Orfice Size Question.

[LBZ]

So over in the PPE forum, there was the following thread:
http://www.mcratracing.com/forum/showthread.php?t=2194

I'm still curious as to why GM would make this orfice so small and what we are doing with our tuning to need to disregard the engineering god's original design?

 

[McRat]

Long ago we found out that there was a restrictor in the end of the driver's side rail near the front. This is how the passenger side gets fed. The CP3 feeds the driver's side, then goes through the restrictor to feed the passenger side rail. The restrictor is .75mm (.03").

So we opened it up to .125" (3mm) to improve the flow. However, we did not see a HP increase at the time, nor were their any side effects that we could see. Our HP level was 475rwhp.

Is it a good mod? Dunno. It's hard to undrill a hole and go back to testing, and I'm not buying a $400 rail to prove a point.

I can say this. We are making STOOPID power on stock injectors on fuel-only with a stock cam, and are 100% streetable. Certainly the drill-out mod did not hurt.

 

[McRat]

PS - Do the math. One injector flows .0059" dia X 7 holes vs. 0.030" dia.

 

[LarryJewell]

I installed the PPE Valve last weekend, I cant tell that it helped or hurt either. I do feel better knowing thats its there though, along with the BD manifold and the EGR delete. Couldn't tell a difference with either of those mods either, but I can at least say that they are done.