Restrictor Plate for Emissions

[RHeld24]

Just wanted to bounce an idea off you guys...

My last smog (CA) was barely passing in the NOx category and it's that time of year again. From what I've learned, nitrogen oxides (NOx) are created by high cylinder temps as a result of high compression, a lean air/fuel ratio, pre-detonation or a combination of the above.

What I was wondering is, if I fabbed a restrictor plate in the airbox before the filter/maf sensor, would that help cut my emissions down? If less air = less fuel (because of the maf and a/f ratio sensor) then less air and fuel = less emissions, right?

I know this will cause some power loss, but, will it even work in the first place? A bigger/less restrictive intake should work inversely by the same idea...

This is all theoretical, I've already done plugs, wires, fuel filter, oil change, atf change (2qts.), coolant flush and running premium fuel (91) in preparation for the smog test. Just wanted to see what you guys thought.

 

[iowajosh]

Try some searchin. I think most people conquer such things by cleaning the MAF and maybe a new O2 senser or cat.

 

[RHeld24]

I cleaned the MAF about a year ago. I also read that old 02 sensors tend to have the engine run more rich than new units (so I be in favor of my old one). As for cats, what I've found in my search is that they only clean up hydrocarbons (they burn the unburned fuel in exhaust - which is why cats are so hot during use). Also, my 4Runner is a 96', which means that it does NOT have an EGR.

To clarify, my question is: would a restrictor plate in the airbox lessen emissions?

 

[Toms97]

A restrictor plate will do a great job of making your engine struggle more and more as the RPMs go up, and not really change the emission numbers a whole lot. Want to improve your emissions?

Clean or change MAF, yes you cleaned it a year ago, only takes a few minutes to do it again. It has been a year, I know I do mine every 2 oil changes just to keep up on it.

Change your O2 sensor, it isn't as young as it used to be.

Change your cat, as they age they develop problems and become less efficient.

What you want is for the engine to get the air/fuel mix right so that it burns it as efficiently as possible. Doing so gives better emissions, better fuel mileage and better power. The sensors doing their job well lets the computer keep things going nice and smooth.

As a side note, cats don't actually burn the unburned fuel. They use a series of chemical reactions to change the different chemicals in exhaust into less harmful chemicals. Most modern cats do this with a series of 3 reactions, catalytic pretty much just means that it contains catalysts for chemical reactions (like platinum). They are hot because the exhaust is hot, they often run in the 600 - 800 degree range but they aren't the hottest part of the exhaust. The manifolds/headers on quite a few engines can reach over 1000 degrees.

 

[Singtoe]

I cleaned the MAF about a year ago. I also read that old 02 sensors tend to have the engine run more rich than new units (so I be in favor of my old one). As for cats, what I've found in my search is that they only clean up hydrocarbons (they burn the unburned fuel in exhaust - which is why cats are so hot during use). Also, my 4Runner is a 96', which means that it does NOT have an EGR.

To clarify, my question is: would a restrictor plate in the airbox lessen emissions?

A restrictor plate would not change anything unless you drove wide open throttle . This would be helpful if you were one continuous left turn.


If you want to make it run richer, you would need to trick the ECM.

Here is what you need. Underdog Racing Development