TommiM

iTrader: (19)

So I've been reading and researching trying to gather information on pros and cons of high impedance and low impedance injectors. After reading Im still undecided as to which will be best suited for me. I understand that high impedance injectors are pricier than a low impedance equivalent. From what Ive gathered, it seems that high impedance injectors are supposed to produce better driveability and behave better at increased fuel demands, but at lower IDC don't lower impedance injectors perform better?.

I might be considering going E85, so compatibility is important. The new high z doesn't state whether or not its E85 compatible but the other one does. Last question is really more just trying to get everyones input on which one of these would you recommend and why.

The injectors I have seem to narrow down to are the new FIC low impedance 1120cc injectors.. http://www.maperformance.com/fuel-in...s126-1120.html

and the FIC high z 1050cc SP .... http://www.maperformance.com/fic-inj...6-1050hsp.html

Im getting injectors to be tuned on these mods so this is why Im trying to decide on which injectors I need. A few tuners out in this area seem to like RC injectors. I know to go with what tuners like, but these seem to be old school compared to whats available now. Also, FIC being ball and seat seem to be better than RC's pintle style from what Ive gathered as well.


Heres my list of mods, fwiw.

MAP stage 1 head (no port work), standard size valves, ss intake/Inconel exhaust
Tomei 270 cams 10.7/10.2 lift
BC springs titanium retainers
evo 9 turbo
buschur ported oem exh manifold
Titek O2
RRE 3"dp
oem cat
HKS sport 3" catback
ETS licp
ARC intercooler
ETS uicp
walboro 255lph

Fast_Freddie

iTrader: (50)

To be honest with those mods you would be fine on a low-z injector...

Plus you dont have to bypass the resistor box and alk that...

TommiM

iTrader: (19)

edit..

after more reading up, think Im gonna do the low z 1120cc FIC injectors. Thanks for the reply

Ted B

iTrader: (6)

To give the Cliff notes ...

- Hi-Z injectors are traditionally too slow for high performance use.

- Lo-Z injectors are faster, and are intended for high performance and racing, where larger capacity injectors and shorter pulsewidths are required.

- The newer Bosch EV4 style injectors represent a new generation of Hi-Z injector that is fast enough for high performance use.

- Pintle style injectors are slower than ball and seat type due to the greater mass of the pintle mechanism.

- Pintle style injectors should be avoided if E85 is used. The residues sometimes precipitated from E85 can foul pintle injectors to the point whereby they cause a cylinder to run lean, resulting in engine damage. More than one member here has experienced this. Ball types are comparatively unaffected by E85.

I hope this helps.

TommiM

iTrader: (19)

that answered pretty much what I was wanting to know. Thanks TedB.

mrfred

iTrader: (50)

Unless you are planning to run E85, that's an unneccessarily large injector for your mod list. For your mods on pump gas, a 700 cc/min injector would be fine. One challenge with bigger injectors is maintaining good drivability. An 1100 cc/min injector can idle and drive well on pump gas, but it takes a little more work than a 700 cc/min injector. When I was running FIC 1050s on pump gas, they idled pretty well, but I could tell that it was not quite as good as the stock injectors.

However, if you are set on an 1100 cc/min injector, one area where the new breed of high Z injectors shine is at idle and cruise conditions. The Bosch high Z injectors have a tighter tolerance on the performance characteristics, so the variation in performance from one injector to the next is smaller. In addition, removing the resistor pack also reduces cylinder-to-cylinder fuelling differences because the resistor pack has four resistors, and there is some variability in resistance among the four resistors. Eliminating the resistor pack eliminates an extra source of fuelling variability.

kikiturbo

also, resistor pack removal is super easy and can be done with a plug and play connector.. no need to cut anything..

TommiM

iTrader: (19)

the post I edited was asking that very thing MrFred was stating. At my mods I do agree that doing the math a 700cc injector should be plenty for my mods. Yet, 3 shops I asked out here, 2 in socal, 1 in Norcal are recommending 1000cc,1050,etc injectors. I figure they must know something I dont, to be honest the tuning/fueling aspect of our evos is still on the more unfamiliar territory to me so thats why Im asking all these questions.

I do plan to eventually do a dual map for E85/ pump gas. I plan to swap out my fuel pump for one that is better compatible for E85 fuels as well when I do so. The issue is I would like to not have to buy injectors twice, meaning buy 700cc now and then buy a 1120cc later in a few months or year from now.

It seems that what Ted B wrote and what MrFred wrote seem to be contradicting. removing a resistor pack isnt an issue, the issue is whether or not I can benefit from that setup.

The car right now is gonna be doing mostly street/commuting me to work and weekend drives through the mountains. The wife wont be too happy I take it to the track just yet as I dumped quite a bit of funds to get it running as it is from the last track failure. Plus ive been a bit too busy to be able to go to track days just yet anyhow. that is another reason Im holding off from going E85. If Im just gonna be commuting no point doing that just yet.

I would ideally like to go like a 700-780cc size FIC injector. but like I said when I tell most tuners about my mods and wanting a pump gas tune, they have all recommended 1000cc to me, which seems overkill. Thanks everyone for the advice, its been helpful.

TommiM

iTrader: (19)

Its these details about the characteristics of these injectors that I hadnt known. idle and cruise characeteristics are just as important and want to have the correct injectors to maximize the best idle and yet supply the needed fuel for my setup.

kikiturbo

I have the same "problem " as you do... I need a bit bigger injectors for a slightly larger turbo, mostly for street but also some track work.. What I have seen is that people can map correctly the larger injectors with no problems... so I went with high impedance ASNU injectors 1000 cc.. while in reality I could have gone for 800 CC..

TheBoz

iTrader: (9)

Fic 1050sp and call it done. They are good to mid 400's on e85. More if you up the bfp. So really it comes down to fuel type and hp goals. For me under 500 1050sp over 500 2150. Also iD has a new 1300cc injector out.

TommiM

iTrader: (19)

Ya. Im just trying to figure out which is the better route to go. Its sort of like asking what turbo that will make you 350 hp. FPgreen can get you there, but hell so can a FP Black. One is just more overkill. Im just trying to get an understanding of why so many shops are recommending what I feel is an overkill size of an injector. Im asking on here to make sure Im not missing something because I would assume a 750cc should be plenty.

Here's another question. With everything tuned and dialed in, will 750cc injectors in general idle better than a 1120cc injector?

Ted B

iTrader: (6)

The logic with sizing injectors is no different than the logic for selecting a turbo. With a realistic power goal in mind, take the smallest size that will comfortably get you there.

TommiM

iTrader: (19)

Im thinking that realistic power goals are maybe 310-330ish awhp, 91 pump gas. Although, I don't really know what type of numbers these new round of mods will net me honestly. Im just looking for an injector that will get me what I need without over working it running high IDC or on the other side of it, using an injector that's way overkill.

Ted B

iTrader: (6)

In that case, as mrfred pointed out, a 700-750cc/min injector will get you there, with room for more, and will deliver factory-like driving qualities.