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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
I contacted an Injector Test and cleaning company with some questions to see if he could help.

This is his reply:


Hello Keith,

Thank you for your e-mail.

I highly doubt that the OEM CIS injectors could produce double the flow rate required to appx double the HP production, even with mods to the distribution head to produce more fuel pressure. The limit being the opening size of the injector orifice.

The major problem is there is damn near no info available on CIS injector flow rates. Bosch does not publish that info, and info that may be found on the net is dubious at best. I have very little info in CIS injector flow rates, and I doubt anything I have would be pertinent to the Porsche CIS injectors.

I should think, the start point would determine what the flow rates are for the injectors as fitted, with no mods in fuel pressure via mods in pressure on the distribution head. That would also require info on what the initial distribution manifold head pressure was/is. Once that base line flow rate is determined for the OEM injector, then calcs can be performed to determine flow rates with an increase in fuel pressure, up to a indicated above.

The next step would be locating a substitute injector, with double the flow rate...assuming no change to the distribution head. That's the hard once again, nobody publishes that info.

It ends up being trial and error.

Wish I could be more definitive, but engine tuning to produce more HP, is a rather "guarded" science.

If you have a few OEM CIS injectors, I would be glad to test them, at cost per my website. I think about $18/each.

SD Faircloth
Jaguar Fuel Injector Service
Jacksonville, Florida USA

Old 01-04-2010, 10:16 AM
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