Tii fuel pressure regulator mod question

[bnam]

Has anyone tried or considered removing the fuel pressure regulator in the return nozzle of the Kfish pump and replacing with a straight thru outlet and instead running an external adjustable fuel pressure regulator - set up so that at cruise/low throttle openings it provides 28psi, but at wider throttle openings it provides enrichment - say 30psi? This could be modulated by plenum vacuum.

My Tii came with a 292cam so thinking about options to provide additional fuel at higher RPMs

Byas

[c.d.iesel]

...that would not alter the fuel amount or opening duration

at the mechanical injectors -

this is why you move on to Electronic Injection

[bnam]

Why not? Fuel amount is controlled by 2 variables -- fuel pressure and duration of injector opening. I'm increasing one of those -- why would that not increase the fuel injected? What am I missing?

Byas

[BillWilliams]

The Kugelfischer puts fuel to the injectors at 400+ psi and the injectors open at that psi, I think it is 450psi. I do not think what you suggest changes that pressure. And since the flow from the Kugelfischer is timed via the cogged belt, the pressure drops immediately not sure that would allow the added fuel you suggest.

But if you are not convinced, give it a go and report back

[c.d.iesel]

because a mechanical fuel injector nozzle opens at a determined

pressure. The volume and spray pattern remains the same

because of the 'pop-off' opening of the pintle tip/spring/shims in the injector.

Altering the system pressure will not increase volume

out of the injector tip. You could adjust the pressure opening

setting of the injector with different tip shims - done to match the 4

injectors for balance. But you are not able to change it to respond

richer/leaner for varing manifold pressure/fuel pressure/boost pressure.

the 2002 turbo injection pump does have additonal compensation

during boost pressure - butyour asking about normally asperated motor

I assume.

[FB73tii]

Because the KF pump is a positive displacement mechanical pump. The amount of fuel sent to the injector is determined by the volume of each (of the four) pistons in the KF. At the pressure we are talking about gasoline is an incompressible fluid, so higher pressure does not "pack more gas" into the volume of fluid delivered to injector.

Edit: Geez, I am going to have to type quicker! Two replies while I was busy composing my response.

Fred 74tii

[bnam]

Thanks! This (all 3 replies) helped. I get it now...

Because the KF pump is a positive displacement mechanical pump. The amount of fuel sent to the injector is determined by the volume of each (of the four) piston in the KF. At the pressure we are talking about gasoline is an incompressible fluid, so higher pressure does not "pack more gas" into the volume of fluid delivered to injector.

Fred 74tii

[c.d.iesel]

[aa/fd]

A phone call to Wes Ingram would remove any questions as if the bypass valve setting could make enough of a change that the additional linkage on the mixture control arm be unnecessary.

[Marty]

I think CD andBill ought to put a clamp on the fuel return line and report back that the car is running lean, I know when the fuel return on my74 TIi was pluged the thing was running in the tear gas rich mode. I mean do you think the Germans put a fuel return line in for no reason?