5.4L tuning / mod questions

[XP900]

VMP removed a lot of their older information about their GEN2R superchargers from their web site!
Not sure why and I should have printed it all out.

What is the safe boost limit with 93 octane using at near sea level? I thought it was 18lbs on a stock motor?

Let's say I have a 2.5" pulley (using their adjustable idler pulley and no slippage), if I was at 17 and installed the 2.4 to get to 18 would changing that pulley really require a retune? If I recall a .1" pulley change was worth 1 lb of boost on the Gen2r.

Next question: Is there any reason for a retune check simply changing out a set of injectors with the same exact manufacturers model?

If you changed injectors - like a 1000cc to the Ford 56 lbs, I suspect it would require a retune but would it be driveable without getting into boost?

 

[Willie]

First, when you increase boost, you may or may not need a retune. The basics: This is a screenshot of the stock spark table for a 2008 GT500. Ford calls it "Borderline Knock".

The y-axis is Load. It's max is 1.60. This equates to approx 8.5 psig. So let's say you make 10 psig. What does the PCM do when you are "off the chart"? It carries the last known timing value. In this example at 6200 rpms, 18 degrees of advance will stay constant for any load value above 1.60. Essentially, going off the chart does not cause the PCM to be confused, which is a good thing. Now let's say you're making substantially more boost, i.e. 15 psig. Well, this could be an issue if your tuner needs to bring down the timing from 18 deg.

What I do is increase the y-axis to maybe 2.50 which equates to 20 psig. Doing this will mean you do not need a retune as long as you keep it at 20 psig or less. So do you need a retune? That depends on what your maximum load is in this table. Hope this makes sense.

Injectors. First, flow values. All else being equal, if you install larger injectors, the PCM will not know there's been a change, and it will continue to command the same injector duty cycle. But with larger injectors, you'll be flowing way more fuel. So just this one fact does require a tune change. Second, different injectors have different values for breakpoint, low / high slopes, pressure drops, minimum pulse width, blah, blah, blah. So when you change injectors, you really do need a retune.

And to answer your question, if you replace with exactly the same injector, no retune required. But if you replace with the same manufacturer for a different flow rate, YES you do.

 

[1Kona_Venom]

Running a 2.4 will require more than 93 octane. I could only run a 2.5 safely on 93.

 

[XP900]

Thanks .....now that my clutch is slipping I won't be able to verify my current boost until the spring...I may order a 2.4 just to have on hand but I suspect the 2.5 would be the limit too on my Gen2R 5.4L.

 

[einehund]

I am at 20 psi on the stock block with the gen2r