Dag12141987

HELLO EVERYONE,
I am a newer member here. I am doing a ls1 swap in a 2005 rx8. I plan on posting a pretty detailed build thread on it for anyone that was thinking about doing this swap. Ive seen a couple of people on here that have. And really appreciate them posting the issues and the speed bumps they had to over come because it really lets you understand what your gettin into. I have over 500 pictures and 25 to 30 videos so far. once my 30 day mark has passed i will share it. BUT i am here today becuase i am getting into the fuel part of my project and was just curious about a couple different things. I already replaced the fuel pump with a 320lph. but when i was about to get into ripping out the old lines and running 6an lines, it just hit me that there are 2 lines. Didnt think these were setup for return style fuel system? so if the bigger one is the main fuel line that delivers fuel from the fuel tank to the motor , whats the other line to? is it a return line? if so can i just replace my main fuel line with an6 line and cut the return line by the tank and hook the cut line up to a return port on the ls1 return style fuel filter? also was kind of wondering if i would have to put a new feed line in? how much psi does the factory rx8 feed line support? And i know some people do not beleave in these swaps and hate them and i respect your thoughts. But i had my rx8 loose compression and shop said some crazy *** price , forget what it was but im thinking it was like $4000 or somthing like that. And 2 weeks later i totalled my gto, but motor and trans were fine. So i seen this swap online, thought about it for couple weeks and woke up one day and said screw it. didnt know much about rotary motors , but i know v8s. lol so it only made since. just wanted to get that out of the way. So PLEASE PLEASE PLEASE HELP.
THANKS IN ADVANCE FOR ANY IDEAS, THOUGHTS, OR ANSWERS.
I know theres alot of hard core mazda people who know all the answers to all my questions. so please take a couple seconds to help me. and thanks for reading at least.
THANKS

zendrums

iTrader: (2)

Sounds like you're talking about the evap. It goes back above the diff and connects to a charcoal canister. Either hook up the ls purge solenoid to that line, or cap it off and put a one way filter on your ls intake.

I believe stock psi for the rx8 I'd 59? Ls requires about the same. You're going to have problems with your 320lph pump pushing too much. My 320 pegs 70 psi, adding another in line regulator at some point.

Good luck

Dag12141987

Thanks for the wick reply. The ls fuel rail is a returnless one already. I just bought a return style fuel filter cause I thought it was better. But I think I'm just gonna do what u said and get returnless style filter. I was already thinking about pump pushing to much. Where should I put a regulater? Any kind or brand you would recommend? I'm also hoping the pump won't be too much for stock fuel line that goes from pump itself to the quick connect fitting in top the pump assembly. It's on with tit clamps. But might have to end up changing. U said stock psi is about the same. Would that mean my stock pump could run the ls motor? I guess just thinking about the size difference I was thinking it would need more psi.

Dag12141987

Also anyone that know about the electronic power steering in the rx8? From my understanding it gets a signal from the mazda shaft sensor. The wheel behind the pully has notches and 2 flat spots. I'm guessing the flat spots send a pause to ecu to let it know it's completed a full turn and depending on how fast it's turning the ecu sends power out a signal back to let it know how much to assist. Curious if that's right? And if so can I Fake the signal to make it operate normal? Or do I need to rig up this wheel and sensor on my ls somewhere?

zendrums

iTrader: (2)

I think we might be talking past each other a little bit here. To clarify, the RX8 is a returnless style system with an evap system that routes fuel to a charcoal canister. You need to do something about this when you do your swap. The 8 already has a fuel pump regulator (FPR) built in to the fuel pump housing. You cannot (shouldn't?) use the stock fuel lines for the LS swap. Pressure is important, but pressure @ what volume is also important, and AN6 is the correct size to use for an NA or non-insanely boosted LS. The problem you're going to have, which I'm currently having on my returnless setup, is that even with the built in FPR and the AN6 lines, you'll hit about 70 PSI, which is ~10 PSI too much, with a 320 lph pump. I went with the pump cause the first one I bought from Deeds Performance turned out to be a fake and blew up in my tank after it blew a fuse. I know it's a fake cause I chopped it open and contact Walbro. I won't get into it, but apparently even big name retailers got fake pumps, so it's pretty much impossible to know if you have a fake or not unless you slice it apart. Since I was gun shy, I bought an AEM 320. What I'd recommend you do if it isn't too late is to return the 320 for a 250. That pump pegged 58/60 PSI for me. I went ahead and grabbed a 320 instead because I plan on swapping to a return style setup and adding boost over winter. If your plan isn't 500+ hp, I'd go back to the 250 and save yourself the trouble of adding the vette fuel filter. If you do add the vette filter, then yes, it does return fuel back to the tank, so you'll need to plumb another AN6 line from the filter back to your tank.

Dag12141987

So going off of what I have already bought. I got 6an line. Couple fittings a aem 320lph pump. And ls1 return style filter/regulator. It's probably best and cheaper to just run a return line to the tank right? Motor is around 380hp plan on building it up a little more to maybe get around 500hp after I get the swap done. But anyways how would I go about running a return line? Don't sound hard but wanna make sure I do it right and safe. Do I want the return top of bottem of tank? Probably towards bottem on side maybe? What kind of fitting am I looking for? Would 6an line be ok for return too? Or should I get smaller? First time I have messed with fuel system so I wanna learn. Thanks

zendrums

iTrader: (2)

If you want to run a return from the vette filter, just drill another hole into the fuel pump housing and add a fitting.

https://www.rx8club.com/non-rotary-s...-build-254761/

I did what this guy did for the an6 line and cut out the existing quick disconnect and put in a barb + AN fitting. You would want to do another of the same thing to dump the fuel back into the tank (double check the fitting size for the vette filter). You should definitely not put holes directly into the fuel tank if you can avoid it. I'm currently running a 5.3 using the same kit as Stubbs (guy from the link) with plans to boost, but my build is pretty much the same as his. I went a different route with my radiator and obviously have a slower car...for now. I'll say that my double pass 24" radiator with a single 18" fan has served me very well. It's been almost 100 degrees out here and I've driven it around town for 30 minutes. My peak temp was 201.6 degrees. Normal operating temp of the engine is supposed to be 210-215, 220 is a problem.

Sorry for getting off topic. Good luck with your build.

Dag12141987

Not off topic at all I will be working on radiator and trans cooler next. So it's giving me insight. I see he uses the bulkhead fitting. Puts it exactly where the quick connect used to be. But he must not be running a return line. Or I didn't see where he tapped it in. Is it safe to put another bulkhead fitting any where on top just like the other for my return? And after I do that. On the bottem side of it where it's coming in... do I just wanna let it drop from there? Or maybe run I line down the length of the pump assembly compressed so it's dumping it down towards the bottem?

Dag12141987

And thanks for hanging in there with me man. I just wanna make sure I get things right.

Dag12141987

Might as well get this ? Out there too. As far as the power to the pump. I did the stand alone harness by following I think it was lt1 swap. So I have the fuel pump power coming off of a relay on the gm harness. Do I want to hook that straight into my fuel pump wiring. Or I think that link u posted the guy looked like he was hooking it up to the relay in the rx8 fuse box? If so what wire does the green connect to? And does it just tap into it? Or do u cut the wire and connect it straight?

Dag12141987

Wait it looks like he pulled the pin and wire from his fuse box that goes directly to the fuel pump and said would be wired in to gm harness relay. Probably the one off the built relay and fuse panel? The grey wire conning off of that I beleave

zendrums

iTrader: (2)

I can't speak to how he wired things. I kept the 8s ecu cause I was thinking I could get the abs and traction control working at some point, so I used the existing fuse and relay set and tapped the GM wiring in to it. The green wire from the GM ecu needs to go to ground for the fuel pump relay control if I'm remembering things correctly. GM turns on ground to trip the relay. I basically made the secondary fuel pump relay the primary cause it's the full speed relay. The other has an inline resistor.

As for the return line, no Stubbs does not have one. You should be able to just put it anywhere on that fuel pump assembly. I wouldn't worry about letting it just dump without a hose. The amount of fuel you'll be returning isn't that much.

I'm telling you these things off the top of my head btw, so check your work before just trusting what I say. I wired it all a while ago. I can't really dig in to things more into late this weekend.

Dag12141987

Little bit afraid of just dropping the fuel right there down the assembly. But was thinking I could pendant just tap a return line into the bottem of the filler neck. Or is that a bad idea?

Dag12141987

As long as it's a air tight seal should be good right?

Dag12141987

I'm just thinking u said fuel pump will be pushing about 70 psi and ls1 only takes about 57psi I think is what I have read. So the pump will be trying to push fuel that's not moving as fast as the pump is. But if I instal this return style filter/regulator the motor will be getting the 57 psi it needs and more when it needs it and the pump will be working pushing and pushing at the speed it does and the extra fuel caused by the 10 or so extra psi the pump is making will be going back to the tank to be used when it's needed. Right? Am I thinking clearly? Like I said new to messing with fuel systems so please please correct me if any of this don't make sense or is not safe

Dag12141987

But I think i do need to install a bulk head fitting and maybe rubber hose inside the assembly cause I was thinking that thick plastic factory one would work. But u got me rethinking that so will probably add that to my list.

zendrums

iTrader: (2)

Pressure != volume. If you put your thumb over a garden hose on full blast, you're creating more pressure by restricting flow. Less water is getting through, but the pressure is still high. You need 58 PSI @ the volume of an an6 line (well, there's fuel line distance, blah blah blah, but that's virtually the same on all vehicles). That's precisely why the 320 lph pump is over pressuring. The FPR is just a bypass to relieve pressure down to a certain amount. I have too much pressure cause of that pump even with the FPR, which is making 70 psi with the an6 line. If I bumped it up to an an8 line, my pressure would drop, but the fuel volume would increase. I never tried to run the LS with the RX-8 lines, but a quick google search will tell you that to run an LS motor, you need 58 PSI on a 3/8 line.

This is just the first result I found on google

fuel line sizes??? - LS1TECH

As far as the return, yes, the fuel extra fuel from the pump will just flow back into the tank. I don't know why you would bother tapping the filler neck instead of just the fuel pump housing. Your assembly is inside your tank, so I'm not sure what the concern with dropping gasoline on it would be. It's already submerged. I've only ever seen return lines come back through the housing, and that's 100% what I intend to do.

https://www.google.com/search?tbm=is...return+housing

Dag12141987

What's the difference in 6an straight fittings and 6an flare? Is one better for fuel? Are they compatible with each other?

Dag12141987

Should I remove the fuel pressure regulator that is inside the rx8 pump assembly?