RonSSNova

iTrader: (3)

I noted in my logs last year that the fuel pressure quit tracking with boost past 5000 rpm when I turned the boost to 19 psi.
AFR was fine, but it's a sign.....

So I'm adding a second pump on a pressure switch.

The question I have is do you see a spike in FP when the second pump comes on?

You guys turn it in early? Or just ahead of where you start seeing the fuel pressure fall?

I prob need bigger injectors as well, but I'm doing this first.

ID1000's on E85 btw.

I'll just add that I've also added a 150 amp alternator, 4ga charge wire to the rear mounted batt and 75A relays with 8ga wire to the pumps. My logs also showed poor system voltage.

Ron

truckdoug

iTrader: (25)

wow thats some serious wire.

can I ask what pumps and fuel line diameter you're using?

RonSSNova

iTrader: (3)

Big pump is fed with -10
The small pump will be fed with -8

Filter is a paper spin on 10 micron diesel type fed with now a -10 and a -8 from the fuel cell.

Feed and return are -8

Holley pumps

Forcefed86

iTrader: (4)

I saw a spike when I ran a single 255 and had another come on in boost. Had mine set to come on at 1 psi. It did very little to my tune. Was using E85 so its pretty forgiving. I didn't even try/need to tune around the activation point.

Are you seeing a spike in pressure? I'm sure the closed loop fuel control would be able to adjust for it pretty easily?

oscs

iTrader: (19)

I had two 4303's one would kick on at 15lbs. I didn't see any spikes but I had the big boy aeromotive regulator.

RonSSNova

iTrader: (3)

I'm on the factory ECU, so no closed loop fuel control.
I just finished plumbing it, so it is untested at this point.

The pressure switch I bought has adjustment from 12-24 psi, I forgot about that when I wrote my post. So I guess the point is moot and I'll just have to find out!

I'm running the Holley regulator as well.

Ron

oscs

iTrader: (19)

I would think a properly sized regulator to pump selection would keep the fuel pressure in line at all times.

Beanslsxnova

iTrader: (1)

On my stock truck rails and regulator I have seen a spike from 54 to 90psi when my second 044 comes on. It stays there until I let off then returns to 54. This is on pump gas/meth

RonSSNova

iTrader: (3)

I tuned a friends setup with two Bosch 044's on the factory corvette Reg setup and it was the same. It couldn't control the pressure of two pumps.

Sleeperls

I'm going to run.my single aem until I get used to it. Then run a double with 10an feed 8 return. Should be fine for my power goals

ScottyBG

I run 2 340 lph pumps with the second one on a Hobbs switch. I have 2 switches both a 7psi
and a 2psi. I bought them both just for tuning purposes, so I could turn the 2nd pump on at the correct point. I run out of pump about the 7psi point for the first pump by calculation but in practice I hit 7psi low enough in RPM there is no problem. I do get a slight increase in pressure for about 0.2 seconds. Bumps up about 10 psi, then bleeds off nearly instantly if your watching the needle. Really just a quick blip. The fuel pressure regulator is a mechanical device and it does have to react. It is however barely noticeable on the data log. It is so small I wouldn't worry about it. The AFR drops rich by about 0.1-0.2 for a small fraction of a second. The quality of the regulator I'm told is a factor, some regulators are "faster" than others. I just have an inexpensive Racetronix one and it works great.

RonSSNova

iTrader: (3)

Thanks for the info Scotty. I think I'll be fine turning on the second at 15psi when the volume needed is pretty high.
I bet in fact that improving the charging system and wiring is going to help as well.

Eventually though, I'll need bigger injectors......

oscs

iTrader: (19)

That's what I use to do. Never had issues.

Forcefed86

iTrader: (4)

If you're trying to push small injectors it would probably be better to have a regulator that's overrun by the second pump. That way you can cruise around with standard pressure and when the second pump comes on you'll basically have larger injectors. Assuming you have enough pump, going from 50's to 90's+ pressure wise in boost would be a good thing. Esp. for those using 80lb injectors. Trigger the second pump early and then your entire positive KPA map would be pretty linear.

80lb injectors would effectively be 115lb injectors at 90psi.