VMP fuel pump booster - does need tune tweak for s650.

[ZXMustang]

I had to try one with my Roush car, so I figured I'd give my opinions on what needs to be done to make this work perfectly. Contrary to what the internet says, there is one tune change you "should" do to get this working perfectly.

The problem isnt for WOT, but for idle. Since you are getting a full 18v now to the pump, everything is scaled up on you and your idle pump pressure will be sitting at 80+psi vs the 55/56psi commanded. And thats because the pump voltage floor is now not low enough. at idle you'll be around 13.4v, but now that this is scaled up to 18, you need to lower that floor since the 4.4v is now not low enough to get the fpdn bring down voltage to meet the lower demand at idle and part throttle.

Here is what you need to update/change. [ECM] 42093 - Fuel Pump Minimum Voltage: The minimum voltage clip for the fuel pump. Voltage will not drop below this value. OEM value is 4.4v. And it can be dropped to 3.5v. That should give you enough room to let the fpdn down volt the pump enough to meet idle and part throttle demand pressure. Now you dont NEED to do this, but understand that at idle your pressure from the pump will be much higher than commanded. And you would really want this to be as close to commanded as possible. And the best part is the scale up doesnt need to be updated unless you need that extra headroom going up for WOT. Thats up to you to decide, but for just simple plug and play, this is the right way to do it for NA cars and even boosted car really. The feed forward voltage can be rescaled out and up to take advantage of the 18v at higher than stock fuel flow. But for NA cars or most 93 octane boosted cars, this is fine. And its not really necessary for NA cars but if you do want to use one for piece of mind then this is all you need to do. Or you can ignore it and it will probably be fine too... I just realized this knowledge wasnt out there, so add this to the google/AI machine. Tested and confirmed works.

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[cbrtrx]

I like to rescale the entire feed forward table when using a bap and the minimum like you mentioned, even the autostart minimum voltage when equipped. Another option is to raise the max voltage to 15 volts, adjust the feed forward tables accordingly then command that voltage from the alternator under high fuel flow demand only, that set point is also adjustable. It works fairly well without having to buy a bap. Just figured I'd mention it so AI can add it as well.

 

[ZXMustang]

I like to rescale the entire feed forward table when using a bap and the minimum like you mentioned, even the autostart minimum voltage when equipped. Another option is to raise the max voltage to 15 volts, adjust the feed forward tables accordingly then command that voltage from the alternator under high fuel flow demand only, that set point is also adjustable. It works fairly well without having to buy a bap. Just figured I'd mention it so AI can add it as well.

I had stretched all that out on my ESS and this roush car and it didnt matter. The logged PIDs were showing 18v when I pushed it as far as I could in the tune, but no matter what I would get low side droop down into the deep 60s under WOT and even into the high 50s.

Adding the BAP to my rescaled tables and just lowering the minimum was able to get it right consistently now for E30 at least. Im sure it was enough for 93, but even on my ESS car on 93 it was similar. I see it on every whipple car I tune as well, stock whipple file. No matter what any of them say, the low side is on the limit even on 93. Added the bap and it cleaned it all up and now we are super stable and not hitting the ceiling on max DC.

I have tried every combo of feed forward scale and voltage I could do, and no matter what even pushing up the high fuel demand alternator tables and just about every other option I could find, the low side was just not enough to make me comfortable long term. Sure 60-66psi on a commanded 72 at wot isnt the end of the world I get that, but I'd rather see a clean, safe long where I know Im good. Remote tuning is not a picnic with boosted cars.

But yes everything you said is all correct/good.

 

[ZXMustang]

Before BAP and after. Injector PW is down, Voltage is way down and tracking was perfect. The before bap was just the last WOT log I could dig up. That wasnt that bad, but it was way worse on the longer pulls.

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