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Different exhaust affect on tuning.

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Hello ive started getting comfortable mapping motorcycles, using the courses on here. I mainly been dynoing my own motorcycles (600cc 4-cylinder N/A) with good results. My question is regarding exhaust replacement. Due to noise regulations i have to use a more restrictive exhaust for some trackdays. This will naturally increase back-pressure, and exhaust temp (approcimately 5-10% decrease in max engine performance). Do you have any experience as to what i might expect to see differently using this exhaust, compared to the non-restrictive exhaust? Ignition, fuel ect. For these days i prefer reliability and safe engine operation above outright power. Best Afr with the current exhaust is around 13,6 - 12,8 from low to high load, and about 36 degress igniton advance during peak torque.

Kind Regards Kaare Jensen

I think it's time to make different thread here related to bike tuning,right? Also from this world,do you flash stock ECU?

You will likely get less VE at a given MAP, so you will probably need to remove a few percent fuel. If the ECU uses a Lamba sensor for closed-loop fuel control in WOT conditions, you may not have to do anything as the ECU could make the necessary compensation based on the O2 readings.

Is there any ECU that uses closed loop narrowband labmda for WOT or accel? Never heard about that...

Not closed loop narrow band. Closed loop wideband is used on many stand-alone ECUs. Narrow-band O2 is only useful for emissions compliance (and perhaps catalytic converter longevity).

Yes, it makes sense