Just a little background first....2000 RCSB 1500 with a BorgWarner S475 and BTR stage 2 turbo cam. We put a Walbro 450 in tank and recently put a TH400 with a PTC converter in the truck. The truck is on Deka 80lb'er on stock LM7 fuel rails and lines on e85. The ethanol content of what is currently in the tank should be somewhere around 65-70%

We got the truck on the dyno and we saw that IDC was in the 90% range...So we put a mechanical gauge onto the schrader valve that is on the passenger side of the fuel rail. Base pressure was 57-58 psi. Great! Truck gets moving on the rollers and we start getting into boost (~13psi) and the fuel pressure reaches 67-68 psi, even better, until we reach about 4200rpm and the pressure tanks to the low 40's. The truck was making 443 whp. After doing some research and looking around I feel like the way the system is right now it should be able to support more than that. I have read that the stock regulator can become an issue when seeing all the pressure from the 450, is that possibly why we are seeing the crazy drop? Am I maxing out the lines? Am I actually just out of pump? Would a clogged fuel filter cause this kind of a drop? If it is time for a fuel system than my all means I will sort one out, but something just does not seem right as it sits.

Would appreciate any insight!

 

Stock regulator should be replaced on a 450 upgrade.

At a guess you likely will run out of injector very soon too, figure the 80's could go like 600-700 no problem but then cut that back by 30% at the minimum when you are talking E85 because of the extra fuel flow needed.

 

When I was doing my research I recall someone saying that there was a blockoff plate/bolt for the regulator on the rail, but I can not seem to find anything.

 

Fuel Pressure Regulator Bypass - Atomic F&P

 

Much appreciated

 

If pressure is dropping its not the regulator, its something else. The issues with the 450 and stock regulator happen at idle because that regulator cant flow enough to control pressure from the 450. If you are having pressure drop during boost you have a pump issue.

You upgrade the wiring, right? Replacing the fuel filter wouldnt be a bad idea as the stock one is not meant for E85 anyway.

 

I am not sure if the wiring was upgraded or not. I did not personally do the install of the pump so I can not speak for it. I will try and get the fuel filter done today and then check the wiring.