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rb25 fuel table


john samsung
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Hi guys

Quick question, when mapping RB25 DET with Link G4, What input would you base the fuel table on, MGP, MAP,TP etc etc ?

Reason i ask i had the car tuned and pulled the pcl file off to have a look myself to try play with the PC link software a little on the laptop, and notice the fuel table is based on throttle position yet i see a lot of threads on here talking about mgp, the ignition table is mapped by mgp

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Hi John,

Here is some general fuel table load axis setup advice depending on engine setup:

Naturally aspirated engines with stable intake manifold pressures.

Fuel Equation - Load = MAP

Fuel table load axis - MGP

Naturally aspirated engine with unstable intake manifold pressures.

Fuel Equation - Load = BAP

Fuel table load axis - TP(Main)

Turbo/super charged engines with stable intake manifold pressures.

Fuel Equation - Load = MAP

Fuel table load axis - MGP

Turbo/super charged engine with unstable intake manifold pressures below atmospheric pressure.

Fuel Equation - Load = BAP/MAP Xover

Fuel table 1 load axis - TP(Main)

4D fuel table load axis - MGP

The RB engines with individual throttle bodies often have trouble maintaining a stable intake pressure, which is why they often have the main fuel table on TP(Main).

Scott

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  • 1 month later...

Hi John,

Yes, for an RB25DET I would agree that MGP is the best choice. 

Ideally MGP would be used for the fuel table axis on all setups, however the problem is that some engines have very unstable manifold vacuum. Quite often this occurs on vehicles where each cylinder has an individual throttle body (like the RB26DETT). For these engines they are better off using TPS as the system is then more stable. Once the engine comes up on boost the manifold pressure is more stable, and therefore we recommend using MGP on a 4D table above atmospheric pressure.

Cheers,

Scott

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