injector size ? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Nismo240SX · 11-13-2003, 11:26 AM

what cc is a good injector size for a n/a built sohc? i'm looking into buying them used, but i can't find much. i know the rb20dett injectors fit, but they're like 444cc or so, and thats definnetly too big for non-turbo. thanks.

*sykikchimp* · 11-13-2003, 12:37 PM

why do you need bigger injectors? Unless you plan to max out flow on your current injectors, then you don't need new injectors.

To figure out what size injectors you need, use the following calc..

Injector Size = Expected BHP (brake horsepower (at flywheel)) x BSFC (brake specific fuel consumption)/Number of injectors x duty cycle

A good BSFC for a performance NA street engine is .45-.50 to be on the safe side, lets use .50.

Lets use 90% duty cycle..

So if you expect 220 bhp.. 220 x .50 /4x.9 = 30.5 lb/hr injectors.. round up. so 31 lb/hr

to find cc/min multiply 31 x 10.5 = 325.5 cc.. in general, if you have two injectors sizes to choose from one being 310, and one being 360cc.. always round up to the next closest size.

so.. plug in your own #'s and figure it out.

Steeles · 11-13-2003, 12:41 PM

learning something new... what numbers would I put in that equation for a turbo engine?

*sykikchimp* · 11-13-2003, 01:34 PM

turbo's generally run a bit richer than NA engines.. .55 is a good all around number for the BSFC for turbo cars.

Nismo240SX · 11-13-2003, 04:35 PM

well, i'm thinking i will be hitting around 200hp if i'm lucky. would 310cc be too rich for that? i'm probably going to buy the safc so i could play around with that right???

misnomer · 11-13-2003, 05:22 PM

You'll definitely deen an AFC or some sort of fuel controlling system if you plan to upgrade your injectors. Dropping bigger injectors without compensating for it will cause you to run very very rich.

RedlineRacer · 11-14-2003, 06:51 AM

Quote:

Originally posted by misnomer
You'll definitely deen an AFC or some sort of fuel controlling system if you plan to upgrade your injectors. Dropping bigger injectors without compensating for it will cause you to run very very rich.

You could just increase your MAFS size if you drop something like 370cc.

*sykikchimp* · 11-14-2003, 08:59 AM

At 200 HP your stock 270cc injectors will work fine. An AFC would be nice to help you tune the car to get the most from your upgrades though.

Nismo240SX · 11-14-2003, 09:06 AM

well if stock injectors are fine, how would i go about cleaning them... i know fuel injector cleainer is one way, but is there any way to just pop them out and place the tips in some sort of solution? how much are oem injectors? where can i get them? i know my closest nissan dealer can't get much for the s13... but yeah. thanks.

*sykikchimp* · 11-14-2003, 09:20 AM

what you could do is pull your injectors and test them for flow. If they are flowing the proper amount of fuel, then they don't need to be cleaned or anything.

All you need is a graduated cylinder, a battery (9v works well), a watch, and your fuel rail/fpr/and injectors removed from the car, but still attached to the fuel source.

Attach the battery to the contacts on a single injector, and let it flow for 1 min into the Graduated Cylinder. The amount left is the cc/min flow.

andrave · 11-14-2003, 12:39 PM

send them off to RC, they will clean and flow test them, and if you need more flow I believe they can rebuild them to flow more.
service is like 25 per injector to clean and test.

*sykikchimp* · 03-03-2004, 11:14 AM

I've recently discovered that KA's and SR's are both closer to a .40-.45 bsfc. just fyi

11-13-2003, 11:26 AM	#1
Nismo240SX Zilvia Addict Join Date: Sep 2001 Location: Marion, Virginia. Age: 35 Posts: 855 Trader Rating: (0) Feedback Score: 0 reviews	injector size ? what cc is a good injector size for a n/a built sohc? i'm looking into buying them used, but i can't find much. i know the rb20dett injectors fit, but they're like 444cc or so, and thats definnetly too big for non-turbo. thanks. __________________ 1990 Nissan 240sx:s13 blacktop, s13.5 front

11-13-2003, 12:37 PM	#2
sykikchimp WOW addicted Join Date: Dec 2001 Location: the moon Age: 40 Posts: 6,518 Trader Rating: (0) Feedback Score: 0 reviews	why do you need bigger injectors? Unless you plan to max out flow on your current injectors, then you don't need new injectors. To figure out what size injectors you need, use the following calc.. Injector Size = Expected BHP (brake horsepower (at flywheel)) x BSFC (brake specific fuel consumption)/Number of injectors x duty cycle A good BSFC for a performance NA street engine is .45-.50 to be on the safe side, lets use .50. Lets use 90% duty cycle.. So if you expect 220 bhp.. 220 x .50 /4x.9 = 30.5 lb/hr injectors.. round up. so 31 lb/hr to find cc/min multiply 31 x 10.5 = 325.5 cc.. in general, if you have two injectors sizes to choose from one being 310, and one being 360cc.. always round up to the next closest size. so.. plug in your own #'s and figure it out. __________________

11-13-2003, 12:41 PM	#3
Steeles Post Whore! Join Date: Sep 2002 Location: 7th layer of hell, special pit of anger Age: 45 Posts: 3,785 Trader Rating: (0) Feedback Score: 0 reviews	learning something new... what numbers would I put in that equation for a turbo engine? __________________ Keeping it Godzira bishes. So I murdered another turbo

11-13-2003, 01:34 PM	#4
sykikchimp WOW addicted Join Date: Dec 2001 Location: the moon Age: 40 Posts: 6,518 Trader Rating: (0) Feedback Score: 0 reviews	turbo's generally run a bit richer than NA engines.. .55 is a good all around number for the BSFC for turbo cars. __________________

11-13-2003, 04:35 PM	#5
Nismo240SX Zilvia Addict Join Date: Sep 2001 Location: Marion, Virginia. Age: 35 Posts: 855 Trader Rating: (0) Feedback Score: 0 reviews	well, i'm thinking i will be hitting around 200hp if i'm lucky. would 310cc be too rich for that? i'm probably going to buy the safc so i could play around with that right??? __________________ 1990 Nissan 240sx:s13 blacktop, s13.5 front

11-13-2003, 05:22 PM	#6
misnomer Nissanaholic! Join Date: Jul 2001 Location: Nevada Posts: 2,293 Trader Rating: (0) Feedback Score: 0 reviews	You'll definitely deen an AFC or some sort of fuel controlling system if you plan to upgrade your injectors. Dropping bigger injectors without compensating for it will cause you to run very very rich. __________________ Rowsdower saves us and saves all the world!

11-14-2003, 08:59 AM	#8
sykikchimp WOW addicted Join Date: Dec 2001 Location: the moon Age: 40 Posts: 6,518 Trader Rating: (0) Feedback Score: 0 reviews	At 200 HP your stock 270cc injectors will work fine. An AFC would be nice to help you tune the car to get the most from your upgrades though. __________________

11-14-2003, 09:06 AM	#9
Nismo240SX Zilvia Addict Join Date: Sep 2001 Location: Marion, Virginia. Age: 35 Posts: 855 Trader Rating: (0) Feedback Score: 0 reviews	well if stock injectors are fine, how would i go about cleaning them... i know fuel injector cleainer is one way, but is there any way to just pop them out and place the tips in some sort of solution? how much are oem injectors? where can i get them? i know my closest nissan dealer can't get much for the s13... but yeah. thanks. __________________ 1990 Nissan 240sx:s13 blacktop, s13.5 front

11-14-2003, 09:20 AM	#10
sykikchimp WOW addicted Join Date: Dec 2001 Location: the moon Age: 40 Posts: 6,518 Trader Rating: (0) Feedback Score: 0 reviews	what you could do is pull your injectors and test them for flow. If they are flowing the proper amount of fuel, then they don't need to be cleaned or anything. All you need is a graduated cylinder, a battery (9v works well), a watch, and your fuel rail/fpr/and injectors removed from the car, but still attached to the fuel source. Attach the battery to the contacts on a single injector, and let it flow for 1 min into the Graduated Cylinder. The amount left is the cc/min flow. __________________

11-14-2003, 12:39 PM	#11
andrave BANNED Join Date: Apr 2002 Location: Burton WV Posts: 2,350 Trader Rating: (0) Feedback Score: 0 reviews	send them off to RC, they will clean and flow test them, and if you need more flow I believe they can rebuild them to flow more. service is like 25 per injector to clean and test.

03-03-2004, 11:14 AM	#12
sykikchimp WOW addicted Join Date: Dec 2001 Location: the moon Age: 40 Posts: 6,518 Trader Rating: (0) Feedback Score: 0 reviews	I've recently discovered that KA's and SR's are both closer to a .40-.45 bsfc. just fyi __________________

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode