I do not understand the need to change to parallel plumbing if I go to identical injectors in my Crossfire. I need to go to bigger injectors because of upgrades, but if the OEM flow is 67 and 68, like just posted, that is only 1.5% difference. If I did it right, that is equivalent to 0.4 PSI fuel pressure. Or another way to look at it is AFR, which could be 14.7 on one bank and up to 14.9 on the other, assuming no mixing in the manifold. I suspect the injectors are not even calibrated to 1 %.

Seems like no big deal, help me understand.

Regards.

Ken

 

I'm not sure that lance m p is correct in stating:

"the 1st # is the front rated at 67lbs/hr the 2nd # is rear rated at 68lbs/hr"

I would tend to believe that it is just the opposite for there to be equal gasoline flow out of each throttle body. No disrespect intended, lance m p. The reason I say this is because if this statement is correct that I found from http://chevythunder.com/cross_fire_i..._19821984.htm:

"The fuel injectors are specifically calibrated for each unit and must be installed in its respective throttle body unit. Due to the slight difference in fuel pressure drop across injectors. The fuel enters the left hand (drivers side# unit and then is delivered to the right side before being returned to the tank. The right hand #front) unit contains the actually fuel pressure regulator, while the rear unit has an dampener-accumulator spring."

I bought my car used, and it had been hacked together at some point in it's previous life, so I am not positive on what is original. I have also been looking for the specifics on the two different fuel injectors, flow and pressure, but I have not found anything. So, if the fuel feed is coming into the back throttle body, there is a higher feed pressure on the back throttle body, than on the front throttle body, because there is an additional pressure drop when leaving the back and going to the front. If the flow rate of the injector is rated at the same feed pressure, then the higher flow rate injector should be on the front and the lower flow rate injector on the rear.

Now this is all assuming that the SCFM is equal on both throttle bodies. I would not be suprised if they were not, due to the additional EGR runner on the backside of the manifold. So that throws another variable into the system.

Ken, to address your question, my opinion is that you are correct. Do you NEED to go to parallel plumbing? Probably not, unless you are wanting the exact feed pressure at each throttle body. It would definitely make your fuel injector flow rate closer to equal if you have equally sized injectors. But then how much variability is in the SCFM between the two TBs? If there is a different amount of air, then you will have a different air/fuel ratio between the two TBs.

So, the choice is up to you. Isn't hot rodding fun?