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Discussion Starter · #1 ·
Thanks to Glen / Fangshui for the rearsets and Daryl / cwmoss for the Yoshi full exhaust. Definitely makes our already sleek bikes look even sleeker!

Now a question for the crowd - I thought that adding a freeflowing exhaust would help increase the horsepower of an engine, as it offloads backpressure.

But many posts mention that a full exhaust decrease output on our R3's if you don't remap the ECU. Why is this?

Something related to the O2 sensor getting different readings and injecting more fuel than needed?
 

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Get a fuel controller and smog block off plate.

Bike looks excellent. I wish I had stuck with my original purchase of red. I actually went back and changed to blue. Regretting that.

You got a smoking deal on the exhaust so that will take the sting out of the extra items to get the most out of it.
 

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Red is nice but I cannot resist the blue wheels. Awe-some.

Anyhow, the standard mapping is based to let the stock engine+exhaust ok. Not brilliant, but ok. Why, because they have to deal with plenty emission regulations. Let's say that your full system is made for optimal performance, now it gets the same treatment as stock.

All this is once explained (better;))in a topic about the power commander, plenty of info there.

All this is why I've chosen to stick with the R77 slip-on :$
 

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Discussion Starter · #4 ·
So to quote Xyzzy from the other Power Commander thread
"When you open up the bike with intake and exhaust mods you allow more air into the engine. The engine is really just an air pump. So you have a lot of extra air but the stock amount of fuel. The map in the ECU can make minor modifications to the fueling to accommodate altitude changes or humidity/temperature changes, but it cannot accommodate huge changes. So you end up running lean all over. To do all of this properly you need a dyno and an air-fuel ratio meter."

So essentially a full exhaust just makes the engine run too lean? And you need an ECU remap to get it to dump in more fuel, to regain the lost horsepower?
 

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So to quote Xyzzy from the other Power Commander thread
"When you open up the bike with intake and exhaust mods you allow more air into the engine. The engine is really just an air pump. So you have a lot of extra air but the stock amount of fuel. The map in the ECU can make minor modifications to the fueling to accommodate altitude changes or humidity/temperature changes, but it cannot accommodate huge changes. So you end up running lean all over. To do all of this properly you need a dyno and an air-fuel ratio meter."

So essentially a full exhaust just makes the engine run too lean? And you need an ECU remap to get it to dump in more fuel, to regain the lost horsepower?
Motorcyles are already set to run very lean in order to meet emissions regulations/standards. Opening up the airbox can allow more air flow and make a bike run even leaner.

Same with a less restrictive exhaust. Here you're altering exhaust flow velocity, too.

A re-map or A PC module can compensate.

Here is a pretty good artcile on Exhaust Theory. It's aimed at cars, but same, same for motorcycles.

http://www.gomog.com/allmorgan/exhaustbackpressure.html

Spears Racing would be a great source for in-depth knowledge on this subject.
 

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Generally, even with the stock exhaust, you'll gain power if you do an ECU remap. That's how constricted the factory ECU is to meet emissions requirements.
 

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All of the full exhaust systems have a larger diameter pipe, this will just kill the bikes performance, while working with M-4, I was able to give them my findings on the systems to that point(yosh, akro) that I had dyno'd..all lost HP while making more noise..

So the bikes come here to the USA very lean to pass any of the emission standards, a block off plate and a PCV will make a big difference...Also remember when you purchase a PCV from us you will get a map for your exhaust system(not like some of the other vendors that state the same,they are just getting a map from Dyno jet)
 
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