Upgraded fuel pump

[SuperSonic]

Hey guys, in my last thread I tried to determine if I had an aftermarket fuel pump. Towards the end I bought the injectors and just said throw them in and tune it. If it still runs out it's obvious I need a pump and worst case buy a pump. Someone said it will need a new tune because the pump pumps more pressure. I'm on vacation now and was going to try to get it tuned with these injectors. My question is why would I need a new tune. I hear a bunch of people say when their oem stops just throw a walbro in. I'm not switching the fpr. It's still the oem fpr, so I guess I don't see why changing fuel pumps matters. Isn't that the point of the fuel pressure regulator to "regulate" how much gets by? I started thinking of a few prime ppls that dropped in an walbro on stock cars cause theirs took a dump. No need to buy an ecu just to run a walbro. Someone correct me if I'm wrong. I am under the assumption the fpr will regulate this anyways. Thanks

 

[jones83]

You do not need to get a new tune if you upgrade the pump. I have never had to retune any of my cars due to changing out the pump. Ever. Your fuel pressure regulator will control your fuel. An aftermarket fpr is not a bad upgrade to have however. I personally like to change both out at the same time.

 

[NSX-Files]

I have first hand experience on this on both of my NSXs. Yes the FPR is supposed to regulate the fuel pressure at specified levels. Changing from the stock fuel pump to a Walbro 255 HP results in the FPR NOT BEING CAPABLE of bypassing enough fuel to maintain fuel pressure within factory specs. Whereas my car with the stock pump and stock FPR would have 43 psi with a new filter, once I put in the Walbro, the stock FPR could no longer cope with the added pressure, so the lowest the pressure would be was something like 50 psi. If you don't change out the FPR for an adjustable one, then having the fuel pressure 7 psi higher than what the ECU thinks the injectors are seeing WILL result in too rich a mixture when the car is in open loop mode. Now in closed loop, the ECU would trim fuel away based on what the O2 sensors are telling it, but that doesn't happen under wide open throttle or when the ECU reverts to a fixed fueling map. As a result I had to install an AEM adjustable FPR to tune the pressure back down to stock levels. If you do this, then yes it is correct you may not need to retune your car.

 

[angus]

I have first hand experience on this on both of my NSXs. Yes the FPR is supposed to regulate the fuel pressure at specified levels. Changing from the stock fuel pump to a Walbro 255 HP results in the FPR NOT BEING CAPABLE of bypassing enough fuel to maintain fuel pressure within factory specs. Whereas my car with the stock pump and stock FPR would have 43 psi with a new filter, once I put in the Walbro, the stock FPR could no longer cope with the added pressure, so the lowest the pressure would be was something like 50 psi. If you don't change out the FPR for an adjustable one, then having the fuel pressure 7 psi higher than what the ECU thinks the injectors are seeing WILL result in too rich a mixture when the car is in open loop mode. Now in closed loop, the ECU would trim fuel away based on what the O2 sensors are telling it, but that doesn't happen under wide open throttle or when the ECU reverts to a fixed fueling map. As a result I had to install an AEM adjustable FPR to tune the pressure back down to stock levels. If you do this, then yes it is correct you may not need to retune your car.

I said this to you before.