forgot 2 things:

standard fuel line was too small i believe as if i held it on boost for a long enough period it would cut just like there was no fuel then i would back off and put the boot back in and it would be fine (unfortunately the worst part i think is changing the outlet neck on the tank)

and the above setup did not require a return fuel line (i was gonna tap into the rubber filler neck for a return line initially but thankfully didnt need too)

Steve [phunkdoctaspok]
By name calling, i have assumed that you allude to the revised version of your longish "nickname" There was no offence intended, but i kind of reverse engineered the thing & summarised.
The Doctor Spock part was easy enough & i converted the "ph" to the phoenitic "f", then removed the "n" to come up with..... well you know what i came up with. The less offensive version of it was "screw", then add the abreviated "doc" Spock, 'n there you have it.
I had assumed that i was right, but perhaps not.


For those who want to learn some basics.

As to the fuel pump, these things are masterpiece in simplicity. The diaphragm is [ususlly] the floor of a chamber that has two one way valves in it. One to let the fuel in, & the other lets it out. The diaphragm is pulled down by the mechanical action of the cam eccentric & the relevant linkage. This means that the chamber gets larger & the reduction of pressure inside "sucks" the fuel in from the tank. Nothing comes in from the carb side because the one way valve won't let it.

The linkage has a "lost motion" function which allows the arm to stay on the cam eccentric without affecting anything else. This linkage only pulls the diaphragm down, nothing else.

The spring underneath the diaphragm pushes it up, reducing the volume of the chamber. The fuel can get out only through the one way valve on the carb side. The other one stops it from returning to the tank.
The diaphram stops emptying its chamber either when it can't go up any more, or when the cyclic action of the linkage pulls it down again on the next rotation of the eccentric. This is in fact what happens in normal operation, & in cruise mode, the diaphragm usually moves up & down only a very tiny distance. The strength of the spring under the diaphragm controls the fuel pressure & the one in a 1200GX pump is stronger than a stock one.

The fuel pressure generated at idle, when the needle & seat are for all practical intents & purposes, shut, does not "push" the diaphragm down, it simply "holds" it down. The eccentric & the linkage pull it down.

Most pumps have a seal on the round shaft that the diaphragm as atached to so that there can be a separate chamber under the diaphragm that is vented to the atmosphere. This allows the diaphragm to pump air in & out of that chamber so that it is always at atmospheric pressure, & to allow any fuel that leaks past a damaged diaphragm to escape. The seal keeps oil from the engine out of the pump, & any leaking fuel, out of the oil. This diaphragm pump seal is not really designed to handle boost on one side only, so i have seen attempts to seal up the actuating mechanism. I have not laid eyes on a successfull attempt as yet, & probably never will. Most just pressurise the pump & check the seal whenever they get around to it.

The real advantage of using the stock pump in a box, is that as a result of the fact that both pump & float bowl see whatever the boost pressure is, the fuel pressure will ALWAYS be at the same level above whatever the boost pressure is. It is self regulating

Electric pumps solve some problems, but without some means of regulating fuel pressure to a fixed level above boost pressure, which can vary quite a bit, you are likely to have too much fuel pressure some of the time, & perhaps not enough pressure at other times.

I hope that i have managed to make it just a little clearer than muddy water in a beer bottle in a coal mine at midnight in a blackout.

Chris

Chris did it take you long to come up with that way to cover your tracks?

In your description of the pumps operation you use the term one way valve, this is like i described but I used the term resistance pressure, meaning if the diaphragm cannot reduce the volume of the pump because of the needle and seats operation the diaphragm although not being pushed down it will still get a resistance pressure because it cannot compress anymore to reduce the chambers volume.

As for the spring I can picture it now.
What threw me off was you saying previously it will add 3 to 4 psi, I took this as increasing the pressure by 3 to 4 psi but in actual fact it is just keeping the pressure the 3 to 4 psi above ambient pressure like it was designed to do from the start.

This brings me to another question you could possibly answer, Why does the 1200GX require a higher pressure pump?
I understand what you are say by the stronger spring compresses the diaphragm quicker with this creating the higher presssue. but why does the 1200 gx need this extra pressure? I can understand increased flow, but pressure?

Sneaky track cover dodgeman used wasnt it. Good one though!

I think the fuel pressure is increased to aid supply to two carbs, at higher RPM, in the GX engine. The higher fuel pressure helps ensure the drag on supply from passing through small lines doesnt cause mixture lean out at higher RPM.

Any other ideas????

Sounds like a good explination to me.
And it was nice and short and simple too.

Thanks guys, Cheers Steve.

Something that I haven't seen mentioned yet (but that doesn't neccessarily mean it isn't hidden deep in one of these million posts ) in the comparison of superchargers and turbos is that a turbo is inherently more efficient. A blower is mechanically driven off the crank, and as boost and blower speed (for positive displacement type blowers) increases, so does the energy required to drive it, negating some of the gained bhp. The turbo on the other hand is driven by a waste product that does not increase the load on the engine in any way.

Quote:
1200rc, just curious about what fuel delivery issues you mean, and what other advantages you think the blow through setup has that would justify the extra effort and expense?

I've used a draw through setup before on an A14 with up to 12psi boost, on premium ULP, in Brisbane summer weather (>30 C), with just a .030" headsaver to lower compression without any detonation issues. We used the standard mechanical fuel pump and lines and had absolutely no fuel delivery issues.

The wet manifold design of the draw through system offers a form of intercooling that has been proven to net measurable bhp increases even in NA cars. A bit of water injection is another extremely cheap and simple form of charge cooling and detonation suppression.

The BOV is not an advantage of the blow-thru system - it's required to help overcome one of its problems! And its a problem that does not affect the draw through setup.

Hey well done L18_B110. You're the first person to come up with some real advantages of a suck-through system! Before I read that I couldn't see why anyone would bother with them. thanks

i dindt go back and re read but i have a feeling i was thinking of the fuel going through the turbo and many other pipes on its way to the head, i was wondering also about how the hell these suck through superchargers using a plenum arangement expect fuel to distribute evenly let alone not pool in the plenum???

whats the "wet manifold design"? is that fuel seperating from air and pooling in plumbing and stuff? doesnt sound very good to me

i was reading an article on water/toulene injection just last night, im still not 100% sure on how it is setup but it sounds alright, basically just increase octane from what i read, a stainless exhaust would be expensive though??

the main advantage of the BOV is the sound! i spose i dint make it obvious but i was reffering to the wank factor of it (even thoughi realise it does have performance/reliability effects too)

gotta cruise but ill think about why blow is better and post again

HEY!!
GUESS WHAT I JUST BOUGHT?
A SUCK THROUGH MANIFOLD!
No turbo but he did give me a carby; a sromburg, looks a bit old but with a spit and polish(and a carby kit) should come up brand new! A bloke at work had a mate of a mate who made it for a rally project, but fortuate for me he lost interest. whole motor and manifold for $500. The motor is a rebuild A12 thats been bored out 40thou, and by the look of it he is using a spacer plate between the head and head gasket, i guess to change the compression, Mind you!, this is going on what he told me so in reality i don't know what's been done to it!?
I'll have to take some pictures and post them to see what you think.Everyones opion is welcome!
The way i see it is that the blow through system might be better, i think this is a good place to start, because i only have basic knowledge on turbos which when you think about it, is very little! and i'll admit that. this is basically a quest for knowledge! I think my next project will be a blowthrough system well......... maybe, we'll see what happens

L18_B110, I've heard the same thing about turbos being inherently more efficient.
Quote:
I don't agree. Let's see how do I word this... I think of the turbine as a restriction in the exhaust. I believe the turbine needs some amount of exhaust pressure to drive it. The engine has to work againt this pressure. Isn't this the reason why an engine with a relatively small turbo would spool up real fast at first, then fall on it face when the engine speed gets high enough?
Please don't slam me
I don't have a turbo. I'd like to someday install one and have been following this thread closely and learning a lot.