[radz28]

10/30/31 - UPDATE:

After finally getting some boost weather (lower 60's and 102kPa baro'), in conjunction with our maximum pump E' content (about 75%), this 85mm upper pulley seems to be requiring too much fuel to stay within the limits of this method. I didn't really think I would, as mild as my combination is, but this would appear to be the case. Perhaps the Magnuson 90mm would barely be okay, but it seems this 85mm, just pushes from around 30% PI to closer to 35%. Admittedly - I didn't finalize the 90mm tune on 75% E' in boost weather, but it was pretty dang close.

This method seems to only tolerate about a 25% compensation. There is a limit HPTuners imposes for the multiplier (2.0), and if it were higher, I could "over report" injector flow rate higher, to flow less fuel from the DI to keep the HIGH SIDE from going crazy, but this is not the case. Because I already played with VTT/DD/etc, not much more compensation for TORQUE settings was necessary, so except for the EQ RATIO changes, I didn't change much. I started/continued pulling my PE down, from about .83-.84, and didn't start getting much positive return in HIGH SIDE FUEL PRESSURE until I got to about .95. REFLEX was still showing I was LEAN, and HIGH SIDE PRESSURE was falling to the floor as soon as I rolled into the hit, and IPW immediately went through the roof. Nothing got under reasonable control until after I pulled about 5% FUEL from the E92 MAF CURVE. Temperatures for those hits were in the upper 60's (baro' was still about 102kPa though), but all it took to upset the HPFP/IPWs was pedal'ing the throttle because my bald@$$ ET Streets weren't getting traction and spinning (not ball'd-up like before, but into the tread indicators) like crazy. I had also tried pulling about 15% FUEL from the INJECTOR OFFSET 3 table, trying to get a little more dribble out of the DI, but that wasn't enough, and HIGH SIDE FUEL PRESSURE (LOW SIDE tanked, too) didn't back up to steam by the end of that hit, at red line (LOW SIDE came back up though). It seemed like when I stayed in the THROTTLE, pressure was completely fine, and held at about 20 mPa for all the hits, though.

So - what I'm exploring now is a blend of the usual method and this one. I don't want to stay on the edge (which I feel pretty confident I am, even this last tune), because I don't want to be running out of fuel when it's in the 50's. Although - I can't think of a scenario where I could/would be going WOT, at all, even on fresh/sticky tires, so I'm trying to fight the OCD in making the tune right for that... Still - I admit that's not a likely scenario.



Is there a good reason why I COULDN'T pull HIGH PRESSURE DESIRED - DESIRED FUEL PRESSURE [17071] down, LOWER than 20mPa?... WOT FUELL PRESSURE, STOCK, is right at 20mPa. What I have done is pulled the most HPTuners will allow me to (in this definition), but I'm only getting about 25% of FLOW RATE reduction (1.4456/2.0000 = 0.72, or about a 28% reduction). If I go lower in pressure, the OEM factor/multiplier for 18mPa would give me about a 32% decrease in FLOW RATE (1.3665/2.0000 = 0.68, or about 32% reduction). SO - is there a reason why I can't/shouldn't command DESIRED FUEL PRESSURE [17071] to like 18mPa, or something like that? Am I missing something? I know this is not the conventional method (or it would seem that way, as I have only seen it in ONE place), and could this be one of the reasons why? There's just such a low limit that it doesn't work, even on simple builds like mine? Is it because no one does this kind of combination without a camshaft, which makes up for a lot of the HIGH SIDE deficiencies that I have, because I'm on a stock cam?

So yeah - I'm a little defeated. I might be fine, if I change back to the 90mm upper, but what fun is that?... I also recognize that I can't hardly hook from a roll now, so it's not like I NEED the more power necessarily. I'm just looking to see if anyone has insight, because I know there's lots I can't fathom at my experience level. I have a couple other feelers out there, and if I get any feedback, I'll report back. I thought I'd just add this here, because I was hoping I wouldn't find a limitation at my level and combination. It seems I have, though.