Graves Garage-Why use Smog Block off Plates? What do they do? - Sportbikes.net
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post #1 of 5 (permalink) Old 01-16-2009, 04:17 PM Thread Starter
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Graves Garage-Why use Smog Block off Plates? What do they do?

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 tell me “they don’t make any horsepower so why should I spend the $35 and take the time to install them”.

Here is a quick but complete explanation on the benefits of using the pair valve 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 and through a bunch of hoses and fittings it pumps that fresh air into your exhaust ports on your cylinder head and sends it through your exhaust
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 O2 to the exhaust so that as the unburned fuel come into contact with the extremely hot catalytic converter, the additional fresh air will cool the exhaust and aerate the fuel for a more efficient burn. This equals less emissions being released. Plus the additional O2 in the exhaust the lower the emissions reading. I have heard a number of reasons this is done but I will stick with the basic theories that I am aware of.
(1) This requires a catalytic converter to really complete its job. Once you have installed a full race system and have removed the cat, all this fresh air will do it
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. The dyno “sniffer” is picking up false readings from the additional O2 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 only I 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
de-acceleration. 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
Graves Motorsports - Exhaust Systems, Performance Parts, AMA Supersport Team
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post #2 of 5 (permalink) Old 05-24-2012, 04:49 PM
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hmmmm okay but .... because most engines designed today are built with a certain amount of back pressure needed for them to run correctly ,so back pressure helps produce more horse power in smaller engines by holding back exhaust,and it helps them to build rpm,s if you completely remove an exhaust system from some cars they wont even run .
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post #3 of 5 (permalink) Old 05-29-2012, 08:49 AM
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The emissions plates do not alter back pressure characteristics from the exhaust. They will reduce the popping sometimes experienced from un burnt gasses on deceleration though...

The graves smg block off plates are standard add-ons for thousands of race bikes all over the world.


Graves Motorsports Smog Block Off Plates for Yamaha + Kawasaki Sport Bikes





Graves Motorsports Smog Block Off Plates for Yamaha and Kawasaki model Sport Bikes. Graves Motorsports Smog Block Off Plates are designed to seal off the ports on the valve cover used by the air injection system (a.k.a smog pumps or AIS). Sold in pairs

Fitment:
Yamaha R1 2004-2012 + R6 2003-2012 + R6S 2006-2009 + FZ1 All + FZ8 All + FZ6 All
Kawasaki ZX6R 2003-2008 + ZX6RR 2004-2006 + ZX10R All + ZX12 2004-2005 + ZX14R ALL


The air induction system (AIS) burns unburned exhaust gases by injecting fresh air (secondary air) into the exhaust port, reducing the emission of hydrocarbons.

Once these are capped off the air injection system can be safely removed. These Smog Block Off Plates are made from CNC'ed billet aluminum and feature the Graves Motorsports "G" logo. There are three reasons why you want to remove the air injection system from your bike;

1. If you are using your motorcycle on a closed course (racing, track days, etc.) you will want to remove all unnecessary equipment from your bike for reduced weight and ease of maintenance.
2. To get an accurate Air:Fuel (A/F) ratio when dynoing the bike. The air injection system pumps fresh air directly into the exhaust stream in order to burn off any unused fuel. Unfortunately by doing this the A/F ratio is thrown off by the extra "fresh air" in the exhaust stream. By removing the air injection system you can achieve an accurate A/F ratio.
3. This addition will typically remove the majority of popping on deceleration that can be experienced with un-burnt gasses within the emission charcoal chamber. Note: Proper tuning may be needed and this is general feedback.

.


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post #4 of 5 (permalink) Old 05-29-2012, 05:16 PM
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Ok so in that case simply capped mine off and it works fine. The plates are fancy looking...but you don't ever get to see them and for $1 you can just cap it off.
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post #5 of 5 (permalink) Old 05-29-2012, 07:57 PM
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I actually got rid of my TLS because of the PAIR valves. With Yosh pipes it had this stupid annoying backfire at 3200 rpm if I recall, on coastdown. Annoying as hell. Blockoff plates FTW.

KeS


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