i run a carb and it is a known fact that the stock qjets put out less than 800cfm. most of the time much less. now with my friends tpi, i was wondering why everyone says they run out of breath so quickley, usually before 4 grand. now i also read that the tpi can intake 120cfm in EACH runner. 120 mulitiplied by 8 is a whopping 960 cfm. why then do the tpis run out of breath and make less power after 4 grand than a carb?

i was just wondering this info, so if im completly wrong, please feel free to give me the correct information.

o ya, DO NOT EVEN THINK THAT THIS THREAD SHOULD BE TURNED INTO ANY KIND OF FLAME WAR. if it does, mods just lock it.

 

TPI has 2 main restrictions.

1- horrible design. Air make a 90' turn in a turbulent plenum, then a tight 180' loop in the runner, then a quick angled transition sideways into the base then run it straight into the roof of the head port. All around NOT how to make an intake perform well. All those transitions and curves eat up energy that isnt all able to be quantified with a flow number.


2- long runners. Long runners by design create more friction on the incoming column of air, also aggravated by the bends. It also means the column of air leading into the head port has a lot of inertia. Which means that each intake pulse has a big mass of air to accelerate everytime the valve opens. That extra inertia gives it some help in the midrange, but is just a liability at high rpms. Again, this phenomena cannot be measured as a flow number.

 

so how does the superram make such good numbers when it looks like the same design?

 

Shorter and much bigger runners. Also usuaully ported and on top of a well matched combo.

 

I would hope a TPI runner would flow more than that... Im pretty sure a stock head will flow more than 120cfm.

 

the head may flow better than that, but there are serious restictions on intake systems.

 

Obviously the intake is a restriction, but mainly due to the runner length and the narrow rpm band it is designed to operate in. The runners have to flow over 120cfm or the engine probably wouldnt make over 150hp in stock trim.