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22-05-2007, 10:06 AM

#41

Stu @ M Developments

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Quote:

Originally Posted by JjCoDeX75

Quote:

Originally Posted by Stu @ M Developments

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Originally Posted by Rick

Stu, what is the minimum pulse witdh change that L8 can do, and what sort of pulse width do u see on a 2 litre with 1000cc injectors? And does this factor in the injector opening time? THe actual fuel delivery period must be under .2mS!

Ive never had to go sub 1% mate, so have never had any way to really try, bar winding the fuel pressure up for the hell of it, which ive no interest in doing. I will maybe try tomorrow just to see what the datalogger will report.

1000cc at std fuel pressure requires around 1.3ms total time at idle.

Stupid laymans question coming up.....

Given the above, and the limitations of the computer speeds of the time (compared to the modern stuff), in the hypothetical situation where an injector at idle required an open time of 0.2ms, would the solution not be to reduce the fuelling pressure on the rail in order to allow the injector to work for a longer period?

JJ

Yes... in some cases, however, your base pressure must always be a suitable amount above the intended boost pressure to enusre fual atomisation when the plenum is pressurised, so going much below 3.5bar absolute could result in poor fuel atomisation at high boost and engine speed, leading to a meltdown or running issues.

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22-05-2007, 11:30 AM

#42

JjCoDeX75

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Interesting. So presumably the engine design and injector location etc affects the susceptibility to poor fuel atomisation. I only ask because I understand that the Scoobies for example work at a lower fuel pressure than the cos?

JJ