Yes I know how headers operate. And I can tell you the AFR doesn't change all that much over the RPM range from cylinder to cylinder just because you are running un-equal length headers (I should know, we ran several dyno tests in college where AFR and EGT was being monitored on all cylinders; and none of the engines we dynoed had equal length tube headers). Does the AFR differentiate between cylinders over the RPM band? Sure; but not enough to make much of a difference in the way the engine runs. In fact we found that intake manifold selection affected this more so than I think headers would have. Now if you can provide some dyno tests that prove otherwise, I would like to see your numbers. But I simply haven't seen enough proof or tests that justifies the absolute need for equal length tubes.The Dark Side of Will wrote:
I'm sure I don't have to tell you how headers operate. Just remember that they affect the shape of the VE curve. So different length tubes will bias the VE curves of different cylinders to different RPM. This means that some cylinders will ALWAYS be running lean and some will ALWAYS be rich, even when the engine or bank as a whole is stoich. These variations in mixture can't be tuned out because they aren't constant across the RPM range. You've done a lot of tuning, you know how important correct mixture is to good engine running and health...
The ultimate question is how much USABLE gain will you see out of equal length headers vs. non-equal length headers? And do the gains offset the added cost of the equal tube units for a street application? That is the question that matters to most people. How hard is it going to be to sell someone on a say $300 price increase for a set of headers that have equal length tubes if they will only gain a few more hp on a 350hp engine? Would you be willing to spend that extra $300 just to pick up say 5hp when that $300 could be spent more effectively on another mod? When faced with that question myself I can think of far better places to spend the money that will gain more than 5hp.
Again, if you can find some conclusive dyno tests that pit identical spec headers, a set with unequal length primaries and a set with equal length, that shows a substantial gain in usable power using the equal length units, then I will defer to your findings.