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Old 12-15-2009, 03:46 PM   #28
Former Vendor
Member#: 160427
Join Date: Sep 2007

Originally Posted by J Howerton View Post
I would like to add my experience to the discussion. From what we've experienced, the further away from the TB the better, with the exception of the BOV issue. Here are a few rough calc's and an example.

Using the numbers a couple of posts ago, 40lbs/min and a 2.5" ID pipe for simplicity, the air is roughly at 177mph or 3128 inches per second of travel. This means each inch of air passes the jet in roughly .0003sec. At the molecular level of evaporation, this is quite a long time.
Pretty good calcs! But what you have to consider is the amount of time the air spends post TB and pre-cylinder heads. This will be much longer in a lof of cases where you have a fairly large aftermarket plenum chamber relative to a normal size IC pipe. So lets say we get a nozzle a full 2 feet before the TB, you then have about .007 seconds by those calcs before it is past the TB. You likely have much more than that long between the TB and the intake valve, which is where a lot of the cooling will occur.

The other thing to consider is that cooling in the combustion chamber is often just as important in these applications as it is in the intake plumbing. The cooler air charge before the intake valve will help get more 02 in, and basically help with volumetric efficiency. But the detonation prevention aspects of reduced cylinder temps are at least as important, particularly if we have a FMIC in place already. And when you look at the time spent in the combustion chamber, and the pressures, temperatures, and flow characteristics inside the chamber, every last bit of the liquid is going to absorb as much as it possibly can (unless something is very wrong).

In the end it is spliting hairs a bit, and a nozzle right after the IC might have the benefit of showing a bit more cooling on an IAT sensor. So really its more of a case by case basis. Most of our customers find that the biggest concern regarding placement is more of an installation and functional one rather than the theoretical, even when they do have an FMIC.

Great discussion guys!
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