What's the deal with injector duty?
04-15-2014, 04:25 PM
#1
What's the deal with injector duty? Help me understand the exact reasoning behind the magic 80% rule of injector duty cycle where above that it's usually recommended to upgrade to larger injectors.
What I do understand is the fact that injectors can only deliver so much fuel, and when that is not enough for an engine (and the AFR suffers and cannot get rich enough) that is when you upgrade injectors.
But besides that, where is the "safety" portion of running an injector at 50% idc vs. running one at 85% idc? If one of them fails and stops injecting fuel then it doesn't matter if it's at 50 or 90 idc, it's going to be catastrophic for that piston regardless.
So can an injector fail only "halfway" in which case it's good to have a big enough injector where the other half can completely fulfill the engine needs? Otherwise what's the point of upgrading injectors if a certain size can deliver the desired AFR across the board but doing so at 85%+ of it's capabilities?
What I do understand is the fact that injectors can only deliver so much fuel, and when that is not enough for an engine (and the AFR suffers and cannot get rich enough) that is when you upgrade injectors.
But besides that, where is the "safety" portion of running an injector at 50% idc vs. running one at 85% idc? If one of them fails and stops injecting fuel then it doesn't matter if it's at 50 or 90 idc, it's going to be catastrophic for that piston regardless.
So can an injector fail only "halfway" in which case it's good to have a big enough injector where the other half can completely fulfill the engine needs? Otherwise what's the point of upgrading injectors if a certain size can deliver the desired AFR across the board but doing so at 85%+ of it's capabilities?
04-15-2014, 07:13 PM
#2
My take? That 80% is a guideline, not a "rule". There are lots of peeps perfectly happy running near 100% dc, then there are others that freak out when they get near 80%. Most vehicles are at WOT (and thus high dc) for such a short duration the chance of damaging a modern injector are minimal. As long as AFR doesn't suffer, I don't see an issue.
