floatyghosthat

iTrader: (5)

I just want to apologize in advance. I've been into tuning cars for years, but I've never really gotten too much into fuel delivery.

This is a stupid question that has bothered me for a while, but I wouldn't dare ask any of my friends, and it's too basic to be in any of my tuning books. I'm hoping the relative anonymity of the internet will save me some embarassment.

Here we go...

Fuel pumps. I'd like to give my FD a bit more flow and drop in a Walbro. Now, if I merely drop in a stronger, faster flowing fuel pump, will it increase the amount of fuel delivered to the engine? Basic math dictates that an injector running the same duty cycle will flow more fuel if it's at a higher pressure (I.E. flow rate). So, without adjusting the injector duty or cycle, I would see more flow, correct?

What about the FPR? I realize that it will limit the flow coming from the fuel pump, but will it keep it at a constant pressure, regardless of which pump I have? Is the stock FD FPR constant or is it variable in relation to the rate of flow?

Basically, the reason that I'm asking is that I have a Power FC and am just in the beginning stages of learning to tune. I'd LIKE to drop in a better, more powerful pump, BUT I'd like to keep the exact same flow and tune I have now. Will throwing a better pump mess with that, or will the FPR restrict it to stock flow rates? Is there anything built into the PowerFC or stock ecu to compensate for a better flowing pump?

I feel like such an idiot for asking this, but I need to know.

Any help would be appreciated....

Mahjik

iTrader: (1)

The FD stock FPR is a 1:1. What that means is that the fuel pressure rises equally with the boost. Having said that, the FPR should keep the fuel pressure the same with a higher flowing fuel pump. However, it is possible to overwork the FPR with too strong of a fuel pump thus increasing the amount of fuel being delivered. This sounds like a like a good thing for a rotary to keep it safe, but it's actually a bad thing since you cannot control it.

Having said that, the Walbro should be fine with the OEM FPR. The plus side of using a better flowing fuel pump even though the injectors should still only see the same amount of fuel is not having the fuel pressure drop off as the boost gets higher (and the fuel pump gets older). People have tested older OEM fuel pumps only to see them dropping off pressure at higher boost levels.

floatyghosthat

iTrader: (5)

Thanks!


So, what exactly keeps the FPR at a 1:1? I haven't had a chance ot take a good look at mine. Is it a vacuum system, or electrical? Either way, should the Power FC have any effect on it?

Mahjik

iTrader: (1)

It's not ECU controlled.