Quote:
Originally Posted by AleroB888
You can do that, but you would have a whole (missing) section of the Spark tables that could not be optimized, past 0.92 g/cyl. If any KR is generated in that range, you could not tell exactly at what boost level it occurred.
If no KR is detected, and acceptable WOT power is achieved with the limited stock timing table, of course that's workable.
But I think you'd be leaving some performance on the "table" haha, pun intended  |
Once you have a decent amount of power, it doesn't take very much to get past .92 g/cyl, so you're already in that region anyways. I had my laptop stolen out of my truck last year and lost a lot of the scans we had for people's cars over the past few years prior, but I did happen to find a scan of one of my race car passes, and it clearly shows the g/cyl exceeding .92 at 4000 rpm, just .891 seconds after launch. This is with the T67 and 10psi of boost. In this same run, you can also see it hit over 10,900 Hz on the MAF. The MAF I was using was a LT1/LS1 (aluminum) MAF, but it was running off a 3x00 pcm. I don't remember if that was with or without the mini-AFC, but pretty sure it had mini-AFC. If you have a value set at the bottom corner of the spark table, and want to modify it to be something else, you can always modify the RPM threshold and commanded spark after that threshold to command a certain amount of spark after whatever rpm you input as the threshold, but personally, I use this value as a spark-controlled rev-limiter. The bottom line is once you go past a certain point, spark is constant, but that doesn't mean you're losing power because of it.
Boost is pretty constant after you've spooled the turbo, thanks to the wastegate bleeding off any excess pressure, so assuming you know how much boost you've got the system adjusted to, you should know exactly how much boost you have when x amount of knock happens. I don't know anyone who has a boost controller who doesn't have a boost gauge of some kind to see their actual boost. Also the biggest chance of knock to occur happens not at max rpm, but at torque peak.
Paul, we use a custom mini-AFC to exceed the limits of the stock MAF. All of our turbo kits we sell for the 3100 and 3400 use the stock MAF sensor, and those that wish to exceed the limits of the stock MAF (which is somewhere around 350whp with our setup) use the mini-AFC we make to scale back the MAF frequency to give it more range.