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Saab Classic 900 Performance, Mods & Tuning Covers Tuning & Performance modifications for the Classic Saab 900

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  #1  
Old 03-04-04
Johann F Johann F is offline
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Default Removed RRFPR

Fed up with having to check and reset the pressure every few weeks (requiring a lot of messing about) I put back the stock 3.0bar unit. With my multimeter hooked up to the Lambda sensor I'm still getting a .85v reading at WOT which was exactly the same as I had with the rising rate unit. Either the Rising rate unit was not supplying any more fuel than the stock one at WOT or the output of the sensor maxes out at .85? Either way I'm unable to feel any degrading in performance - infact I even felt the power is a little better at the top end at WOT- the boost held steady at nearly 1/2 the in the red.
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  #2  
Old 03-04-04
alan forsyth alan forsyth is offline
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i was thinking of getting one of those as well,what brand were you using ? i'm running a 3 bar one at the moment and thought it would run a bit better with the rrfpr
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  #3  
Old 03-04-04
Johann F Johann F is offline
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FSE/malpassi - just dismantled it to figure out how it works - Large spring acts on 2 diaphram's instead of 1. Logicaly the base setting ( no vac) must be identical to standard unit. When vac applied and spring compressed reduction of pressure must be effected by area of diaphram and air pocket between the 2 diaphram's ? When bost is applied I can't see how more force can be applied to the valve to increase fuel pressure over a 1:1 ratio. Therefore fueling is unaffected at WOT. I can only presume that changes in fuel pressure are quicker than the stock unit however last time I hooked up a guage to a stock unit and connected or disconected the vac hose - teh change in pressure was instantaneous. Looking at the components I may be able to remove one of the diagphrams and spacers and return it to a Fixed rate adjustable unit but I still can't see any advantage over the stock Lucas fixed unit. Anybody else had one apart and can explain it's functioning?
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Old 03-04-04
Johann F Johann F is offline
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Further examination shows wear on the valve seat - it's a simple plate that pushes against the end of a tube. The side looks worn where uneven spring pressure has been applied everytime the unit actuated. It's not far off wearing enough to create a leak The standard needle valve looks a much better design as it's self leveling. This junk is going in the bin. If you want more fuel pressure get a higher rated fixed unit or an adjustable unit as done by Webber.
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  #5  
Old 03-04-04
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Alex Alex is offline
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When I had the Malpassi unit connected to my car, which also has a fuel pressure gauge connected, the change in fuel pressure when connecting or disconnecting the vacuum line at idle was only around the 0.6bar level not the 1bar level that I would have been expecting if the unit was working correctly.
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