Question regarding injectors

[KiD-ViD]

Ok, I am building a CSP miata with ITBs and the whole works. This is the most technically knowledgeable forum I have ever been so I figure I will bug you guys a bit. Anyway, our throttle bodies came with 380cc injectors and our tuner is having a hard time getting the car to idle with such big injectors on such a small engine. He said he turned down the fuel pressure all the way and set the fuel map on our AEM standalone to the lowest setting at idle and it is still running 10:1 air/fuel ratio. So we told him to use the stock injectors we gave him and to this he answered that the fittings on the stock injectors were too small for both our new fuel rail and our new throttle bodies. I was under the impression that all injectors were the same size, it was just the internal valving or whatever that was different. Our autocross is this coming weekend so seeking a quick solution he offered to trade us our 380s for a set of injectors off of his civic, claiming that even though its a smaller engine (1.6 vs our 1.8) it still makes about the same power so it should flow enough. Sounds logical to me. He also said he wouldnt mind since he is putting in a turbo soon and needs bigger injectors. My question to you is, is he trying to scam us out of our bigger/better injectors. This is trading brand new RC injectors for a set of used stock injectors. Could he be making up/exaggerating this problem to score some injectors for his turbo build up? Thanks in advance for your time and expertise guys.

[Austenp405]

I'm not an expert on injectors (or anything else motor related for that matter) but it sounds a little fishy to me.

[sims76]

Hey Kid,

 

1. It is very possible that your stockers won't fit the fuel rail (must be a near exact fit because they are holding back 40+ psi of fuel pressure), but they should fit the TB with the right washer or whatever you seal them with.

 

2. It is also possible that your car will have difficulty idling with the 380's. I have 440's on my 2.8L and my duty cycle at 1000RPM is in the 2ms range. 380' s on a 1.8L would be like me having 600 cc/min on my 2.8. That would push the duty cycle into the 1ms range or less which might cause problems.

 

Copied from another website:

"Capabilities

The minimum pulse width cycle time for most pintle type fuel injectors (Bosh/Nippon-Denso) is 2.0Ms for the Peak and Hold and 2.5Ms for the Saturated injectors. Alternatively, disc type injectors (Lucas) will cycle as low as 1.0Ms for Peak and Hold and 2.0Ms for Saturated. The difference in pulse widths between the pintle and disk type injectors can be attributed to weight differences."

 

3. If his injectors are stock and used, I think you should also try to negotiate some cash to make up the difference.

 

Good luck.