In the meantime, has anyone installed either one of these in their GSR/EVO yet? The Walbro 400lph is definitely a bit longer and wider at the base and was wondering if there were any issues?
Also if you do install one, take note that the exit diameter of the Walbro 400lph pump is 5/16" so you would want to make sure that ALL your plumbing from the pump itself to the fuel rail was a minimum of 3/8" hose diameter with 6AN fittings all the way through!! This should still give good enough power for 600hp E85 setups, or you may wish to upgrade to 1/2" and 8AN lines.
For those who might not know yet, the OEM fuel pump power wiring simply WILL NOT provide enough amperage to run these hi powered fuel pumps properly. You will need to change your power supply to the fuel pump via direct power cable from the battery and having your tiny OEM power wire used as the switch on a 30A relay.
Tonight I revisited the stock metal pipe fittings on the outside of our EVO I-III and GSR fuel pump cradles and when you unscrew the metal fitting and look inside it, it certainly does have a massive restriction. But when comparing it to the outlet of the Walbro 255lph they are the exact same size! So even though the OEM hoses and hardlines are supposed to be 5/16" in diameter, the Walbro 255 outlet and hard OEM fittings on the outside of the fuel cradle, plus the end adapters on either side of the OEM fuel rail are still very restrictive. See attached pics.
Therefore when you do want to install a single intank fuel pump larger than a Walbro 255lph, you will NEED to consider modifying the top cover of the intank pump assembly to allow for a 6AN fitting or larger to be installed through it and straight to high flowing intank fuel pumps with 5/16" outlets or bigger.
In the coming weeks Im finally going to get rid of the OEM hard line under my car and replace it with either 3/8" alloy tubing and 6AN connectors, or 1/2" tubing with 8AN connectors from the firewall to the fuel tank. I have already upgraded my engine bay plumbing to 8AN fuel lines and fuel filter etc when I did all the inital engine work, so its just a matter of upsizing the fuel flow from the firewall backwards that needs attention now.
As part of the works I'll be installing a bulkhead into the fuel pump cradle lid too with hose connection to the pump. Cost... maybe not even $200 worth of parts including shipping from Summit Racing. Parts will include the alloy line, some braided lines and anodised fittings and adapters. I'll do a DIY write up with pics and part numbers about it when I get it sorted.
Just take a look at the Walbro 255 outlet and the OEM fuel cradle hard line adapter vs the larger diameter of a 6AN fuel connection. 8AN is even bigger obviously lol...
Edited by EVO-00X, 05 May 2012 - 08:18 AM.