Hi there, I just bought 720 cc injectors to replace the stock injectors for when i turbo my miata. I have been looking at other peoples builds on the forum and else where, and im pretty sure this is WAY too much, cause i see that some people are putting on 450cc injectors and even less! So i am wondering is this too much? And if it is, is this possibly bad for the car?

 

as long as you have a megasquirt to control them and you know how to use it they will be fine

 

Post more information. Is it really that difficult?

Which injectors are they? What ECU do you have? Why do you need 720cc injectors? Why do you think this is WAY too much? What power do you plan to make? What fuel do you plan to run? Do you know how to search? I'm guessing the answer to that is no, because you'd realize that there are only 2 injectors that have been recommended in the past several years. Finding these two injectors and why people recommend them will probably answer your question.

 

LOL he couldn't make the question more vague and totally worthless if he tried.

 

The larger the injector, the harder it is to control precisely at very small pulsewidths. Lets say you needed 5cc of fuel for a single cylinder squirt. For a smaller injector, that would require 5ms of open time (note: I'm pulling numbers out of my *** here). For an injector ~5x larger, that would mean it would need to be 1ms of open time. But things are rarely perfect - so instead of 1ms open time, the injector for whatever reason is open for an additional .3ms. On a smaller injector, this 5.3ms of open time results in 5.3cc of fuel - 6% too much. However, on the larger injector this error results in 6.5cc of fuel - 30% more fuel than required.

That said - it also depends on the injector and fuel system. Batch vs Sequential, injector type, management. A new EV14 injector is waaaaaay better than 30 year old RX7 injectors, and can be driven much more precisely. There's loads more factors I'm not including here (open time, battery correction, humidity, fuel pressure, intake temperatures, etc). I ran 750's and had a pretty good idle once I had it tuned.

 

They are RX-8 injectors, I have a bone stock ECU but getting a MSPNP, and i need bigger injectors to because I am going turbo. And at the end of it all i am wanting to be over 250 ponies at the crank, and im going to be going high octane 93, and only TWO types of injectors have been recommended! Wow i did't know that but i have been looking at the Deatsch Werks, Uremco, also the 949Racing Injector Dynamics, i dont plan on spending that much, or the Fiveo injectors, ehhh they have a bad reputation, i almost bought the AUS Injectors. But after all my research i found a good deal on Ebay by a fellow who was selling RX-8 injectors for a one hell of deal i couldn't pass up. So i come here to ask for help, cause i have done my research and cant seem to find anything, But instead i get told that i should search more, Ha, funny. Thanks for the help.

 

lol

You bought 720cc rx8 injectors? What part of your research lead you to believe that's a good idea? You had one job, buy rx8 injectors, and you fucked it up.

Bet they are awesome, though. You'll idle with enough fuel to make 250 ponies.

 

You should have bought Flowforce injectors. With ev14 going too big is not a problem, with ev6 it is. You got the ev6. Now you will have sloppy fueling.
/thread

*EDIT:

Just because I know there will be many others to make the same stupid mistake: JUST because you can't find THE EXACT answer to your EXACT situation or search terms DOES NOT MEAN that you have "done your research" and put in the effort.
Research takes time. Reading threads. Seeing what people used before you. Discussions about injectors. Discussions about fueling.

The answer is not always obtained in 5 minutes of "searching" (ie: plugging in some weird random search query and calling it a day).

We have talked about injectors on this site so often, that it's like second nature. SOOOOOOOOOO many threads. It really takes effort to make stupid mistakes at this point.

 

Injector Dynamics 1,000 cc idle at 14.7 pefectly. Always. You got the wrong injectors. Trying to save a hundred bucks, you are now going to spend more than the price of ID' s just to get the EV14's .

Don't use those turds that you purchased, unless you want headaches from day one, and until it dies.

Let's review now. You started your first thread saying that you already had all the parts and we're going to show us how to turbo for 700 bucks, and we were going to pull our hair out.

Now you have a turbo to manifold connection that doesn't work and will require more parts and scabs. The rad injectors you bought are completely wrong. So that's like what, 400 doars worth of wrong parts?

Sounds like you should have done more reading and less poking on the paypal button.

 

They never learn. Never.

 

Well this is my first car, i'll learn eventually.

 

Good
It's the cheapest and easiest car to learn on.

Re-sell the wrong injectors and get the right ones and be happy.

 

Really it was just the "I'm gonna show you" attitude. Then directly to fail.

Ps, keep all this stuff in one thread. Not a new thread for every question.

 

Would it be possible to update the turbo FAQ sticky? That might help with some of the learning.