MAF to TB Plumbing


Active Member

Been a while since I posted but still messing with my ‘64 Riviera hybrid. I’ve finally reached the point of getting a real FMIC vs. a scooped stock unit so new plumbing. The FMIC has 3in outlets, the MAF takes 3.75in hose (85mm LQ4 style), and of course the stock TB takes 2.5in hose. Since I‘m running a 4in MAFless inlet pipe and have enough room for a straight run the MAF is post turbo and intercooler. My question, should I go straight from the 3.75in MAF coupler to 2.5in tubing immediately or back to 3in for a few inches then down to 2.5 right before the 30deg bend heading into the TB? Unfortunately I have to stick to 2.5in right off the TB as the 4in inlet pipe is a hairs breadth away from hitting the 2.5in pipe as it is. Not too concerned with the lumpy look of the nearly sequential reducers on the multi-step idea.

MAF post turbo? Wow, that seems like a lot of pressure on a fairly delicate piece of equipment but people do it, it seems. Neck down won't hurt anything, doesn't have to be a long transition. Kind of like those old snake oil Vortex swirl things they used to sell, it did nothing.