Intake air/fuel mixture

[Rufe0]

Hi All

I know this isn't strictly model making but if its a decent theory I might setup a small engine to test all these variables out.

I've been doing alot of research into modifying my car recently. As I understand alot of the automotive intake technology; variable geometry intake, tuned runners, variable valve timing etc all boil down to (at least in part) trying to achieve good air/fuel mixture. That being a highly diffused mixture. They use restrictions to increase air velocity and turbulence with the aim of achieving a well mixed charge. A more diffuse mixture increases efficiency and reduces emissions. The problem is to do this they must 'tune' the system for a specific power and rpm range. Outside of this range the system preforms poorly, so the solution is to have two or more tuned systems and switch between them.

This strikes me as odd, they are using tricks to diffuse the fuel in a shorter time and a smaller volume. Why do this when there is often ample space under the hood for a large diffusion chamber? If they used throttle body injection and a large inlet manifold on the order of perhaps 10 to 20 times the engine volume then the fuel would have plenty of time to diffuse and it would work at all rpm ranges, no tricks required.

The only problem I can see with this is throttle lag, however you could still use a closed loop engine control system for efficiency and emissions.

Or how about a combined system whereby you would have two independent fuel delivery control loops. The first would be my large diffusion chamber system(minus the throttle) which would supply a mixture of around 13:1 air/fuel ratio. That would then supply air to the normal modern system, with the throttle body and multiport fuel injection in close proximity to the intake valves. This way you have a highly diffused fuel mixture coming in from the diffusion chamber and the fast responsive control loop and all the efficiency and emissions benefits that brings.

Am I missing something?

Thanks Adam

 

[mu38&Bg#]

You are misunderstanding what the intake system does. The intake system is designed to fill the cylinder with as much air as possible, not mix air with fuel. The newest gasoline burning engines have direct injection, so fuel is only added to air in the cylinder and this works very well and is efficient. There is no problem mixing fuel with air.

Greg

 

[Rufe0]

You are misunderstanding what the intake system does. The intake system is designed to fill the cylinder with as much air as possible, not mix air with fuel. The newest gasoline burning engines have direct injection, so fuel is only added to air in the cylinder and this works very well and is efficient. There is no problem mixing fuel with air.

Greg

Not strictly true from what i've read. One quick example from http://en.wikipedia.org/wiki/Variable-length_intake_manifold

Variable geometry can create a beneficial air swirl pattern, or turbulence in the combustion chamber. The swirling helps distribute the fuel and form a homogeneous air-fuel mixture - this aids the initiation of the combustion process, helps minimise engine knocking, and helps facilitate complete combustion. At low revolutions per minute (rpm), the speed of the airflow is increased by directing the air through a longer path with limited capacity (i.e., cross-sectional area) - and this assists in improving low engine speed torque.

 

[mu38&Bg#]

I don't see anything convincing in that article. The same swirl can be had with fixed geometry intakes. The benefit of variable geometry is being tuned for more than on RPM.

 

[canadianhorsepower]

Not strictly true from what i've read. One quick example from http://en.wikipedia.org/wiki/Variable-length_intake_manifold

What you read, and reality is not the same thing.:hDe:

and dieselpilot is wright, an intake takes care of the air, and then gas was causing the problem. Liquid gas (not propane but gas in a liquid state) burn but does not explode "burning efficiency" That's when aluminium intake came to the scene not only for weight purpose but also for gas atomisation getting in contact with a hotter part. New technology is direct injection and it does solve a good part of the equation but not all. That article is referencing to old technology 2009 . The problem with the intake is the wave length of the frequency at the operating RPM. and that's cause by intake and valve timing A perfect intake length for a wide RPM good luck even F1 technology is not their yet. the closest one on the car manufacturer today is Honda with the I-VTEC

check this link
http://world.honda.com/automobile-technology/i-VTEC/

the other part you were talking about is called scavenging then again a frequency will kill all your good number if your not at the proper RPM or frequency

Hope it help a bit
cheers

 

[Rufe0]

I know about Helmholtz resonance, again one of those things tuned for a specific rpm, go outside that and it has no effect or can even have a negative effect. I see that as a negative, surely its more desirable to have a flat torque curve.

If it where just the case that as much air as possible where the goal then we would all be driving cars with oversized intake manifolds, minimum runners, high lift and duration cams. That would give you maximum airflow throughout the rev range.

 

[canadianhorsepower]

, high lift and duration cams. That would give you maximum airflow throughout the rev range.

with this answer , it's clear to see that your lacking information regarding engine performance:hDe:

your missing a lot of factor here .

High lift and duration is good for high RPM only

just think about it, if it would be a simple answer to this ideal intake tuning
it would already be in use