Date: Fri, 03 Nov 2006 07:42:46 -0500 From: Fred W <Malt_Houndnospamm-me-not*yahoo.com> Subject: Re: Cold Air Intake
- Bob - wrote: > On Thu, 02 Nov 2006 21:45:28 +0000, Colin Stamp > <col.dustbinnospamp.plus.com> wrote: > > >>I have to say, I disagree a bit here too. Like you say, the boost >>*pressure* won't change, but if the air is cooler, then the mass will >>be greater for the same pressure. > > > Yes... exactly. I have some semi-scientific testing done. I use an MBC > on my engine. Using an MBC eliminates the computer's ability to adjust > boost (the very intent). However, the computer still maintains final > authority and if it detects "too much" boost, it will cut the fuel, a > rather radical, but effective way, to prevent overboost as set by the > factory. > > I have the MBC set up to run well in the Summer. It boosts very nicely > into the red and holds there - but never hits fuel cut. Recently temps > dropped around here, by about 30 degrees average over Summer. First, I > do notice a substantial increase in power, both seat of the pants as > well as watching the boost gauge. In addition, I managed to hit boost > cut accidentally the other day. I was not running WOT, just > accelerating hard. Still, I hit it. So, how much of an effective boost > increase do I get? One lb? Two? I don't know... but I know it's there, > no question about it, and it's reliably detectable with the > temperature change from the seasons. OK, so you're saying that in the cooler weather, your manual boost control allows higher boost pressure which results in more power? Well, wasn't that my whole point all along? Yes, in a normally aspirated engine colder (denser) air results in more power. But we aren't talking about NA engines here... I said the way to increased power is increased boost all along. I was just advocating doing it with an improved software map in the APC (Automatic Performance Control) instead of a MBC and colder temps. The bigger advantage to sticking with an APC being that the APC can back down the performance marginally if / when you have to run lower octane fuel or as weather conditions & altitude vary. It does that by monitoring the ignition performance through the direct ignition cassette. In that way, with the right software, you can run the boost right up to the point of preignition. With a MBC you need to leave some margin so you don't get detonation, or risk blowing the engine. But I'm not saying the stock APC program will do all of that. Just that the potential is there with remapped software. -- -Fred W
