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properly modding stock injectors

19K views 16 replies 6 participants last post by  ColoWRXer 
#1 ·
i have read the DIYs and will be attempting this mod myself. my question is about the benching and flow testing. first, i don't understand what bench testing is??? i will be sending the injectors to witchhunter but don't know what services to buy. if my injector flows are radically different what are my options? can they be fixed or will i have to buy some aftermarket ones?
 
#3 ·
i persoanlly would never try to do injector modding myself, that's too risky of a thing to F* up... i suppose if they are totally wack in flow, you could just give up and buy new aftermarket ones, or take the highest flow rating injector and get witch hunter to mod the rest to that flow...
 
#4 ·
The actual modding part is not hard. It is important to get them flow tested. If they do come out drastically different, some places will do matching. Other people send theirs in and they try to mix and match using the flow rates.

Although modded injectors are a great way to save cash and still get the proper performance, I should note the downsides. Some tuners refuse to tune modded injectors. No idea why, but that's their choice. You'll more than likely throw a few CELs including misfires. Nothing to be majorly concerned about. Basically, the injectors are now so large, the interval of time the need to stay open during idle is so small that they sometimes don't even open at all. You may also experience a worse idle. Most never really notice it.

And yes, I am running modded injectors. They were modded and flow tested at PDXtuning.
 
#10 ·
Although modded injectors are a great way to save cash and still get the proper performance, I should note the downsides. Some tuners refuse to tune modded injectors. No idea why, but that's their choice. You'll more than likely throw a few CELs including misfires. Nothing to be majorly concerned about. Basically, the injectors are now so large, the interval of time the need to stay open during idle is so small that they sometimes don't even open at all. You may also experience a worse idle. Most never really notice it.
This is only true depending on the size of the turbo you are using.The bigger the turbo,the less of a problem you will have.Don't know why tuners don't want to use them considering they don't have to play with injector latency.The only complication could be proper fuel atomization.That is what the purpose of the disk/cap is,to help atomize the fuel as it comes out of the injector.
 
#6 ·
thanks for the replies. i should have added that i am doing this mod to go up to an 18g w/ supporting mods and get tuned. already asked my tuner about it and he had no problem with it.

i'm not worried about screwing it up, i'm surprised at what i've been able to do modding things and like vew said, it doesn't seem too tough. i'll just have to take my time and be careful. if i can do it myself it will cost far less than the $150 pdx charges.

you say i'll probably throw cels and may misfire??? and also say it's not a big deal? i've read a lot about this mod but never read that. i suppose if it is do to the fact that the injectors are so large this would happen to any aftermarket large injector right?

i know sti pinks are too small for an 18g so is there no way to avoid possible misfires and a rough idle? thanks for the info vew and i'm glad to know you are running them regardless.
 
#14 ·
Better atomization = better performance.I think it was either Tim Bailey or Clark Turner that said the modded injectors work great but any other injectors (Sard,PE) flowing the same rate seem to constantly make more power.This would be due to that they use a diffuser cap in place and have better fuel atomization/spray pattern.
 
#15 ·
great, well now i seem to have an understanding for this whole thing. i think i can sacrifice a little bit of power to save a few hundred bucks, atleast for now.....say i modded mine, they were flow tested and turned out to be around 850cc. then i got tuned. could i then buy some aftermarket 850cc injectors with diffusor caps later on and just install them? or would i have to get tuned for them?
 
#16 ·
You would have to be retuned more than likely.One,different manufacturer injectors have different latency values and better fuel atomization = better burn = leaner AFR(possibly).Cobb has an injector calibration worksheet on thier forums with most of the major manufacturers and their latency values.
 
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