So that everyone is clear on this:

When hardwired to deliver its full rated capacity, neither the OE feed line nor the OE return line is large enough to support a Walbro 267 (E85) pump.

There is no if, but, or maybe in this sentence. It is a fact as certain as death and taxes. Drilling the return siphon should be done when the return line is upgraded, but it will not fix this issue. The factory lines, BOTH of them, are much too small for this pump. The only proper fix is to upgrade the lines ... both of them.

 

Put the factory low voltage back on it and it will be fine. My car runs fine on the stock FPR and fuel lines. All I did was drill the siphon to 9/64's.

 

The low voltage circuit will reduce the load on the return line, but the friction losses of the OE feed line reduce pump capacity.

Just FYI

 

Ted, I installed one of these pumps and upgraded the lines. However I am curious why you say the lines must be upgraded. Have you or anyone else measured the flow with stock lines to see how it compares to a Walbro 255? I know from personal experience that without rewiring it, it doesn't perform, but I didn't do any experimentation with the lines.

 

The OE system is designed around a smaller pump with a low voltage setting. A single hardwired 255 lph pump is enough to create high FP issues at idle. Drilling the siphon is usually enough to relieve some of the pressure backlog, although it exposes the limits of the OE return system, which is not designed to return such a large volume of fuel.

A hardwired Walbro E85 pump cannot be compared to a 255. It draws substantially more current than a 255, and pumps substantially more fuel. It completely overruns the OE return line at low speeds. The uncontrollably high pressure one gets at idle is proof of this. There is no way around it except to upgrade the tiny return line.

As for the OE feed line, it was sized around a <300hp application. A setup making 600hp with gasoline is asking that line to flow >2X its original design. A setup making 600whp with E85 is asking that line to flow >2.5X its original design. As flow in the line is increased, it creates a backlog of pressure due to friction losses. This increases resistance against the pump, which reduces flow from the pump. This means the pressure the pump sees is significantly greater than the actual pressure at the rail. A glance at any Walbro flow vs. pressure chart shows what happens when the pressure the pump sees rises. IIRC, mrfred observed this when he upgraded his feed line.

Any way one chooses to slice it, there is no way to get the full flow potential of a Walbro E85 pump with either OE feed or return lines any more than one can get the full handling capabilities of this car by fitting skinny 70 series tires to it.

 

Yes. Once I build the short block and am able to push the red to its potential, I will be upgrading the fuel lines, rail, and regulator. Right now, yes, it's harder on the pump, but they're not too expensive if they last a year..

 

A restriction in the feed line shouldn't hurt the pump. The pump just 'thinks' it's working at a high pressure, which reduces its volumetric capacity.

The more immediate issue is uncontrollably high FP at idle when the pump is hardwired for full time v high voltage, and only upgrading the return can fix that.

 

I have mine wired to the OEM system, and the hard wire only comes on when the high voltage is activated, so it should be good. I didn't have to make any changes to injector scaling or latency when I switched from the 255 to the 450, so I think it's useable on the stock stuff if you're not trying to push the limits of the pump's advertised flow ratings. I did drill the siphon to 9/64's so I'm sure that helped some.


And I agree, hardwiring the 450 to run at full voltage all the time would not work.


I can't tell if you think I'm saying you're wrong, I'm not. I'm simply saying that with proper wiring and a small mod (drilling the siphon) you can use the 450 on the stock fuel system if you're out of fuel on the 255, but not trying to find the limit of the 450. A good example being a car like mine, stock block with a turbo capable of 500-550hp on the stock block needs more fuel than a 255, and a "choked up" 450 on the stock fuel system does the job wonderfully with minimal work and proper wiring.

 

It will work just fine, but not without the proper upgrades. To be clear, everything I've written on this subject in this discussion specifies a full-time hardwired pump.

 

Is there a how to somewhere on how to drill out the return siphon? I want to look into doing that.

 

There is, but if the pump is hardwired for full-time max voltage, don't expect this to cure the problem:

https://www.evolutionm.net/forums/ev...ould-know.html

I needed this fix because I was already running an AN -6 return and having pressure issues at idle.

 

Ok so here is an update... I got the FPR installed and the car starts up and runs fine. Only problem is when we went to adjust the base pressure it would not change from 20 psi.. We tried tightening it almost to the point where it is maxed out and it did not go up at all. You figure the AFR's would be super lean but they are actually way richer than before (12.5-13.X) at idle... I let it idle for a few minutes while trying to adjust the fuel pressure and nothing. Any ideas?

 

Is this with the vacuum line on or off?

 

I bought the double pump setup but it isn't needed any longer. I used to be a walbro fan until I bought a full blown single 340 lph fuel pump that outflows a 255 by alot at 75psi its good for 785hp. Stop using ****ty walbros there loud as hell too.

 

The Walbro E85 pump is dead quiet, but that's a different discussion.