'75 turbo (4290652) FS in Houston

[PaulTWinterton]

Yum!  Let me see...$30K down payment...$2K per month mortgage for 72 months...whadayasay Honey?  Should we buy it?

 

Oh yeah that's $150K US...$200K Canadian.

 

Never mind.

 

 

[Preyupy]

7 hours ago, Simeon said:

 

Ahh I thought (going by my voracious reading of the McCartney book and similar but no real life experience of turbos) that the altitude compensator was a barometer type bellows attached to the KFish pump? Did they vary in production? 

No they were all the same,  the altitude compensator was always mounted separately from the KF pump.  There is more than enough going on around the KF already. 

As for the way the system works it is very simple in reality but a bit hard to understand if you can't sit down and study the way everything works together.  The "Readers Digest" version is:

There is a Aneroid on the back of the pump with a piston in it, there are springs on the top and bottom of that piston.  With the engine off the piston is held in a neutral position close to the middle of the piston travel.  This piston is attached to a shaft that turns the fuel mixture cone inside the KF pump.  When this piston is pushed down by boost pressure the KF pump delivers more fuel.  When the piston is pulled up by vacuum (off throttle, manifold vacuum) the KF pump delivers less fuel. There is also the throttle position lever on the outside of the KF pump just like the Tii that also adjusts the fuel delivery (notice I am not talking fuel mixture I'm just talking fuel delivery volume). There is some bleed by around the piston in the Boost Aneroid on the back of the KF pump, under boost air that gets around the aneroid piston comes out though the Altitude Compensator if you restrict the airflow the pressure on both sides of the piston tend to equalize and the springs with move the piston toward the middle position thus reducing the fuel delivery volume.  Under vacuum the same thing happens but the air is going the other way through the Altitude Compensator but in this case if you restrict the airflow you will increase the fuel delivery.  The actual "compensating" part of the system, the small bellows,  makes much more difference under vacuum conditions (Idle and part throttle off boost) that it does under boost. 

 

Just remember that the KF pump has no idea how much air is ACTUALLY going into the engine, it has been built so that at a certain position of the external arm and a certain position of the Boost Aneroid piston it delivers a known number of CC's of fuel per intake event. This does not change with engine RPM, ie: at 50% travel on the external arm (attached to the throttle butterfly) with the piston in Boost Aneroid at the position dictated by 2psi of boost (for instance) the KF pump will deliver X number of CC's of fuel PER INTAKE CYCLE of the engine at 1000 rpm and exactly the same amount at 6500 rpm.  Obviously the amount of TOTAL fuel / time goes up as the engine speed increases but the amount of fuel / intake event stays the same.   

[Simeon]

Thanks for the explanation! It sounds like it is there just as much to compensate and adjust for boost as it is altitude.