fuel injectors - Team Camaro Tech
Engine General Engine Discussion.

LinkBack Thread Tools Display Modes
post #1 of 5 (permalink) Old Sep 14th, 04, 06:18 PM Thread Starter
Join Date: Aug 2004
Location: Selma, Texas
Posts: 9

I'm looking at about 475 hp out of a lt-1. I used this formula to figure out size. But is this rerally necessary?

470 x .5 = 237.5
8 x .8 = 6.4
237.5 / 6.4 = 37.10

According to this formula I would need 38#ers. Is this right it seems a little extreme. From what I've read on boards 30s are fine. Possibly 36.
Any input?
Arctic_Z is offline  
Sponsored Links
post #2 of 5 (permalink) Old Sep 15th, 04, 04:23 AM
Senior Tech
Join Date: Nov 2002
Location: Ontario & Oceanside CA.
Posts: 1,321

Try this site. They're a little more into this sort of thing. http://web.camaross.com/forums/index...095b18765c23e7
GMJim is offline  
post #3 of 5 (permalink) Old Sep 15th, 04, 05:33 AM
Gold Lifetime Member
camcojb's Avatar
Join Date: Jan 2000
Location: Wilton, Ca. USA
Posts: 10,178

I made 458 HP and 465 ft lbs on my 93 Vette LT1 with the stock 24 pound injectors. 30's are fine for that power range.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
camcojb is offline  
post #4 of 5 (permalink) Old Sep 15th, 04, 03:25 PM
Join Date: May 2003
Posts: 416

The biggest problem with figuring out injector size is what BSFC to use. The modern day heads, cams, and intakes (mostly head chamber design) are getting todays engines in the .36 to .42 BSFC range.

You can also run the injectors up to 85% to 90% duty cycle (DC). I prefer to size them at 85% DC.

The other side of the coin is at what RPM is the HP peak going to be at. The higher the RPM the larger the required injector. This is due to the time available to inject the fuel getting less and less. For a DC less then static there is a finite amount of time to open the injector. This eats into the actual time the injector is flowing fuel.

With all that said, at 475 HP, negating RPM limitations, at 85% DC, and .40 BSFC:

475 (HP) * .40 (BSFC) = 190
190 / 8 (injectors) = 23.75#/hr
23.75 / .85 (DC) = 28 #/hr

If willing to go to 90% DC:

23.75 / .90 (DC) = 26 #/hr

Running them static with 24 #/hr is enough fuel too. Can also run the numbers with a BSFC of .36. Don't need much injector at all then. Of course using a BSFC of .45 would be a more conservative approach.

And, this is for an N/A engine, boosted apps use BSFC in he .55 to .60 range.

a67 is offline  
post #5 of 5 (permalink) Old Sep 15th, 04, 04:59 PM
Senior Tech
Join Date: Apr 2004
Location: cinci, oh
Posts: 565

Plus, one of the biggest noob errors ppl make with injectors is going bigger is better.... not true with EFI... since it is the pulse width, duty cylcle that is important. Are you using a MAF or MAP for you airflow sensing?

67 Camaro | 350 | 650 Speed Demon | Dual plane GMPP intake | MSD ignition | Secret Cam (I don't know what it IS!) | 2.02/1.60 Camel Humps ported | Thorley Tri-Y's | 8.5 10 bolt 3.73 | M22
jethro is offline  
Sponsored Links

Quick Reply

Register Now

In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.

Email Address:


Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome