blown engine post successful dyno tune, ideas on what might have happened?
03-26-16, 11:20 AM
#51
If the 15A Engine fuse pops, that will stop sending power to trigger the Fuel Pump Relay, and EGI Main Relay. When the EGI Main Relay turns off, the injectors will stop functioning completely (assuming they are wired like stock). This won't make the engine run lean, it would just result in all the injectors shutting off at once which is safe.
However, if you follow the purple highlight you can see that the 15A Engine fuse isn't powering anything substantial, just triggering those three relays to turn on. Upgrading the fuel pump shouldn't cause the 15A Engine fuse to see any more current, assuming the wiring has never been modified.
What would cause a problem is if the Fuel Pump Relay (Speed) somehow failed... that relay sends full power to the fuel pump (highlighted in green). The stock ECU only activates that relay at high load, when it turns off at idle and low load the fuel pump gets powered through the Fuel Pump Resistor (highlighted in yellow). The Fuel Pump resistor prevents the fuel pump from running at full speed, this will not allow enough fuel pressure to support even 200whp without running lean. I suggest you check the Fuel Pump Relay (Speed) to confirm it is working properly. The stock ECU triggers it by grounding out pin 1K, so it's a good idea to find out what this pin is doing with the Adaptronic setup.
If the fuel pump wiring or injector wiring has been modified from stock, then it's difficult to say.
However, if you follow the purple highlight you can see that the 15A Engine fuse isn't powering anything substantial, just triggering those three relays to turn on. Upgrading the fuel pump shouldn't cause the 15A Engine fuse to see any more current, assuming the wiring has never been modified.
What would cause a problem is if the Fuel Pump Relay (Speed) somehow failed... that relay sends full power to the fuel pump (highlighted in green). The stock ECU only activates that relay at high load, when it turns off at idle and low load the fuel pump gets powered through the Fuel Pump Resistor (highlighted in yellow). The Fuel Pump resistor prevents the fuel pump from running at full speed, this will not allow enough fuel pressure to support even 200whp without running lean. I suggest you check the Fuel Pump Relay (Speed) to confirm it is working properly. The stock ECU triggers it by grounding out pin 1K, so it's a good idea to find out what this pin is doing with the Adaptronic setup.
If the fuel pump wiring or injector wiring has been modified from stock, then it's difficult to say.
Last edited by scotty305; 03-26-16 at 11:25 AM.
03-26-16, 11:30 AM
#52
Something to consider is that automotive fuses don't die immediately when they are slightly overloaded. For instance, the fuel pump wiring could be modified so the 15A Engine fuse was supplying power directly to the fuel pump (by jumping some pins on the FP Speed Relay). In this situation, the pump would run anytime the ignition key is on, it would not prime for a few seconds and then turn off when the engine is not running like the stock setup does.
If that were the case, and the fuel pump was trying to draw 16A through the 15A fuse, the fuse would not pop immediately... it would heat up before breaking connection, and during that time the fuel pressure might be temporarily low before the EGI Main Relay cuts power to the injectors... low fuel pressure results in sustained lean conditions, this can hurt engines. This is just a theory and would depend on very specific changes to the stock wiring, but after reading through your older posts again it seems plausible.
If that were the case, and the fuel pump was trying to draw 16A through the 15A fuse, the fuse would not pop immediately... it would heat up before breaking connection, and during that time the fuel pressure might be temporarily low before the EGI Main Relay cuts power to the injectors... low fuel pressure results in sustained lean conditions, this can hurt engines. This is just a theory and would depend on very specific changes to the stock wiring, but after reading through your older posts again it seems plausible.
Last edited by scotty305; 03-26-16 at 11:40 AM.
03-27-16, 12:36 PM
#53
Something to consider is that automotive fuses don't die immediately when they are slightly overloaded. For instance, the fuel pump wiring could be modified so the 15A Engine fuse was supplying power directly to the fuel pump (by jumping some pins on the FP Speed Relay). In this situation, the pump would run anytime the ignition key is on, it would not prime for a few seconds and then turn off when the engine is not running like the stock setup does.
If that were the case, and the fuel pump was trying to draw 16A through the 15A fuse, the fuse would not pop immediately... it would heat up before breaking connection, and during that time the fuel pressure might be temporarily low before the EGI Main Relay cuts power to the injectors... low fuel pressure results in sustained lean conditions, this can hurt engines. This is just a theory and would depend on very specific changes to the stock wiring, but after reading through your older posts again it seems plausible.
If that were the case, and the fuel pump was trying to draw 16A through the 15A fuse, the fuse would not pop immediately... it would heat up before breaking connection, and during that time the fuel pressure might be temporarily low before the EGI Main Relay cuts power to the injectors... low fuel pressure results in sustained lean conditions, this can hurt engines. This is just a theory and would depend on very specific changes to the stock wiring, but after reading through your older posts again it seems plausible.
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