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157 - Direct Injector Timing

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First time tuner here, working on my stock 3.5L Ecoboost Taurus SHO with an inadequate factory high pressure fuel pump. I'm hoping someone can provide some further insight, advice or warnings about adjusting the SOI angles among other things to get the most fuel delivery I can. My main concerns are as follows:

1. In the webinar demonstration, SOI had a dramatic negative effect on torque when the injectors were over-advanced. But clearly in that case the required pulsewidth was much smaller than the available injection window. But what about when you need to use all available timing? Does it generally make sense to advance the SOI to support a higher air load? Or is it possible that doing so could be counterproductive and I may be better off with less load and optimized injector timing?

2. As mentioned, I'm currently pushing my OEM HPFP to the absolute limit. I'm at the point that I'm not even sure whether widening the injection angle will flow more fuel or just drop my rail pressure further while maintaining the same flow. My rail pressure is already hovering around 1500 psi when commanding 2150 psi. What are the consequences of running really low pressure, say 1000-1200 psi? Is there a bottom limit to what's considered a safe rail pressure under high load? My thought process is that as long as I'm not going lean then it should be okay, and the fuel pump actually has higher VE at lower head pressure. But I don't know what I don't know, and figure there must be a good reason why GDI systems are run at 2000 psi as opposed to 1000.

3. Kinda unrelated, but my lambda targets (0.75 peak) are definitely handicapping my airflow potential and contributing to fuel stresses. Being that this is my first time tuning, I'm very gun shy about running the leaner targets that I see "experts" targeting in commercial email tunes. Most run .79-.82 but I've seen some claim as high as .85 with no ill effects. The factory calibration, on the other hand, goes as rich as 0.73. I've watched the AFR course a couple times and I understand the concepts but with no practical experience or guidance I don't have the confidence to make such large deviations from OEM, particularly at significantly higher loads than the engine was originally intended to see. I know it's something that gets asked to death, but any direct input or guidance on this topic would be greatly appreciated. I'm currently seeing cat temps hit 1530 degrees F (830 C) following 3rd gear road pulls.

Thank you,


Hi Shane I’ll try to unpack your questions but my only experience with an ecoboost was with a Life Racing stand alone so I’m not familiar with the OEM calibration strategy.

part 1, are you just using a single injection event or multiple? Generally SOI can be optimised with a 5 gas analyser paying attention to UHC to monitor combustion efficiency and MBT, ideally optimum SOI happens When UHC is lowest and it’s usually around MBT. If you find MBT is at a high level of UHC this will point you in the direction of increasing combustion efficiency usually through optimising squish, swirl, tumble characteristics and increasing rail pressure or injection event frequency.

part 2, as stated above low rail pressure leads to low combustion efficiency. The port and combustion chamber shape is developed with a specific rail pressure range in mind so increasing that should a high priority. I believe Bosch Motorsport do higher flowing pump and there maybe options to change the cam driving it.

point 3, and the required AFR to meet MBT is a function of combustion efficiency and hardware limits. There’s no point hosing fuel in beyond MBT if components can handle it.

looking at this balance of performance document for the FIA is quite interesting because it states the minimum regulated lambda values, the Ford GT is 0.9 lambda - of course this is a motorsport version of the ecoboost v6 with it’s engine components designed to handle the temperature but it gives a good picture of what’s possible. The Ferrari 488 is 1.1 for comparison.


hope this helps steer you in the right direction...

Just to chip in on point 3:

OEM calibrations enrich quite a bit for cooling and component safety (above performance/combustion gains) there are a lot of tables looking at temperatures within the engine and exhaust which might contribute to the engine enrichening for component protection.

In Europe/UK, the next set of regulations won't allow any enrichment and the OEM's have to target lambda 1 at all times; this is causing no end of headaches in the industry as they try to design packages to handle the heat generated from not being able to add fuel to cool at higher load.

What is even more scary, and a little insight into the future is that there is discussions on the next set of regulations making the manufacturers target lambda 2!!

So when thinking about leaning off always take into account the heat being generated as a result; but otherwise as Scott has said and the tuition from HPA MBT is what you are aiming for.

Hope this helps a little.

Thank you for the responses! I am road tuning without a dyno, and a 5-gas is not quite in the budget. I do intend to rent some dyno time at some point, but for now I'm just trying to get everything as optimized as I can without it. I suppose I can glean the optimum injection settings from timed accelerations as well.

Though the similarities between my engine and the GT's probably stop at the deck, I have noticed that my OEM calibration has a lambda efficiency correction table which coincidentally also indicates best torque is at 0.90 lambda. And Ford use fuel enleanment torque cuts that had me nearly reaching stoich early in my tuning, which makes me wonder how much enrichment is really necessary if Ford would intentionally lean the engine out at high loads. I read over and over again that DI engines tend to be capable of running leaner, but this OEM .73 target has had me really scratching my head.

The turbines on these vehicles are incredibly restrictive with EMAPs well over 500 kPa at high RPM. Is such a condition something that generally would require excess fueling beyond the norm? I'd imagine a lot of reversion would occur at certain cam angles, and that might cause heat to build up rather quickly.

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