Joe Perez

iTrader: (8)

Agreed- return style has several advantages, and is preferable if available. It's certainly easier to tune for.

That said, lots of OEMs are using returnless systems these days, and they've certainly gotten the engines running pretty well on them. You don't hear much about things like hot-restart problems or mixture instability on unmodified cars.

18psi

iTrader: (76)

True, but they're also not using megasquirt.

And even on the ultra-awesome modern OEM ecu's there is difficulty with hot restarts once you upgrade injectors: example - Subaru and ID1000's run into multiple mis-fires SPECIFICALLY on hot re-starts.

To the point that Cobb had to create specific tables/parameters to fix this very issue. They "solved" it by lowering fuel pump duty/voltage on hot re-start, otherwise no matter what you do you either get uber rich to the point of flooding, or lean, or mis-fires. So the "fix" is more of a bandaid. Returnless systems still suck and IMO are a cost cutting measure more than an evolution in technology.

Chiburbian

iTrader: (1)

Good discussion thanks. I was just hoping for an easy all in one solution.

Joe Perez

iTrader: (8)

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I can't recall the exact diameter of a Miata fuel line off the top of my head, but that's basically the simple solution.

Combine it with either an NA or aftermarket return-style, MAP-referenced fuel pressure regulator, and you've got a complete fuel solution. If you use an aftermarket regulator, you can mount it on the firewall if clearance is an issue.

18psi

iTrader: (76)

yup, or just do the "cheater" method and use the oem tank vent line as a return and figure out a vent solution near the tank so you don't need to run a whole nother line

aidandj

iTrader: (5)

5/16" fuel line. 1/4" evap line.

Chiburbian

iTrader: (1)

i'm not interested in using the evap line. I have no problem spending the money and time to run a dedicated return line, especially considering I was considering buying the $950 FM kit...

Time to do research on exactly what parts I need to make this happen. Anyone have a favorite vacuum referenced pressure regulator?

aidandj

iTrader: (5)

Fuel lab makes good stuff. Best return line IMO is to replace the evap line with another NB fuel line. It fits prefect.

If you want to run AN6 lines: You need a bunch of 5/16 quick disconnect to 6an. The aluminum screw in kind. Not the plastic snap in kind. You need a way to bypass the stock FPR. I recommend the Turbo smart 0402-1002. Then just assorted AN fittings.

If you want to run rubber line: you just need 5/16 quick disconnect to hose barb, and adapters from your FPR to hose barb.

18psi

iTrader: (76)

check out what G did (EO2K). that should be all you need to do it 100% proper
he outlined it all in his thread iirc

Chiburbian

iTrader: (1)

School is winding down so I may get the spare motor disassembled and off to be chemically stripped. Any reason this is a bad idea?

I stopped at the machine shop a week and a half ago and we agreed that they would do all the machine work and I would handle the assembly (either myself or find another builder). This shop has about a 14 month wait if I was going to have them build it.

G3ML1NGZ

I was just about to ask if that was a possibility. Any explanation on why that's not a preferred method?

Chiburbian

iTrader: (1)

The only complaint that I can recall hearing is that the vent line is not as big as the supply line. I still would like to retain the charcoal cannister and OEM evap system. Don't ask me to give a good reason why. lol.

G3ML1NGZ

hahah fair enough

DNMakinson

iTrader: (3)

MS will not control it in any manner. I.E., it will never purge.

18psi

iTrader: (76)

lol yep and it takes all of 5 minutes to yank that whole rats nest, intact, out of there, and significantly clean up the bay. And re-install will be another 5 minutes cause it just drops back in together.

Chiburbian

iTrader: (1)

Not true (in all applications). My megasquirt 3x is setup to draw a vacuum through the charcoal cannister during certain conditions. Certainly this makes tuning a bit more complicated because I have to remember to turn it off when doing VEAL, but when cruising using EGO it adjusts fine.

When I get the MSpnpPro is installed I will see if I can duplicate the functionality if not I will have no choice.

DNMakinson

iTrader: (3)

Oh yeah, I do recall now someone setting an MS3X to do that. Was looking for information on when stock system purged. OK then.

The only reason I regret pulling and trashing my Evap and EGR stuff is that now that I want to use active barrometric compensation, I need the MAP (BOOST) sensor that I threw away.

Joe Perez

iTrader: (8)

The stock control system is PWM-based. It varies the duty cycle of the purge valve proportionally to engine load (MAF / VAF), after warmup is complete, and whenever:
Also, don't forget the canister drain valve, on vehicles which are so equipped.

Chiburbian

iTrader: (1)

Interesting. Mine is set to be simple on/off. I have the rpm window somewhere. I'll pull it when I have time.

maybe I'll pull the canister after all. I just prefer to leave everything as functional as possible so there is less to reverse come emissions time.

edit: just pulled my setup spreadsheet and I had it set to purge between 48 and 88kpa.

Joe Perez

iTrader: (8)

Yeah, that's similar to how I did mine on the MS1.

I'm sure there's some minor technical justification for the use of PWM rather than on/off, but in the end, on/off seems to work fine.