fuel injectors + rail??

for the guys who have bought new injectors, did you have to buy a fuel rail too? i know they're supposed to support something like 115psig stock but if i'm getting something in the neighbourhood of 350-400cc injectors and aiming for 200-220whp (with the ka-t), will i need a new fuel rail?? and are 350-400cc injectors too big? should i go smaller since i know i won't be going over 250whp?? or does it go by crank hp?? lots a questions, feel free to answer bit by bit..

for the guys who have bought new injectors, did you have to buy a fuel rail too? i know they're supposed to support something like 115psig stock but if i'm getting something in the neighbourhood of 350-400cc injectors and aiming for 200-220whp (with the ka-t), will i need a new fuel rail?? and are 350-400cc injectors too big? should i go smaller since i know i won't be going over 250whp?? or does it go by crank hp?? lots a questions, feel free to answer bit by bit..


115 is way too high. stock is 45ish and almost all injectors start to act up above 60. Since im pretty sure SR injectors will fit Id say go with OEM S15 444cc injectors They're good till about 350ish. A new fuel rail wont be nessicary.

cool, thanks man

you might want to consider going a bit larger for your injectors. if you're only planning on making a little over 250hp, i would buy much larger injectors, especially since you'll want more than 250 (i know i do)
before i purchased mine, my goals suggested i would only need 550s, but 680s were the same price... so...

which ones did you buy and how much were they?

i bought pte 680s and got them for 315. i'm not sure that we use the same injectors... i can never remember if dsm are hi or lo impedence
what's quite humorous though, i won't need injectors that big until i get a new turbo; that will take a while because i'm planning to get a fmic and intake manifold first

SR20DET 370cc injectors. A dime a dozen and a direct swap to the KA24DE fuel rail. Your MAFS will max out before they will. I believe the stock MAFS is good to aobut 250WHP and the injectors are good until about 280WHP. The 440cc's will obviously support more but I don't know how much more. Probably a little harder to comeby and a little more expensive. You can buy Nismo sidefeeds in 550cc's and they swap right to the stock fuel rail. I believe they actually flow 615cc. Ask Tat about that one.

Now what are you talking about with the 115psig? The point in buying larger injectors is so you don't have to crank up fuel pressure to support horsepower. There are two ways of increasing fuel supply:
1) Add more pressure behind the injector
2) Increase the pulsewidth of the injector(make it stay open longer)

Now 270cc only flow that much because if the pulsewidth is opened any longer, the injector will freeze up. That means it just stays open and dumps fuel. Now if you just increase the fuel pressure, the injector is forced to flow more fuel through each opening of the injector. Its not really as bad of a way to increase fuel as everyone says it is. I use one on my 6psi setup and it works great. Plugs are tan, narrowband reads rich, no detonation, and compression is fine after 1100 miles of pretty hard driving and testing. Another thing you may want to consider if you upgrade injectors and buy a piggyback is that the factory ECU is going slowly put you back into the stock closed loop fuel maps. It will work as promised in open loop(WOT), but you'll see it correct the fuel settings at part throttle. What I'm saying is one day at part throttle, you could just go to factory settings and lean out. Especially if you plan on drifting. I would suggest a wideband if you go that route. Another thing is if you start messing with MAFS voltage, you start messing with timing maps.

thanks for all that nissanfanatic.. i'm actually getting a z32 mafs for $40USD and the kit to install it for about $110USD so i'm gonna put new injectors in after that and then have my fuel remapped. i'm guessing i'll have to have the timing retarded a bit too though..should i be considering a SAFC after all this??

Thats what I'm saying about the SAFC. It controlls fuel well in open-loop, but closed-loop is a completely different game. The factory ECU uses the stock O2 sensor to adjust fuel and it tunes for 14.7. So if you use something that will make boost at part-throttle, you will be running 14.7AF's under boost. You'll have a KA-boom one day. It doesn't happen overnight or anything, but slowly the factory settings take over. A JWT 370cc tune should be fine. The JWT ECU may actually take care of timing for you so ask them if you call. You will have to send them your injectors so they can test-flow them.

its also good to go alittle bigger becuase trust me, you'll never have enough power. its better to spend the money one time, then to spend it over and over again.

i know a guy who is selling is 480cc side feed injectors off his KA-T those 480's came off a S15 originally. his car made 280whp with the 480cc and was still running pig rich.

if you want to know the price i can call him up whenever you want. just let me know

also about the part throttle on the safc

there are 2 throttle settings and 2 curves that you gotta put in when you tune a SAFC.

there will be a low throttle % and a high throttle %.

lets use my settings for an example. my low throttle is set at 35% and my high throttle is set at 65%.

now what this means is that whenever my throttle is below 35% its considered low throttle, so this will use the low throttle fuel map that i inputed which is around -18% all around.

when i hit 65-100% throttle, that will tell the SAFC to switch over to the high throttle fuel map that i have set ( which i forgot )

anything inbetween the SAFC will calculate the average curve between high and low for the mid throttle position ( between 35-65% throttle )

thanks tat.. but some of that is greek to me, but i saved it on my computer for future reference.. are safc's car specific? would i have to get one for the 240?
and don't worry about the injectors.. i have to wait for my credit card to be cleared and i won't have the money to do that for another couple of weeks.. i'll let you know or i'll just find some on ebay.
another thing, is there any difference between side feed and top feed?? besides aesthetics??
one problem i feel as though i might run into is running lean after adding injectors and a fuel pump (looking for one on ebay, shouldn't be more than $100).. if i DON'T get the safc, will running lean be an issue? or is that circumstantial?? i'm gonna get my compression done soon and i'll let you guys know what it is
thanks again

getting a more powerful fuel pump and bigger injectors won't make you lean, it will make you rich... which won't cause your engine to predetonate

No, it won't because the ECU is still sending the same emount of fuel, it's just that the injectors and pump will be at like 20% efficiency instead of 70% or whatever it is stock.

ok i see.. i think i meant rich instead of lean.. i went ahead and bought a Walbro 255LPH fuel pump tonight so that should be here in a few days and i'll throw it in next week when it gets warm again.. but for the injectors, i found thesehttp://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7944962593&category=33742&sspagename=WDVW.. how reliable would this be?? these are the only ones i've seen in a long time.. they're the only ones on ebay that i can find!! if these aren't reliable then where do you guys think i should get them? i know phatka-t.com sells a whole fuel system but i don't think i need everything in it.. and i don't know how to convert the lbs to ccs on boostdesigns.com..HELP!!

edit: there are 2 other sets. what do you guys think?? i'm asking cause i have little ebay experience http://search.ebay.ca/sr20det-injectors_W0QQmaxrecordsreturnedZ300QQsorecordsper pageZ50

Nope. If you just add injectors, you will run pretty rich in open loop. IIRC closed loop(part throttle) the ECU will correct it based upon 02 sensor readings, but in open loop, it is the factory fuel map which is pretty rich with stock injectors so you can imagine what its like with 370cc. The only possible, stupid thing I could think of would be to make about 280whp maxxing the injectors out. But the thing is you need to control them everywhere from spool on. SAFCs are not car specific unless you get a V-AFC which is for V-Tec engines. I believe top feeds flow a little better than side feeds, but the main thing is that most of your top of the line, high power injectors are top feed, like the MSDs. You usually get a higher volume rail with top feed rails. Stick with the stocker for now. There are plenty of fuel injectors avaliable for the stock fuel rail. Plus every side feed set for the SR already fits it.:)

And don't worry about converting lb to cc, generally the number of lbX10 is the number of HP the injectors will support.:) Well it is a roundabout anyway. So 50lb injectors are capable of supporting approx. 500hp. Not a good idea though, so most people go with 72lb. Good luck.

i don't think a 02 sensor will be able to correct the amount of fuel enough for larger injectors even if it is in closed loop mode. you have to remember that the ecu has no clue that the injectors are X % larger then stock. when the 02 sensor sees a rich reading, it will lean out the larger injectors the amount it would if it was a stock injector. which means it will not lean it out anywhere near as much. if you try to run my car with the SAFC off, even in closed loop, the engine is bogging, and blowing up tons of black smoke from running rich. the ECU compensate for alittle, but its not a miracle worker, it can't make big things happen with so little.

so i should be getting a safc before i drive my car with the new injectors and fuel pump?

I'm pretty sure that Ivan was saying that over a certian period of time, the factory ECU will take over and the injectors will lean out in part throttle. That was the problem with using piggy-backs. No problems in open loop, but in closed loop, the ECU will eventually lean it out to factory "stoich" level. I don't think the ECU needs to know what size injectors you're running to lean them out. It just senses a rich condition and takes the pulsewidth down until stoich. But on the AF guage, its jumping around constantly. I have a narrowband so it goes between about 13-16 in closed loop. If it did know, the AF wouldn't jump around. It would just use TP to judge what PW to run.

Don't use what I'm saying as inspiration for not getting a fuel controller. I'm saying that in time it will correct closed loop. Get a fuel controller if you get bigger injectors. No question about it.

ok i get it..i guessthe safc will come right before the turbo!!

BTW GO CANADA GO

(for those of you who live under rocks, they play russia in the finals of the world junior hockey championship tonight!!)

Did they win? I was at work all night........ :-((

i live an hour south of grand forks... and i didn't know :p

GO RUSSIA GO!!!!!!!!!!!!!!!!!!!!!!!
With larger injectors, E-manage should fix the problem. (MAF Too)

WE WON WE WON!!!!!! 6-1!!!!!!! WE CREAMED THE RUSKIES!!!!!!!!!!!!!!!!!!! YYAAAAAHHHOOOOOOOO!!!!!.....ok, I'm done...

well if ivan said it, then i guess its definitly a possibility. but i've been running my piggy back for over a year and i've never had the thing lean out on me in closed loop.

I think the problem occurs with the really small turbos. Mine won't spool until I press the throttle about half-way to the floor. Thats past 3500 too. I suppose if you had a really small one, like a T25, it would spool if you tapped the gas. So essentially, it may spool in closed loop. Then the ECU tries to create a 14.7 AF in boost and KA-BOOM.

I think a RRFPR, 370s, and a SAFC is the way to go.

i guess thats why big turbo owns you. however as i said, i guess you can prevent that from happening by changing the low and hi throttle settlings. if the turbo becomes that responsive, just make the high throttle in like 25% and it should be good.

can one of you explain open and closed loop a little better? i know one is at low rpm and the other is high but thats it.. is it in the ecu??

Closed loop is low throttle cruising. If you had an air/fuel guage, you would see that the ECU is trying to get a 14.7AF. Open loop is hard acceleration. The ECU riches out the mixture to be safe. I think it disreagards O2 sensor readings at this time. Pretty sure it just uses MAFS voltage to determine how much fuel to dump. These are just names of different fuel maps in the ECU.

its just a different type of operating mode that the car runs in.

closed loop is short for closed feedback loop mode. what this means is that this mode will come on when it reaches over 600 degrees in the exhuast. this is usually when hte 02 sensor will start to work. the 02 sensor will send out a signal from the amount of oxygen it has in the exhuast and the computer will try to keep the car is stoichimeteric a/f ratio ( 14.7:1) however the 02 sensor is not the only input that the ecu receives. it also takes signals from the mass air flow meter, air intake temp sensor, crank angle sensor, knock sensor ( if its knocking ), throttle position sensor etc.

however when you go into wide open throttle, the ECU will disreguard the 02 sensor signal since its no longer tryin to keep it in stoich and its more towards performance. it will take inputs from all of the above sensors to determine how much fuel to dump into the engine.

the car is stoichimeteric a/f ratio ( 14.7:1)

man tat big word there buddie, english please.. lol j/k

:cwm27:

just means the difference in air/fuel and exhaust.. its basically a word for a chemical reaction

14.7 units of air + 1 unit of gas = the most efficient exhaust gas