Do 12a turbo injectors plug straight in to a 13b turbo? And do they replace the primary or secondary injectors? Are any mods needed to do this? Sorry, I know to use search, but in real hurry. Thanx

 

I'm pretty sure the 12a turbo was carbed. so there would be no injectors.

 

In japan they had a FB with a 12AT motor. I thought it was fuel injected...

But Mazda didn't import that engine to America, and it was never in a FC, so you might have better luck posting in the first gen forum.

 

erm NO

They had a PAIR of injectors, either blue 720cc or green 800cc injectors in them

 

really? I though it was a blown though carb setup... o well...

 

I thought that too.
In fact, when we tore apart my friends 12a, I didn't see any evidence of injectors...

 

The 12A Turbo was definitely fuel injected. I owned one, so I get the last word! Mazda has never made a carb'd rotary turbo.
The 82-83 Cosmo had 720cc/min injectors, the 84-88 Cosmo and 84-85 RX-7 Turbo had 800cc/min ones. These are a drop-in replacement for FC injectors.

 

I'm pretty sure the non- turbo 12a had 680's on the fuel injection model. I've read this on the Racing Beat or the Mazdatrix site. To be drop ins in the secondary fuel rail on the low impedence 87 turbo models.

 

I've got 720's from an 85 GSL-SE (13B) in my secondaries, plug and play. Still waiting for an S-AFC, though

 

Yo. I see where I wrote 12a when I shoulda written 13B for the 84/85 model. I'm still confused about the 720's. I distinctly remember reading in the Mazdatrix manual that they were 680's for those two years. Talking american version, non turbo but fuel injected. Puzzled.

 

i thought the gsl-se ones were 680cc's too.

mike

 

they are 680cc'and they're orange

 

84 GSL-SE has 680's
85 GSL-SE has 720's

per my rotary mechanic.

 

Where I really went wrong was in not noticing that LOWMAZ was from NEWZEALAND and that he had written 12a (I assumed the 12a was a mistake and he meant 13B). I didn't know until last week that the first generation 12a were turbocharged in Japan (NZ also?) but not the USA. Just carb 12a's in the USA and fuel injected 13B for the 84-85. The MAZDATRIX site list only one number for the 84-85 year sooooooo, for right now I'm going with the 680's stated by Turborudebosy and J9FD3S, for 84-85.

Sorry about messing up your thread LOWMAZDA

And JIMMEYV13 is pretty sure that 85 13B fuel injection was 720's, per his mechanic. Non of this has much to do with LOWMAZ. Just tying to clear up the 680/720 issue.

 

I emailed Mazdatrix, and they said that 84 & 85 -SE's both came with 680 low impedence injectors.

I'm going to have to do some investigating on my injectors now. I got them from a guy that races 1st gen RX-7's and he told me they were 720's from an 85-SE.

 

Getting back to the original question, yes they drop right in, you replace the secondaries (or all four), and you’ll need a fuel controller or it’ll run like ****.
It you just throw them into the secondaries without any control, it’ll run fine up to 3800rpm when the secondaries kick in, then it’ll start running very, very rich. The ECU still thinks the 550’s are in, so the same pulsewidth on the bigger injectors will mean too much fuel is injected. In this case you’ll be injecting 23% too much fuel from 3800rpm on, meaning black smoke and a loss of power! No offence, but I hate it when people say this. It means they’re rushing the work, which is a recipe for disaster when modifying a car yourself. Take your time and plan everything first. Find out the answers to your questions before you rip everything apart and slap it back together wrong! Not a flame, just some advice.

 

Well I got some 680s from an -SE but I'm not sure what year. They are the orange ones. While we're on this, where is the secondary fuel rail? Is it the one thats right under the upper intake? Sorry if this is a dumb question.

 

I am going to put my 680s in while I change my PD. Do you think it will run really rich with a 3" DP/MP, intake a 3" TID? And if so what about with a custom 3" dual catback? Thanks. I'm going to have my egt gauge in a few weeks but wanted to know how bad its going to be until I get my s-afc.

 

This isn’t specifically aimed at you Chris (I see you’ve upgraded your pump), but when it comes to 13BT’s leaning out, I think people throwing bigger injectors into mildly tuned engines are going about it all wrong. It leans at the top end because the fuel pump can’t keep up. Throwing in bigger injectors way overcome this (by going too rich instead), an even if you throw in a fuel controller, you’re still not overcoming the system’s inherent weakness, the stock pump. The injectors themselves are big enough to flow a safe 290hp, which is 60% over stock for a S4. If you sort out the pump, then tune it all properly with a fuel controller, there’s no need to upgrade the injectors unless you plan on exceeding 300hp.

 

(applause)

I think the term "injectors" is a misnomer. They don't inject anything, they are just poppet valves. The fuel pump supplies the volume and pressure for "injecting".