All, I have installed an AEM Infinity ECU in my Mondial 8. Things are really coming together! Finally able to drive a bit harder but ECU cuts off the engine at 5-6K rpm. I have logs of it occuring at 5800, 6500, 6500 -- has occured at lower RPM too. All seems good (engine sync, not lean) but then it suddenly cuts off. By staring at the graphs (see below), I think the fuel gets cut off, then the mixture goes lean because engine spinning with no fuel, then eventually everything goes down (I can restart after coasting a bit). Potential causes: 1. fuel pressure not maintained: fuel pump and filter are new; at no load I see in my gauge in the engine compartment pressure is fine; however, I would think if it cannot keep up with the fuel requirement with load, the AFR would gradually go lean and not suddenly -- thoughts? 2. fuel injector flow rate issue; my injectors are 32 lbs/hr (=336 cc/min) which should be more than enough; however, to bring the AFR into a reasonable range I had to "tell the ECU" my injectors flow at around 200 cc/min and still had to increase the VE table to the 50-150 range (in theory should not exceed 100) -- however, these are just numbers that are fed into an equation that determines the injector pulse time. For 1: I just ordered a fuel pressure sending unit...lets see... For 2: this gets into the weeds...at 7500 RPM (my set engine rev limit) it means 62.5 revs per second in a 4-stroke engine. So that means 16 ms max per revolution. I guess that means each injector can be "firing" up to 16 ms (=100% duty time). In the log I see the injector pulse time to be near 9ms when the cut off occurs (or 56% duty time) -- that seems ok. Correct? Ideas? Image Unavailable, Please Login
Aftermarket EFI + fuel injection seems the way to go with these classic engines if you care more about performance vs originality AND your state allows such modifications (aka not CA). Q: How does the ECU know the RPM? Is it measured by a crank position sensor? Dumb question but is there any play in the tone ring or whatever triggers the sensor? Q: More for my curiosity than to solve your problem, I suspect the AEM setup controls spark as well. If so, does it replace the two Digiplex modules as well? Seems very tool to use modern ECU control on a vintage engine.
AEM Infinity ECU uses a crankwheel sensor (like other modern ECUs do as well)....this means I attached to the crankwheel a gear with 58 teeth (two missing) and a hall sensor (=magnetic sensor). This gives the ECU rotation information. I did not place a cam sensor, so it just keeps track of 720 degrees of rotation to equal one full 4-stroke rotation. The ECU tells me, in this case, that it does not lose the sync signal so at least it thinks it is always aware of the engine's rotation. The ECU also controls spark. I placed one coil per spark ("coil in plug") and thus run semi-sequential (meaning each cylinder fires in the correct order but its not fully sequential because I do not have a cam sensor). I will post more details of my full setup, which has been underway for quite a while, once it is complete. This RPM issue is the near the end of problems I have/had...
