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Old 12-11-2013, 03:25 PM   #1
90R
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Default do I really need bigger injectors?

I'm having a hard time seeing how.
It's a 1.6 @ 15psi, on MS1. Currently there are 550cc RC EV1 style injectors in the car. My last datalog of a 3rd gear pull to 7500 showed the DC at 98% with an AFR of 11.7 @ 192kpa. DC crossed 80% around 170kpa. This is a 40psi system.

Is this tuning or hardware issue?
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Last edited by 90R; 12-11-2013 at 03:48 PM.
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Old 12-11-2013, 04:34 PM   #2
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No idea how useless and potentially devastating this advise will be, but I've been in the exact same situation and just ignored it. My first miata ran RC550 injectors on a MS1, I didn't really pay much attention to injector duty because I knew I had plenty of headroom. When I was going through a log I noticed it recorded over 100% duty cycle. I asked about it on the forum at the time, but never really got a clear cut answer. I just ran it like that until I ended up parting the car out and never had any issues.

I just kept a close eye on AFR's and on my fuel map. I never saw the upper right of my fuel map increasing abnormally in an attempt to compensate for the injectors being too small so I just kind of ignored it.

Here's the thread I made at the time: https://www.miataturbo.net/megasquir...y-cycle-35394/
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Old 12-11-2013, 04:34 PM   #3
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Quote:
Originally Posted by 90R View Post
I'm having a hard time seeing how.
It's a 1.6 @ 15psi, on MS1. Currently there are 550cc RC EV1 style injectors in the car. My last datalog of a 3rd gear pull to 7500 showed the DC at 98% with an AFR of 11.7 @ 192kpa. DC crossed 80% around 170kpa. This is a 40psi system.

Is this tuning or hardware issue?
found the problem

another thing to keep in mind is that the ecu calculates idc based on what you tell it about the injectors its running
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Old 12-11-2013, 04:36 PM   #4
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15psi on what turbo, exactly? Shitty old injectors or not, i can't think of any reason why a sane-sized turbo on a 1.6 @ 15psi would result in enough power that you'd max out 550cc injectors.
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Old 12-11-2013, 04:41 PM   #5
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Quote:
Originally Posted by concealer404 View Post
15psi on what turbo, exactly? Shitty old injectors or not, i can't think of any reason why a sane-sized turbo on a 1.6 @ 15psi would result in enough power that you'd max out 550cc injectors.
It's a VJ11 turbine bolted to a VF30 compressor.
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Old 12-11-2013, 04:42 PM   #6
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I mean... i'm never one to say "Oh no, don't buy some modern EV14 injectors, upgrades SUCK!" but there's no reason why you should be maxing those injectors out.
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Old 12-11-2013, 04:47 PM   #7
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Quote:
Originally Posted by concealer404 View Post
I mean... i'm never one to say "Oh no, don't buy some modern EV14 injectors, upgrades SUCK!" but there's no reason why you should be maxing those injectors out.
The cost of set of injectors could be better spent on tires!

That's why I'm asking. I know it's a tiny turbo and should only be 200-ish. So I'm confused why I'm getting this DC
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Old 12-11-2013, 04:49 PM   #8
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Hard to tell without knowing how it's tuned. Is your fuel pump healthy?
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Old 12-11-2013, 05:03 PM   #9
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Fuel pump is good, the filters been replaced.
Heres the latest msq. It's fat up top. But when I run VE analyze. It's pulling fuel if I get up there.

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Old 12-11-2013, 05:06 PM   #10
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Quote:
Originally Posted by 18psi View Post
another thing to keep in mind is that the ecu calculates idc based on what you tell it about the injectors its running
isn't that info taken from the REQFUEL info?
I know thats correct.
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