so im only 19 and have never really had a chance to mess with mechanical fuel injections before so how does it work? ive been around efi but thats too much wiring for my tastes. is fuel injection more for all out hp or does it help torque to. just wondering if someone could explain to me how such a system works as im always looking to learn about cool mechanical stuff. no wonder im going to school for mechanical engineering.

Howdy,



There's been several mechanical injection systems over the years. One that comes to mind is the system GM put on the mid 50's Corvettes. Another is the system used on Continental and Lycoming aircraft engines.



Most are essentially full-flow systems. I.E. They flow fuel any time there's fuel pressure on the throttle body and the throttle position is idle-WOT.



Hilborn has a good description of theirs. http://www.hilborninjection.com/tech_mech_overview.asp



There's also a Wiki http://en.wikipedia.org/wiki/Mechanical_fuel_injection





The amount of fuel flow is dependent on fuel pressure and throttle position. Not very efficient. Also, even though there's an injector at the intake for each cyl, each injector is not switched on and off like it would be if electronically controlled.





Here's a good diagram of a mechanical fuel injection system for a Continental 470 cu-in engine



http://www.kellyaerospace.com/articles/ContinuousFlow.pdf





The simplest (and best) mechanical fuel injection system is a carburetor!!







Cheers,





Rick














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yea ive been doing some research on them and they sound pretty involved for a carb junkie like my but i still wanna learn how they work and play with it sometime just for the hell of it really. that and they sound like a major pita to tune for anything but full out racing

Rochester (GM) did one on Scrubs and Pontiacs in the late 50's /early 60's. Mercedes has done it on the early 300's, And there was a Bendix version used on AMC (Nash) and others. You should be able to Google those and find out what you need to know. Basically it's mechanical control of fuel pressure from throttle position/RPM/ and manifold pressure. It DOES NOT necessarily make more HP or torque than a carb. Often just the opposite.

Frank/Rebop

Bristol, In ( by Elkhart) 

In the late '70s and early '80s VW Rabbits had Bosch  "L" jetronic injection that was said to be electronic but was very mechanical.  L was for "Luft" and all it was was a big air valve with a rocker arm that was connected to a fuel metering system, as the engine used more air it got more fuel. Simple! and worked very well. (there was also enrichening for heavy loads and cold starts)  Most Mechanical injection systems worked very well when tuned properly but that was not very often, we wont go into the Lucas mech. injection, I heard that Zora Duntov even said about the "scrubjection" that "if fuel injection was the only thing out there and someone invented a new device called the 'carburetor' I'd buy one"  (very loosely quoted )

   God Bless.   Tim                           http://yblockguy.com/

350ci Y-Block FED "Elwood", 301ci Y-Block Unibody LSR "Jake", 312ci Y-Block '58 F-100, 338ci Y-Block powered Model A Tudor

tim@yblockguy.com  Visalia, California    Just west of the Sequoias

I have a friend with a '62 corvette which was originally injected. He's running a carb now but has all of the injection components.


Lawrenceville, GA

The Kinsler site has a great deal if information about various types of FI including some discussion of Lucas and Hilborn mechanical FI.  The Rochester system was very a clever design but if I am not mistaken it had a gear type constant displacement pump driven by a flexible shaft off the distributor,  A'la T bird tachs. I believe it was a constant flow system using various vacuum and position signals with mechanical linkages, cams and stuff to compute the fuel necessary.

Doug T

The Highlands, Louisville, Ky.

Call me old fashioned ,old school or just old ??? When you are 100 mile from nowhere ,that's when you are going to breakdown ( Murphy's law ) .Petrol motors are mostly easy to fix .They only need 3 basic things ( yes ,I know I didn't mention compression ) to make them work ,clean air ,spark and gas .Fuel injection on the other hand , seems to be great on the track for racing ,but when it stops in the middle of nowhere ????????.I just prefer to track down one of the 3 basic items .Maybe I'm just old and lazy ???That's my opinion .

Lon

yblocksdownunder

You can make injected V8 with two four cylinder K-Jetronic Injection systems.

It's simple system and fuel pump is only electric devise, if I remember right.


Hyvinkää, FI