Graves Garage-Why use Smog Block off Plates? What do they do?
This seems to be a popular set of questions over here at Graves Motorsports. Most people say to me.....
they dont make any horsepower so why should I spend the $35 and take the time to install them?.
Here is some info on the benefits of using the smog block off plates on just about every model motorcycle.
*This is for off road racing applications and not meant to be used on the street.
If you have something to add please feel free.
From the factory most motorcycles will come with a pair valve system on them. This is basically an air pump that pulls fresh air from your air box, sends it through a bunch of hoses, and then pumps that fresh air into your exhaust ports on your cylinder head.
There is unburned fuel that makes it through the combustion stroke, exits the cylinder head, and makes its way down the exhaust system to finally exit into the atmosphere. The pair valve system adds fresh Oxygen to the exhaust so that as the unburned fuel comes into contact with the extremely hot catalytic converter, the additional fresh air will aerate the fuel for a more efficient burn and keep the exhaust cooler. This equals less emissions being released into the atmosphere and lower emission readings when tested. Here are some of the main reasons you should consider installing the smog block off kit on your motorcycle.
(1) The pair valve system really requires a catalytic converter to complete its job of burning off excess fuel. Once you have installed a full race system and have removed the cat, all this fresh air will do is mix with the unburned fuel vapors and beginning to burn up while exiting the exhaust. This create the popping and back firing that throws those incredibly cool but damaging flames out of your exhaust. Great for night riding, but terrible for tail sections and leg hairs. To eliminate this add the smog block off plates.
(2) If you decide to have your bike dyno tuned then you cannot run the pair valve system because as it adds oxygen to the exhaust gases. This causes dyno sniffer (reads the air/fuel mixture exiting the motor) to pick up false A/F readings due to the additional Oxygen that is added after combustion. When it reads the extra O2 it thinks the bike is running lean and will compensate by adding fuel to the fuel map. Now you have a map that is much fat (too much fuel) and the bike will run terrible. The person that is tuning the bike will have to pinch these off every time you dyno the bike. To eliminate this add the smog block off plates.
(3) The tubes, pump, and wires that are included in the pair valve smog system add unnecessary clutter and weight to the motorcycle. To eliminate this add the smog block off plates.
(4) This is the last reason I have found to run the plates but it is NOT A FACT. It seems, not everyone have noticed this and nobody has proven it right or wrong so do not take this as absolute. It could very well be just by brain acting up.
I believe I felt it help my engine breaking a little. Before I installed them I felt like the bike (08 R6) had a really strong engine breaking and would pop and back fire a lot on decceleration. When I installed the plates I would swear that the engine breaking became more suitable. It was not as abrupt and not nearly as strong. Again this was only a guess and has no proof to it, however I did talk amongst a few tech savvy buddies and we worked out a somewhat scientific theory. Possibly as the hot engine gases are pouring smoothly out of the cylinder head like melted butter this cold fresh oxygen is forced into the exhaust ports. This could very well slow those gases down and create more back pressure which in theory could possibly cause stronger engine breaking. So?..maybe Im not crazy.
Taige Webster
Graves Motorsports
http://www.gravesport.com