I was wondering If you use the JG intake manifold that has the secondary injector boss's. would you get more performance putting the injectors up there instead of putting them right at the edge of the head.

I remember reading a while back about ITB setups and they placed the injectors spaced out from the stacks instead of having them in the factory location and they picked up some HP.

How would this play with a FI setup?

 

The general idea is that you'll make more power but lose some idle quality. When my RC injectors failed on my car, in diagnosing the problem I tuned off the primary injectors and turned on the secondaries (through the computer). I didn't really notice any difference in idle quality. Might be better to test on a setup that has adjustable injection timing because it's probably going to be significantly different as far as what works best.

How much power you'd gain, if any, i have no idea.

 

i picked up power in the higher rpm when i moved the injectors back in my big stroke comp4 motors with the jg manifold. it idles fine when i built the turbo motor i left them there when i was trying to find a misfire problem i moved them to the stock location to get ride of variables the power pretty much stayed the same

 

Generally, by moving the injectors farther upstream, you shift the powerband to a higher RPM. With my old ITB turbo setup, the higher injector location did hurt the idle quality and I wasn't able to idle the car below 900 RPM anymore. I don't have any direct comparisons though with different injector placements versus power and powerband.

I am not sure how that would work with a regular intake manifold though. With ITB's, the throttle plate/tapered neck area has the highest air velocity, and the injectors are placed right at that location. With a regular intake manifold, this could be completely different and probably makes no difference in power or powerband except for hurting idle quality.