Sorry for the noob questions but i can't figure it out from search results i've found.

Installing MS (hopefully next weekend) on my s/c 1.8. I'm assuming I can ditch the AFPR. If I do this will I need larger injectors?

My goal is 250whp with a turbo next year. If I don't need new injectors yet I'd rather wait. If I do, I want to buy something with the 250hp goal in mind.

I bought my car with the whole JR Kool-Aid package installed by the previous owner - M45, fuel pump, afpr, header, cat, and I think clutch as well......

 

Yes, and yes.

If you're going to install the MS now, I somewhat advise you to do the larger injectors at the same time, so you don't have to completely generate all new fuel tables twice. Granted, you'll have to re-tune the fuel table anyway when you switch from S/C to Turbo, but it'll be more of a fine-tuning. There's no reason you can't run with a set of 550s while the S/C is still in place and making 140 HP. Remember that technically, most of us running big injectors are only making 30 - 40 HP 90% of the time.

It sounds like you've already purchased your MS. Which one did you buy?

 

Dang. I was afraid of that. Another expense i hadn't counted on.
So what's a good (read - inexpensive) source for Hi Z injectors? How big should I go?

 

I got one off the MT classifieds. One that Brain built but was never installed. Ver. 3 board. Made for a 1.6 so I'm gonna have to change some stuff first. I THINK I'd like to do a knock sensor and I'm contemplating a simple DIY WI setup. Don't yet know if the MS will need to be involved in that. I'll probably ditch it for an IC once I go turbo.

 

https://www.miataturbo.net/forum/showthread.php?t=10821
post #3, figure out which injectors you want to use, and then find them whereever they may be hiding. I got my 550cc RX7 injectors from a guy out of Bellingham WA who posted in the Seattle Craigslist who a friend of mine in NC saw and emailed me about and I got them for $70 shipped. Will this happen to you, i don't know, but keep your eye out, I think a lot of people get them from RX7club.com or something...
Get creative, they will not find you. Also, check the classifieds here, sometimes they pop up.

 

Thanks Zabac. I'm good at 'finding' stuff. What I should have asked was - what injectors are plug - n -play. i.e. what cars are good sources. But you answered that. So the RX-7s plug right in? I don't want to monkey with resistors and converting low Z to hi Z stuff if I can avoid it. I like simple....

 

OK, I suck. I read that whole thing a month ago and forgot about it!

I'm at around 9psi right now. The search is on for 550s I guess.

 

If you do go for RX7 injectors, make tripple sure they are the correct part number...you never know man

 

id go with 460s. you dont need 550s for that power.

 

he wants headroom for 250ish, yeah he does

 

250ish
i think 460 will do it.

 

I run at 11.5psi (about 220bhp) on 320cc no problem.

 

and although some people on this forum disagree with me, make sure you get the high z regardless of part #. A guy at witch-hunter told me he's seen high and low z rx7 550's with the same part #.

 

250hp on a jr m45?

 

read the op

 

oops.

 

www.mx6.com

a 90-92 mx-6 / 626 / ford probe turbo will get you a set of 320's for around $50 shipped. I just bought four sets of them at an average of $60 shipped a set.

-meaty

 

I'm just afraid those won't be big enough in the long run. I'd rather not swap and pay twice when I could do it once and do it right with a little patience. I MAY have found a newly cleaned set of RX& Hi Z 550s for $150.

 

If you change to larger injectors after a base map has been created, you have to alter the entire fuel table?

I was thinking all you had to change was REQ FUEL since the injector size CHANGE is the constant across the whole table.

Since my wife is going out of town this weekend, I was going to finally install my larger injectors in the Miata before the turbo build really gets started... you know, one change at a time...

but does the whole fuel table need to retuned?

 

In the OP's case, the proposed change was both to add larger injectors and remove an AFPR. Because AFPRs are non-linear by design, removing one would necessitate a complete re-tuning of the VE table, rather than a simple re-scaling or Req_Fuel recalculation.