MFI Pump Timing Out By 180 deg?!!

[Kjell]

Hi All, just replaced the belt on my MFI pump. Checked timing it was out by
180 degrees! As if it had been timed 40 deg afte TDC #1 instead of #4.
This car is new to me and have only driven about 20 miles, ran pretty
well I thought. So, here's my question, how can it run with the timing so far
off? Engine was rebuilt about 40K miles ago and pump has been rebuilt
by the Porsche factory at some point.

[Tom F.]

I think that the timing of mechanical injection in a port injected gasoline engine is not too important, at least for everyday driving.

Mercedes ran a similar Bosch system in its gasoline engines in the 50s and 60s. On the 220SEs the pump only had two plungers, and each plunger fed a group of three cylinders. So, the injection pump strokes were not timed to the intake valves. What seems to matter is getting the fuel really well atomized before it gets sucked into the cylinder, not the timing.

Same idea as CIS, I guess.

Of course, with direct cylinder injection, as on a diesel, timing is critical, but that's a completely different story.

Maybe fuel injection timing becomes critical in a gasoline engine with really high overlap timing, or at really high engine speeds, but those old 220SE motors would rev over 6,000 rpm, and sounded great.

[Bobboloo]

Toms right.

The injection waits in the port until the intake valve opens. I guess the only downside would be a little wetting of the port when the head is cold. Once warm it probably doesn't matter.

I would think worse case scenerio would be a late pulse where the injector was still spraying while the valve is closing thereby splitting the pulse.

[Eric911S]

Hello; You guys need to play with the pump timing on a Dyno. The results will change your opinion about correct timing of the pump. Thanks Eric

[Kjell]

Hello; You guys need to play with the pump timing on a Dyno. The results will change your opinion about correct timing of the pump. Thanks Eric

OK, so should I expect to have to reset my mixture for example once I start her up?

[Tom F.]

Hello; You guys need to play with the pump timing on a Dyno. The results will change your opinion about correct timing of the pump. Thanks Eric

Like I said, I don't know what happens at high rpm, or with a lot of valve timing overlap. So, what do you see on the dyno?

[Eric911S]

Hello: If you time the pump without the marks you will get more power. I won't tell you how many teeth advanced or retarded since every engine is different. Just some of things I've learned over time and playing around. Thanks Eric