I haven't read beyond the first page yet and I jumped from the start of page 2 to the most recent posts. I just thought I'd throw in my own experiences. The thread was started with the question on exhaust back pressure vs. intake boost pressure ratios. What ratios were common, which were desireable and which were impossible to obtain. Was crossover really possible?
I've obtained the mystical tip ratio of better than 1:1. Somewhere between .85-.95:1. That being done with a small cube V6, small heads, a camshaft with too much duration, too much overlap, low lobe separation angle, long tube headers, a turbo that is way too big, a short 3.06" stroke, and a 9.25 CR that is very low for a blown alcohol application.
The tradeoff for this level of efficiency is that I have to use a 1-2 second shot of nitrous to spool the turbo. And, I wouldn't have it any other way. :biggrin:
I've obtained the mystical tip ratio of better than 1:1. Somewhere between .85-.95:1. That being done with a small cube V6, small heads, a camshaft with too much duration, too much overlap, low lobe separation angle, long tube headers, a turbo that is way too big, a short 3.06" stroke, and a 9.25 CR that is very low for a blown alcohol application.
The tradeoff for this level of efficiency is that I have to use a 1-2 second shot of nitrous to spool the turbo. And, I wouldn't have it any other way. :biggrin: