i have 8 green 315cc injectors in my position that i am going to install in spring time . but should i upgraded the fuel pump also or stick with what i got will i have to re run on the dyno or should i try to tune it my self (as dumb as that sounds)

 

what are you using to tune with and what fuel pump are you using currently?

 

The stock computer can alter fuel delivery +/- 20% to maintain the proper mixture based on various inputs. It does this by short term and long term fuel trimming/adding. In the short term, the computer can adjust +/- 10%. When the short term (on the fly) adjustment exceeds 10%, the long term (overall) fuel map is accordingly altered.

The stock injectors are 215cc. The jump to 315cc exceeds the +/- 20% adjustment that the stock computer is capable of making. Using the 315cc injectors on an otherwise stock fuel system is a bad idea. You will run super rich. The combustion mixture may not even ignite.

You will need a piggyback computer to manage the injectors. Most piggyback units are able to make a percentage-based baseline adjustment to the sensor outputs to trick the stock computer into altering its fuel map by a certain percentage greater than the +/- 20% that the stock computer will allow.

To determine the percentage that you will need to alter the fuel deliavery by way of the piggyback controller, you simply set up a ratio: (215cc- 315cc)/(315cc) = -32%

Thus, you will need to trim -32% with a piggyback to maintain the stock fuel map with the higher output injectors. This is more than the stock computer can do on its own.

Do you have plans of forced induction? If not, the 315cc/min injectors will be more hassle than they are worth. Even if you do, a FPR on the stock 215cc injectors can get the injectors to outflow 215cc/min and still make enough fuel for a modest boosted application.

 

Since the injectors are a lil over 30% stock, you should be able to run ethanol. I plan on doing it on my sc4, I'm currently running it on my 240, but going 30% more on injector size.

 

i was going to do have to re tune my safc 2 with the new injectors

 

I thought stock injectors were 330's?

 

...maybe on your 3L. Our V8 has 215s.

 

i think it would open up some more power from mid to high range but i am on the stock fuel pump and i and looking a a ebay walbro ( wish the one from my 7m fit) also btw my wife says hi to everyone on the forum she says she be here soon

 

Without a turbo or a supercharger, the 315cc injectors will do nothing that the stock 215cc injectors can't.

Scotturnot (7psi on his M90) and KC95SC400 (7psi on his V9) are both running rich at the redline with the stock fuel system. With a FPR, Neil Griffiths is making 9psi on his M90 down in Australia with an otherwise stock fuel system.

If you want to make more power in the mid to high range by way of the SAFC, all you need is the SAFC on your stock fuel system. 315s and a Walbro is overkill unless you have a turbocharger or supercharger running in excess of 10psi.

Although, I do agree with you that power can be had darn near everywhere on the power band once you go WOT and the computer starts running the engine rich. Here is an example of an SAFC doing its magic: https://www.clublexus.com/forums/sho...d.php?t=213175

 

I got to agree with Mark (Blizzy) on this one

 

Aren't the stockies 251cc's?

If the injectors are used and you insist on putting them in, I would reccomend a professional clean and balance.

KC

 

yep, your are right, Mark has a touch of Dyslexic (just kidding Mark)

 

That upgrade will definately be a downgrade on a stock engine. Im still using my stock injectors at 17 psi and still run rich up top. Like blizzy said a super afc will be a better in your case. If you want more power put a nos kit on the ge

 

na no nos but i have already bought the injecotrs but my asain boi is a wis with yotas but i we shall se what happens

 

Dyslexic am I.

They stock injectors are indeed 251cc. That puts 315cc at a -21% adjustment...slightly more than the maximum capable by the stock computer.

Here is a good website I found with lots of injector information:
http://www.autospeed.com/cms/A_0102/...popularArticle