return line to gas tank

[Greg Hermann]

>>
>> at injector pressures you going to have a hell of a time boiling
>> fuel.....period.....
>
>No, No, No.  Get your self to southeastern MT, and you'll see
>plenty of vapor lock problems.  Main culprits are Fords, but Dodge
>runs pretty close 2nd.  And beyond a doubt, it happens in PFI
>applications.  I worked on plenty, and I mean plenty, of them this
>summer.  The fuel would vaporize in the fuel rail as fast as it could
>enter, and the injectors couldn't purge it fast enough.  The rail was
>so hot you couldn't touch it.  But guess what, system pressure on a
>gauge was normal!  I could start them every time by releasing the
>pressure test fitting and cranking the engine until the VAPOR blew out
>of the line and there was enough fuel in the rail to cool it.  I'm a
>competent mechanic.  Believe me when I say I diagnosed it well enough
>to be sure
>it was vapor lock

And if you think it happens in MT, get yourself to an eight mile stretch of
7% plus grade, all above 9K ft above sea level on a summer day. You will
feel like you wrote a post doctoral thesis on vapor lock. The guys who
watch the TV cameras in the Eisenhower tunnel (11K feet) on I-70 and drive
the push trucks can tell you pretty infallibly what vapor locks and what
doesn't!!
>
>
>and in a carb, assuming it is NOT suspended above a glowing
>> red cast iron exhaust manifold in a close engine compartment,  will allow the
>> fuel to blow off the top (hopefully down the stack) and the rest of the
>>fuel is
>> drawn into the jets from the BOTTOM of the carb.....anything less is poor
>> design....period....
>> ><snip>
>> > >Modern stock engines run too hot anyway, those stat's are set at 195 to
>> > >open, as
>> > >a min engine temp. the fans in most cases don't turn on untill ~230
>>degrees
>> > >coolent temp....that is WAY TOO HOT....good for EPA readings,  bad
>>for engine
>> > >longevity, seals, rings,
>> >
>ASK the guys who wrench in the dealerships day in and day out if they
>see vehicles lasting longer.  Pickups and cars are being traded in
>with 100Kmi or more, and after 5 years of hard use.  This is some
>pretty tough country on trucks, and there are relatively few of them
>needing engines before they're traded.  Not like it was a few years
>ago.  And most of the engine swaps are because of lack of
>maintainence.  I haven't seen a late model engine with anywhere near
>the cylinder wear as the older blocks have.  And it's pretty unusual
>for me to find a late Chevy pickup with an engine soaked from end to
>end with oil.  That's a lot of progress from the old ways.

Not much question that you get better lubrication (keeps the oil drier and
cleaner and gets it into more places) and less bore washing with somewhat
higher temps.
>
>
><snip>
>>
>> the fuel slosh problem is caused by my doing a DPFI system with that
>>antequated
>> Bosch patented pressure regulator device, requiring a return line,  thereby
>> requiring a rate of continuous feed from the tank that allows the slosh
>>problem
>> and temporary line air suction to be a problem in engine operation...I
>> personally have not found an adequate solution to the problem as yet,
>>but I am
>> looking at a pressure modulated fuel pump electronically driven as to a
>> possibility of solving that problem in MY '72 vette which came with a
>>carb, and
>> never had the problem to begin with.....
>
>Baffles in the tank.  That's it.  The fuel could slosh away from the
>pickup for short periods with a carb, because the fuel bowl could
>cover it.  FI swaps require some type of baffle system to prevent the
>slosh.  No reason not to run the return line, no need to modulate the
>pump, find a way to put in baffles.
>
And, for those who are serious about going really fast around corners, not
just performing crumpet catching maneuvers, there are fuel accumulators out
there which will cover for when even the baffles don't do it. But a (tall,
skinny) intermediate pressure vapor separator tank and float vents are also
important pieces of the solution.

Thanks for the support, Shannen, but at this point I think it is obvious to
most that some feel the need to squall like a mashed cat (or maybe like a
#^^%&*^&& "screamin' demon" Jimmy two stroke diesel) when shown to be all
wet!

Regards, Greg