I wasn't sure if this deserved its own thread but since there's a huge lack of Mazdaspeed info out there, I figured, screw it.

I'm trying to get my head around the fuel system for this car to be e85 capable. Here is what I have come up with in my head, does this look correct for routing?




I have two lines in my 'Speed. It looks like it has a return style setup maybe? The parts diagrams and Mellens haven't been super clear on this. I believe the NB1's are all return-less but not sure about the 2's. Any one know for sure which line is the feed and if the other one is truly a return? I will be removing that loop routing as well, since I already took out the charcoal canister but wasn't sure if I needed that second damper or not.

 

Well I've been doing a lot more reading while work is slow. I think my drawn diagram is fine, except for ALL NB's are return-less, so that orange taped line is for evap and isn't back to the tank...yet.

So I will be converting to a return-style system so I can mount my Adjustable Fuel Pressure Regulator in the engine bay for tuning ease.

Check out this amazing thread for how to make a return system. Since I took out the charcoal canister, I can utilize the evap line just like flounder did in their thread.

https://www.miataturbo.net/diy-turbo...l-style-74629/

 

you got it....not sure but i think you'll need to plumb back a line for the return....

if you cna find it, use a NA return line, alresdy pre-bent and will fit in nicely.

 

So that orange taped line is the evap system that goes to the charcoal canister in the back passenger wheel well. Trying to work out now how to utilize that line as the return. I will probably remove the charcoal canister altogether, just gotta work out how to allow the gas tank to vent to atmo. I don't mind the smell of a little gas anyways. ​​​​​​​

 

Figured I should write a post showing the almost end result of how this turned out for anyone that may want to see it.

I'll just throw all the pics in here and if theres any questions please post em!


DW400 with bulkhead connectors. RTV is on there because I put them too close to the edge initially and then had to redrill and then trim off some of the bracket for the fuel level sensor. Don't do what I did, measure and drill correctly the first time! Also removed the NB fuel pressure regulator on the return side.




(This next pic was taken before realizing my holes were badly placed)


You can see the return line right off the radium fuel rail with a 90 that goes to the side of the fuel lab regulator



Said regulator. Custom bracket and the return line continues out the bottom from a 90 degree fitting on to the flex sensor.



Reused the oem line mounting location and bracket, holds the sensor very snug. Its the good ol GM/Continental sensor with AN adapters.




The fuel filter on another custom bracket. I removed all of the evap systems stuff and the rubber vent hose is just venting to atmosphere. You can seen the flex sensor and its location before I put the engine in.