Q16 Race Gas: Ignition Advance & Lambda Targets

Hello everyone.

I am aware that each engine combination is different, and that ultimately testing on the dyno is the way to reveal the optimal values for that particular combo.

But generally speaking, when running a high octane oxygenated fuel like VP Racing's 116 Octane Q16, are there general guidelines and expectations compared to pump 93 in terms of lambda targets and ignition advance or maybe even fuel timing? Or is it simply run leaner if you make more power and you wont knock since your running significantly higher octane?

Since I have briefly researched Q16 on different forums and have seen some claim that to get the benefits of the oxygenation from Q16 you should run leaner lambda targets, even if those leaner targets did not benefit you on pump gas?

If I am using Q16, and my engine is a turbocharged 1FZ-FE GEN 2 Stroker with a 108mm crank and 102mm flat pistons (5.295L) with a 1mm head mill and a 2.0mm MLS head gasket. Running one bar of boost with a Garrett G42, at that 1 bar of boost would I target 0.80 lambda as a starting point or go even leaner? Currently I am running 18 degrees of ignition advance and 0.80 lambda at 1 bar.

I am asking for opinions since I want to know how much I can push my engine with Q16 as well, I have not had enough experience with enough engine builds to know.

Also does Q16 want more ignition advance in general to run well compared to pump 93, I remember reading something that had to do with flame front speed.

Thank you.

I had hoped someone else would have commented with more helpful informatation, but my 5 cents' worth...

There is an old expression - the engine will tell you what it wants.

I can't make specific suggestions, but as a guide, you will need more fueling to offset the oxygen in the fuel - maybe around 4%? - but the actual lambda would come down to best torque while keeping exhaust temp's within the limitations of the turbo' and other components.

Same with timing, keep it short of detonation and/or at peak torque - a little playing with the lambda against timing may give a slight advantage.

On those two points, REMEMBER, timing and fuelling will vary with load and rpm - you may be able to bring in a little more timing towards peak rpm, after peak torque.

With that fuel, unless there are other limiting factors, I'd be looking at increasing the boost - while watching the charge temp' and it's affect on timing and torque. A little more fuel may be an acceptable trade-off to lower charge temp's in the engine a little.

Oh, if using an inertia dyno', don't forget there'll be possible compromises required in the settings when the vehicle is actually used, because of heat soak, etc.

I've found best power by adding ~6% fuel while also reading leaner numbers and 3-4 degrees more timing as compared to standard 100 octane gas on a few NA rotaries that have wanted to run Q16. Don't have experience under boost with it though, and I'd imagine you'd see more gains by timing on conventional piston engines that want it.

I've used Q16 for a couple of years and my experience with it on 4g63 is that for the best power I would use the same lambda value regardless of fuel type- it's 0.75. As far as ignition goes it's up to 7 degrees of additional advance with 3+ Bar of boost comparing to RON 100 pump gas.

Hamad,

Given that you've already optimized a tune for 93, and your lambda target is both reasonable and not overly rich, I'd start with the same lambda target and ignition values, then follow your normal optimization process. No immediate change in lambda target of ignition timing is required to get things going, just be sure to account for the stoich point change. How you do that will vary with the ECU fitted, ranging from entering detailed fuel properties, to perhaps skewing injector scaling if fuel characterization isn't possible on your system.