You don't add 40% more fuel/air mixture, you make the mixture 40% richer. Fuel is such a small part of the fuel/air mixture that 40% more fuel volume has virtua

You don't add 40% more fuel/air mixture, you make the mixture 40% richer. Fuel is such a small part of the fuel/air mixture that 40% more fuel volume has virtually no effect on the compression stroke. Timing out the injectors is an issue if they are marginally sized, and the ECU can throw a fit because it thinks the injector timing can't possibly be as off as the lambda sensor tells it. On my old VW Passat, you could program an offset into the ECU to account for the latter problem. I test-ran it on up to about E85 without any other changes, and got noticeably less knock retard until the injector time saturated somewhere around E60.