Injector Flow Rates

[Mike 99GSX]

I was hoping someone could give me an explaination for this. When I changed from RC550 injectors to the FIC 650cc ball disk injectors, I did not have to change the settings on my VPC/GCC at all to compensate for the "bigger" injector when trying to maintain the same A/F ratio of .92. No other variables on the car were changed. Am I missing something here or does this say that either the RCs are conservatively rated and/or these new injectors are not flowing what there advertised at?

 

[tsitalon1]

I'm not a fuel injector expert, but possibly the fuel injector dead time could be the cause here.

Just my $.02
James

 

[Mike 99GSX]

Please explain if you can.

 

[tsitalon1]

Again, I'm no expert. But from what I've read. Larger injectors have larger dead times (time delay from when ecu sends "open" signal to when it actually get the injector open)

Since 650's are much larger than 550's, There might not be as much of a tuning gap as you might think. But I would assume you could up the boost anytime you want

Also, What fuel pump do you have ? and at what pressure ?

James

 

[Mike 99GSX]

255HP at 43.5 w/out vacuum.

 

[tsitalon1]

hmmm

I agree you should have seen a tuning gap. I would have thought you would have to have leaned at least -15 %.

What boost are you pushing ?

James

 

[pneumo]

At what pressure does the manufacturer rate their injectors? I know RC used 43 psi, which is the standard test pressure for DSM injectors. You might want to contact FIC and ask what pressure their injectors are flow tested. I've seen a few other companies that test their injectors at 55 psi because some other cars run higher fuel pressure.

If you turn up the fuel pressure to 55 psi when using RC 550's they flow about 630 cc's.

 

[Mike 99GSX]

I'm running 19 PSI on 94 pump gas which didn't change from the setup with the 550s. I don't actually own these injectors. I am just borrowing them from a friend to see how successfully I could tune my VPC/GCC with bigger injectors using the 550 chip because they don't have a 660/650 chip for 2gs. I think after discovering this, I'm going to go with the Denso 660s which are flow tested at 43 psi. It seems like everybody is buying the ball disk type right now though, but with a 2g pocketlogger, I can't see duty cycles or anything so its hard for me to tell where these are working at. I can only conclude with the data that I have available, that they flow very close to the same as RC550s.