Lotus Elan

Timing again...

PostPost by: nigelrbfurness » Sat Dec 30, 2017 10:00 am

You should be using a 41189 distributor. Check its condition first especially for play in the shaft. You can get parts from the distributor doctor online. Fit new springs and points and a new cap then time it statically at 10-12 deg btdc.
Now set your carbs to initial start up state as described in the book. Start the engine and set it to a fast tickover with the throttle stop screws. Let it warm up a bit then go through the usual carb sequence of adjustments from scratch. Once you've done that, take it for a drive to get it thoroughly warm then adjust the timing until revs just start to rise on tick over. Then take it to someone with a rolling road who can fine tune tbe carbs for you.
Last edited by nigelrbfurness on Sat Dec 30, 2017 10:02 am, edited 1 time in total.
1970 S4SE/1760cc big valve/SA-AX block, L2s, 45DCOEs, 1978 Jensen GT, 1962 AH Sprite, Alfa-Romeo 159, 1966 Bristol Bus, 1947 AEC Regal bus.
nigelrbfurness
Third Gear
Third Gear
 
Posts: 398
Joined: 04 Apr 2008
Location: Dunmow, Essex, UK

PostPost by: JonB » Sat Dec 30, 2017 10:02 am

How do I identify the distributor (in situ)?
User avatar
JonB
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 2105
Joined: 14 Nov 2017
Location: South Coast, UK

PostPost by: oldelanman » Sat Dec 30, 2017 11:24 am

JonB wrote:How do I identify the distributor (in situ)?


The type number and build date are stamped on the body and you may be able to see that in-situ with the aid of a morror but the maximum advance is stamped on the cam plate and you would need to remove the fixed points plate to verify that I'm afraid.
distributor-a.jpg and
distributor-40953-001.jpg and
distributor-40953-002.jpg and


Pics are of a Stromberg engine so yours would (hopefully) be a different number.
Roger
S4 DHC
oldelanman
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1676
Joined: 02 Jan 2008
Location: Dorset UK

PostPost by: JonB » Sat Dec 30, 2017 11:51 am

It is...

img_4409.jpg and
My dizzy


Looks to be 6 years younger than the car.

Anyway. I've chosen the right ignition curve from the book. Went back in and double checked the marks. Maybe I was thinking TDC was 10 degrees. When I looked with the strobe, it seems that is exactly what I'd done, so I advanced to the second ridge plus about 20% the gap between it and the third ridge. In other words, 12 degrees @ 1000 RPM.

That seems to have done it (along with the carbs being set up a bit, see other thread). Might not be perfect, but it's running quite well now. No hesitation, misfires, etc and smooth power on acceleration.

Hooray!

Next job please (indicators packed in)...
User avatar
JonB
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 2105
Joined: 14 Nov 2017
Location: South Coast, UK

PostPost by: JJDraper » Sat Dec 30, 2017 5:27 pm

Not sure the numbers refer to the age of the dizzy, as mine have 79 at the end of the numbers. Maybe someone can shed light on what the numbers mean.

Jeremy
PS my dizzy probably needs a rebuild as the timing dances about with the strobe light...
Attachments
23d4-lo-res.jpg and
dizzy-lo-res.jpg and
User avatar
JJDraper
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1012
Joined: 17 Oct 2004
Location: Buckingham, UK

PostPost by: oldelanman » Sat Dec 30, 2017 6:03 pm

JJDraper wrote:Not sure the numbers refer to the age of the dizzy, as mine have 79 at the end of the numbers. Maybe someone can shed light on what the numbers mean.


Have a look here.....

http://mgaguru.com/mgtech/ignition/pdf/ ... s_dist.pdf

"All Lucas distributors have identification numbers stamped on the side. These numbers
include two important pieces of information: the service number and date of
manufacture. A listing of service numbers is available which includes the factory built-in
advance curve, applications and other data. (other link below) These data should also be included in the
workshop manual for the vehicle on which you are working. The distributor manufacture
date is in week/year format and can give a rough guide to the date of manufacture of
the vehicle it came from."

This related info is also interesting although not entirely definitive as the 41189 suffix E is not listed ... suffix A is however listed as a Lotus application.

http://www.mgaroadster.co.uk/Technical_ ... /lucas.pdf
Roger
S4 DHC
oldelanman
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1676
Joined: 02 Jan 2008
Location: Dorset UK

PostPost by: 661 » Sun Dec 31, 2017 11:07 am

Long shot.....vacuum T piece leaking?
Graeme
S4 SE
S2 GTS
Peterson JPS Exige
User avatar
661
Fourth Gear
Fourth Gear
 
Posts: 841
Joined: 29 Mar 2012
Location: East Sussex

PostPost by: JonB » Sun Dec 31, 2017 11:30 am

661 wrote:Long shot.....vacuum T piece leaking?


This distributor has no vacuum advance. It uses weights and springs to set advance relative to engine speed, according to the centrifugal force generated as the distributor shaft rotates.
User avatar
JonB
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 2105
Joined: 14 Nov 2017
Location: South Coast, UK

PostPost by: JonB » Sun Dec 31, 2017 11:45 am

Something just occurred to me.

I have electronic points on my engine but the advance curve is still governed by the springs and bob weights. Is there a way of replacing this with a programmable electronic advance, without going all the way to electronic fuel injection?

Edit: I found this interesting thesis from 1977 that describes just such a system: https://preserve.lehigh.edu/cgi/viewcon ... ontext=etd

..although it also concludes that there's not much performance or efficiency to be gained using electronic over mechanical or vacuum advance. However, the test engine's distributor was probably in better condition than the 43 year old item fitted to my car. I didn't read it fully, but I can see it just uses the impulse from the points to determine engine RPM, but I couldn't see how it determines actual crank position (TDC). It also retains the rotor and distributor cap, and measures vacuum and engine temperature (these are used along with engine speed as parameters for the advance curve generation).

Given this design uses 8-bit technology prevalent at the time with a 25 khz sampling rate, I think it should be possible to implement something similar using a cheap modern embedded computing module like an Arduino, with a higher sample rate.
User avatar
JonB
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 2105
Joined: 14 Nov 2017
Location: South Coast, UK

PostPost by: paddy » Sun Dec 31, 2017 12:33 pm

JonB wrote:I have electronic points on my engine but the advance curve is still governed by the springs and bob weights. Is there a way of replacing this with a programmable electronic advance, without going all the way to electronic fuel injection?


Yes - someone recommended the 123 distributor to me but I've not tried it:

http://www.123ignition.nl/product.phtml?id=282

paddy
1963 Elan S1
User avatar
paddy
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1191
Joined: 27 Oct 2008
Location: Woking, Surrey

PostPost by: MarkDa » Sun Dec 31, 2017 12:45 pm

The 123 system can match the advance curves for twinks but is not what you'd call cheap at c?400+.
However if existing dizzie is completely worn out may be comparable to a rebuild, electronic ignition and rev limiter.
You can also run more than curve if that takes your fancy!
MarkDa
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1148
Joined: 15 Apr 2017
Location: Stroud

PostPost by: billwill » Sun Dec 31, 2017 12:47 pm

JonB wrote:
661 wrote:Long shot.....vacuum T piece leaking?


This distributor has no vacuum advance. It uses weights and springs to set advance relative to engine speed, according to the centrifugal force generated as the distributor shaft rotates.


I think he meant the vacuum takeoff for the headlights & brake servo.
It is screwed into the head in the inlet of the front cylinder
Bill Williams

36/6725 S3 Coupe OGU108E Yellow over Black.
billwill
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 4721
Joined: 19 Apr 2008
Location: London UK

PostPost by: JonB » Sun Dec 31, 2017 12:54 pm

Ah OK. Checking those would entail listening for leaks (hissing) and / or spraying carb cleaner on each joint and seeing if it affects engine speed, yes?
User avatar
JonB
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 2105
Joined: 14 Nov 2017
Location: South Coast, UK

PostPost by: alan.barker » Sun Dec 31, 2017 2:31 pm

On a +2 there is no "T" piece screwed into the head, that is only on a baby Elan.
The "T" piece he is talking about is on the chassis cross member for vacuum take off.
On the +2 there is a vacuum take off screwed into n?1 inlet tract for the Head Lamps and a take off screwed into n?4 inlet tract for the Servo.
Alan
Alan.b Brittany 1972 elan sprint fhc Lagoon Blue 0460E
alan.barker
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 2354
Joined: 06 Dec 2008
Location: BRITTANY FRANCE
Previous

Total Online:

Users browsing this forum: No registered users and 14 guests