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  #1  
Old 23-01-2008, 06:21 PM
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Default Decapped injectors

I done a search for this and didnt find what I was looking for, so either its not here, or Im blind

Question is, Im trying to decide on to decap my injectors or buy 2nd hand STi injectors for my car (Ill be installing a VF43 turbo & TMIC upgraded of course) into a MY02 WRX

With the decaps, does that change the amount of fuel used while the car is cruising as opposed to how much putting the STi injectors would while cruising?

So, basically, would there be any fuel usage difference between decaps and STi injectors if they had the same mods done on the car? (tuned of course)

Im leaning towards decaps at the moment, unless someone has some tragic stories to tell (was going to get ASG to decap them)
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Old 23-01-2008, 06:23 PM
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decaps or standard injectors will use identicle amounts of fuel if tuned for.

all it means is you injector duty moves from 50% with 550cc injectors to 35% (thereabouts) with 816cc injectors...
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Old 23-01-2008, 06:23 PM
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Decaps flow at 816cc, the STi injectors flow at 550cc. So yes a decapped injector will probably use slightly more fuel.

When I first swapped over to decaps with the TD04 I still kept basically the same fuel efficiency (~500km per tank). But, of course when I flog the tits out of it on a track day, it uses more fuel.
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Old 23-01-2008, 06:24 PM
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Once the ECU has been tuned for the decaps, your cruise economy wont be changed. Might be better with a good tune. You just end up running lower duty cycles.
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Old 23-01-2008, 09:13 PM
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Thanks for the help
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Old 23-01-2008, 09:26 PM
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Out of interest mate (if you don't mind me asking) what's it worth to have your injectors decaped all up (Labour & parts)....
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Old 23-01-2008, 09:34 PM
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abouts $400 I believe
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Old 23-01-2008, 10:33 PM
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Less $ than that.

No, it won't change fuel economy - That's all in your tune.
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Old 24-01-2008, 10:24 PM
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Dont know if this is relevent but I will add anyway.I have some old side feeds from a EJ22 (red ones) and while messing about with this and that, I decided to pull apart the injector. I removed the plastic cap and underneath was a thin metal plate with 3 or 4 holes in it, I then grabbed my side cutters and literally peeled off the plate and was left with a single hole.
If this is what decapping is then $400.00 dollars is a bit much.
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Old 24-01-2008, 10:30 PM
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Lol, youll be left with useless injectors if you do that. Grind it off.

Decapping still leaves the same 3/4 holes in the injector AFAIK.

Edit: For reference:

http://forums.nasioc.com/forums/showthread.php?t=478921

http://www.perth-wrx.com/vb/showthre...ighlight=decap
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Last edited by vyper; 24-01-2008 at 10:36 PM.
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