Quote:
Originally Posted by Ron
Sam or Phunk.. what do you think about a fuel return system for FI.. most people here don't get them with their kits. But owners of other platforms consider it a necessity when going FI for stable/adjustable pressure. What are your thoughts on this?
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It really depends on the horsepower levels. For anything up to 550whp, you can get away without installing a return fuel system no problem. A few reasons for this are:
1) simpler is better and more reliable. Not having a rising rate fuel pressure regulator, fewer lines will minimize leaks, vacuum lines popping off, etc.
2) The other main reason is that when Nissan develops an ECU map for these cars, they have gone through serious amount of testing and development of all aspects of this engine and its characteristics as far as air flow and individual cylinder VE. For example, if you take a look at the engine management for a well developed platform (Subaru, Evo), you will see that there are many fuel maps that are designed and put in place based on that particular engine. So you will see a low fuel det map (engine is happy and ignition advance multiplexor at it's peak), and you will see a high det fuel map (richer map) that will have more fuel for knock detection condition. Also, you will see that there will be 4 individual cylinder fuel maps that are all different since there is no way that the OEM intake can supply the same amount of air to each cylinder. So you see, all this technology is already in the factory ECU mapping and fuel curves. The minute you add your return fuel system which will change the fuel curve and is not based on load and MAF voltage, you just threw all that out the window. Of course in some cases you will have to do that. Take for example our White Dragon project. Once we installed a return fuel system, we also installed 6 EGT sensors (one for each exhaust runner), dual Knock device to monitor both banks, so we can make sure that we're not overfueling or underfueling any individual cylinder. That's what it really takes once you are no longer relying on the back end of the ECU to do the work for you.
Sam