Proper Injector Size...Please Help Me - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Pudula · 06-27-2003, 10:00 PM

I have reached the end of the internet and back trying to find out the proper injector size for my sr20det that i'm building. I will break 300whp (easily, i found out) and am using the stock fuel rail. Some sources say 555 is too small, and I cannot find a 660 in side feed, and 740 is too big??!

What ever shall i do?!

Thanks, Ryan

mrdaniel · 06-28-2003, 01:46 AM

there is no such thing as an injector that is to big,

there are two ways of going at this situation,
1. top feed conversion
2. 740cc injectors with proper tune

I'd rather have the 740cc with proper tune - its just a matter of getting the car on the dyno adjusting the k constant value to the ve map which is really easy.

top feed fuel rails can be had from unstable hybrids, they should also sell injectors too, the conversion is 1lb/hr is about 100cc so 72# injectors comes out to about 740cc give or take...

Racer X · 06-28-2003, 08:09 PM

there is such a thing as too big of injector. too big could = bad idle and low end bogging. if you keep high impedence too big can happen easier than with low impedence. (they open and close slower.) ive seen 550cc put 400 to the wheels. do a little math and play with pressure. that affects injector flow alot. injectors are rated at 3bar (43.5 psi) a 555 at 70psi flows roughly 740cc/min the formula is (try to follow this) new flow rate= the square root of (new pressure, divided by the old pressure), multiplied by orginal flow rate. generaly maximum injector pressure is 70 psi but i know of a vw that runs well at over 100psi.
btw i currently have 740cc injectors the only thing thats bad is the over rich on deceleration pops a flame at 1500 rpm every time (im getting sick of it, but also all i have for engine management is an hks afr and a different mass airflow sensor. better engine mangement will cure this situation

mrdaniel · 06-28-2003, 08:20 PM

Quote:

Originally posted by mrdaniel

2. 740cc injectors with proper tune

I'd rather have the 740cc with proper tune - its just a matter of getting the car on the dyno adjusting the k constant value to the ve map which is really easy.

see....proper tune....thats why you shoot fire at 1500 rpm etc., you dont have a fully set fuel curve and at low rpm you run rich and therefore shoot fire....its nice to read before you post isnt it?

Racer X · 06-28-2003, 08:23 PM

if you read my post u would notice that it says that better engine management would cure this problem. and that i was basicaly saying that my engine management is crude. my car was on the dyno when spec stage 3 clutch gave up and we only got to tune low boost 1 run at highboost and the clutch quit. dont worry its going back after i get my new clutch

mrdaniel · 06-28-2003, 08:31 PM

i did read your post

spec3 clutch? damn thats a little harsh dont you think?

the fact of the matter is

it boils down to how you tune it not what you get.

Pudula · 06-28-2003, 10:23 PM

Quote:

Originally posted by Racer X
my car was on the dyno when spec stage 3 clutch gave up and we

So you would not recommend a spec stage 3? I was planning on getting a sprung 6 puck, but maybe not now! Give me some ideas on that clutch

Ryan

Racer X · 06-29-2003, 07:12 PM

i not going to say that spec clutch was bad. but not very good either. thats just my opinion.(lot of peple love it) drop the cluch and that thing hits hard. but ever since i went to bigger stickier tires (255/40 kuhmo mx) the clutch would slip a little on hard up shifts. ive had (255/40 yoko es100 and 245/45 kuhmo 712 on it and itwould just light those tires up.) i think it was a combo of more power and a puck that was wearing out. pucks dont last too long and mine had about 5k on it. it also saw a fair amout of drifting. the bad thing about this clutch is that the friction material is just as hard as the flywheel and presure plate. it left grooves in the flywheel and pressure plate. (jun flywheel) this time im having clutchnet.com build me a pressure plate(3100 lbs) and using an exedy full face sprung disk. if this doesent work ill go to twin disk. spec stage 3 is a good clutch, but i would get an exedy for a little more if you want a puck set up? (daisen cluctch makes stock sr clutch daisen is to exedy as nissan is to nismo.)

Quote:

it boils down to how you tune it not what you get.

that is what i would say too. (soon to be the new owner of a power fc)

06-27-2003, 10:00 PM	#1
Pudula Zilvia Junkie Join Date: Jun 2003 Location: Tucson, w00tizona Age: 41 Posts: 532 Trader Rating: (0) Feedback Score: 0 reviews	Proper Injector Size...Please Help Me I have reached the end of the internet and back trying to find out the proper injector size for my sr20det that i'm building. I will break 300whp (easily, i found out) and am using the stock fuel rail. Some sources say 555 is too small, and I cannot find a 660 in side feed, and 740 is too big??! What ever shall i do?! Thanks, Ryan

06-28-2003, 08:09 PM	#3
Racer X Zilvia Junkie Join Date: Apr 2002 Location: brooklyn park Age: 42 Posts: 334 Trader Rating: (2) Feedback Score: 2 reviews	there is such a thing as too big of injector. too big could = bad idle and low end bogging. if you keep high impedence too big can happen easier than with low impedence. (they open and close slower.) ive seen 550cc put 400 to the wheels. do a little math and play with pressure. that affects injector flow alot. injectors are rated at 3bar (43.5 psi) a 555 at 70psi flows roughly 740cc/min the formula is (try to follow this) new flow rate= the square root of (new pressure, divided by the old pressure), multiplied by orginal flow rate. generaly maximum injector pressure is 70 psi but i know of a vw that runs well at over 100psi. btw i currently have 740cc injectors the only thing thats bad is the over rich on deceleration pops a flame at 1500 rpm every time (im getting sick of it, but also all i have for engine management is an hks afr and a different mass airflow sensor. better engine mangement will cure this situation __________________ Twin67 ls1/awd in the works Last edited by Racer X; 06-28-2003 at 08:14 PM..

06-28-2003, 08:23 PM	#5
Racer X Zilvia Junkie Join Date: Apr 2002 Location: brooklyn park Age: 42 Posts: 334 Trader Rating: (2) Feedback Score: 2 reviews	if you read my post u would notice that it says that better engine management would cure this problem. and that i was basicaly saying that my engine management is crude. my car was on the dyno when spec stage 3 clutch gave up and we only got to tune low boost 1 run at highboost and the clutch quit. dont worry its going back after i get my new clutch __________________ Twin67 ls1/awd in the works Last edited by Racer X; 06-28-2003 at 08:26 PM..

06-28-2003, 01:46 AM	#2
mrdaniel Join Date: Oct 2002 Posts: 47 Trader Rating: (0) Feedback Score: 0 reviews	there is no such thing as an injector that is to big, there are two ways of going at this situation, 1. top feed conversion 2. 740cc injectors with proper tune I'd rather have the 740cc with proper tune - its just a matter of getting the car on the dyno adjusting the k constant value to the ve map which is really easy. top feed fuel rails can be had from unstable hybrids, they should also sell injectors too, the conversion is 1lb/hr is about 100cc so 72# injectors comes out to about 740cc give or take...

06-28-2003, 08:31 PM	#6
mrdaniel Join Date: Oct 2002 Posts: 47 Trader Rating: (0) Feedback Score: 0 reviews	i did read your post spec3 clutch? damn thats a little harsh dont you think? the fact of the matter is it boils down to how you tune it not what you get.