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, Wed, 28 Nov 2001 16:01:15
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We are getting mixed signals from the C900 and NG900 owners.
The C900 systems can have fuel delivery issues and boost taper can avoid leaning out. The boost taper may not be intended but may be neccessary when increasing boost levels.
The NG900's have no issues with leaning out or needing larger injectors that I have ever seen.
With the NG900's the boost taper is a result of restritive iar boxes, filter elements and the IC etc. The 94 to 99 throttle body transistion casting design flaw also is a big problem. Some of these things can be fixed with DIY projects. The turbo is a bit undersized to help it spin up faster, somewhat also to compensate for the boost lag induced by the BPC valve which although an ECU modualated control valve, is still a bleeder valve. So the undersized turbo is inefficient at really high flow volume and at higher pressures. So the turbo works less effientently and with an BMC, the pressure drops after the MBC pressure tap point drop the pressure at the manifold.
Why use the MBC? It is not perfect by any means, but it is cheap and effective given its limitations. It allows the boost lag to be that of the turbo itself, not that imposed by the stock electric bleeder valve. With the MBC, the boost comes on faster and you can set it higher and get that boost in the 1st 2 gears as well. This is balanced by the other drawbacks of ideal location of the pressure tap and pressure overshoots that were discusssed earlier in the thread.
In hot weather, my Hallman MBC with a tap at the manifold gave me 15 PSI of boost with little or no boost taper at the high end of the tach. It was not useable in cold weather... mostly the fault of the location of the tap. So you enjoy the benefits and the limitations or drop the $$$ for a modefied ECU. So it all boils down to a choice. The MBC might be a simple cheap stepping stone before you have the fun money for a modified ECU.
95SET, modified air box, K&N, Sports exhaust, reworked throttle body transistion casting and removed the turbo compressor discharge silencer, Turbo XS MBC and bypass valve. These also help the turbo spin up faster.
posted by 208.24.179.2...
, Wed, 28 Nov 2001 17:15:11, Wed, 28 Nov 2001 16:01:15, Thu, 29 Nov 2001 09:11:50
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