Is there a reason anyone with 300-450whp doesn't just put ID2000 injectors in the primary rail and block of the secondaries? With the newer style injectors (better control) and good engine management, it seems like secondaries are no longer needed if shooting for less than 500whp.

I was thinking about upgrading and was surprised to see all the focus on secondaries like there was 10 years ago.

 

I think it's because many people a running a Power FC, which can't handle such large injectors for primaries.

 

It's a good idea except that the primary injectors fire into the primary intake ports and the secondary injectors fire into the secondary intake ports.

I imagine you could just do primaries but I have a feeling there's a good reason to have fuel going to the secondary ports as well.

BTW, primary ports - the intake ports on the center iron on the engine. Secondary ports - the intake ports on the front and rear irons.

Dale

 

 

Show me where this magical 80% duty cycle limit comes from. 4000cc of injector (especially modern injectors) is plenty for 400whp. Even the stock system can do 300+whp.

If a modern injector can run at 80%, it is no less reliable at 90% or even 95% as long as the ecu is capable of controlling it (which any modern ecu is). This is not the old days with a microtech and 850cc stock injectors modded to 1300cc.

I hear Dale's point though. I wonder if there is an issue with fuel entering only from the center iron. It's a relatively small combustion chamber, I feel like it should still mix pretty thoroughly.

 

Regarding the 80% duty cycle concept, there is some duty cycle for most solenoids where they are receiving enough energy to simply stay open rather than closing. It's pretty common to see this in boost control solenoids, going from 80% to 90% duty won't often result in a different amount of boost. This is less common to happen with fuel injectors, but for older fuel injectors it might have been around 80-85%. Some designs will overheat if you run them at high duty cycle for an extended length of time, but I haven't heard about this happening for any OEM injectors. The main concern with running over 85% duty cycle on a modern ECU with modern injectors is you don't have much headroom left if conditions change. There might be 15% more fuel available, but there might not.

 

I imagine different types of injectors have different max duty cycles. I don't think that much of it is ECU control, it's a pretty basic thing the ECU is doing to send a pulse width to the injector. I could see the injector itself not being able to cope with higher duty cycles. Slower-responding injectors would have trouble at high duty cycles - they get a signal to open, they start opening, then by the time the next signal to fire comes they are already open. Or the fuel pressure keeps the injector from closing, or any number of factors, I think it starts getting technical.

I do think a lot of it has to do with the primary/secondary ports. The primary ports are a lot smaller than secondary for better idle and low-speed drivability. If you only had primary injectors you would only have an air/fuel mix going through the 2 smallest ports and the 2 large ports would only be pumping air. That would probably make for a weird air/fuel mix in the combustion chamber.

Dale

 

You will never get as good atomization with running just 2 injectors vs 4. Also, unless you have a very good ecu like a new Haltech you will never get a good idle with 2000cc primaries.

 

GSL-SE ran 680cc primary injectors only. Of course they were 80s injectors.

 

Yes they did. Emissions and fuel economy were not as strict as they are now.

 

It was a N/A which is far more forgiving to lean conditions. It also had 3mm apex seals.

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The problem I foresee is that on a FI application the engine would not be getting any additional fuel beyond the closing point of the primary intake port, where the secondary runners would still be supplying forced air until a much later closing point, potentially causing a lean condition. There is a chance you could dump in enough fuel to maintain a decent fuel mixture. You could always try it and let everyone know how it worked for you.