- Mon Apr 05, 2021 2:48 pm
#49473
Air bubbles (different from vapor bubbles) are still a big problem with deadhead rails. This makes fuel system design especially important, in order to avoid and eliminate any entry of air, from micro-bubbles to fuel slosh ingestion to assembly entrapment. Your system must avoid entry of air or the performance will suffer and enleanment damage is possible. Fuel pumps must have cooling-flow bypasses or PWM control, or both (see my image below). There are many styles of returnless and semi-returnless systems, and they tend to be more complicated to deal with the side-effects, but are tolerated for the emissions benefits.
While obviously air replacing fuel will affect running, this has caused engine damage in situations you can imagine, such as a trapped bubble building at one end of a rail causing one cylinder to run intermittently lean as the air passes-through that one end injector. If you are not positive your system can run air-free, or does not have compensation features for deadhead effects, it would be generally recommended to use a return system in order to avoid the various issues that can accompany deadhead rails. Engine Specific Output is a factor, with stock engines likely able to cope better than performance engines that are closer to the edge.
Note in the module, a bypass serves multiple functions, powering a low-pressure venturi pump for fuel pickup to the air-separation sump area, while also providing bypass flow for pump cooling. Modules like this can be used for return and deadhead (semi-returnless and returnless) systems:
While obviously air replacing fuel will affect running, this has caused engine damage in situations you can imagine, such as a trapped bubble building at one end of a rail causing one cylinder to run intermittently lean as the air passes-through that one end injector. If you are not positive your system can run air-free, or does not have compensation features for deadhead effects, it would be generally recommended to use a return system in order to avoid the various issues that can accompany deadhead rails. Engine Specific Output is a factor, with stock engines likely able to cope better than performance engines that are closer to the edge.
Note in the module, a bypass serves multiple functions, powering a low-pressure venturi pump for fuel pickup to the air-separation sump area, while also providing bypass flow for pump cooling. Modules like this can be used for return and deadhead (semi-returnless and returnless) systems:
-= If it was easy, everyone would do it =-