Bad boost a pump?

[kenand1988]

Purchased a used vortech boost a pump about a year ago. Used it with the oem fuel pump and a walbro 525. At idle the low side pressure would be around 65 which is what the ecu commanded. Then I switched to a dw400 and my low side pressure went to 80psi constantly unless I'm giving it a lot of gas. It's been like this for a couple months. Just on a hunch I removed the bap and lo and behold the psi dropped to 65. Now to me this would seek like the bap is not doing its job. It shouldn't be doing anything while the car is just idling. From my understanding it should only be upping voltage past 50% throttle. So idk do you guys think the bap is dead?

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[Andy13186]

... your logic makes no sense. Vortech BAP also are constant BAP I believe. You removed it and the pressure dropped then you suspected its not doing anything? That makes no sense to me.

Why did you remove it though, are you having issues?

 

[cbrtrx]

Purchased a used vortech boost a pump about a year ago. Used it with the oem fuel pump and a walbro 525. At idle the low side pressure would be around 65 which is what the ecu commanded. Then I switched to a dw400 and my low side pressure went to 80psi constantly unless I'm giving it a lot of gas. It's been like this for a couple months. Just on a hunch I removed the bap and lo and behold the psi dropped to 65. Now to me this would seek like the bap is not doing its job. It shouldn't be doing anything while the car is just idling. From my understanding it should only be upping voltage past 50% throttle. So idk do you guys think the bap is dead?

Like mentioned that would be normal, that bap takes what voltage goes in and outputs it to 18.5 volts.

 

[engineermike]

The BAP increases the supply voltage TO the fuel pump driver module (FPDM) to 18 volts. The FPDM sends a pulsewidth modulated (PWM) voltage to the fuel pump ranging from 13 to 100% duty cycle to achieve commanded fuel pressure, and uses a PID control loop to hold it. Stock it would average 1.5 to 12 volts, but with the BAP it’s more like 2.3 to 18 volts. At idle, 2.3v is too much to lower the pressure down to commanded, so it rides on the bypass valve at 80 psi. It’s still slowing the fuel pump down, but not enough to drop the pressure.

I spent a lot of time trying to fix this problem in the tune. It’s not intuitive. There’s a voltage vs pressure vs flow table that didn’t improve the situation. There’s also a min and max duty cycle that didn’t help me any. Ultimately, I found that altering the voltage slope and offset was the key to retaining functional accurate control over the fuel pressure.

Most tuners will say it’s fine at 80 psi though, and not mess with the slope and offset. On a gen3, they’re not completely wrong. Then gen3 measures the fuel pressure on both systems real-time and adjusts the pulsewidth as-needed to get the flow they desire, so as long as the injector pressure vs flow data is correct in the cal, it won’t go rich when fuel pressure is higher than desired.

 

[kenand1988]

Then why would it not be the same with the walbro vs the dw400

The 525 showed 65 psi with the bap

 

[engineermike]

Then why would it not be the same with the walbro vs the dw400

The 525 showed 65 psi with the bap

One possibility is that at the 2.3 volts, the walbro is flowing less than the dw.

 

[kenand1988]

... your logic makes no sense. Vortech BAP also are constant BAP I believe. You removed it and the pressure dropped then you suspected its not doing anything? That makes no sense to me.

Why did you remove it though, are you having issues?

Its not that I didn't think it wasn't doing anything. I wasn't aware they are constant voltage like I was saying in my post I thought the bap only over volts paste 50% throttle. Since I had the bap on with a different fuel pump, the w525 and it was reading 65 psi at idle then when I put the dw400 in and it went to 80 psi I thought either my pressure regulator could be bad or the bap isn't working correctly. I thought it could be delivering a constant voltage but again I did not know that's how they work.

 

[engineermike]

Your BAP doesn’t have a throttle position input does it? How would it even know when you’re past 50% throttle?

 

[Cory S]

The BAP is just a regulator/buffer DC/DC converter. They either work as designed, or they don’t work at all (shady installation shorting etc).

 

[TEXAS HEAT]

Its not that I didn't think it wasn't doing anything. I wasn't aware they are constant voltage like I was saying in my post I thought the bap only over volts paste 50% throttle. Since I had the bap on with a different fuel pump, the w525 and it was reading 65 psi at idle then when I put the dw400 in and it went to 80 psi I thought either my pressure regulator could be bad or the bap isn't working correctly. I thought it could be delivering a constant voltage but again I did not know that's how they work.

I have a VMP BAP that supplies a constant 18v. My lift pump pressures on the stock pump at idle are also 80psi with the BAP plugged in versus the commanded 65psi.

With it BAP unplugged it see's the commanded 65psi at idle.

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