I've been wanting to give some information to go along with Chuck's tests for awhile. I've finally got around to doing some testing with a Power FC, and fortunately my results were similar. I started by doing an All Data Init. I'll have to do a comparison to see which map this PFC has (it appears to be the more conservative map based on the timing).

I found similar problems as Chuck.

1) Fuel was a little lean for my liking at WOT (appx 13psi, row 17) up until appx 6500 RPM. Close to redline, the a:f would drop significantly, it appeared to even be hitting the 10's. I added 5% with the PIM RPM setting up to about 6000 RPM, then I only added about 2.3%, and at 7000 RPM I added 0%. This brought my a:f down into the 11.X:1 range (before, it was mid/low 12:1 range.

2) Low RPMs were lean just about everywhere. I didn't make changes for this because I don't plan on using the PFC for long and I figured I'd just stay out of the gas down there. Pretty much all the way up to 2500 or 3000 RPM it runs very lean. I don't like this because my car can easily boost in this RPM range and I think this causes damage to a lot of unsuspecting owners (several of us have got our cars to knock like this, even stock cars) I have the boost area at < 3000 RPMs richened a bit in my normal setup.

3) The car felt particularly slow so I upped the timing (in row 17 and 18) to 15 degrees (the initial values in these cells were in the 9-11 range) from about 5000 RPM up the RPMS until the base map would exceed 15 (near redline). I did some minor smoothing of the graph. I didn't fear running this timing because my PMS logs show about 17 degrees up to over 20 degrees, this is with 4-5 degrees retard compared to stock. My engine is stock and not ported. I just changed this because I didn't feel I needed to run that much retard, I have no plans to tune the timing or measure the difference or anything.

I think the most important thing to note here is that I also found the base maps to be a bit on the lean side too.

My relevant engine stuff:
CWC intake
M2 large IC
DP/MP/Greddy SP catback
Crane HI-6
fuel system set to stock pressure for these tests
stock engine
sequential turbos
About 13psi boost for these tests

Wade

 

I'd like to chime in and confirm this as well. With a nearly identical setup as Wade's, and at 0.90 boost, I was seeing low 12's A/F on the dyno. This was with PIM at 100% across the board running Tim Benton's maps. Tim's maps are essentially BaseMod with a little more fuel in the high boost/rpm range. Funny thing is, Tim sees very rich conditions with his maps (O2 > 1.0). Weird.

Wade, how is the condition of your fuel filter? I may be richer when I swap it (don't know how old it is).

Is your goal to have your A/F "curve" infact be a straight line, like a carbureted automobile? For instance, 12.1 from 1000 rpm all the way to redline. Can someone tell us if this is even desireable?

Thanks for the info.

-Scott

 

I suspect Tim's O2 readings aren't meaningful, not only are they just from a standard o2 sensor (which I have never found to be accurate) but I thought an o2 sensor's max output was 1 volt. This makes me think his readings are totally unreliable. Though Tim's a:f might be okay depending on his mods, I don't remember them offhand.

My fuel filter is fine, I clean it every time I have the upper intake manifold off the car, which is typically 2-3 times a year. It is a K&N reusable billet AL filter. There is never much in it. I don't think this is an issue anyway because it would be indicated on my fuel pressure gauge if clogging was a problem (fuel pressure dropping when it shouldn't).

I'm sure everyone has their own way they like to tune their car. The stock ECU and the PFC base maps go from pretty lean below 3000 (13-14:1 range), to pretty rich in the mid range, to really rich near redline (10:1 stock ECU). I prefer lowish 11:1 range at full boost from about 3k up to redline. Also, I don't like seeing 14:1 when my car is making 15psi in a high gear and low RPM on the highway (I don't like 14:1 while at boost no matter what the RPM!) So on my standard PMS setup I richen up the low end boost ranges to get a:f in the 12's. A lot of people don't do this, but since a stock car can be made to knock at low RPM, and I've heard mine knock at low RPM, I choose to add some fuel (compared to stock ECU or Power FC) in an attempt to reduce this problem. If I make it go into the 11's down there, the car tends to cough and puff smoke. I also try to avoid lugging the engine, I suspect more rotaries are damaged at < 3k rpm than we usually think.

Anyway, this is generally how I set up my car. The only thing I'm really curious about is how much of a power difference there is between 12:1, 11:1, and 10:1. One of these days I might test it and find out, or maybe Chuck will do it.

Wade