Thread: MFI in a 930
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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
I still have a lot to learn about MFI.

I think I have the Porsche Bosch unit down reasonably well.

Porsche MFI pumps primarily just use a space cam which basically is imprinted with the fuel delivery programing.

Being a reference system. If any thing varies from expectation, the AFR will suffer.

That is at 5000rpm and 100% throttle it is going to send an amount of fuel as predetermened by the programing carved into the space cam.

The LDA can add boost enrichment to our space cam or reference style MFI. This adds a boost sensing capability.

One could build a turbo with out an LDA but it would not compensate for different levels of boost and at a given RPM and percentage of throttle will deliver a predetermined amount of fuel.

The LDA also looks like it can add a level of pressure sensing at other times (think MAP).

Thus, it could if set up to do so, adjust for load from cruse to on boost. This might even eliminate or reduce the need for a space cam as changes in vacuum and boost change fuel quantities delivered could be made by the LDA.

For example, non turbo diesel MBZ pumps still have an LDA.

I suspect other non Porsche MFI injection pumps might depend on the LDA to adjust for differences in load and not use any space cam or a very simplified space cam.

New stuff and kind of cool.
Old 01-13-2010, 08:53 AM
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