Holley COMMANDER 950 - Manual (Page 68)

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Tuning a Race Engine: By far the best way to tune a high horsepower race engine is on the engine dyno. The dyno must
provide certain feedback as to the brake specific fuel consumption (BSFC), and/or Air/Fuel Ratio to help initial tuning. Exhaust
gas temperatures also provide helpful feedback. If the engine is already installed in the vehicle, a chassis dyno can be used
for power measurement but is not near as useful as an engine dyno. High stall torque converters also makes tuning on the
chassis dyno more complicated. Having a wide-band air/fuel ratio meter is extremely helpful.
Supercharged and Turbocharged Engines: Supercharged and turbocharged engines must run speed density so that they can
sense boost and the the proper amount of fuel. A 2 or 3 bar MAP sensor needs to be used. A 2 bar sensor will register up to
14.7 psi of boost and a 3 bar will register up to 29.4 psi of boost. When you select 2 or 3 bar MAP sensor from the engine
parameters screen, the manifold pressure scale on the fuel map will automatically change from 0 to 100 kPa to 0 to 200 kPa
(2 bar) or 0 to 300 kPa (3 bar). The only downside to this is that the resolution of the screen becomes less when you change
to a 2 or 3 bar MAP sensor. The engine can still be precisely tuned, but the tuning must be more exact. Due to this it is
recommended that you carefully select whether to use a 3 bar map sensor if you are only running slightly over 14.7 psi of
boost. If you are running a maximum of 16 psi for example, you are better off using a 2 bar and just tune the 14.7 psi fuel
point to provide enough fuel for 16 psi of boost. This allows you to retain the 2 bar MAP scale resolution without a penalty in
performance.
TBI Specific Tuning Information
TBI systems have some additional parameters that MUST be correct in order for the system to operate properly. Also
included is some TBI specific tuning information that you will find helpful.
TBI systems are inherently less efficient than Multi-port EFI systems. This shows up in the fuel required during cold engine
operation and transient (when the engine speed changes) engine operation. The extra fuel required when the engine is cold
(on a percentage basis) is higher with a TBI system than with a Multi-port system. The MAP based acceleration enrichment is
usually higher than it would be with a Multi-port system. Base maps that are for TBI should have values that reflect this. Keep
this in mind when you are tuning TBI systems.
Figure 53