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Old 09-17-2008, 01:43 AM   #1
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Default Injector question

What's the largest injector I can run without an ECU upgrade?

I read the faqs section and did a search but it didn't quite answer my question. In the faqs it says The 1.6 ECU should be able to idle up to 330cc injectors.

So does this mean if I put an rx-7 afm on my 90' Miata I can run the 326 injectors off the mx-6 without needing an ECU?

Just an fyi cause this is my first post I have a 90 miata with a Begi-S kit on it plus intercooler and spec stage2 clutch walbro 190hp... tein flex suspension. I have the gt2560 for my turbo. Oh yeah I also have a 2.5" Custom exhaust with magnaflow muf. Those are all the mods off the top of my head. Motor is in good condition.

My goal isn't a specific hp but rather the most i can get without doing an ecu upgrade. But still having my car run efficient and smooth. I'd prefer not to have dyno time and ecu costs. Maybe down the road i'll go that route but i don't plan on going over 250hp and i'm sure i'll be happy between 200 & 250.

And if 326 is as high as i can go what boost do you think that'll max at. If any other injectors are recommended please state what you think max boost would be at that size. thanks!

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Old 09-17-2008, 02:07 AM   #2
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So many variables...

It's not so much that there is a dividing line that says "this injector is ok, but this one is not." It's pretty much a matter of your individual tolerance for crappy idle and reduced open-loop economy. The 265cc injectors (tan-top) out of a '94-'97 Miata will drop in and run without much of a penalty. As you start moving up from there, you just get further and further away from concepts like "smooth".

Some folks like to open up the AFM and diddle around with the spring inside, others think it's enough to just let the O2 sensor do its thing in closed-loop mode, and to hell with startup. Forget about the RX7 AFM. Waste of time and money.

First thing I'd do if I were you is to get a wideband O2 sensor with gauge- either an AEM UEGO or an Innovate LC1. That'll be a handy guide as you start moving up in boost and fueling. Fortunately, that Walbro 190HP and the Bell AFPR are a proven combo that will take you places.

I worry about your stated power goal given that you have no means of ignition retard and an apparent desire not to install one, especially with the 91 octane fuel you have there in Tucson. I can't see you getting to 200 WHP (much less 250) without dialing back the static timing so far that you've got **** for torque when off boost. We're talking about more than doubling the engine's output here.

My opinion is this: making safe, reliable turbo power on the Miata requires three things:
1- Good engine management.
2- Good engine management.
3- Good engine management.
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Old 09-17-2008, 02:58 AM   #3
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That's the exact answer im looking for thank you very much. I just wanted to know how well the stock ecu managed even with those "band aids" I'm all about doing it the right way so I guess im just going to have to man up and buy a ms-pnp or hydra or something and get it tuned.
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Old 09-17-2008, 05:08 AM   #4
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Quote:
Originally Posted by krissetsfire View Post
That's the exact answer im looking for thank you very much. I just wanted to know how well the stock ecu managed even with those "band aids" I'm all about doing it the right way so I guess im just going to have to man up and buy a ms-pnp or hydra or something and get it tuned.
And you can recoup some of the cost by selling your fpr and fuel pump after the ecu upgrade.
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Old 09-17-2008, 08:33 AM   #5
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i have 345 in mine out of the 626 turbo and its fine no stumbles and sit right at 900 to 1000 rpm's
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Old 09-17-2008, 02:45 PM   #6
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blue turbo - with what mods? what boost?

I live in az so i have to do emissions every year. What's my best ecu choice? Other than MS-PnP parallel? I have done some reading on link and people seem to be selling them. Ive been doing searches but can't figure out why. Is my best option to pickup a used link?
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Old 09-17-2008, 04:11 PM   #7
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yes, a used Link would be a great option.
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