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the 10 degrees or so is retard only .... Posted by jak [Email]  (#195) [Profile/Gallery]
(more from jak) on Wed, 20 Dec 2006 10:09:11
In Reply to: Question for Jak, re: Vac Advance Mod, Notnoel  [Profile/Gallery]
, Mon, 18 Dec 2006 10:47:08
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there is the advance side s well which operates under part throttle vacum
this advances mabey another 10-15* durring non boost operation
then as you cross O the vacum signal is gone & there is no boost yet so it is at the timing setting you would normally make for OE spec
then as boost aproaches 7PSI the diaphram flops over to the full retard position this may give a full sweep of like 25*?
I generally set the timing with a pressure signal on the hose to the diaphram & set it to 10BTDC
on trionic cars the timing under higher loads, timing goes to after TDC or 0 as the turbo peaks boost & then advances the timing up to between 6 & 10*BTDC as RPMs increase but aside from that it sort of resembles how the diaphram works
the biggest problem with the diaphram is that the boost retard is fairly static so if you set the timing so that the car dosent ping at 3000RPM you dont have enough timing higher in the RPMS to make it pull there & if you set it properly for 5500RPM its way too advanced at 3000RPM
so 10*btdc is a bit too far advanced to say 22PSI at 3000RPM but would work well for say 18PSI at 5500RPM
the diaphram just isent verry dynamic & I think the C900 would greatly benifit from a programmable ignition system which uses load & RPM to determine the timing
brad has done verry well with water injection on these cars to keep down pre ignition so more timing can be run
defeating the retart section of the diaphram & using a BTM is a good idea & definatly better then the diaphram alone but still retards X amount per lb of boost not nesessarily based on RPM although inherant boost taper may help with that a bit
I hope that helps :-)
happy holidays
JAK
, Mon, 18 Dec 2006 10:47:08, Wed, 20 Dec 2006 10:09:11 <-- Viewing This Message, Thu, 21 Dec 2006 07:33:54, Mon, 18 Dec 2006 17:17:10, Mon, 18 Dec 2006 17:38:53, Mon, 18 Dec 2006 18:38:33
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