8 replies to this topic

[hatchssv8]

Greetings all, I was discussing the EFI set up with Herne and we got stuck. I am also going injection and need to establish if my proposed set up will work.

I will be using a drop tank and will be modifying it to accept a VZ type in tank fuel pump and pot. At the moment I have the pump with the integrated reg, fuel in and out pipes. I may go to the 3 pipe type which incorporates the vapour in pipe if I cannot find a suitable location for the vapour in to the tank elsewhere(hope this makes sense)

I will also use the original vapour line as the fuel return after the reg at the fuel rail.

My problem? atm is to find out the following-
If I only have a single fuel line from tank, via fuel filter, to the fuel rail (and block off the return line at the fuel line) will there be equal fuel pressure at each injector as regulated by the internal reg on the in tank fue pump. Basically the fuel is syphoned from the pot, pumped out of tank to the fuel filter, at this point is a t junction(one to the fuel rail, the other back into the tank where it feeds into the pressure regulator) the fuel line to the rail gets filled, then the return line is filled and pressure is regulated in tank. This is identical to Gen III set up.

If I have missed something or not made myself clear, just ask.

Looking forward to your replies, Max

[Dr Terry]

Hi Guys.

These are the 2 different ways of supplying fuel to the injectors in EFI systems. VZs use the latter.

The 1st is the system that's been around since the Bosch D-Jetronic days of late '60s. It used the rear pump, a supply line to the rail, a regulator at the end of the rail & a return line to the tank. This works well, self bleeding & always a cool supply of fuel to all the injectors.

The 2nd system is getting popular on newer cars. They've done away with the return line & put the regulator in the tank. Now they only have the 1 line feeding the fuel rail, & no return, so it would take longer to bleed & the fuel doesn't recirculate to the tank, so just sits there gets hot. Fuel supply performance will be the same, but I don't like the idea of the fuel sitting at underbonnet temperatures. I can't think of any advantages of the newer system, except saving the 'enormous' cost of the return line.

Dr Terry.

[hatchssv8]

Thanks Doc,
As I stated I will use the vapour line as a fuel return from the rail. I had not considered the underbonnet temps affect on fuel. Are the fuel temps considerable enough to effect performance?

I can bypass the 'enormous' cost by routing another vapour line from a Torana. What would a new fuel line cost anyway?

Thanks again, Max

[Dr Terry]

Hi Guys.

My use of the word 'enormous' was in jest, of course, but it is amazing to see how car manufacturers think.

If you think about it, in production a steel fuel line & its associated clamps etc would be no more than a few dollars. Be generous & call it $5-00. If they produce 100,000 cars per year that is a saving of half a million dollars. Not bad eh !

On the temperature thing, my worry would be purcolation, similar to that in a carby bowl. In theory, the fact that the fuel is at pressure would raise the boiling point of the petrol. Obviously its not a problem, there are plenty of VZs & oythers with similar systems sitting in traffic in summer no worries.

Dr Terry

[hatchssv8]

Hey Doc,
I know exactly what you mean. In a recent VA/VE excercise, one of my proposals was 3 cents per unit (EAV 14000) and was one of the first to be approved.
The excercise alone cost more than 420 folded, but there is a bigger picture of course.
Max.

[Statler]

I hope this thread isn't dead. Is it a requirement for certification that the fuel & return lines be steel or flexable? Do they have to run external or can they be routed inside the body? Is it allowable to qld rego to have the swirl pot & filters mounted in the boot? Just a couple of questions. Thanx