Some of the guys over on the EFILive forum are giving me pointers on what appears to be the best way to set up a completely Speed Density tune on my car, since my plan of using the MAF got shot down. One of the guys seems quite familiar with working with boosted engines and said that my fueling was a bit too rich right before going into boost, so it would likely bog down under the right conditions. The only time I experienced anything like that was in high gear at low rpms but I just wrote that off as being the nature of the beast. But it might very well explain the soft throttle response I've noticed at low rpms as well.
Apparently I was also looking at the Power Enrichment tables incorrectly as well. Back in the old days, there used to be a device on carburetors called the accelerator pump. This was used to provide a squirt of raw gasoline into the carburetor upon pressure of the gas pedal being applied. This helped to keep the opening carburetor plate from causing a lean spike which could cause a flat response in acceleration. I assumed that the Power Enrichment tables were the electronic equivalent of this manual accelerator pump of old. Apparently this is not the case. It is simply a method of applying a richer AFR mixture when commanded depending on throttle position. Kind of sounds like the same thing to me, but apparently it is different enough to have thrown me off with what I was trying to do.
What was suggested to me was to simply use the Commanded Fuel vs RPM (Normal) table {B3647} for naturally aspirated fueling, commanding stoich from 20 to 80 kPa, and then from 85 to 100 kPa gradually make the fueling slightly richer (.96 to .86 Lambda). When boost begins to kick in at 105 kPa set up Power Enrichment to enable at 110 kPa using the PE MAP threshold switch {B3613}, and then control PE fueling via the table for PE Modifier Based on RPM {B3618}.
So that's what I have in the new tune that I'm waiting to try out when weather permits.
He also said that the way my timing is being implemented is not optimal neither. It is marginally OK, but using strictly the high octane table doesn't fully compensate for the needs when boost kicks in. Apparently there is also a separate timing table that is best utilized on a boosted engine instead of trying to do this solely with the standard timing tables. So when we get the fueling ironed out, he will help me get the timing optimized.
But, of course, the weather is getting in the way. The drought seems to be over with now, and we've been getting rain every day, but in patches. I'm watching the radar constantly, and even if I'm not getting raid directly overhead, there will be rain all around me. Which, of course, means I can't take the car out. I need to run the rpms up to do adequate data logging all across the rpm spectrum, but I certainly don't want to be putting a lot of power to the rear wheels on wet roads. Heck, I just now walked out to the garage to put the latest tune in, and the sun was shining and the sky looked pretty clear, even though the radar showed rain to the south. I loaded in the tune, and then came out of the garage to feel it starting to rain.
Oh well.... It's that time of year, I guess.
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