NWOleman Posted June 28, 2011 Report Share Posted June 28, 2011 Does anyone on here have the factory service manual for a datsun 510 or a datsun 620 with an L18 or L20b motor? I need a copy of the advance curve for one or both of these motors so i can get a map made for my megajolt setup i'm gonna be running in my wagon. Thanks guys. Quote Link to comment
datzenmike Posted June 28, 2011 Report Share Posted June 28, 2011 I have a '78 620 FSM but the curve isn't published in it. Never seen one. Here's some stuff. Quote Link to comment
albyneau Posted June 28, 2011 Report Share Posted June 28, 2011 Does anyone on here have the factory service manual for a datsun 510 or a datsun 620 with an L18 or L20b motor? I need a copy of the advance curve for one or both of these motors so i can get a map made for my megajolt setup i'm gonna be running in my wagon. Thanks guys. Does "gonna be" mean not installed, or not programmed? Hopefully the former... Rather than go by the FSM, my path to follow would be to gather up the right tools (seperate digital tach and dwell meters, and an adjustable timing light) and map it yourself. Factory specs in my book are a "blind man with a shotgun" approach to tuneups~ they have to work on *EVERY* motor, irregardless of production tolerances (stacking), usage, wear-n-tear, etc.. This is exactly why I preach and practice vacuum gauge ignition timing~ it optimizes timing (and in your case curve) to YOUR MOTOR. If you're going programmable, isn't the idea to get as anally accurate as possible? Quote Link to comment
datzenmike Posted June 28, 2011 Report Share Posted June 28, 2011 Perhaps he wants a base line to start with so it runs. Then tweak it. Quote Link to comment
albyneau Posted June 28, 2011 Report Share Posted June 28, 2011 Perhaps he wants a base line to start with so it runs. Then tweak it. Most likely~ I was just thinking, the more info you've got going in, the less tweaking you've gotta do when you get there... Quote Link to comment
NWOleman Posted June 28, 2011 Author Report Share Posted June 28, 2011 yeah that's what i was wanting is just somewhere to start then i planned on dialing it in. Thanks for the input and info guys! And yes i have the megajolt at home and the EDIS stuff with the trigger wheel. I will put all the info i get on my project thread when i get to it. HOPEFULLY SOON! Quote Link to comment
NWOleman Posted June 28, 2011 Author Report Share Posted June 28, 2011 I wonder if any nissan dealers might have a manual lying around? Quote Link to comment
Bleach Posted June 28, 2011 Report Share Posted June 28, 2011 Bam diggity! http://www.olddatsuns.com/620tech.htm#wd ;) I also have a real FSM for a 620 for sale. Not sure what years I have left. I think 1979 and 1978 Quote Link to comment
NWOleman Posted June 28, 2011 Author Report Share Posted June 28, 2011 thanks bleach! how much you want for one of those? Quote Link to comment
ggzilla Posted June 29, 2011 Report Share Posted June 29, 2011 Mike, the advance curves are in the factory service manual under section EE (Engine Electrical). For the 1974 620 it is: Vacuum advance: 0°/5.91 in.HG to 3.5°/9.84 inches HGMechanical advance: 0°/550 RPM to 10°/2150 RPM Yes, these are not the right curves for performance, they are for emission control. But the engine will run like a new L18 with this curve. Anyone know how much total advance the L-series likes? Quote Link to comment
datzenmike Posted June 29, 2011 Report Share Posted June 29, 2011 I have specs but no graph. Total advance is around 32-34 degrees. Quote Link to comment
ggzilla Posted June 29, 2011 Report Share Posted June 29, 2011 Yep, no graphic, but the curve specs are there. Both are straight curves more or less so a graph is not necessary. Quote Link to comment
NWOleman Posted June 29, 2011 Author Report Share Posted June 29, 2011 Damn Ratsun members are the best! Thanks guys! Quote Link to comment
datzenmike Posted June 29, 2011 Report Share Posted June 29, 2011 Yep, no graphic, but the curve specs are there. Both are straight curves more or less so a graph is not necessary. Crap, then I have several 'curves' Damn Ratsun members are the best! Thanks guys! There are probably dozens of 'curves' depending on year, model, weight, emission standards at the time, altitude on and on. Yes they have little to do with performance and everything to do with emissions. Quote Link to comment
hogboy52 Posted June 29, 2011 Report Share Posted June 29, 2011 There are any number of different timing setups even on the same motor. What could be considered a typical "performance" curve from a later Porsche 1600 Super 90 (it's hard to find curves). 5 deg. @ 800rpm 20 deg. @ 1300rpm 35 deg. @ 3200rpm It's mostly just two straight lines from one weak and one strong advance weight. There was no vacuum advance. lesser tuned motors reached full advance at 2800-3000rpm. I'm not familiar with what you are running but I'm thinking it has no vacuum advance? Quote Link to comment
datzenmike Posted June 29, 2011 Report Share Posted June 29, 2011 All Datsuns have vacuum advance but it has nothing to do with top end performance and everything to do with low speed (under 3000RPM) driv-ability and economy. Quote Link to comment
NWOleman Posted June 29, 2011 Author Report Share Posted June 29, 2011 the megajolt has a vacum port on it so i assume that it has something to do with the vacum advance curve. Quote Link to comment
ggzilla Posted June 29, 2011 Report Share Posted June 29, 2011 Vaccuum advance is all about part-throttle driveability and fuel economy -- and nothing to do with emissions. To limit emissions they bypass the vacuum advance (disable it) via the Top Gear switch, thermal switch on the head and other emission controls. Or add a vacuum retard (those distributors with two hose connectors). The Porsche puts full advance in by 3200 RPM. For emission control vehicles they typically prevent this, so the Datsun goes to 4300 RPM before getting full advance. Change that in the datsun to 3600 or 3200, and you might pick up a lot of power. 5 deg. @ 800rpm 20 deg. @ 1300rpm 35 deg. @ 3200rpm 35 degrees is great for the Porsche combustion chamber. For the L16 32 degrees might be optimum. Or maybe it is 34 degrees. The best engines need less total advance, and the latest cylinder heads need less advance to make maximum power. Quote Link to comment
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