Re: starts breaking up at 4500 rpm.
 

May be a really stupid question but check that the return is not connected to the vent on the cell, as its a one way check. This would dead head the pump and the regulator, the check may allow some flow but I would be surprised.

Re: starts breaking up at 4500 rpm.
 

return is unblocked. -8 line for a vent line.

Re: starts breaking up at 4500 rpm.
 

Is this a Fast system ?

Re: starts breaking up at 4500 rpm.
 

nope. stock with a Anderson pms, then I hooked up my rpm extender, then I tried just my stock ecu. all acted the same.

Re: starts breaking up at 4500 rpm.
 

You might try putting some foam in the cell... I don't have a lot of experience with injection, but sure sounds like it is running out of fuel or getting air in it.
With higher pressure of injection and a lot of return at high pressure, if it is putting air in the cell, getting air in the line, it will cause headaches...

Keep working on it, you will find it.

Ken
Stock 412

Re: starts breaking up at 4500 rpm.
 

thanks. I will try that.

Re: starts breaking up at 4500 rpm.
 

Bob, does your return have a dip hose inside the tank so it's putting the fuel in below the fuel level? Personally if you were getting air in the system I would think you would be able to hear the pump surging and you would see pressure fluctuations. Have you ever looked in the tank with pump running to see if it looks like the fuel is being aerated? When you say it starts to go lean, does it go a full number or just a few points lean and if your bring it back below 4500 does the AFR come back to normal?

Re: starts breaking up at 4500 rpm.
 

Is the fuel cell outlet facing to the rear of the car?

Re: starts breaking up at 4500 rpm.
 

yes fuel outlet to the rear. return is right above it on the top of the cell. no foam so I think we have a winner with the airiation from the return. gonna put a tube in there and see how that works.

Re: starts breaking up at 4500 rpm.
 

For testing purpose dump the return line into a separate container. That would fully eliminate any aeration from the return