garrycol wrote: ↑Thu Feb 11, 2021 1:09 am
GDCobra wrote: ↑Wed Feb 10, 2021 6:48 pm
garrycol wrote: ↑Tue Feb 09, 2021 11:17 pm
Of course vac advance or retard must not be all that relevant to a dizzy system as the mechanical system is because some cars do not even have vacuum advance or retard. My 24v 3.5 RV8 in my 101 does not have vac advance and neither does my Haflinger - neither has it so must not be all that important.
I think the other reason many people tend not to run vac' advance is because they see race engines not using it and think it must be better without stoping to think that a road engine has to work in a much broader range of conditions. Of course it also means it must be 'cooler' which may be even more important.
My RV8 and Haflinger are not race engines and not modified - they are as built by the manufacturer ie the manufacturer decided they did not need vacuum advance and the RV8 in the Land Rover pulls like a train from idle with plenty of torque.
I guess we have to be careful to separate 'need' from 'want' (or nice to have). Arguably you could run the engine without any variation in advance at all, just a constant advance value (in fact on a previous thread someone mentioned that they could run their EDIS based system at a constant 10° and it ran just fine), for whatever reason whoever built/manufactured your engines decided to omit load based advance, presumably this was done on a cost vs benefit basis. Does that mean that there is not benefit to be had, for most engines the answer seems to be 'no' but there may be something specific about your engines that would result in only a limited benefit, difficult to say without any background.
Worth bearing in mind that the load based advance will have limited effect on the pulling like a train capability as this would indicate using a lot of throttle opening hence vacuum advance being removed anyhow.
As I say I think the initial focus should be on getting the RPM based advance sorted for WoT (and simlar) conditions then adding the vacuum advance for a bit of finesse at part throttle and idle.
The idle condition is particularly important to me as lower underbonnet temp's are very nice to have.