Lotus Elan

Puzzled with really poor running Plus 2

PostPost by: Matt Elan » Tue Jan 23, 2024 5:24 pm

So there is some light at the end of the tunnel....I drained off the old fuel and added a couple of gallons of new stuff and there was no change. So I'm moving to the ignition system and put a new coil on - no change. I was about to fit new HT leads when I thought about Rohan's suggestion of hotter plugs. I'd been running on NGK BP6ES (and B6ES and BPR6ES) all with the same results. So I bought some B5ES (they were all the shop had) the car started well and I managed to drive the car a mile down the road and even got back OK! It's still a bit sensitive to throttle position but does pull decent revs and hasn't yet gone down to three or two cylinders. So a bit more faffing about is needed but it is tending yo look like plugs. I'll update as and when I have any more breakthroughs but I an hoping that the issue is thais simple.....
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PostPost by: rgh0 » Tue Jan 23, 2024 11:24 pm

Possibly still a overly rich mixture problem that the hotter pugs are helping compensate for

cheers
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PostPost by: Lotus54 » Wed Jan 24, 2024 12:28 am

Here in the States, it seems NGK has discontinued the non-resistor plugs. So may want to stock up if you need those.

Yes, overly rich mixture and poor spark both can require hotter plugs not to foul. I actually had best results with a multifire ignition and very hot coil at about .060” sparking plug gap. But the cap only last a very short time (lesson learned). Sure ran well though. I finally found about .035” would work and help a poor progression circuit. This was on a 74 Lotus Elite with Webers rather than the DellOrotos.

I would suggest taking a good look at your e-tubes and see what they are. They make a huge difference in ‘regular road’ driving- at least in my experience. (I think you said it used to be good, but good to know anyway).

Just thoughts off the top of myhead.

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PostPost by: h20hamelan » Wed Jan 24, 2024 7:45 am

Neat thing
With some heat, you can unscrew the ceramic top of a plug and remove the resistor.

Then again, there are some other plugs which may outperform NGK.
Maybe NGK is resting on their laurels?
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PostPost by: rgh0 » Wed Jan 24, 2024 8:07 am

I think you are just seeing product rationalisation by accountants. The non emission plugs such as the BPxES range are having less and less demand so becoming more of a speciality item.
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PostPost by: Matt Elan » Tue Feb 20, 2024 10:27 am

Quick update - I've done about 40 miles now with the B5ES plugs in and have not had to clean them once. The car starts and runs well, and other a definite 'fluffy' period as it transitions off the pilot jets and onto the main jets its running well. And all the electrics seem to be behaving which was the object of the exercise in the first place!
I'm going to get my carb man to take a look at it once I've got a few more miles on it but touch wood its looking good.
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1969 Plus 2S - Currently undergoing nut and bolt restoration
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PostPost by: Dellortofan » Sat Feb 24, 2024 7:49 pm

I am suspicious of shell optimax in classic cars.
I've had a similar problem, won't rev under load. Bit of a weird coincidence...
Not a good coincidence.
Some engines are very plug sensitive. Use whatever it prefers.
Projector nose plugs can improve performance. The spark is closer to the centre of the chamber, almost like advancing the timing...
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PostPost by: Dellortofan » Tue Feb 27, 2024 12:02 pm

I will try the b5es then.
There are triple electrode ngk for electronic ignition. Bp6et. That's my next try.
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PostPost by: Dellortofan » Tue Feb 27, 2024 12:03 pm

Any one else had issues with SHELL v-power?
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PostPost by: Matt Elan » Fri Mar 01, 2024 11:13 am

Another update - the car had a pronounced flat spot as it transitioned from idle to main jets - it had to be 'nursed' on the throttle otherwise it would bog down, but would run ok once it had transitioned. I'd not explained this to my carb guy who has set the carbs up in the workshop so the tick over and balance were spot on, and he was mortified when I drove off with the obvious problem! We had a chat on the phone the day after and decided it must be down to the float height. Now I had reset the float heights when I rebuilt the carb, but had made the mistake (i.e I had not read the manual properly) of setting the height with the float valve fully closed. The float needle is sprung and there is a considerable amount of extra movement of the sprung part once the valve itself has closed. So my setting on the float valve meant the fuel level in the float chamber was far too low. When I re-read the manual and followed my carb guy's advice the transition issue was fixed. So another lesson learnt - including RTFM!
The car is now running nicely and I can happily drive it somewhere, stop and have a good degree of confidence that it will restart!
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1969 Plus 2S - Currently undergoing nut and bolt restoration
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