Low end torque loss after full system change

tarzan1234 · Nov 5, 2017

Hey, I?ve recently changed my stock exhaust to a full system exhaust. May I ask if it?s normal for low end torque losses ? Isit advisable to do an ecu tuning after a full system change ?

crimsonxholic · Nov 5, 2017

Yes, it is advisable to get a tune after changing exhaust and intake components

Jp Freeman · Nov 6, 2017

It is not unusual to lose low end torque when changing to a less restrictive exhaust system.
The HP and torques curves tend to get more peaky towards higher RPMs.
An ECU tuning will not bring back the broad torque curve of the original exhaust.

A less restrictive exhaust and retuning will produce more HP but not at the low end.

Tremonte · Nov 6, 2017

I had the complete opposite effect, and here are all three dyno results overlaid so you can see the increases. Stock(red) vs. Yoshimura Alpha(blue) vs. Exhaust + ECU tune(green).

Cowasaki · Nov 8, 2017

It's the ECU tune that helped and it's usually suggested you do this after modifying the exhaust. But if you're going to get a new air filter and make a few other changes, maybe wait a bit and then tune it with everything installed.

Tremonte · Nov 13, 2017

There was a good month or more gap between adding the exhaust, then getting the ECU and tune done. This was due to waiting on the production release of the Rapid Bike ECU. The largest gain came solely from the exhaust. No losses, only gains at each step in the tuning process. The ECU gained us a bit more power, but it was minor compared to the Yoshimura alone. The biggest thing the ECU did for me was correct the AFR curve, and allow reduced engine braking.

As far as doing everything all at once, then tuning... You can do that if you decide on a Power Commander, or a Bazzaz without the extra auto-tune module. Or, just go ahead and step into the Rapid Bike unit, switch it to auto and it will tune itself and continually monitor the conditions. No dyno tune needed, and it will fully tune within 100-200miles. Want a custom tune that's more aggressive for certain situations or track days? Simple press of the map switch and you're done. A professional tune alone will cost you $200+, not including the unit install for the PC5. Take that cost and get the better unit, and install it yourself. It's plug and play, and you'll come out cheaper.

S2K_MoZo · Nov 13, 2017

May I ask what exhaust system you got? I have yet to purchase an exhaust but I haven't read anywhere about torque loss. Every video/blog I've seen mentions how it opens up this bike.

Low end torque loss after full system change

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