I wasn't going to post here because some of the things here are pretty high end but I need some Fuel Injection 101.
I’m too old to learn new stuff, hang on this technology is older than me. It’s simple right a pump pushes fuel to a nozzle and that gives us one of the three things we need fuel compression and spark. Trouble is we will have too much fuel at lower speeds if we have enough at higher speeds –the solution is to bleed some back to the tank. Easy. How much we will determine by a restriction in the return line. Get it? Got it. Well it sounds pretty straight forward. So how come I’ve lost the plot to the extent I pulled the engine out of the car to stop wasting time on it – now I lie in bed thinking about it.
The system I have is a New Old Stock locally made (Australian) single 4” venturi set up. The metering block incorporates the pill, a fuel shut off and throttle (connected to the butterfly by an adjustable length arm). The guy that designed and made these about 25 years ago as far as I can establish he made about 25 units and then lost interest and moved on to other things. A sedan racer won a national championship series using one so they do work. Well mine doesn’t – least not very well. The system is manufactured for Methanol fuel. I have a new Enderle 80A-1 pump being feed by a # 10 line then #6 to the metering block. Between the pump and metering block I have a test port with a pressure gauge. I have a #6 return line to the tank. I have 31 nozzles and started with a 85 pill. The first set of plugs I had were some really old and dirty Denso W20EX-U at .025” gap fired by an internal coil Vertex. Fired up OK - flames in the pipes and running rough at say 3-4000 RPM broke the first pressure gauge going past 110psi. No fumes in the eyes or throat.
Here it is -
https://www.facebook.com/video.php?v=10201977283752322&set=vb.1792156888&type=2&theater Fitted a set of NGK BP6ES and a new 350psi liquid filled pressure gauge and went to a .105 pil. Fired it up and saw 100psi @ 2000 rpm so figured I needed to lean it out further. As well as looking a bit sooty the plugs looked wet so I figured I needed to go up a step hotter with the plugs as well.
Fitted a set of NGK BP5ES plus @.020”gap. Couldn’t get it started cracked the delivery line at the metering block and at best a dribble on cranking. Cracked the line at the top of the pump and fuel present (gravity). Cracked the lines at the nozzles – nothing while cranking? Drained the tank removed and blew out all the lines blew out the metering block (in situ). Noticed no pressure on cranking so went from a .105 to a .72 pill. With a fair bit of fuel to prime it I got it running but with a bit less that 20psi line pressure @1500 and something in the vicinity of 50psi at 4,000 rpm. Breaking down and rough as guts at 4,000 rpm. What the?? Where has my pressure gone? I have a set of 37 nozzles I would prefer to run because to my thinking % changes to the area of the orifice are going to start to have less impact on a smaller pill if you get my logic. But I’m not keen on to many more changes now that I’ve lost my way.
When I was a kid my long departed father used to say 99% inspiration and 1% perspiration so as a result I’m a chronic over thinker. My heads hurting – thanks Dad.
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