kim Posted April 30, 2001 Share Posted April 30, 2001 Until leaded petrol was withdrawn the timing on my 1600 XF was set as per the book at 14deg BTDC. I now use LRP but the exhaust colour is 'sooty'. On checking the timing (first time since switching to LRP from leaded)last week I noticed that the timing had moved slightly to 15-16BTDC. I put it back to 14 but have noticed that the engine is lacking in lustre. Has anyone got any ideas as to the best ignition timing setup for LRP - does 1 deg make such a difference? Any advice would be greatly appreciated. Thanks Kim Link to comment Share on other sites More sharing options...
R2D2 Posted April 30, 2001 Share Posted April 30, 2001 I think a black exhaust is normal with unleaded and LRP the old light coloured exhaust was a feature of the lead additive. If the car ran better with the15/16 degree setting I would put it back unless there was any sign of pinking. Link to comment Share on other sites More sharing options...
Graham Sewell Posted April 30, 2001 Share Posted April 30, 2001 Spot on. I haven't seen any car that runs unleaded or LRP that has an exhaust colour other than black. The timing should be the same as for leaded (14') but the advance curve may be lacking slightly if this is causing problems. Have a chat Roger King or Aldon Automotive to check what the advance should be at higher revs and then check that as well. Link to comment Share on other sites More sharing options...
Roger King Posted April 30, 2001 Share Posted April 30, 2001 Kim, If your correct tickover timing figure is 14 degrees btdc, you have an 'unleaded' distributor. This will give a maximum advance figure of around 27 degrees btdc whereas the average Crossflow works best with a maximum figure around 34 degrees btdc. By letting your timing creep to 16 degrees btdc you have also advanced the maximum figure nearer to the ideal and your perceived performance improvement is real! Unfortunately, the figure at tickover is now too high and risks engine damage. The real solution is to fit a different distributor with the correct advance curve which will be right at both ends of the scale. It is one of the cheapest ways to gain power on a post 1989 Caterham engine and there is no loss of driveability either. We always promise our customers a refund if they can't tell the difference - so far no-one has asked for their money back. Link to comment Share on other sites More sharing options...
ashaughnessy Posted May 1, 2001 Share Posted May 1, 2001 I have a 1987 supersprint. Am I correct in thinking it has a "leaded" distributor? Does this mean that my advance at tickover should be 10 degrees? This has always been something that worries me because there isn't a big label on the distributor saying "leaded". What kind of advance curve do I get with my leaded distributor? If the original poster had an unleaded distributor, why has he been running on leaded petrol until now? (I've always run on four star, I run nowadays on LRP, mostly because the 750MC rules say you can't use additives.) Anthony Link to comment Share on other sites More sharing options...
kim Posted May 1, 2001 Author Share Posted May 1, 2001 Thank you all for your helpful replies. Roger I am now interested in your distributor mod that has a 'better' advance curve. How much does this cost? As regards the sooty exhaust I will sleep a little easier now that I know that this is normal particularly as I was about to start playing with mixtures!!! Link to comment Share on other sites More sharing options...
Roger King Posted May 2, 2001 Share Posted May 2, 2001 Anthony, A 1987 car should have a leaded dizzy if no-one has altered things. If you have a browny/orange cap on it it is probably a Bosch which should be for leaded. The unleaded dizzies are based on a Lucas body and generally have a black cap. Be warned though, that you do see the occasional aftermarket cap that is the 'wrong' colour. Kim, This forum is not the place for me to start giving out prices and encouraging trade! I think I'd get into trouble. If you e-mail me on info@rogerkingengines or ring on 01992 421111 I can give you the info you ask for Link to comment Share on other sites More sharing options...
Edward Guest Posted May 2, 2001 Share Posted May 2, 2001 So what is the ideal distributor curve for Unleaded with additive since I have soft valve seats. I have the later distibutor @ 14degrees Thanks for any views Link to comment Share on other sites More sharing options...
oilyhands Posted May 2, 2001 Share Posted May 2, 2001 There is a subtantial article on Dave Andrews' website about tailoring your advance curve to get the best from your engine, it gives details of suggested static timing for various cam types and recommended maximum advance figures for most engine/combustion chamber types. It explains why more static advance is needed with hotter cams, how the advance mechanisms work and how the rate of advance is decided, governed and altered. It then details how to modify your existing distributor to the optimum. http://members.aol.com/DVandrews/timing.htm Have a look, it may help Oily Link to comment Share on other sites More sharing options...
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