Running 10-12psi are 550cc inj. overkill and will idle be better with 4XX's ? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 03-09-2010, 02:15 PM   #1
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Default Running 10-12psi are 550cc inj. overkill and will idle be better with 4XX's ?

2002 car - going to run 10psi and maybe even 12 but probably not.



As I learn more about FI and injectors I wonder if I need the 550's that came with my XEDE? My calculations say that 460's or 440's should be ok.

Will I get better idle with a smaller injector?

If it matters I am in a cold climate and will see -15 to -30c for 2 months so very cold starts are the norm in winter if that plays into the injector size.




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Old 03-09-2010, 02:21 PM   #2
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headroom is win.
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Old 03-09-2010, 02:23 PM   #3
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I'm 5 11 so I fit ok even with the hard top.
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Old 03-09-2010, 02:25 PM   #4
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I had to.

But yes I see what your saying - I still thought that idle gets a little compramised
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Old 03-09-2010, 02:25 PM   #5
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I ran 460s for a year, and when I wanted to step up it was a bitch finding 550s.
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Old 03-09-2010, 02:26 PM   #6
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Is there a gas mileage penalty of using 550's over 460's?
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Old 03-09-2010, 02:27 PM   #7
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Quote:
Originally Posted by Landrew View Post
I'm 5 11 so I fit ok even with the hard top.
Context clue fail.


Go with the 550s.
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Old 03-09-2010, 02:31 PM   #8
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It sounds like you already have the 550's in the car. Is the idle that annoying? If it's pissing you off and detracting from enjoying the car go ahead and do the swap.
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Old 03-09-2010, 02:32 PM   #9
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Quote:
Originally Posted by vw_nut View Post
Is there a gas mileage penalty of using 550's over 460's?
for you, yes. For most of us, no.
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Old 03-09-2010, 02:33 PM   #10
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I'll trade my 460s if you dont want those 550s
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Old 03-09-2010, 03:55 PM   #11
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Quote:
Originally Posted by Landrew View Post
I had to.

But yes I see what your saying - I still thought that idle gets a little compramised

Quote:
Originally Posted by Bryce View Post
Context clue fail.


Go with the 550s.

Reading comprehension fail X2.
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Old 03-09-2010, 03:59 PM   #12
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I actually don't have them in the car yet, so I am making assumptions but I had read here and there that you don't want too big of an injector. I am in the final stages of gathering the last bits of my setup and was about to send these off for a cleaning by Deatschwerks. I thought a final question about their place in my build goals would now be the appropriate time to ask.
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Old 03-09-2010, 04:12 PM   #13
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Quote:
Originally Posted by Landrew View Post
Reading comprehension fail X2.
I opened the thread before you made that post. I was gonna quote the dictionary for head room. Taking too long to reply fail!
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Old 03-09-2010, 04:12 PM   #14
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This is just my noob understanding: But it doesnt matter if you have 1000cc injectors. If you tune it properly to have the correct fuel output, then it doesnt matter how big the injectors are.

Correct?
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Old 03-09-2010, 04:13 PM   #15
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Quote:
Originally Posted by Landrew View Post
Reading comprehension fail X2.
I opened the thread before you made that post. I was gonna quote the dictionary for head room. But after all was said and done, several more posts had been made. Taking too long to reply fail!
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Old 03-09-2010, 04:17 PM   #16
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Quote:
Originally Posted by Landrew View Post
I am in the final stages of gathering the last bits of my setup and was about to send these off for a cleaning by Deatschwerks.

Landrew..you are in Edmonton correct? Fuel Injection Plus in the southside of Edmonton, I heard does top notch work according to the local car enthusiast forums..I'm sending my RX7 RC 550cc's to them soon. Would be quicker and save you on shipping and time.
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Old 03-09-2010, 04:18 PM   #17
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That happens so often, you go to reply, think about what you want to say and how to say it, make some spelling changes and then post 7 min later forgetting that the thread and the world does not go on hold while you are making up a post.

No worries.

This site drives people to make open remarks about all our shortcomings and mistakes - sometimes its fun, sometimes people cry themselves to sleep, doesn't sound like you are the latter.
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Old 03-09-2010, 04:26 PM   #18
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Quote:
Originally Posted by Landrew View Post
I actually don't have them in the car yet, so I am making assumptions.

Ah. The first post sounded to me like they were already in and not idling well.

Stick with the 550's. At this point you're trying to fix problems that may not exist. No need to 2nd guess yourself. 550's are popular, common and proven to work fine.
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Old 03-09-2010, 04:26 PM   #19
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Thanks

Hmm, I'll look into it. What do they charge per injector and I wonder if they are as good as other places.
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Old 03-09-2010, 04:30 PM   #20
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I called them up for prices in November of 2009. They said something about at the most is 30 per injector I believe. That includes the initial and after flow testing. I have an acquaintance that drove a yellow turboed crx and he recommended the place to me. It seems thats where most guys in Edmonton go to as well.

Heres a quick google. Fuel Injection Plus - Google Maps

If you are in need of a T25 off of a S13 SR20DET (Equiv. to a Garret 2554, but journal instead of ball bearing)..Let me know! I just got my hands on a T28.
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