Boost your normally aspirated AJ16 to 10.8lbs and mash the fun pedal...

For a couple weeks now (since the weather's turned colder) I've increased my boost pressure and leaned my AFR's out (12.5 AFR at WOT) for a bit of extra power or at least what feels like more power without issue. On Christmas Day, I was delivering Christmas presents to friends and family's doorsteps (mindful of the COVID pandemic) when I stopped to get gas. Needing about half a tank, I stopped to buy 93 octane gas from the same Quick Trip I've used for over 15 years without issue. But after filling my tank and spending a few more hours running around, I noticed the car felt a little different. The next day I grabbed my laptop and headed out to make a few pulls and check the data logs. On the first pull, nearing 4500 RPM at WOT I heard the engine start to "ping" and got out of the throttle as fast as I could. I checked the data log and my AFR was 12.2 @4500 RPM when I heard the engine ping. In full "fix it" mode, (I still had not associated my pinging issue with the fuel bought the day before) I adjusted my fuel table and made another pull, still pinging, the data log indicated 11.0 AFR. It wasn't until I added about 25% more fuel for a resulting AFR of 9.0 that it stopped pinging. Overall power felt a little down but at least it was no longer pinging or suffering from pre-detonation. "Pinging" the auditory example your engine is not happy, pre-detonation could be happing well before you hear the engine making pinging noises. It was until later that same evening when I connected the most recent fuel purchase and my pre-detonation issues. To test that theory, I purchased a bottle of octane booster and added it to my tank. The octane booster's packaging stated it would boost the fuel's octane level by 3 points when added to 25 gallons of fuel. Dubious, to be charitable, I grabbed my laptop and headed out to test my theory I'd gotten some bad gas and the octane booster's claims. After allowing the octane booster to thoroughly mix with my existing fuel, I loaded my previous calibration file into the ECU and made a few test pulls. Guess what? It worked, no pinging at WOT around the 4500 RPM mark with 10.8lbs of boost and an AFR of 12.2

Traditionally, I'm a huge skeptic of any "miracle" product that states it can restore your engine's, transmission's or car's overall performance without a rebuild, but this product appears to have worked. Now the question is, do I continue to trust Quick Trip or go with a name brand supplier? I suppose, any brand who sells fuel can get a bad batch... Should I buy a case of octane booster and add some every time I fill up? Is any XJR owner running octane booster as a prophylactic measure?

 

Pulled my plugs after running them for about an hour with the octane booster additive; the tips are bright orange. I've read the orange deposits on the plug tips is MMT https://en.wikipedia.org/wiki/Methyl...se_tricarbonyl and the Internet consensus is, it appears to be effective in reducing spark knock but the jury still out on the effects of MMT deposits on O2 sensors and catalytic converters. I'm also reading the increase by "3 Points" per the claim on the label is 3/10's of a point, raising 93 octane fuel to 93.3

I continue to remain a skeptic of miracle cures in a can, jar or bottle...

 

I always stick to top tier fuels and have had no problems: Chevron, Shell and Esso.

 

Concur! Thanks @Jagboi64