Does anyone know of an online calculator or formula that can tell me what boost to run at a certain rpm to maintain a certain injector duty cycle? For example, lets say I'm running 15psi boost which at 6000rpm results in a duty cycle of 90%. I want to know what I need to drop the boost to at 6100, 6200 all the way to 7000rpm to maintain 90% duty cycle. All of the online calculators I've found are a lot more complicated with a lot more variables focused around selecting injector size. And yes I know the answer is bigger injectors with an aftermarket ECU, which I have sitting in the cupboard waiting to be installed, but it's not going to happen in the next 2 weeks before Bathurst.
Too many variables moving in different directions to get good results sitting down and calculating it. If you want to try it really coarsely, 7k is about 17% more than 6k so if you assume the ECU uses the same AFR and the engine's volumetric efficiency is constant etc. etc. you want to say your current boost is 1.17 times what you can deliver fuel for, divide 15 by 1.17 and you get about 13psi by 7k. Most people say max 14psi on stock injectors and turbos so I guess that's close enough. I would probably just run 12-13psi across the board, maybe tweak the gain to let it peak a little more, as I think it can take quite a bit of fiddling to actually get a boost controller to reduce boost while you keep pushing more air. Much more fun actually getting the laps in than stuffing around with the tune.
Thanks Fists. I've got a 40min practice, then 2x qualifying sessions, then 2x sprint races before the 1 hour race. So I'll be testing/adjusting this as I go. Hopefully I'll get some decent improvement before the final race :br:
No idea when it comes to online calculators. But if it was me, I'd be recording the data as the car is presently setup in conjunction with the data from a weather station & use that information as a baseline.
