When should I have my second fuel pump kick on?

[Pronto]

Confused, are you running E85 for fuel and then injecting alky as well? My second pump comes on at about 15 psi. Good luck pushing that combo on a stock crank.

 

[ttypewhite]

True. Adjusting around the VE map is one way to accmplish it on XFI.
I would rather change one setting and get it close than chase a bunch of VE cells.

If he had a chip car as 90% of the cars . . . That wouldn't be as simple.

With that thought process of VE table adjustments . . . . would it not make sense to turn it on at 8psi, in case he decides to go e85?

Also . . .
If the XFI FPC is turned on . . . It shouldn't matter much correct?

I have much respect for your accomplishmenrs, and am certainty NO EXPERT. Always learning . . . . .

I appreciate your openness to dialog on this, as my post doesn't carry a tone of voice, so you never know how one will interpretate it. With that being said, I honestly don't see the benefit in bringing the second pump in sooner. Not much is happening at 15psi to worry about reaching the limits of the fuel system before marrying another pump to the equation. The integration of a 2nd pump is not difficult to tune. It's very simple. I don't think the OP is using this for E85 tho....

 

[The Granny]

Btw:
Since you are on XFI . . .
You should look into using the FP correction (FPC) feature. Turn the pump on early, log, study the data and adjust from there.
The FPC is an exceptional feature and works extremely well.

I am sure everyone (well, most?) will agree:
Never use alky as a fuel supply as a crutch. On a 13 aecond car it may work. On a 10 second car, it's a dangerous strategy.

I understand that without looking over my data and testing the car, I won't know exactly when to have it come on. Just looking to get a nice starting point

So with the FPC feature, it'll maintain the correct fuel pressure based on the static fuel pressure then however much boost I have, correct? I've got fuel/oil transducers sitting in their boxes still, once I get my car back from chassis shop I'll be putting them on for sure. I don't plan on having the alky injection as a fuel supply, I'm just trying to factor it into the equation.

If my understandings of the feature are right then I'll still have it come in a little bit earlier than needed, say 14 pounds of boost, and have the fuel pressure correction feature take over that way changes to the VE table are hopefully minimal.

Confused, are you running E85 for fuel and then injecting alky as well? My second pump comes on at about 15 psi. Good luck pushing that combo on a stock crank.

It'll be a 93/meth combo for now. As long as my fuel demands are met for my goals as of now, I don't plan on switching to e85. In the future once I pull this motor out to build a more stout one, I'll more than likely switch to e85 for racing or maybe even 100% meth. Who knows, just an idea.

I appreciate your openness to dialog on this, as my post doesn't carry a tone of voice, so you never know how one will interpretate it. With that being said, I honestly don't see the benefit in bringing the second pump in sooner. Not much is happening at 15psi to worry about reaching the limits of the fuel system before marrying another pump to the equation. The integration of a 2nd pump is not difficult to tune. It's very simple. I don't think the OP is using this for E85 tho....

I think we all mean well on here, we're all learning more about these cars and the different types of set ups

Given everything that's been said, I believe a good starting point for me would be 13-14 psi. I should be picking up my car tonight from a chassis shop that's nearby, then tomorrow morning I'm heading out of town for a week. But I will be back with results

 

[Jerryl]

The fuel pump duty cycle is typically not regulated and it wither on or off. The injected pressure is controlled by the fpr.
When the fp changes, the xfi regulates the injector dc and shows it as a fp correction that can be logged.

The self learning feature should be able to make the VE adjustments to the table to smooth the afr target transition.

If you decide to run e85 someday, you probably want to have the pump come in sooner for obvious reasons.

No harm intended in my response.
I am learning while the car is down . . . Lol