i have a 03 evo with HKS cam gears, hks 272 cams, FMIC, Ic piping, HKS tbe, intake, mbc, and a utec.....and i'm in the process of getting tuned for the first time, so my question is what is a good size injector i should buy before getting tuned? The thing is i dont want to hit up the dyno and them tell me i need other required mods to be able to get the best possible tune. Will i need bigger size injectors? do i need a upgraded fuel rail and fuel pressure regulator? Thanks for any help.

 

just upgrade to 680's stock fuel rail.

you get a FPR and a fuel rail when you hit the 550 and up mark becasue you would have got to the max out point with stock fuel lines and so on.


I got 850's with a fuel rail on stock turbo its very hard to get the car to start at idle right and if it's not tuned right you wont have that great of a mpg .

 

The correct answer is NONE.

You will not reach the practical limit of the factory injectors with your present mods, and there is nothing to be gained by buying larger injectors at this time. What you should do at this time however is upgrade your factory fuel pump to a Walbro 255 lph high pressure unit.

 

I dont know about that answer^^ I have very minimal mods and was at 93% injector duty cycle and the car went lean and I got some serious detonation. I would say with those mods. Yes. Bigger fuel pump and larger injectors.

 

If your car was running lean with those minimal mods, it wasn't due to a fault with the injectors. The factory injectors are absolutely, unquestionably fine for your mods and more.

The fault was with your AEM EMS. The AEM EMS is the reason why your car ran lean prematurely. The AEM EMS is configured for a low performance (high impedance) injector. The EVO comes equipped with a high performance injector (low impedance). As a result, the AEM EMS cannot control a low impedance injector properly. This is why AEM users either have to use a larger injector (the band-aid fix) or spend another $300 for AEM's low impedance driver pack.

This is why if you use an AEM EMS and do NOT have the additional driver pack, you will always need a larger injector than anyone not running an AEM EMS.

FYI

 

I stand corrected. Although, the car ran fine for weeks until the incedent happened..I still dont believe that explained my sudden lean condition that occurred. But I now understand why my duty cycle was so high.

 

With the mods you have, here is nothing to be gained by going with larger injectors. A fuel pump would be a better mod.

 

Definitely fuel pump, but lots of peoplle reach 90-99% IDC on 272s, TBE, FMIC, and a tune. Why does Buschur make 680s part of stage 4? Every car is different and I hit 99% before I built my motor and added a FMIC and 50 Trim. If you do injectors, get at least 780 if you ever plan on adding a new turbo (even a 20G).

 

Thx everyone fo ryour insights, I forgot to mention i do have a walbro 255 not in yet but will definatley be in before i get tuned. But why the different opinions on the fpr and fuel rail is needed? why do some ppl say 500hp you need it and some say with these current mods they'll be needed?

Anyways thx for the advice/help.

 

You do NOT need a new fuel rail or fuel pressure regulator, PERIOD. Even if you made 500whp (and you won't make anything close to that), you still do not need them.

 

Wow buddy...lol...tone down on that aggresion of yours...i wasnt sayin i was gonna make 500whp....just askin when you hit that mark...WHY do some ppl say you need it and others say you dont? But i guess thanks for the info anyways.

 

No aggression intended.

As to why some people say certain things is because like parrots, they only repeat hearsay, for better or worse, without any solid reasoning and/or experience being offered in support. There is plenty of advice being given in this and similar forums. While much of it is generally good, a fair amount of it is inaccurate and/or baseless. If you stick around long enough, you'll eventually be able to do a fairly good job of separating the wheat from the chaff.

 

Because if one does the math, the factory injectors are approaching their practical limit around the 400bhp mark. Any car realistically expected to generate 370+whp (DJ numbers) on gasoline only is a candidate for an injector upgrade.