so initial and idle are the same and the VA comes in at light load and cruise part throttle when engine vaccuums are high. usually around 20 to 24" in the centĪ EGR has the VA on manifold vacuum. Therefore a non EGR dizzy has a lot of cent and far less VA in it. general ball park here is an initial between 8 and 12 and around 7 to 10 degs in the VA all in around 10 to 12" depending on the engine vaccuum characteristics. the VA pulls in advances so idle is initial +VA. Then throw in EGR and non EGR engines.A non egr is usually setup with a lower initial (easy start) engine fires, and VA on manifold vaccuum. This is not quite as critical as the total and aiming for around 2700/ 2800 is what u are looking for in a street vehicle. but a general ball park is between 2600 to 3200. The rpms depends on things like vehicle weight, and driveline ratios. the more duration/ overlap but lower the rpms the more time open, the more 'pressure' escapes the time the inlet and exhaust valves are open at the same time.'bigger' the cam. The cylinder pressure is determined by the compression ration, and complicated by the duration and over lap specs of the cam. The higher the pressure the less the the total advance. more simply the cylinder pressure at that rpms. this is determined basically by the dynamic compression ratio at that load and and rpms. The point at which the advance is all in (cent +intial) will be somewhere between 28 degs and 34 degs. this resulted back in the 80s of LPG getting a rep for burning valves, hard starting, burning starter armatures and hard on bearings. but simply doing that also increases the higher petrol cruise and WoT advances which means the piston is still coming up when fires (not literally but get the idea. hence why many 'cheat' by upping the initial advance. Basically LPG below 3000 needs a faster advance than petrol.
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