So a guy I work with has upgraded his exhaust (full exhaust—head pipe and mufflers) and air cleaner without tuning his bike. Is he running a risk of damaging the bike or is it just not running as well as it could and not optimizing his upgrades?

 

IMHO....you can change the exhaust without a tune but.....once you change the air intake...adjustments need to be made.

 

Now that he has increased air flow his bike is more than likely running too lean. Tell him to buy a tuner. FP3 is easy to use.

 

It will need more petrol to match the increase in air.

I am sure with the right hardware and program the EFI system could of taken care of itself without the need for tuning devices. Unfortunately EPA and EU emission laws probably killed that idea.

 

Here's a simplified, down & dirty about the tune issue....

Any OEM tune, on a bike with O2 sensors, has both open loop & closed loop portions to the tune.

The closed loop portion is constantly adjusted, real time, based on the feedback from the O2 sensors. The closed loop portion is limited by the limits of the OEM narrow band O2 sensors (AFR range of approximately 14.3:1 thru 15.1:1). That range is mostly in the cruise areas of the tune...

The open loop portion is controlled by algorithms, based on how the ECM is programed. It is NOT adjusted on feedback from the O2 sensors. It's parameters are based on what was put into the tune, matching the OEM components. The closed loop is mostly in the extreme portions of the tune, outside the cruise range.

The problem with NOT retuning to match the new added air flow (new air filter & freer flowing exhaust) is not in the cruise portions of the tune. In the cruise portions of the tune, the o2 sensors and ECM can do a fair job of adjusting the tune to fit the new air flow. The problem is in the extreme portions of the tune. The high rpm/high load portions, where the tune is actually more critical...

If you friend does not retune, and doesn't drive aggressively, and doesn't frequently venture into the extreme areas of the tune, he may not even notice... but the bike won't be running at it's most efficient and best... But any time he lugs the engine, or pushes it's limits... he runs a risk of engine damage..

If your friend rides aggressively, likes to "drive it like he stole it"... he will be venturing into the extremes of the tune on a frequent basis... it will not run it's best, and he runs a higher risk of doing some damage to the engine ...

If he has a pre-O2 sensor bike, then the entire tune is open loop, without O2 sensors for feedback... There is a greater risk of engine damage...

Many people don't retune for Stage I engine mods like your friend is doing, and their bikes aren't strewn along the side of the highways...

Many people, myself included, know that even an OEM bike can benefit from a tune, and wouldn't consider modifying the engine without retuning...

Some will dyno tune any engine change, and some will accept a canned map from a reputable shop (and maybe do an Auto tune or two) for all but the most aggressive engine mods.... but that is an entirely different discussion for a different day.....

Again, basic and simplified... but it should allow him to make an informed decision..

 

Open loop - well that seems to make the decision quite straight forward, thank you.

 

hattitude Thanks for putting it into words everyone can understand. Although I totally agree with you , I could not have put it together in such a simple, easy to read statement without confusing people. Thanks again

 

Allow me to simplify. If add both a more open exhaust and Air cleaner, you need a tune. If you get either the V&H or Fuel Moto they have canned maps that will work.

 

Thanks for all the inputs guys. I knew that he should tune---especially with both exhaust & air upgrades. But was wondering about the long term effects...which is what I was hoping would sway him.

 

Long term effects usually become short term effects when running an engine lean. Holes in the pistons and or burnt valves so the engine quits, whichever comes first.