Q16 fuel

[russellauto1]

I have a little bet going with a friend and he says you cannot run Q16 in an EFI car without adding more fuel to injectors.

Is that true? Will the o2 sensors adjust automatically?

Thanks

[Greenlight]

Unfortunately it is not a simple yes or no answer.

Q16 has a different "ideal" (stoichiometric) air/fuel ratio than most other fuels. That value is typically listed at 13.5:1. This ideal value is related to complete combustion of all chemical elements, not the ideal A/F ratio for maximum power.

Generally speaking, most gasolines have an "ideal" A/F ratio of 14.7:1.

The oxygen sensor is actually a "Lambda" sensor, which means it can detect an excess or lack of oxygen in the exhaust as related to the stoichiometric value. A Lambda reading of 1.00 means whatever fuel you are using is operating at the stoichiometric value (1.00 using Q16 = 13.5 A/F ratio).

Your oxygen sensor only inputs a lambda reading into the EFI system. What the system does with that information varies by system. If your particular EFI system is programmed to compensate the injector pulse width base on trying to follow a Lambda vs. RPM map, the EFI system will add/subtract injector pulse width to try an obtain the predetermined Lambda value that the user has set.

If on the other hand you have an EFI system that is operating in "open loop", it will not pay any attention to the lambda value supplied by the O2 sensor and the injector pulse width will not compensate for any changes in Lambda values.

Some EFI systems always assume a Lambda reading of 1.00 means the A/F ratio is 14.7 and plot out an A/F ratio based on Lambda 1.00 = 14.7. This 14.7 value is OK to use for fuels you buy at the pump for your pickup truck but not good enough for fuels used for racing. For example, VP C14 is typically listed as 15.08:1 "ideal" ratio. Sunoco 260 GT Plus is 14.0:1.

So, if you are running in Open Loop, the EFI system will definitely not compensate for the additional fuel required by Q16. If you are running in Closed Loop AND you have the fuel tables set such that compensations are made based on Lambda readings (not A/F ratio readings), it will compensate.

Some high end EFI systems allow you to input the stoichiometric value of your particular fuel. In those cases the A/F ratios that are plotted are the actual A/F ratios, not a ratio based on the standard 14.7:1 ideal value.

I hope this helps.

[buzzinhalfdozen]

Greenlight is correct....the short answer is ,you lost the bet.