I am building a turboed miata and was wondering if it would be worth it to try running it with a rising rate FPR and yellow rx8 injectors on a stock ecu before buying a speedyefi, or if i should just order them all at once

I have a lambda kit to monitor afr so if it is lean i could see

 

You might be able to tune boost with a bunch of ******* around with pressure disks, but the problem is everywhere else. Idle, cruise, start up, even over run will be literally double the required fuel. You’ll be fouling plugs and getting ~10-15mpg. Biggest I’ve ever heard is some 325cc injectors, which have similar problems but manageable. That was back in ~2010 though.

On top of that, there are 0 rx8 injectors I’ve tuned that are anything but complete garbage, and I’ve tuned a dozen or so. Don’t bother, they’re all either knock offs or 20 years old. Get some new tech injectors, a decent ECU, and tune properly.

 

if i used the stock injectors and the rising rate fpr it would be stock fuel pressure through stock injectors at idle and increase the fuel pressure by one psi per pound of boost as the turbo spools. Would the ecu try to correct the higher fuel pressure? Or would this work

 

Yes, that is how we tuned turbos back in 2000. Get a Bipes too, which retards timing in boost. Also an o2 clamp for…reasons. Might as well get a silicone vacuum line kit colored to match your car too.

 

Oh gawd, that **** sucked. And didn't make any power for all the effort and money.

Can you even get an o2 clamp anywhere anymore?

 

Yes, the ECU will pull out fuel. A standalone ECU, injectors, and a wideband O2 sensor are your only path forward. And not the RX7/RX8 550cc injectors unless you want to blow up your engine. They aren't what they are being sold as. They are not going to flow 550cc and they won't flow the same as each other because they are Chinese fakes. One cyl rich and one cyl lean and the wideband only sees the average of the two. The lean one typically detonates.

 

For the love of everything that is Miata, PLEASE listen to these guys! You will either a) spend a lot of time trying to get all of this assemblage to work and end up making ****-poor power, or b) blow up your enging and spend WAY more than you would, buying a decent (used, even) ECU and modern, reliable injectors.

PS - if you want to go cheap, I've got an old MS2PNP sitting around collecting dust. It's old-tech, but it's better than the stock ECU and is better'n nothing.

 

Definitely NOT a good path to follow. To answer another comment, an O2 clamp should still be easy to build, isn't it basically a pressure switch set to trigger at low boost and some basic circuitry? I don't remember the electrical side but you could probably find enough info to recreate one. Only, as others have said, all this crap is 20+ year old technology. I once owned an 1995 Escort GT (BP engine, basically a 323/Protege) that I turbocharged using a 323 GTX turbo and manifold. I isntalled ~460cc injectors with the OEM ECU only I had an Apex'i S-AFC (maybe S-AFC2) piggyback controller wired in. It wasn't a great setup but the S-AFC was able to reduce pulse rate close enough to the original injectors that the ECU didn't freak out during normal operation. Under boost I quickly learned adding fuel based on the variable TPS wasn't good, then I realized I could substitute a 0-5V MAP sensor and the AFC could be set for rising or falling voltage to match the sensor. Adding fuel following the boost curve wasn't as good as an aftermarket ECU you can get today but it solved some of the drivability isses I had. It was pig rich in boost but safe. Not the best for power but it ran for many 10k of miles, maybe 40-50k without issues tuning only by feel/ear and an EGT gauge to make sure the engine wasn't about to melt down from running lean. For timing I wired in a Jacob's Boost Timing Master that allowed base timing advance to 14/16 BTDC and had a **** to set retarde per psi boost. I sold that car back in 2006, the worst part was the OBD2 ECU trying to pull fuel as you dipped into boost, never got around to buying and installing an O2 clamp.

Far, FAR too much time spent wiring these bandaids in with poor results. Save up and spend/cry once or buy over time and delay installation until you have all you need.

EDIT...I forgot to add I first tried a BEGI FMU but it was nothing but a disappointment. I rebuilt it over and over but could never get it working properly. The internal piston would quickly get gummed up so I bypassed it only because I cut the plastic fuel hose under the hood to install it and didn't want to replace fuel hoses or patch it back together. Every time I opened the hood it reminded me not to order anything else from the now defunct BEGI.

 

The vortech RRFPR worked better but wasn't easily adjustable.

I have a starion intercooler I would sell you.

 

There you go! Starion was cutting edge technology in 1982 when they hit the market.

 

OP, with the cost of a speeduino now days there's no reason to run AIDS. Seriously, don't. I still remember my RRFPR + Bipes setup (circa 2006), doing a highway pull and having an I/C coupler pop off, then popping the hood to a GLOWING ORANGE (almost see through) turbo from all the timing retard and extra fuel. Pretty lucky I didn't do permanent damage to that motor, but honestly that's just because B6/BP's are built like tanks.

A speeduino is like $400 and will allow you to properly control the engine and control larger injectors.

 

If you have the answers, why are you here?

This forum is so rich in information, it would take you a year to read it all. Or you could short-cut that by just reading some stickies. Then you would know enough you wouldn't need to ask silly questions.

Put it this way, if you can't afford to do it properly the first time, you can't afford to do it twice.

 

That's been driven home so many times in the :checks calendar: 16 years I have been on this forum. It's a universal truth.

 

Dammit, you made me do math.

There's 8760 hours in a year, 2080 of those are spent working a full time job, 2920ish sleeping, 175ish commuting, and you're left, if you do NOTHING else, with 3585 hours. If you don't include classifieds, there are 1,341,593 (+ this one) posts on this forum at the time of this post, so you'd have 9.6 seconds to read each post. Including Joe Perez's rants. I have my doubts sir.