Some interesting observations.

[Banshee]

Ever since I installed the original MP62 Coldside san "e-cool," I've been getting a pound or 2 more boost than what the equivalent FFS were achieving. Although I haven't tested it, I'm pretty sure my Cat is not clogged as other "early adopters" were getting the same boost level with similar 2001+ setup. That leaves me to conclude that the vvt and ecm was retarding too much timing, or that the intake charge was too hot. Then about a month ago, I started having a misfire code on the 4th cyclinder. Couldn't figure it out for the longest time, but it finally turned out to be a leaky WI check valve. It was letting in water/alcohol at idle and cruise. Now that I got everything all fix, I noticed that my boost is back down to the 7.5-8# range with the 100mm pulley. About a 1-1 1/2# less than before.

Where am I going with all this rambling? Well, I came to a few conclusions.

1) At base trim without anything to cool the intake charge, the intake temp is just too hot, causing "more boost, less flow" and also pinging with just a 95mm pulley.

2) Alcohol/water injection definetly work, and work quite well. (Before when I was just injecting water, I would control my ping, but did not get the reduction in boost as I did when I added alcohol to the mix)

3) I wonder if the WI port is achieving equal distribution to all 4 cyclinders. As noted, I was only getting the misfire in #4 cyclinder when water was leaking in under vacumm. That tells me that the WI port flow will favor that cyclinder. Does this changes under boost? I don't know. But shouldn't the flow pattern be the same under vaccumm or boost? The engine is still sucking in air right?

[Tom @ Fast Forward]

Look at it this way, if you were consuming all the air coming in, no matter how fast the blower was turning, you would have more HP but no boost. Boost occurs when the engine can't take all the air so there is excess and pressure builds up. If you can make the engine flow well, you will have "More flow, less boost". Under boost you get a LOT of turbulence to really mix up the WI or 5th injector fuel. In vacuum, the air flows right through the IM and into the engine but fuel/water distribution is not a matter of concern because the water is turned off and the 5th injector is turned off. When I had issues with the 05, I had cylinder 1 misfire. Not sure the Miata does a good job at guessing which one. Also, a lot of people will tell you that #4 cylinder runs hotter due to poor water flow design (re-route) so it would be the one to show ping first even though the fuel/WI is well distributed under boost.

What occurs if it detects ping is not only to lower timing, which will increase boost because the efficiency has dropped but the 01-05 also pulls back on the valve overlap (VVT) and that exacerbates the problem. That's why getting it all correct is important but I think even distribution is the least of the problem. The 5th injector, for example, only adds a small percentage of the total fuel. It is there mainly to cool the air. If it all went to one cylinder, the other three would still be very close to 12:1.

BTW, personally, I would much rather have 10:1 than 12.5-13:1 under high boost. Anyone who thinks there is ANY oil left on the cylinder walls above the rings before OR after ignition is out of their mind. Besides, if your engine is running properly, there is never any oil above the rings anyhow. If there was, you would have bad rings and be consuming oil. All 10:1 MIGHT do is foul plugs if they are too cold.

Best way to confirm the exhaust is to run on a dyno with it connected and with it off and note the difference.