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 Post subject: Complex Manifolds
PostPosted: Tue Jan 21, 2020 11:22 pm 
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I just wanted to make this quick post showing how convoluded intake manifold designs can cause
problems with high nitrous flow rates. Now, this is assuming that the nitrous system is designed to work
in a single point application. The more poorly the nitrous system design, the more likely problems will arise
from fuel drop out. Simply taking a good look at these photos should tell the story, at least if you have
any slight amount of common sense.

Generally, if the airflow has to make many turns and/or force fuel to a level below that of the valves, then
a direct port system will be required to ensure proper distribution.

Of course, the only proper system to use is WoN!

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 Post subject: Re: Complex Manifolds
PostPosted: Sun Feb 23, 2020 3:52 pm 
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Joined: Thu Feb 16, 2012 10:34 pm
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Location: Oulton Broad, Suffolk, UK
Great Post TurboBox, surprising that the simplest things can cause such a headache before you even get started.

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 Post subject: Re: Complex Manifolds
PostPosted: Mon Feb 24, 2020 4:34 am 
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It's a subject that people don't seem to grasp when I attempt to explain the hazards of such manifolds. I find that no matter how much you spell out the potential problems one can have, especially with generic garbage kits, they just roll the dice anyway. Then when things break, they come to me and ask what went wrong! :lol: :beatstick:


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 Post subject: Re: Complex Manifolds
PostPosted: Wed Feb 26, 2020 9:40 am 
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Location: Oulton Broad, Suffolk, UK
Similar thing I heard about my Scirocco (1990).

Changing the standard Air Intake to a straight piece of tube apparently altered the air flow such that it wasn't good.

Not my engine but same spec.

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I did actually change my to a "Power Rohr" but after speaking with the guys in Holland during a show, converted it back.

In fact mine didn't have the bend so basically was a straight bit of tube.

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So as you say, even the simplest of things like disturbed Airflows can drastically alter the engine and how it performs.

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 Post subject: Re: Complex Manifolds
PostPosted: Wed Feb 26, 2020 2:56 pm 
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I was speaking strictly in terms of fuel drop out issues in some manifold designs using a wet nitrous system, but you did bring up a point.

In terms of DRY type systems with a single nitrous injector (or nozzle), changing even the smallest aspect of the engine airflow can disturb the nitrous distribution. This leads to some cylinders running either too rich and others too lean because of the fixed aspects of using fuel injectors for the supplemental fuel.

For others stumbling upon this post, this is why the use of wet systems is what we mainly go for. By avoiding the issues and complexities of using a dry system, we can get great results with ease. And even if more of the wet system (single point injection) mix reaches a cylinder than others, at least the A/F ratio will not change and there is less danger to the engine. With WoN, the danger is very minimal as smaller nitrous doses can improve engine reliability as opposed to generic systems that greatly reduce it.

The risk in a single point wet system comes at the point the manifold increases the chance it takes for fuel to fall out of the mix and this can happen for a number of reasons. Mainly, A) the time it takes for fuel to get to the valves, B) centrifugal force acting on the fuel from harsh bends in manifold airflow, and C) gravity acting upon the fuel when airflow travels upwards. Of course, there are more aspect to this but those are the main issues and they can exist in combination.

Avoiding such issues on single point wet systems can be done simply by adding a progressive controller (up to a point), and/or converting to direct port. Progressive control helps the intake manifold deal with amount of nitrous/fuel mix so that fuel will have less of a tendency to drop out, but there is a point where progressive control will not be enough. By converting to direct port, the N/F mix bypasses the function of the intake manifold so that the mix remains even and arrives at the valves easily. The result is increased reliability and more greater power increases. :yes:

Now, the one caveat is when the engine/vehicle design doesn't lend itself well to installing a basic direct port system. At that point, more extensive and radical changes to the vehicle may be required in order to accommodate installing the DP components correctly, which is vital for correct nitrous/fuel distribution before it even reaches the induction system.


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 Post subject: Re: Complex Manifolds
PostPosted: Wed Feb 26, 2020 7:58 pm 
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Sorry TB, didn't mean to go off subject too far.

Some really good valid points there TB :yes: , on the Scirocco the airflow is important for those very reasons.

Using the Crossfire as a single point, the airflow is crucial on the secondary stage, hence going back to the original air intake.

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Hope that makes sense?

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 Post subject: Re: Complex Manifolds
PostPosted: Wed Feb 26, 2020 8:42 pm 
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:yes: :cheers:


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