6 replies to this topic

[Anthony Ralston]

Has anyone seen the recent Grassroots article where they saw an under-the-curve improvement by changing NA injectors with NB ones?

 

Would we notice a difference?

[Jim Boemler]

It would be illegal regardless.

[NPiekarski]

I am no expert, but I would believe that the stock injectors have far more fuel than we need in the configuration we run. I have never heard of a legal spec miata starving for fuel. If adding more air (ie: bigger tb, more cam, forced induction) I would think the injectors would be nessesary to make full potential on your modifications. Jim would know the detailed info from his STL car build.

[HoneyBadger - BrianW]

I am no expert, but I would believe that the stock injectors have far more fuel than we need in the configuration we run. I have never heard of a legal spec miata starving for fuel. If adding more air (ie: bigger tb, more cam, forced induction) I would think the injectors would be nessesary to make full potential on your modifications. Jim would know the detailed info from his STL car build.

STL car's will be hurting for fuel with stock injectors. I have found them to run at greater than 80% duty cycle.

[NPiekarski]

STL car's will be hurting for fuel with stock injectors. I have found them to run at greater than 80% duty cycle.

 

I am unsure of the stock sizes of the NA and NB injectors, but i've heard that a 325cc injector is about all that a good STL car needs.

[Brandon]

Which issue of GRM was that in?  I don't think I received that one unfortunately as I'd be curious about their findings.

I heard the difference in the injectors (while being similar in terms of volume/CCs) is the spray pattern.  The NA's have a 3-hole (or was it single hole?) design vs. the NB's 5-hole.

 

And to echo everyone else's response, the different injectors would be easily identifiable in tech/by competitors (should you try) and are not allowed per the rules.

[davew]

As the guy who sits at the injector machine and watches them spray, I have some info.

 

The NA and NB are totally different injectors. They physically look different and the NB's have a much finer spray pattern.

 

Since we want a leaner running engine, adding the bigger injectors is not an advantage. If we had the need for more fuel, then I would go to the red 99-2000 injectors in a 1.6.

 

Dave