explain theory of intake spacer

I'm in the semi-conductor industry. Unfortunately it's not automotive related. We develop systems (or components) used by the major chip and flat panel display companies to manufacture their products. It's interesting work...but doesn't excite me too much really. Rather be designing vehicle systems.

It just so happened I had to design a component to a system to heat Nitrogen flowing over 50 SLPM up to over 200*C in a relatively small amount of space. I did it in such a simple manner too that I would confidently say a nice heat soaked intake manifold does have an affect on the air temp flowing inside..even at a high flow rate.

One thing i did observe makes me wish i had a graph handy to show. Basically what i saw is that if you idled at a low flow for a while and then increased quickly to high flow, you'd get a temp spike that would surge up and then come back down. Basically what that would possibly correlate to is that when you are in the staging lanes, you manifold would absorb a lot of heat and basically store it. When you get to the line and go WOT, the rush of air would produce a dramatic spike in air temp as the heat in the manifold transfers to the air rushing through the intake. So you'd shoot way up pretty quickly. After a certain amount of time, the temp will actually begin to drop after this initial surge. How much time depends on the mass of the manifold that was absorbing the heat. If could be halfway down the track...or 2-3 miles after going WOT..who knows.

If i were to really play around with this, i'd maybe suggest making the manifold out of a material with very low thermal conductivity and polish the inside to reduce heat transfer. Toss a nice spacer on to keep the manifold from heat soaking and i'd think that would be the best at preventing the air charge from spiking when you go from low flow to high flow immediately....or at least lessen the spike.

But we are overthinking this IMHO. I personally run a 3/8" spacer. I also have a Cobra intake, so no coolant lines in my intake. My EGR works too, but i'll tune that out one day.

Lol. That might look funny!

Put about 2 feet worth of spacers, cut a rectangular slot in the hood, close the hood and then bolt on the intake. Then just extend the vacuum lines and wiring up to the intake plenum and let the throttle body sit wide open.

Then you'd have the air blowing past the plenum to cool it off!


Downside is to open the hood, you'd have to unbolt the intake