Lotus Elan

Distributor advance

PostPost by: simonriley11 » Sun Feb 12, 2006 4:57 pm

My car is a UK spec 1973 Big Valve +2 running on Dellortos. I have just stripped the distributor, it has serial no 23D4 type 41189E. When I removed the centre spindle (the bit which carries the rotor arm) I noticed it has a 'cam' attached to it at the bottom just above where the bob weights lie in the distributor. It seems to work by finally registering against a stop when the distributor speeds up thereby controlling maximum advance. This 'cam' is clearly marked with the symbol 10 degrees, which presumably is the maximum advance. However, my manual seems to indicate that the maximum centrifugal advance for a 41189A distributor is 14 degrees, so have I got the correct distributor/advance?
simonriley11
Second Gear
Second Gear
 
Posts: 62
Joined: 19 Jul 2005
Location: UK

PostPost by: john-c-elan+2 » Sun Feb 12, 2006 11:12 pm

Simon, my +2s/130 with del's has exactly same as yours, and I know its correct one. jon
john-c-elan+2
Second Gear
Second Gear
 
Posts: 125
Joined: 22 Sep 2003

PostPost by: rgh0 » Mon Feb 13, 2006 9:43 am

Delortos were supposed to come with a 41225 distributor for compliance with emission regulations ("ECE15" in the manual) when Delortos replaced Strombergs. This 41225 distributor was supposed to have 19 degrees of crank advance maximum.

Now your 41189E distributor is not listed in the manual but the "10" on the cam represents a maximum of 10 degrees of distributor advance or 20 degrees of crank shaft advance.

This 20 degrees of ignition advance in the 41189E ( is E for emissions?) is close enough to the 19 degrees for the 41225 to make no practical difference. Sounds like a typical Lotus fudge where the 41189E distributors were available (and may be cheaper?) so they made an undocumented change for some of the production.

What the right advance for your engine is today on your fuel today is a whole new question previously debated at length. But if running 20 degrees of distributor advance in a normal road engine you will want to set the static advance around 6 to 8 degrees IMHO.

Rohan
User avatar
rgh0
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 7486
Joined: 22 Sep 2003
Location: Melbourne, Australia

PostPost by: john-c-elan+2 » Mon Feb 13, 2006 11:23 am

Lotus workshop manual says: (page 13 of specs) ' Weber & dellorto carbs (s130) - 41189. My pal Brian has an even later +2s130 (chassis 7310___
and that has dellortos with vac retard capsule & 41225 diz. His dellortos are 40dhlaE. Not sure if this helps or hinders you ? john
john-c-elan+2
Second Gear
Second Gear
 
Posts: 125
Joined: 22 Sep 2003

PostPost by: mark030358 » Mon Feb 13, 2006 1:09 pm

Rohan,
My sprint has exactly the same 10 deg weights. Built in November 1972. So if what you are saying is right then I need to reteard the timing even further?

cheers
Mark
User avatar
mark030358
Fourth Gear
Fourth Gear
 
Posts: 916
Joined: 29 May 2004
Location: Willaston, Wirral

PostPost by: rgh0 » Tue Feb 14, 2006 9:17 am

Mark

For Australian premium unleaded fuels a normal road Weber / Delorto twin cam at around 10:1 compression ratio needs around 25 to 28 crank degrees maximum advance. If you have 20 crank degrees centrifugal advance in the distributor then the static setting will be 5 to 8 crank degrees.
The best solution for a road engine is 10 to 12 crank degrees static and 15
crank degrees centrifugal which is in line with the original non emissions Weber / Delorto setting from Lotus for the later twincams.

In Australia you only need more than 28 crank degrees advance in a race engine running high 12:1 compression ratio with Avgas / racing fuel and 7000 to 8000 rpm peak power where the typical maximum total advance is 30 to 32 crank degrees. You typically achieve this with 10 to 12 crank degrees of static advance and 20 crank degrees centrifugal advance

In other countries these numbers may be different depending on the types of fuels produced but I would not expect them to be different by more than a couple of degrees

Rohan
User avatar
rgh0
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 7486
Joined: 22 Sep 2003
Location: Melbourne, Australia

Total Online:

Users browsing this forum: No registered users and 11 guests