740 or 550 fast answer!

[sr20detconv]

I have hard time deciding between nismo 555cc's or 740cc's.The thing is that they are the same price.Is their a downside of 740's with ROM tune like bad idle,hard to tune,etc?I'm not planning to run standalone or safc so it's concerning 740's with ROM tune.
I don't think I will putting more than 340whp but if their is no downside for 740's I don't see any reason not to buy them for any futur upgrade.
Sorry for my bad english.
PS:I did search but did not found a really clear answer.

[eastcoastS14]

what turbo are you using?

[Dousan_PG]

get the 740s

[Nikeboy355]

740s... There is no downside...

[sr20detconv]

using a gt2560r at the moment @17-18psi.So my tuner wont tell me that they are to big and hard to tune.No reason for bad idle or such things?

[Dousan_PG]

i have a great idle w/ the big injectors
depends on your tune

[sr20detconv]

Do you have a ROM tune?

[Dousan_PG]

yes i do at the moment
going haltech in a few months though.
had the rom tune for about..mmm 1.5 years now
my friends w/ PFCs and Haltechs and HKS units run 740s always
its not worth getting 550s

[sr20detconv]

Not more feedback?

[MADE]

Most people that I knew who brought 550 ended up selling them for 740's down the line. Most HP goals will change once your use to it. I have 740's now just so I don't have to upgrade later.

[fliprayzin240sx]

550s start hitting 90-95 duty cycle at around 300whp from what ive seen.

If your tuner says he cant tune your car cuz 740s injectors are too damn big, then its time to change your tuner.

740s, hell even Sard 850s are rom tunable(also cost $150 or so cheaper).

[norcal_black240]

get the 740's. It gives you more room to play if you ever decide to upgrade your setup.

[steve shadows]

you can run larger injectors and control them better with an ecu like the Haltech or AEM.

PFC you have to use a scale value then start tuning. Otherwise the car wont run at all. Thats why you see duty cycle maxing out early.

If you were using a Haltech you could probably push the 550s out to be usable to 380whp with the right fuel pressure.

[sr20detconv]

bought nismo 740's.Thanx!

[johngriff]

Did you?

Bad move, the nismo 740's are denso style 1, should have went for the SARD denso style 2's, they have a faster solenoid, better spray pattern, and lower minimum ms open time, making for a better idle.

But they are better than the deatschwerks so, dont feel so SOL.

[sr20detconv]

thanx for the input. I pretty sure they are not bad injectors...hope so.

[johngriff]

No they are not BAD, but its a pain for a rom tune, and pricing on sard vs nismo is the same.

[sr20detconv]

I hate you!You've could post earlier!:duh:

[eastcoastS14]

call and cancel your order....if its late in the day the most likely wont ship til tomorrow....

[sr20detconv]

I will keep them.I don't think they are that bad.

[Dousan_PG]

they are fine
i run nismo 740s on my enthalpy tune.
idles fine

[sr20detconv]

makes me feel better. Crazy zilvians!:bigok:

[garbury]

got sard 850s on a rom tune. It idles just fine, but cold start is a little iffy if I build a little boost (1 or 2 psi) and then pull out of gear/blow off to a stop quickly. It will just die but it runs perfectly besides that, and this is only a winter occurance and very easy to avoid by just going super easy for the first minute

[Ghostdrifter]

not to thread jack, but what are y'all's opinion of the deatchwerks 740cc injectors

[Dousan_PG]

dont do it
get nismo, sard or tomei

[bardabe]

750's is what you want, unless you plan going big boy then just look into 850's or bigger. Im running 650's on SAFC. I'm fine just timing is kinda crazy timing but once i get a standalone/ rom burner I'll be cool.

[Ghostdrifter]

dont do it
get nismo, sard or tomei

What's so bad about them?

[Dousan_PG]

search my friend
there are lots of posts about them

[jspaeth]

I just picked up a set of 740cc HKS, side feed, low impedance...

what's the review on those???

hope they are good!

[slideways2004]

What's so bad about them?

yes fuel is where you don't want to skimp out on. hell, don't go cheap on your whole car. do it right the first time. it saves you money in the long run

[garbury]

yeah i just bought the sard 850s because the were something like 360 or so on ebay which is better that deatsch. still get 20 mpg city boosting like an idiot and well over 26 highway still not economically minded.

[Kuzumi]

http://www.sr20forum.com/technical-information-library/142897-inj-size-whp-output.html
injector size/hp

[CylonFrakker]

Sard 850cc will give you room to grow too!

[johngriff]

I think room to grow is kind of nonesense.

As steve stated earlier, 90% of the car running well will be the tune.

The deatchswerks have a poor spray pattern because they are just drilled out/ plus low life expectancy because they are used.

[CylonFrakker]

I think room to grow is kind of nonesense.

Room to grow means more boost, which means more power. Besides his duty cycle percentage will be lower at the same power level than the 740cc, which also gives a bigger margin for error if something goes wrong. Yeah so room to grow is a good thing right? I mean i always ran much larger injectors than I needed better to have it and not need it than need it and not have it. Shane ran 1200cc siemens injectors with a topfeed rail and idle is great but that is with the AEM EMS. He still made 716 at 18psi on a GT42R-76 (GTE swapped SC300) and the injector duty cycle was at like 59%. In high boost (40psi) he made upwards of 1076 and was at 89% duty cycle. Which left plenty of room to grow or as i prefer to call it room for error

[Ichito240]

Need some help deciding on injectors also, I have an AFC NEO and and stock S14 turbo and want to upgrade my fuel system to max out the turbo. I wanted to know if I should get the Sard 850cc injectors or something else like Nismo 740cc. I do plan on getting a bigger turbo when I plan on making more than 300whp.

[CylonFrakker]

read the above post!

[usdm180sx]

I have hard time deciding between nismo 555cc's or 740cc's.The thing is that they are the same price.Is their a downside of 740's with ROM tune like bad idle,hard to tune,etc?I'm not planning to run standalone or safc so it's concerning 740's with ROM tune.
I don't think I will putting more than 340whp but if their is no downside for 740's I don't see any reason not to buy them for any futur upgrade.
Sorry for my bad english.
PS:I did search but did not found a really clear answer.

I SEARCHED and found this:

http://www.zilvia.net/f/showthread.php?t=134996

The AFR and Injector size Thread

--------------------------------------------------------------------------------

Alright seems that alot of people have that "what AFR is Ideal" question in mind and search but don't search hard enough or are just too damn lazy. no worries I have taken time out of my so called :valuable life" to write my fellow zilvians the AFR sessentials, Injector size calculator, and come common injector sizes from other cars here we go

Air/Fuel Mixture
6.0 Rich Burn limit (fully warm engine)
9.0 Black Smoke Low Power
11.5 Aproximate rich best torque at WOT
12.2 SAfest best power at WOT
13.3 Aproximate Lean best torque
14.6 Stoichiometric AFR (chemically Ideal)
15.5 Lean Cruise
16.5 Usual Best Economy
18.0 Carburated Burn Limit
22+ EFI Burn Limit

if you are further confused and don't know what to pick here are the answers
11.3 at WOT and full boost
14.6 at idle
12.2 cruise / low thorttle
__________________________________________________ _______________
Injector Size Calculator

Flow Rate = (HP x BSFCX10.5)/ (#injectors x Max Cylce)

Flow rate = CC
HP = at the flywheel
BSFC = Brake specific fuel consumption (0.55 for turbo 0.45 for N/A)

Example:
2.0 Litre SR20DET
Flow= (500HP x 0.55X10.5) / (4 cylinder x 0.8)
Flow = 902cc injectors required
__________________________________________________ _______________

[CylonFrakker]

_______________
Injector Size Calculator

Flow Rate = (HP x BSFCX10.5)/ (#injectors x Max Cylce)

Flow rate = CC
HP = at the flywheel
BSFC = Brake specific fuel consumption (0.55 for turbo 0.45 for N/A)

Example:
2.0 Litre SR20DET
Flow= (500HP x 0.55X10.5) / (4 cylinder x 0.8)
Flow = 902cc injectors required
__________________________________________________

FLOW RATE = (1076HP X.55 X 10.5) / (6 X 89%) = 6213.9/5.34 = 1163cc

So with what I selected for my injectors that works great... I knew it..

So lets work backwards for the 850cc as opposed to the 740cc

850cc = X / (4 injectors at 90%) = X / 3.56 = 850cc * 3.56/1 = X

X = 3026

so the equation turns to

Y = (HP * .55 * 10.5) / (4 x 89%)

Y= TARGETED FLOW RATE TO ATTAIN TARGETED HP
HP= TARGETED HP

LETS PLUG IN 850CC FOR FLOW RATE AND SOLVE FOR HP..

850 = (HP * .55 *10.5)/ (4 * 89%)
850 = (HP * 5.775) / (3.56)
850 = (HP/1) *(5.776/3.56)
850 = (HP/1) * 1.622
850/1.622 = HP
524.04 = HP

So with the 850cc you can max out at about 525 (theoretically with 89% duty cycle)

Now do the 740cc

740 = (HP * .55 *10.5)/ (4 * 89%)
740 = (HP * 5.775) / (3.56)
740 = (HP/1) *(5.776/3.56)
740 = (HP/1) * 1.622
740/1.622 = HP
456.22 = HP

Now do the 550cc
550 = (HP * .55 *10.5)/ (4 * 89%)
550 = (HP * 5.775) / (3.56)
550 = (HP/1) *(5.776/3.56)
550 = (HP/1) * 1.622
550/1.622 = HP
339.08 = HP

so compare

524 theoretical HP on the 850cc as opposed to 456.22 as opposed to the 740ccand 339.08 on the 550cc

DUE NOTE THIS IS AT 90% INJECTOR DUTY CYCLE SO YOU DO NOT HAVE THE INJECTORS MAXXED OUT. NOR SHOULD YOU HAVE THEM MAXED IT OUT. ITS JUST STUPID TO DO SO.

Good Luck

Go with the 850cc its a better injector with room to grow. Some one correct me if i am wrong and please quadruple check your calculations when you do this....