost saving, I would be happy with the original pattern Jenveys as I prefer an 'honest' modification and am more interested in driving than originality so long as the car looks standard on the outside

Best of luck if you go with it!

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PostPost by: JonB » Wed May 02, 2018 3:21 pm

I'm definitely going to watch this thread with interest. My car runs pretty well, but of course it is thirsty and there are various glitches across the rev range at different temperatures. I like the idea of a complete injection kit with a near original look - it's expensive, but then so is pretty well everything else to do with the car...

Nice resto job by the way - would be good to see some more pictures!
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PostPost by: pauljones » Wed May 02, 2018 3:38 pm

Search my posts on EFI and the gallery for my dyno print out.

Put simply, its a fantastic mod.

Yes it is expensive, from recent communications with others your looking at a 3k job.

If anyone fits an emerald system i will email them my rolling road map providing they agree to a donation to elan.net

If your handy with spanners you can fit it all yourself, its the wiring that scared the life out of me so thankfully i helped my mate do it all.

Parts required.

Full tank with supply and demand to suit -8 size.
Stage 1 filter before high pressure pump.
High pressure pump (044).
High pressure filter.
Fuel pressure regulator with return to tank.
Dcoe style bodies look best imo, bike tb's also work well.
Trigger wheel, either crank based on lower pulley or as per zetec, on the flywheel. Both work equally as well.
Blanking plates for dizzy and fuel lift pump as theyre removed.
A large airfilter to fill the gap like mine (see new filter as ramair) or as other suggest a large airbox with nose cone mounted remote filter.
Air trumpets to fit in above,
Ignition module and leads, common item is ford generation 2 and leads from Halfords. Cheap on a trade card.
Wide band lambda senser, not 100% required but helps with auto tune functions and maintaining pre set afr's.
Coolant sender to suit system. Omex needs different to emerald (emerald can read both iirc)

Clearly the wires and fuel pipes too but thats about the complete list.maybe missing some bits but im sure thats enougth to get going.

Ive been asked about the drivability a few times. As expected its great to drive. Starts on the button, drives from cold, no hot start issues, genuine 40mpg or more with 3.54 diff. But thats motorway cruising and we dont have loti for that. A weekend of fun at Thruxton returned me 20mpg on track on average.
Pompey to Thruxton and back was less than ?20 a day in fuel last year. Great commute to be honest.

Bere in mind you wont get much if any increase in wot power but mid range is where it excels.

Would i go back, no.

Hope that helps you.


Kick the tyres and light them fires...!!!!!!!
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PostPost by: RichardHawkins » Wed May 02, 2018 7:59 pm


I went to see Jenvey, and they reckon the all in hardware to be about ?2000, and with time on a rolling road I expect the total cost would be ?3000 or even more.

I have decided to go with a wasted spark Electronic Distributorless Ignition System and retain the carburettors. If I cannot get satisfactory results I will spend the money on the Jenvey fake Webbers. One of the things that put me off Jenvey, is their name cast into the top of the fake Webber. If you want it to look old but go like a current vehicle, the lack of the Webber name is a bit of a stumbling block for me.

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PostPost by: elanman999 » Thu May 03, 2018 6:58 am

As PaulJ says +more.

Yes, it's not cheap but if you want to drive your car then it is worth it. No hiccups, no wetting plugs just drive.
But, if you fit it all yourself you will need to be quite good at wiring.
I have Emerald and Jenvey TB's, fitted 5 years ago. Other TB's and ECU's are available.
PM me if you need more info.
Edit, here is a pic of my setup.

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Last edited by elanman999 on Thu May 03, 2018 7:29 am, edited 1 time in total.
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PostPost by: dougal9887 » Thu May 03, 2018 7:28 am

This is the route I went down, following my restoration. Same year as yours by the looks of it.
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Elan Plus 2S 130/5 1973

Except that I chose to make it a project in itself, which turned out to be hugely rewarding and educational!
My system comprises of Suzuki GSXR throttle bodies, Megasquirt ECU, wasted spark coil packs and high pressure fuel system.
All the above can be self designed and assembled for much less than the costs mentioned, and it's huge fun! Megasquirt has a self tuning function which really simplifies self mapping on the road. I used a rolling road only to have the ignition mapped for max torque, the fuel map was found to be spot on! The results are superb and IMHO make the best of this wonderful engine. First turn of the key starting under any condition including after winter lay-up, great flexibility and surprising fuel economy. I wasn't concerned about originality, however it is all reversible.
Here are a few pics:
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Fuel injected 1700cc Lotus Twincam.

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GSXR throttle bodies.

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High pressure fuel system.

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Megasquirt ECU under construction.

Lots more info and pics if you're interested.
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PostPost by: Orsom Weels » Thu May 03, 2018 7:44 am

I agonised over this 5 or 6 years ago. I was having problems with the Webers after my +2 had spent some time in storage & all the cleaning in the world, including ultrasonic didn't seem to help. Having just put the car back on the road, funds were tight & it was never going to be an every day car again, just t odd weekends through the summer, & I couldn't justify the expense of the Jenvy set up so opted instead for a new pair of 151's at less than a third of the outlay. Spent a little time setting them up & in short, they transformed the car, no flat spots, clean idle & pick up, general performance & fuel consumption much improved. I still like the idea of injection, but for a car that only gets occasional use, for me it' still hard to justify the cost & overall I'm well happy with the route I went.

Regards, Tim
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PostPost by: jimj » Thu May 03, 2018 8:23 am

As ever, with a question about any modification, those who`ve done it will be in favour. It`s human nature. We have 2 Elans, both on Dellortos with mechanical fuel pumps so, OK, if the car hasn`t been used for a while it does require a bit of churning to pull the fuel through but that`s all.
All this talk of flat spots and rough running is, invariably, a result of owners "tuning" their carbs. themselves. I know people like to do that but, personally, I`d recommend having the ignition and carburation set up on a rolling road then DON`T touch `em.
The longest we left a car unused was 6 months, for a particular reason. On that occasion I did put a fuel bulb in line to pump the fuel through, mindful that the battery may be weak. With 4 pumps of the accelerator the car coughed and fired on the first turn and started on the second. Marvellous.
In short I`d say save all that cash and spend a little on a professional set-up, no matter how capable you are.
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PostPost by: nigelrbfurness » Thu May 03, 2018 8:59 am

I tend to agree with Jim inasmuch as if you tune your webers correctly then you can get consistent good behaviour and performance. Add an electric fuel pump and the problem of churning it over to get fuel into the carbs is fixed too. Where theTB efi systems win is that the ecu can constantly retune the fuel delivery for changing ambient conditions. A common weber problem that really upsets driveability is setting the float heights and ensuring the floats are free to move easily. All too often I've had owners grumble about flat spots they can't tune out and it turns out to be a sticking float!
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PostPost by: JonB » Thu May 03, 2018 10:31 am

I suppose this float problem would affect Dellortos too... correct?
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PostPost by: billwill » Thu May 03, 2018 10:44 am

Surely all that high-pressure fuel lines stuff is needed for the Fuel Injection, not for the wasted spark ignition, you can have the ignition stuff without the injection, can you not?

But my advice to the original postee is: Stop Greek Philosophizing, get the the car and DRIVE it.
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PostPost by: elanman999 » Thu May 03, 2018 11:10 am

billwill wrote: you can have the ignition stuff without the injection, can you not?


Yes you can.
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PostPost by: davidc » Thu May 03, 2018 11:25 am

Stop Greek Philosophizing, get the the car and DRIVE it

love to but need to strip carbs down again now :lol: :roll:

thanks for input guys.

QED have confirmed their kit does need lambda sensor adding to exhaust and also a return line to the tank.

i was hoping this wouldn't be the case as i want it to be unmolested to turn back to stock if future needs/owner so desired.

i may fork out for a good rolling road tune up of the webbers and see how i get on but at first sign on it misbehaving i know which route i can take. :wink:
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PostPost by: JonB » Thu May 03, 2018 11:29 am

Let us know how you get on with the Webber tune...
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