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Why do I REALLY need larger injectors than 450s for a Big 16G?

Posted by 4gfun, Dec 25, 2007

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  1. 4gfun

    4gfun Supporting VIP

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    Just don't want to waste my money, and I am very curious about this since this is my second DSM.

    Both of my DSM's were/are alleged 12 second cars. I noticed that both of the previous owners ran 450 cc injectors on them.

    This all seems to be too much of a coincidence for me, it really does.


    In addition, I have read that Bushur had run 120 mph trap speeds on his DSM but turned up the Fuel Pressure.


    If I want to run 22 psi on the street on pump gas, is it REALLY a MUST that I upgrade my injectors?

    Thank you for your time.
     

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  2. TSiAWD666

    TSiAWD666 Freelancer

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    Yep.
     

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  3. RallyEclipse98

    RallyEclipse98 Proven Member

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    Not much bigger then. 550cc's would do just fine for pushing boost into the 20s.
     
  4. dsmmike50t

    dsmmike50t Proven Member

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    Brampton,
    As mentioned above you need injectors ,don't crank it to 22 you'll blow something. To run 22psi safely you'll need injectors and fuel pump. You also need something to compensate for the bigger injectors (safc) and a logger to monitor knock and timing so you can tune your car. Have you checked the link below.


    Tech Guide: 1G 4G63t Upgrades - DSMtuners


    Btw it clearly states "The stock fuel pump will not be able to supply the needed fuel for anything over 16psi of boost", and "If swapping in a 16G turbo, you can get away with 550cc injectors" on the link above.
     

    558  9

    1995 Mitsubishi Eclipse GSX
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  5. GVR4592

    GVR4592 Proven Member

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    Bellingham, Washington
    There are ways to get a little extra out of your fuel system.

    Upgrading the fuel line and filter setup from the factory filter to the fuel rail is a worthwhile upgrade. SteveTek Labs Research: High Flow Fuel Delivery System

    Rewire the fuel pump so it's getting full voltage and it will flow a little more.
    http://vfaq.com/mods/pump-relay.html

    Increase fuel pressure to get a little more out of the injectors.

    Use the SAFC to tune it all and you'll notice a drop in IDC.

    If you're using MMCD to log you should easily be able to see that your IDC is getting close to, or over, 100% if you run 22 psi on pump gas.

    I never saw the car that Buschur ran 120's in, but I heard it was with 550's not 450's. He probably had all of the upgrades I listed above, and he was probably using race gas. With race gas you can run a lot leaner A/F ratio's, which will lower IDC.

    I suggest you start increasing the boost and watch knock and IDC, you'll see how fast your injectors hit 100%.
     
    GVR4592

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  6. 4gfun

    4gfun Supporting VIP

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    Thanks for this link. I don't know if you saw my mods list, but I already have a fuel pump and an SAFC. What I am trying to say here is that I have already seen a few examples of fuel pump plus SAFC but 450s and heavy boost.

    Why is that? Maybe these guys were just ignorant or cheaper than me? Not sure on the Bushur story. Just curious.

    I am checking the link you provided. Thanks!
     

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  7. GVR4592

    GVR4592 Proven Member

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    They are most likely full of sh**. Just try turning up the boost a little bit at a time and watch your IDC closely. Don't listen to what anybody says (including me), just find out for yourself.
     
    GVR4592

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  8. 4gfun

    4gfun Supporting VIP

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    Thanks for this info. I went to log for the first time, but the battery died on my palm...LOL.

    Not sure if I mentioned it, but my fuel rail is upgraded as well.

    I am going to check my IDC out and then take things from there.

    What is the maximum IDC that I want to reasonably see?

    Also, how much could I bump my fuel pressure to get a little bit more out of my injectors?

    I am not asking any of you to be responsible for my engine. I just want to play around a little.

    On Buschur's car I can't verify what injectors were used either. I did a google search and saw that 1 time. It got me thinking about what the two previous owners of my DSM's seemed to have pulled off.
     

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  9. 95blackGsTurbo

    95blackGsTurbo DSM Wiseman

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    Bushur ran 120 with 550cc's not 450cc inj. Short of blowing your crap up you are going to need 550cc injectors. If you just have an SAFC then stick with 550's. Anything bigger and you should really upgrade to a Keydriver or DSMLink to compensate for the over sized injectors. If both of your DSM's were "alleged" 12 second cars on 450's then it must have been a high high 12 with no interior and lots of fuel pressure.
     
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  10. 4gfun

    4gfun Supporting VIP

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    Both had full interior, but I'd be fooling myself by saying anything more than that. :)

    Got you on Buschur's run. Thanks for filling me in.
     

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    awd · manual · Galant VR-4

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  11. GVR4592

    GVR4592 Proven Member

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    Before you play with the fuel pressure, make sure you have a good understanding of how to tune with the safc and datalogger. If you have that all figured out, then turn the base pressure up to somewhere around 50 psi and tune your low throttle settings before you do any WOT tuning.
     
    GVR4592

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  12. dsmmike50t

    dsmmike50t Proven Member

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    Here it is maxing out the 450's link below.

    BSFC of 0.60 and a duty cycle of 0.90OMG but its been done before, Daren peacock mentioned once how he maxed them out @ 107% injector duty cycle but he had the link and he knows his sh**.

    257 horsepower (crank) , so lets say 200whp

    Injector size calculator

    Below 80% is what everyone recomends I would stay below. Therefore, you're limited to around 260 crank hp.
     

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    1995 Mitsubishi Eclipse GSX
    manual · 2G DSM
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  13. 4gfun

    4gfun Supporting VIP

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    Thanks for all of the information folks. If I don't come back well then, LOL you know what happened. I'll be really careful with whatever I decide to do.

    I'll come back with a conclusion (once I get VERY comfortable with the methods of tuning you suggested)

    Happy holidays!
     

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  14. pneumo

    pneumo Proven Member

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    Thanks for the invite to your thread.

    When I ran the time in my profile I had 450cc injectors with 49psi fuel pressure at 22psi of boost. I got away with it because I was running 118 octane gas! The injectors still went over 100% duty cycle a little over 5k rpm and DC keeps climbing with rpm and tends to peak at the HP peak. I still saw a blip of knock at 5k, so that was the absolute limit.

    One of the odd things about these type of threads is that it's not always clear what gas (pump or race?) is being used. So if you read a thread where someone ran a good time at high boost and has small injectors, keep this in mind. The same thing goes for threads where a poster is maxing out big injectors at low boost, aka 'w.t.f. is wrong with the tune?' It might just be the gas. For example, I once had a 16g on my car with 720 injectors and hit 90%DC at 18psi of boost. Crap tune? Nope, 91craptane gas.

    The East Coast tuners can get away with slightly smaller injectors on pumpgas because they get 93 octane at the pump. And if anyone thinks that 93 isn't THAT much better than 91, just try this: Next time you're at the pump, instead of filling with 93 try filling with 91. :) Go ahead, reach for that nozzle, I dare you!
    Can't do it? I wouldn't either!
     

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  15. 4gfun

    4gfun Supporting VIP

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    Lol, sorry for not clarifying that I am running pump gas. Sunoco 93 + (possible 10% ethanol at the pump)....so possibly 94 octane?

    It looks like a real "yes" I need 550's, but I am going to find out for myself and watch the duty cycles.

    Thank you for responding to this thread.

    BTW, what happens if a duty cycle of 100% transpires? How is that possible anyways? Not saying it's not possible, I just don't understand it.
     

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  16. pneumo

    pneumo Proven Member

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    DC can go over 100% since the ecu only calculates the inj. pulsewidth needed for the given airflow and A/F ratio needed. In order to calculate DC you need to factor in rpm. The ecu doesn't look at rpm when calculating inj PW. DC is calculated in the logger, not the ecu.

    Running injectors near 100% DC can lead to leaner A/F ratios. Once the injectors are running over 100% DC they're held open 100% of the time and flow just like an open pipe with a small hole at the end.
     

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    1992 Eagle Talon TSi AWD
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  17. dnhieu

    dnhieu Proven Member

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    im surprised no one has said this. METH INJECTION. also, run 100% meth.
     

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    manual · 2G DSM
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  18. thekellbeast

    thekellbeast Proven Member

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    Or just run injectors properly sized for your setup. Run Meth injection if you want to push the boost past what the octane rating of your fuel would allow.
     
  19. dnhieu

    dnhieu Proven Member

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    octane, timing, and EXTRA FUEL it throws into the engine. meth injection has allowed me to get 23psi out of my 650cc injectors on a holset hx40. im sure he can run around 20 ish psi with stock injectors and a 16g with meth...
     

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  20. awesome_asim187

    awesome_asim187 Proven Member

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    Like I say, If you are doing something do it right, it's not worth the risk.
     
  21. 90laserRSfwd

    90laserRSfwd Proven Member

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    not trying to be mean here but seriously my fellow dsmtuner, brand new 550cc FIC injectors can be had for less then $300 with shipping and new injector seals... Are you really going to risk a $1,000+ engine over a set of $300 ($250 or less used) injectors? Please, please just buy some 550's. If I had an extra set I'd even loan them to ya...
     

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  22. dnhieu

    dnhieu Proven Member

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    you guys are over reacting. if he has ANY kid of data logger he will be fine. you can obviously see what your IDC's are and he should not have a problem. besides, a devils own meth injection kit is only 200 bucks and is the BEST mod i have ever done for my car!
     

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  23. 4gfun

    4gfun Supporting VIP

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    Ok everyone. Thank you for your time.

    I took some 2nd and 3rd gear runs last night up to redline. (Not sure if this was how I was supposed to do it).

    I would like to get my logs exported to my pc once I figure out how to do it. :)

    In the intermission, I would like to advise that (from at least what I could see) that duty cycle remained under 100% in 2nd gear, but went as high as like 176% in third??

    If this is TRULY the case (provided the information I looked at was accurate), I am wondering if 550's are enough for me and if they aren't enough, then why on earth wouldn't they be unless something else is wrong?

    BTW I checked the Fuel Pressure that the previous owner had it set at and it was as follows:

    57 psi with the vacuum line disconnected and 48 psi with the vacuum line in place.

    Waaaay off!

    I guess he was as cheap and defiant as me.
     

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  24. drewvr4

    drewvr4 Proven Member

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    550s will be enough
     

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  25. blcknspo0ln

    blcknspo0ln DSM Wiseman

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    Well for the obvious, IDC over 90% in any gear at WOT is not a good sign. Did you do that log with the crazy fuel pressure? I would adjust it back down to stock FP (37.5psi with line off) and do another log, just to see where IDC sits. As far as WI goes, I would definitely recommend getting a meth kit. I know i'll be getting one soon too. Either way, my personally suggestion would be to get the 550's or 660's first then get meth.

    For reference, back when I was running a e316G + 660's, I was getting ~85% IDC @ 23 psi with a walbro 255 and no AFPR.
     

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