Robert Posted July 7, 2009 Share Posted July 7, 2009 Hi, I figured this needed a new thread after discussing it in another. Im wondering, I got a 1987 L24E engine, AFM style. Now, I m thinking of replacing the camshaft with a performance camshaft, and then someone says, hey, your stock FI system only uses the AFM the first ~4000RPM, then it goes into some preset fuel table, that does not multiply the AFM value! To me it sounds totally insane, but if its actually some licensed Bosch CRAP (like all other bosch stuff), then I guess its possible. If anyone has some good info, links, or knowledge to this FI system, please speak up. I hope my FI system is not like this, as It wont allow any camshaft I guess. ECU Part numbers would be appretiated as well for comparison. Thanks Quote Link to comment Share on other sites More sharing options...
cockerstar Posted July 7, 2009 Share Posted July 7, 2009 To my knowledge, any stuck l series FI isn't going to take to an aftermarket cam well at all. It's better to upgrade of an aftermarket EMS before swapping the cam. Quote Link to comment Share on other sites More sharing options...
Robert Posted July 7, 2009 Author Share Posted July 7, 2009 So Ive heard, but noone has any details, hehe;) This is a 1987 model, so hopefully it has some upgrades. As long as the AFM`s signals are multiplied all the way, there should be no problems... Quote Link to comment Share on other sites More sharing options...
cockerstar Posted July 7, 2009 Share Posted July 7, 2009 Well, from my knowledge the TPS is a throttle position switch, and not a throttle position sensor. There's idle, cruise, and WOT, with nothing in between. But then again, this is off of an '87, so it could be completely different like you're hoping Quote Link to comment Share on other sites More sharing options...
Robert Posted July 7, 2009 Author Share Posted July 7, 2009 Well, from my knowledge the TPS is a throttle position switch, and not a throttle position sensor. There's idle, cruise, and WOT, with nothing in between.But then again, this is off of an '87, so it could be completely different like you're hoping The TPS has no influence on fuel amounts in practicly any FI system, except those systems without a load sensor (MAP or MASMAF sensor). But the AFM SHOULD be the main source of calculation in fuel amount at ANY RPM or load. A preset table sounds like crap. By the way, Top end performance claim the cam should work. Also, Schneider says they never heard it does not work.. Im so lost right now, I really want to try though.... Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted July 7, 2009 Administrators Share Posted July 7, 2009 (edited) To me it sounds totally insane, but if its actually some licensed Bosch CRAP (like all other bosch stuff), then I guess its possible. But the AFM SHOULD be the main source of calculation in fuel amount at ANY RPM or load. A preset table sounds like crap. A little perspective may help... how many cars can you think of came with Multiport EFI in 1975? Here's a hint, it took GM another ten years to include it on their sports car. So Ive heard, but noone has any details, hehe;) Not sure what details you're looking for, but I can tell you from my own experience that cams and stock ECU don't play well together. Will it run? Sure. Will it run 'correctly', ie appropriate AFR's across the board? Not in my observations. The TPS has no influence on fuel amounts in practicly any FI system, except those systems without a load sensor (MAP or MASMAF sensor). Not true of L-Jet. The TPS *is* part of the load scheme, and its part of the reason a topped out AFM can serve the original design goals. By the way, Top end performance claim the cam should work. Also, Schneider says they never heard it does not work.. Im so lost right now, I really want to try though.... Try it and tell us what you think. Edited July 7, 2009 by RTz Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted July 7, 2009 Administrators Share Posted July 7, 2009 The stock Z car EFI does NOT play well with aftermarket cams! I have beating that drum for as long as some of you youngens have been alive! I personally have seen it time and again, tried to tune them time and again, and have learned over those numerous years as a professional engine builder/machinist, building and tuning Datsun Z cars, that the stock EFI does NOT play well with aftermarket cams! The milder the cam, the less the compromise though still a compromise in the tune will be made! I don’t give a rats arse WHAT those cam companies tell any of you, the stock Z car EFI can not be tuned to be just as drivable AND take advantage of the power gains an aftermarket cam “can†deliver, PERIOD! Even if you tuned the EFI the best you could for only WOT performance with an aftermarket cam, any power gain you might get would be doubled, more like tripled and better with an aftermarket EFI system! A quick search revealed more than few threads discussing the incompatibly of the Stock Z car EFI with aftermarket camshafts. Here are few that I recall specifically giving my $.02 in… http://forums.hybridz.org/showthread.php?t=123950 http://forums.hybridz.org/showthread.php?t=147745 http://forums.hybridz.org/showthread.php?t=146548 http://forums.hybridz.org/showthread.php?t=131214 http://forums.hybridz.org/showthread.php?t=115088 Hope that helps, Paul Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted July 8, 2009 Share Posted July 8, 2009 This is because the stock fuel system uses both mechanical and electronic "computers". The mechanical computing done by the air flow meter is carried out by the spring tension and rate through it's range of travel on the airflow meter flap and flow through the bypass port. (yes the bypass port affects more than just idle and does have an effect on light throttle cruising) The ignition timing mechanical computing is done by the the vacuum diaphragm diameter and spring tension working against it as well as the mass of the mechanical advance weights and the spring tension . A high performance camshaft will require a "re-calibration" of both the mechanical computational devices and the electronic computer to yield good results in all circumstances. If you ever spent time recurving a distributor back in the 60s or 70s, you will know how much trial and error is required and try to imagine the additional work required to "re-curve" the mechanical computation portion of the fuel system as well.....but without the benefit much information at all since only a few have attempted it. Think of it as setting up carbs and distributor curves which is difficult enough and then add a computer that has it's own "curves" and was carefully designed to work with the stock parameters of the distributor and airflow meter. Going to a Z31 engine management system with MAF and an editing suite like nistune would be a lot easier to make the engine happy across a variety of hardware changes. Quote Link to comment Share on other sites More sharing options...
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