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Mix Fuel C16 + Pump Gas

Understanding AFR

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what afr can i go with when i mix the fuel btw VP C16 & Pump Gas.

im about to tune my car and thinking of using mix fuel.

Can i go lil leaner with mix fuel than with Pump gas only ??

and what target should i look for ?

my car 4 cylinder NA with high lift cam

First I'd be very cautious if you are going to mix fuel like this. While there is nothing wrong with doing this in theory, in practice it doesn't take very much error in your mix to create quite a large change in overall octane. If you're relying on the octane to prevent knock, this can potentially damage your engine.

With that out of the way I find that C16 responds with very similar lambda targets to what I use on pump gas - On either fuel I'd expect to be in the region of 0.88-0.92 lambda. You can test on the dyno to see which offers the best power. In general with the better quality race fuels like C16 you can tune a little leaner as you're probably not going to require a rich mixture to help cool the combustion charge and help avoid knock.

As an aside, I'd recommend that you consider Q16 if it's legal for whatever you're doing. I've done back to back tests on turbo engines between C16 and Q16 and always seen a healthy increase in power on Q16 due to the fact it's oxygenated. In NZ Q16 actually ended up cheaper than C16 too although it's been a long time since I last bought it.

Hi Andre,

That's really help.

Thank you for your info and reply

Hi Andre, being that the Q16 is oxygenated, will the 0.88-0.92 lambda suggestion work as well with that fuel and, what boost level is that lambda meant to be used with...20, 30, 40-psi?

@ Mr. Lee - The lambda targets I mentioned above were suited for an N/A engine as per the OP's question. With Q16 I tend to target similar lambda numbers to C16 but you need to add additional fuel in order to achieve your target if you're coming from a C16 tune.

You can't apply a single lambda target to every tuning task - You need to test and find how your particular engine responds. As an example, with a 2.2 litre 4G63 drag engine I tuned on Q16, I used a lambda target of 0.82 @ 42 psi boost and made 1001 whp on a dynapack dyno.

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