Lotus Elan

AFR wideband primitive data logging

PostPost by: gjz30075 » Sat Aug 20, 2016 6:24 pm

Has anyone ever played with one of these things? Pretty cool, I think. I purchased an AEM wideband analog
kit recently to see exactly what goes on with the air/fuel ratio throughout the rev range.
Some specs first: 1720cc engine
40 DCOE 151 Webers -
33 mm chokes
50F8 idle
130 mains
170 air
F11 emulsion
Timing is 12 degrees initial, at roughly 900 rpm (curved to be a 40953 spec)

Plugs are BP5ES (plug #1 is on the left

Bung attachment point

I experience a slight stumble on initial acceleration. I think the gauge shows that it goes very lean
at that point.

Heres the 'data logging' bit:
http://s262.photobucket.com/user/gjz300 ... sort=3&o=3

No real question here, just some of your thoughts on this whole setup.
Attachments
dsc08377.jpg and
bp5es.jpg and
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36/5727 pre airflow coupe
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PostPost by: Grizzly » Sat Aug 20, 2016 7:12 pm

Have you checked your Pump jets?

As you might have noticed Wide bands are good for telling you if there is a fault but not what is faulty. There great on EFI cars because you just datalog and compare AFR at different loads and at different air temps etc then adjust the Injectors accordingly but with carbs it just gives you a rough idea (not enough data)
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PostPost by: gjz30075 » Sat Aug 20, 2016 7:36 pm

I don't know what the pump jet size is but all were working when I put the carbs on. From the looks of
the needle going very rich at tip in, I guess they're working.

Some back story here: Car was running fantastic before I pulled the engine to seal it up. It was leaking
badly and the previous builder had put in valve seals on the exhaust side and was blowing smoke, too, due
to a broken seal. Why it would blow smoke with a broken seal when oem design has no seals, I don't know. Despite all that the car ran great, plugs were tan, and no hesitation at tip in.

Now, after the engine is back in with the only significant changes being tighter valve clearances, a leak free and smoke free running engine, and me installing the carbs back on, I now have the stumble on tip in, a slight popping sound with a constant throttle and plugs looking a bit on the lean side. All indications seem to
point to an air leak somewhere but I can't find it.
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PostPost by: mbell » Sat Aug 20, 2016 7:48 pm

Will probably get a bung fitted in exhaust while I have access. But agree that that afr is interesting but with out other data (at least rpm, throttle position) it pretty hard to use it to tune.

Any one know what Keith Frank's does? Only ever seen him post afr plots but would have thought he had a much more comprehensive setup.
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: gjz30075 » Sat Aug 20, 2016 7:55 pm

Mbell, you're right, which is why I call this primitive. At least you can hear the revs, when I accelerate and
when I back off. Even a steady throttle can be heard. It's crude, at best :)

This kit has extra wires and I think they are used to connect to their data logging device but I'll still need
a tps, I'm sure.
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PostPost by: john.p.clegg » Sat Aug 20, 2016 8:10 pm

Greg
Thanks,you've pointed me in the right direction for solo tuning,record the data screen while voicing over the comments...just what I've been lacking,just need to work out the settings on the iphone...

John :wink:
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PostPost by: webbslinger » Sun Aug 21, 2016 4:58 am

I too bought an AFR guage and put the bung in the exhaust. We used it on the dyno after rebuild to confirm that the jetting wasn't too lean. The shop used their gear and computer. I believe we were looking for readings between 12 to 13 and up to 14 at tops, but don't take that as expert advice. I haven't hooked up my guage because I don't need any more distractions or stuff to worry about, but having the bung at least is a good way to be able tk confirm initially on a dyno that you aren't running too lean at high rpms. At the session, I don't think we discussed using the AFR information for anything else.
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PostPost by: holywood3645 » Wed Jun 26, 2019 6:40 pm

Greg Z
I also have a similar set up on my elan
1700cc QED super sprint 420S spec engine
QED 420s cams
Lucas CE ignition with 40DCOE151 carbs
140/150 hp spec


The QED jetting spec
Choke 34
Main 140
Air Corr 155
Emulsion F16
Idle 45F8
Timing 10 deg

Jetting seemed pretty close with good fuel economy and plugs looking good. However I had a slight stumble around 3k rpm at slow throttle progression. I changed the idle jet to 50F8 and cured the issue... the only issue I seemed to have was very slight pre-ign at low RPM under load (hills). But nothing to worry about.

I had also visited Keith Frank while attending GG West coast meet about a month ago along with Rob Walker (prezoom) and fitted his VF tubes. The car felt it had more torque and felt good. However after a 400 mile trip home my fuel consumption had dropped to 23 MPG and the plugs were very sooty. Talked to Keith who had also
Seen same on a BRM spec motor and had redesigned a second set of tubes more suited to my engine spec. I fitted them last week end and the car is performing as good, if not better than before (QED 420s jetting with the 50F8’s)
A noticeable improvement is the pre-ignition has gone. I need to do a long run and check plugs and fuel consumption.
An interesting point also is, my friend Rob (prezoom) Zetec with 45’s runs good with the orginal version of the VF’s
With performance, plugs, and mileage good.

James

Old VF tubes on left new on right
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PostPost by: Greg Foster » Sun Jul 28, 2019 1:57 pm

How do you get to Keith's store?
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'72 +2 S130
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PostPost by: gjz30075 » Sun Jul 28, 2019 2:56 pm

Greg Z
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PostPost by: prezoom » Sun Jul 28, 2019 4:00 pm

Along with what James said, absolutely love the way the Zetec Plus2 runs. Gearing wise, it has a close ratio with 3.54 diff. Bought another set of the original VF tubes along with a set of his adjustable jets from Keith for the S2, but am having serious problems getting it to run right. Bought an AEM against Keith's advice, but have not installed it as "honeydo's" are taking up all my time. I did installed a port for an O2 sensor when I built the exhaust system for the Plus2, but when Keith installed the new VF tubes in the 152G's he used an exhaust probe. Back to the construction projects.......... For those who understand, I call my wife Mrs. Winchester.
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PostPost by: oldchieft » Mon Jul 29, 2019 12:12 pm

looking at what might have got disturbed during engine work.

I would be looking at sucking air at the carbs or a float got damaged or moved and your fuel level needs adjusting.

I would check the float chamber levels first

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