Tunes Gearhead or ortiz???
Hey guys I’m getting a tuner and right now I’m leaning very heavily on the Gearhead tune and performance package with the plugs map sensor thermostat you guys know what I’m talking about, but I’d like some input from the community I just recently found Ortiz so I’m not very educated on them is...
shoforum.com
I highlighted the key fact of the above sentence. This guy seriously doesn't even know how to read a log and yet he's out there trying to play tuner expert. In his video he pointed out a fuel pressure dip to 1400 psi [9.92 MPa]. But then a guy mistakenly commented that it was the lpfp and he agreed, saying that "the lpfp shouldn't get that low WOT." Fuel Rear Pressure in Livelink is rail pressure. Has this clown ever even opened his own datalog before??? I doubt it.
Really??? lift pump pressure shouldn't be so low as 9.92 MPa?! Wow, that's news to me! Didn't know there was such a capable in-tank pump on the market! What kind of fuel line do I need to install to handle that kind of pressure?? LMAO This just goes to show that he has zero actual interest or understanding of tuning but is just clambering for anything he can sensationalize for clickbait without the slightest idea of what it means.
Now I'm going to waste a shit ton of time trying to educate him. Maybe if I can open his eyes to just how ignorant he really is, it might encourage him to do some self reflection and stop being such an insufferable dou.chenozzle at the expense of peoples' livelihoods. If not, I may at least be able to help others see what an unreliable and irrelevant source of information he is and stop watching him.
Fuel pressure, by itself, means absolutely nothing in comparing tunes. It's really not that effective indicator of a problem on its own, either. If Ortiz runs a flat 0.81 lambda (which he does) and experiences a slight FRP drop, but GH runs more lean with a tapered target of .85 to .82 lambda (which he does) and there is no decline in rail pressure, which one is safer assuming identical airflow? ORTIZ. The richer tune wins. Ortiz runs 3.6% richer for cooler combustion charge temperatures, which puts more load on the HPFP, hence the higher potential for rail pressure dips. But mechanically nothing changes. The capacity of you HPFP is what it is, and pumping greater fuel via lower AFR's does not create a more dangerous situation IN ANY WAY WHATSOEVER.
Gearhead lambda targets:
Ortiz lambda target:
Both of the above logs are from the same owner/vehicle and same mods. Does this imply that Gearhead is tuning around a problem? I'm sure some will think that, but that is not true either. The reality is that the amount of fuel required to maintain cylinder temperatures is dependent on the amount of heat generated. Lower RPM = less horsepower = less heat generated -> less charge cooling necessary.
"But Stripsho, if my fuel rail pressure dips below setpoint, won't my engine lean out and blow up?!" Well, no, very unlikely.
-First of all, the PCM has built-in protection and will automatically close the throttle if the injector duty cycle approaches maximum.
-Second, rail pressure loss is most common to occur at low to mid RPMs due to HPFP capacity being proportional to engine speed. See my comments in the previous paragraph regarding RPM and effective cooling requirements.
-Third, and corollary to the previous point, max injector pulsewidth (window of injection) is inversely proportional to engine speed. At lower RPM there is more time available to inject fuel, so you do not need as much pressure to meet fuel demands. Look at this log below, 5th chart. You can see me plummet all the way to 900 psi rail pressure yet I'm still only using 82% injector duty cycle at that point. Shortly thereafter, I hit max pulsewidth and stay near max pulsewidth even though rail pressure is increasing AND air load is decreasing. By 5600 RPM I've nearly doubled my rail pressure, load has dropped 15%, but I'm still 95% inj. duty cycle. It's due to the injection window shrinking as well as my progressively lower lambda targets.
Oh btw this is from expirimental testing specifically seeking out these limits. I'm swinging for 20 psi and .78 lambda on a stock fuel system. Spare me any criticisms of what you may see.
Now let's dive into some meat and potatoes about the fuel system. Below are some specs and volumetric efficiency table of a stock HPFP.
Source: HPTuners Tune Repository, 2013 Taurus SHO stock calibration
WARNING: MATH INCOMING!
The HPFP has a displacement of 0.0171 cubic inches, or 0.0683 cubic inches per cam revolution. Using the provided fuel density 46.82 lb/ft^3, we arrive at a theoretical pump capacity of (0.0683 cu.in/cam rev) * (1 cu.ft/1728 cu.in) * (1 cam rev/2 engine rev) * (46.82 lb/cu.ft) = 0.0009259 lb fuel per engine revolution at 100% volumetric efficiency. V.E. of the pump is inversely proportional to rail pressure, and also varies with RPM as the table and 3d chart illustrate.
Let's use this data to expound on various tuners' lambda target decisions and how this impacts rail pressure. As an illustrative example, let's take an engine operating at 4000 rpm and 1.90 Load, running E10 pump gas with a stoichiometric AFR of 14.1:1. A 3.5L engine displaces 0.00157 lb of standard air per cylinder, per intake stroke. This represents 1.00 Load. So let's multiply this out: (.00157 lb per cylinder load) * (6 cylinders) * (4000 RPM / 2 RPM per intake stroke) * 1.90 Load = 35.80 lb/min mass air flow.
Consider first the GH tune running 0.84 lambda at 4000 rpm. That's 14.1 Stoich * .84 = 11.844 AFR. The required fuel mass flow rate is: (35.80 lb/min airmass) / (11.844 AFR) = 3.02 lb/min fuel flow requirement. Now, we can actually look at the pump data and figure out what rail pressure it is able to sustain at this flow. We need (3.02 lb/min req) / (3.70 lb/min [100% VE]) = .816 or 82% V.E. At 4000 RPM this interpolates to the 2176 psi row of our pump's VE table.
Now let's do the same thing for an Ortiz tune. 0.81 lambda at 4000 rpm = 11.421 AFR. The required fuel mass flow rate is: (35.80 lb/min airmass) / (11.421 AFR) = 3.13 lb/min fuel flow requirement. 3.13/3.70 = .846 or 85% minimum pump VE to sustain flow. This interpolates to a rail pressure capability of 1631 psi.
There you have it. 545 psi difference in rail pressure just by having a 3.6% richer (and therefore safer) fuel target. Not because of running too much boost or any other "mistake". Additionally, the richer lambda setpoint would trigger Insufficient Fuel Flow mode faster in the event of a problem. It is completely illogical and bass ackwards to say an Ortiz tune is dangerous or flawed because of a dip in rail pressure. IT MEANS NOTHING.
Now, since the log in question within his video is an e30 log, I could dive into all the factors with the latent cooling properties of ethanol and the over-the-top margin of safety inherent to the physics of it. But I'm afraid this is where the free lesson ends. Hopefully this has been sufficient to open the eyes of some of you to the intricacies and mechanics of tuning a car and encourages you to not be influenced by irreverent and incompetent attenion wh.ores.
. Why did it stutter then take about 4 seconds to recover? If it was running fine. 
