Careless Posted April 15, 2008 Share Posted April 15, 2008 There was a pretty lenghthy thread on the AEM and CAS issue awhile back, with a lot of people chiming in. AEM does have a fix for cars with the issue in the form of a CAS wheel with a reduced number of slots, and I believe a few other vendors have similar discs. Also many people chimed in to state that this issue is evident on more than just the AEM EMS and seems to be an issue on any high hp high rpm car. I personally have not had any issues with my car and the EMS but at the moment the engine is stock and I am only reving it a bit beyond 8K. it's been covered before, specifically here on HZ. It is an issue with the CAS, and not with the AEM unit. most people i've talked to on SAU seem to think it's because the belt has a tendency to stretch enough for one of the 360 slotted holes to be recounted, making the 360 degree revolution out of sync with the falling/leading edge cylinder holes used on the inner portion of the CAS. This is completely understandable, as the 360 marks are so close together, the computer does something erratic with the timing if it counts anywhere from say... 355 - 365 degree slots. All completely possible because belts will stretch under load. I'll bet the tiny CAS shaft that connects the slotted receiver to the cam has a bit of twist in it too, unless it's hardened steel or something. Either way, it has to do with the slots being too close to be computed as accurately as Nissan intended for higher RPM session. I can see AEM probably cutting the timing slots to 90, 45 count, all the way around the perimiter of the disc. Underground was selling modified RB26 CAS wheels through AEM, as I remember. Ron Tyler came up with a solution to drill a small 1/8 inch hole about 1/8 after the 1st cylinder square hold in the cas disc. This gives the ECU a double-beat and signifies first cylinder TDC. Ron can explain it better than I, but it was covered already, so if anyone is interested, a search will tell the tale. Quote Link to comment Share on other sites More sharing options...
280zg Posted April 15, 2008 Share Posted April 15, 2008 I can see what your saying, I should have said " who is using a standalone and the idle air control". I have heard that people can tune around it for start up etc. Just wanted some more input as not all of the standalones support idle air. Or is the idle air even a concern once the switch to a standalone is made ? I should have been more careful in my wording ! On the R32 and the LinkPlus, I use the stock idle components, and the Link controls it perfect. On my Z it don`t have much idle control stock, just cold starting. But, I compensate some of the idle ignition with the autronic, and if the idle rpm drops, it gives more ignition, and the rpm goes up again. On start up, it`s no problem to just compensate with ignition, instead of idle air. Or just step a little on the gas pedal... Quote Link to comment Share on other sites More sharing options...
triple B Posted April 15, 2008 Share Posted April 15, 2008 it's been covered before, specifically here on HZ. It is an issue with the CAS, and not with the AEM unit. most people i've talked to on SAU seem to think it's because the belt has a tendency to stretch enough for one of the 360 slotted holes to be recounted, making the 360 degree revolution out of sync with the falling/leading edge cylinder holes used on the inner portion of the CAS. This is completely understandable, as the 360 marks are so close together, the computer does something erratic with the timing if it counts anywhere from say... 355 - 365 degree slots. All completely possible because belts will stretch under load. I'll bet the tiny CAS shaft that connects the slotted receiver to the cam has a bit of twist in it too, unless it's hardened steel or something. Either way, it has to do with the slots being too close to be computed as accurately as Nissan intended for higher RPM session. I can see AEM probably cutting the timing slots to 90, 45 count, all the way around the perimiter of the disc. Underground was selling modified RB26 CAS wheels through AEM, as I remember. Ron Tyler came up with a solution to drill a small 1/8 inch hole about 1/8 after the 1st cylinder square hold in the cas disc. This gives the ECU a double-beat and signifies first cylinder TDC. Ron can explain it better than I, but it was covered already, so if anyone is interested, a search will tell the tale. well technically it is the fault of the AEM since it can't compensate like the stock ECU does for belt stretch. the modified CAS has way less holes in it from the pictures i have seen of it. if i remember correctly there are 6 holes Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted April 16, 2008 Share Posted April 16, 2008 I'm not understanding why there are so many notches in the first place. Couldn't they simply have one for tdc and program the ecu to figure it out? I'm super new to the whole idea though. I guess someone will just tell me I should search to find out more about how it works... Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted April 16, 2008 Administrators Share Posted April 16, 2008 Couldn't they simply have one for tdc and program the ecu to figure it out? In theory, that could work. In reality, the lack of resolution would be a problem in many cases. Its not steady RPM that poses the difficulty, rather the transient RPM. Take an extreme example... cresting a hill, unloading the tires, and generating significant wheel spin accompanied with an abrupt RPM increase (or a boat that went air born). The 'instant' RPM increase can cause the ECU to 'get behind'. This is not a simple thing, as I understand it. It has a lot to do with internal algorithm's, processing power, trigger priority, etc. Keep in mind, this is not an externally obvious characteristic. There are some systems that implement a 36-1 wheel... but they 'ignore' some teeth. In other words, just because an EMS requires a 36-1 wheel, doesn't mean it calculates 36 teeth... it may very well evaluate every sixth tooth, for example. Quote Link to comment Share on other sites More sharing options...
Careless Posted April 16, 2008 Share Posted April 16, 2008 well technically it is the fault of the AEM since it can't compensate like the stock ECU does for belt stretch. the modified CAS has way less holes in it from the pictures i have seen of it. if i remember correctly there are 6 holes Who's to say the factory ECU doesn't pose these problems at power and rotating speed levels at which the AEM (and other EMS systems) perform. It's not just AEM. That's been proven on a number of GTR and Skyline boards. Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted April 16, 2008 Share Posted April 16, 2008 It seems like if a system counted every sixth tooth or something of that nature, and there was some sort of error and it missed one, such as with belt tension changes, it would be like a chain skipping a tooth and from then on be off by one. If there are key teeth however, then I guess the extras could be for redundancy? I can't imagine that the ecu would get that far behind, far enough to cause a real scheduling difference. I mean if in the time of one revolution, which is like .01 seconds, the rpm jumped from 5000 to 5500, then the ecu would be behind about .001 seconds. But I guess I'll just trust the engineers that designed the thing. Either way belt stretch would keep the ecu from ever being 100% accurate, the only difference would seem to be in keeping it from recounting or skipping teeth so that a miss wouldn't ripple into the next cycle. But like I said, if there are key teeth, it fixes itself on the next cycle such as in the way you suggested drilling a hole at tdc. Food for thought, on some twin engine planes with systems that syncrophase the propellers, I've noticed that the control unit gets two signals from wheels mounted behind each prop. One wheel has 60 or so teeth and is strictly used to determine the rpm of the prop, and the other wheel has one tooth for each blade to determine the phase angle. In this analogy the phase angle would be like the crank tdc, only of course on props there are more than one position to worry about. Quote Link to comment Share on other sites More sharing options...
synthtk Posted April 16, 2008 Share Posted April 16, 2008 Food for thought, on some twin engine planes with systems that syncrophase the propellers, I've noticed that the control unit gets two signals from wheels mounted behind each prop. One wheel has 60 or so teeth and is strictly used to determine the rpm of the prop, and the other wheel has one tooth for each blade to determine the phase angle. In this analogy the phase angle would be like the crank tdc, only of course on props there are more than one position to worry about. Good thing none of these standalone guys work on planes then Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted April 16, 2008 Administrators Share Posted April 16, 2008 Food for thought, on some twin engine planes with systems that syncrophase the propellers, I've noticed that the control unit gets two signals from wheels mounted behind each prop. One wheel has 60 or so teeth and is strictly used to determine the rpm of the prop, and the other wheel has one tooth for each blade to determine the phase angle. In this analogy the phase angle would be like the crank tdc, only of course on props there are more than one position to worry about. The problem with this comparison is that airplane engines don't transition (and they don't need to). Ever fly one? If you jam the throttle open, they puke. Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted April 17, 2008 Share Posted April 17, 2008 What do you mean by transition? They certainly speed up and slow down... The orientation of the shaft in this case isn't used for fuel metering and the like, I'll give you that. The synchrophase system however is to keep the rpm of both engines and alternate the blades passing by the cockpit for noise and vibration suppression. I'm thinking since they are governed, WOT would only prove to be not so efficient for cruise flight. But no, I've never personally flown... Quote Link to comment Share on other sites More sharing options...
Careless Posted April 17, 2008 Share Posted April 17, 2008 What I think Ron is trying to say is that since the motors are moving something (the prop) that is operating in free-air, there is no transition phase from when a motor in a boat goes from in the water to out of the water and revving up to redline instantly (due to lack of resistance), or a car taking a leap and letting the drive wheels free. Prop engines only have special needs when operate in varying altitudes, but I think that's as far as it gets in terms of transition. Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted April 18, 2008 Share Posted April 18, 2008 Oh, slow transition to different attitudes. I now understand what he meant by jam. Yes, turbines don't like that much. I wasn't saying pilots gunning it is why they worry about having two wheels for redundancy, I was just saying it's an idea, proof of theory. The real reason they have two wheels doesn't apply to cars at all... Anyway!! How bout them dodgers... How about, which aftermarket ems don't use the wheel? I'm always one of those, there-has-to-be-a-better-way kinda guy. Can they not talk to the stock cas? Cut out the middleman, or rather, don't add that greedy middleman in the first place, right? Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted April 18, 2008 Administrators Share Posted April 18, 2008 Transition was in reference to the loads the engines sees, rate of those loads being applied/absorbed and when those loads are applied at what RPM’s. In an air plane, from idle, if you “stab†the throttle wide open abruptly, the engine will sputter, RPMs WILL decrease, and if the engine doesn’t quit, it will slowly rev up to full power, and not very smoothly either, within 1-3 seconds, as OE Aircraft carbs and mechanical Fuel injection have very rudimentary acceleration enrichments circuits. In short, there is no REAL need to “stab†the throttle open and closed in an aircraft. In a car, especially a performance application, we are CONSTANTLY stabbing the throttle open and closed and everywhere in-between and at varying rates. Modern EFI for cars has many diverse ways of allowing the tuner to adjust the acceleration enrichment allowing the engine to transition those abrupt load changes smoothly and quickly. As for the trigger wheel. The ECU needs some form of reference as to what the engine is doing, i.e. RPM. If the ECU does NOT know how the fast the engine is turning, it has no idea how much fuel to inject and when! The more intricate the trigger wheel, the more accurate the ECU can be in knowing exactly where in the cycle each piston is at. For EFI systems that also incorporate Distributor-less ignition control and sequential fuel injection, that sort of accuracy is imperative, or it just doesn’t work. With wheels that have 360 holes, it can tell where that engine is at within 1 degree accuracy. Why the heck am writing all this? This most basic of how and why EFI systems work, its sensors and the trigger wheels the use and why, is all over the internet. The MegaSquirt online manual is good source for that kind of information. Peruse through that, you will learn a lot there. Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted April 18, 2008 Share Posted April 18, 2008 Yeah... Got it! We're on the same team here, I was agreeing with Ron. Turbines, as in gas turbine engines: no carb here. Revving too quickly causes a compressor stall. I wasn't asking what a trigger wheel was, I was asking if all the major aftermarket em's incorporate the crank disk method or if there are some that go a different route, seeing as how the stock ecu seems to work fine without the use of a big ugly disk and a magnet... But I digress. I guess it is best to search around for the ecu's that work best, rather than discuss it in a thread titled "which ecu's work best"... Quote Link to comment Share on other sites More sharing options...
Calgary280ZT Posted April 19, 2008 Share Posted April 19, 2008 Well, I guess I thought the Wolf V500 system was pretty good because I just bought one. Comes with a dashboard tuner, which I'm kinda excited about. Member posted on this thread (I think) about the problems he was having with the EMS on an RB motor, emailed him, now the problem child is mine. LOL Quote Link to comment Share on other sites More sharing options...
Careless Posted April 19, 2008 Share Posted April 19, 2008 Well, I guess I thought the Wolf V500 system was pretty good because I just bought one. Comes with a dashboard tuner, which I'm kinda excited about. Member posted on this thread (I think) about the problems he was having with the EMS on an RB motor, emailed him, now the problem child is mine. LOL Unless its the unit itself that is pooched (and it happens to every ECU no matter what brand), I wouldn't worry. You should be able to get it to run fine, and the Wolf is as powerful as any system for the price it is. I can only imagine what price you got it for, and what is considered "the competition" at your buying price. Quote Link to comment Share on other sites More sharing options...
Calgary280ZT Posted April 19, 2008 Share Posted April 19, 2008 Unless its the unit itself that is pooched (and it happens to every ECU no matter what brand), I wouldn't worry. You should be able to get it to run fine, and the Wolf is as powerful as any system for the price it is. I can only imagine what price you got it for, and what is considered "the competition" at your buying price. Seller says the unit never ran properly because their tuner had no experience with Wolf and wasn't interested in learning...he bought a Power FC(?) because that was what the tuner knew and Wolf unit became available. If that info is correct, the unit is essentially brand new. I won't say exactly what I paid, but it was well under a grand...he said he paid $500 for the dashboard tuner but I see the cheapest unit on Wolf's site is $1,800+. So looks like I got a good deal. Considering I was going to pay $600ish for a MS, I'm a happy camper. Quote Link to comment Share on other sites More sharing options...
Careless Posted April 21, 2008 Share Posted April 21, 2008 i know what the feeling is like Quote Link to comment Share on other sites More sharing options...
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