y do u need good fuel?>

If your query is in context with timing as per the earlier part of the thread then "good" fuel is generally the one that resists detonation and that means higher octane... ulp is about 91 to 92 and pretty basic, 15 deg timing will be fine. pulp is 94-95 which you can prob get away with 17 to 18 deg Hi-octane is 98 or so *but* it doesnt mean you can add another 2-3 deg to timing as you are reaching the design limit. All the fuels have the same basic chemicals its just the mix that changes and fuels have varying quality as well as resistance to detonation. Some brand PULP actually has a little more bang as well and can tolerate leaner running, I generally use PULP for country and ULP for city, in that situation the higher cost of PULP is worth the extra bang (more energy) but this is not always the case. Very often petrol fuels with different octanes will have same energy and burn at the same rate... Its the resistance to detonation which is the most important issue, though some high end PULP will also have some extra volatile detergents. edit: typos - I said PUMP <guh>

Quote: Originally Posted by Niche If your query is in context with timing as per the earlier part of the thread then "good" fuel is generally the one that resists detonation and that means higher octane... ulp is about 91 to 92 and pretty basic, 15 deg timing will be fine. pulp is 94-95 which you can prob get away with 17 to 18 deg Hi-octane is 98 or so *but* it doesnt mean you can add another 2-3 deg to timing as you are reaching the design limit. All the fuels have the same basic chemicals its just the mix that changes and fuels have varying quality as well as resistance to detonation. Some brand PULP actually has a little more bang as well and can tolerate leaner running, I generally use PUMP for country and ULP for city, in that situation the higher cost of PULP is worth the extra bang (more energy) but this is not always the case. Very often petrol fuels with different octanes will have same energy and burn at the same rate... Its the resistance to detonation which is the most important issue, though some high end PULP will also have some extra volatile detergents. the "bang" you talk about is the MON rating as i understand it, been years since i did chemistry so i could be completly off lol

Quote: Computer does not control the timing at all... The computer does control the timing, all you're doing by advancing the timing through the dizzy adjustment is effectively trimming the whole timing map up or down a certain value. The timing (whole map) is also advanced with temp, I think the map runs +5 deg advance up to 40C, then +3 or so until 50C (need to go check that on my car to confirm). This is also the reason you should set your timing at normal operating conditions and at the specified rpm. I used to run my car when it was NA on 20 btdc on 91 fuel, never pinged. All engines are different though so what works for one won't necessarily work for another. RE the diagnostic mode it means nothing when 'trimming' the timing with the dizzy. The computer still thinks the timing is at 15btdc which is the factory setting regardless of what you set it to, however, the timing will actually be advanced or retarded throughout the whole map depending on what you set at the dizzy. If that makes any sense....lol...hopefully you get what I mean.

also like to add onto CJW post as he hasnt said it striaght out for people that dont know, is that the timing doesnt stay the same through out the rev range, the higher the revs get the more it advances it.

Quote: Originally Posted by MARMO. the "bang" you talk about is the MON rating as i understand it, been years since i did chemistry so i could be completly off lol geesh, my memory must be bad, I dont remember that, did octane, cetane, btus etc but MON, is that more bang for the fuel on a Monday so it lasts the whole week hey MARMO. dont forget my f/back ? Some original photos have not been recovered yet.