Arrow Exhaust

Hi, I have the arrow slipon on my V2 and everything is fine when warm, but on a cold start if I do a tiny blip of the throttle after a minute of idleing it stalls and then is hard to start again.

Im running the t800+ UpMap. I have disconnected the O2 sensor as well.

Is this normal?


Thanks

Your symptoms—stalling on a cold start after a small throttle blip and difficulty restarting—aren’t necessarily "normal," but they’re not unheard of with aftermarket exhausts and ECU tweaks, especially when the O2 sensor is out of the picture. Here’s what could be at play:

1. Cold Start and Fueling: Motorcycles, especially modern ones like the V2, rely on the ECU to adjust fueling based on inputs like engine temperature and O2 sensor data. Disconnecting the O2 sensor forces the bike into open-loop mode, where it runs off a pre-programmed fuel map instead of real-time feedback. The T800+ UpMap is designed to account for this with a tune tailored for the Arrow slip-on, but if the map isn’t perfectly dialed in for cold-start conditions, the air-fuel ratio (AFR) might be off—likely too lean—causing the stall when you blip the throttle. That would also explain the hard restart, as the engine might be flooded or struggling to find the right mixture.
2. Throttle Blip Sensitivity: When cold, the idle is typically higher and more delicate. A sudden throttle input can disrupt the airflow and fueling balance, especially without the O2 sensor to help the ECU adapt on the fly. With the stock setup, the ECU would use closed-loop feedback to smooth things out, but in open-loop mode with the UpMap, it’s less forgiving.
3. T800+ UpMap Calibration: The T800+ UpMap for the Arrow slip-on should, in theory, disable O2 sensor errors and optimize fueling for the exhaust. However, not all maps are created equal. If the specific map you loaded wasn’t designed with cold-start behavior in mind—or if it’s a generic tune not perfectly matched to your setup (e.g., altitude, air filter, or other mods)—it could leave the bike running suboptimally when cold.
4. Hardware Factors: The Arrow slip-on itself changes exhaust flow, and without the catalytic converter or exhaust valve (if removed), backpressure is reduced. This can exaggerate fueling issues during cold starts. Also, double-check that your install is airtight—no exhaust leaks—since that could throw off the system further.

Is This Normal?
Not entirely. Many riders run slip-ons with UpMaps and disconnected O2 sensors without major issues, but cold-start stalling isn’t a universal experience. Some report needing a few heat cycles for the ECU to "settle" after installing a slip-on, while others notice quirks like yours if the tune isn’t spot-on. Your bike should be able to handle a small throttle blip without dying, even when cold, so this suggests something’s slightly off.
What You Can Try

• Let It Warm Up Longer: Give it a solid 2-3 minutes of idle before touching the throttle. See if that stabilizes things. Modern ECUs often enrich the mixture during warmup, and the UpMap might need more time to get into its groove without O2 feedback.
• Check the UpMap Version: Confirm you’re using the latest T800+ map for the Arrow slip-on on the V2 (e.g., the "SR" or a specific Arrow tune if available). Older or mismatched maps (like one for a Termignoni or SBK exhaust) might not play nice with your setup.
• Reconnect the O2 Sensor Temporarily: Plug it back in and see if the behavior changes. If it improves, the UpMap might not be fully disabling closed-loop operation or compensating properly. This would be a clue the tune needs tweaking.
• Idle Speed Adjustment: If the idle feels too low when cold (below 1200-1400 RPM, depending on the V2’s spec), the UpMap or a dealer might need to bump it up slightly.
• Heat Cycles: Run a few full warmup/cooldown cycles. Some riders find the ECU adapts better after this, though with the O2 sensor disconnected, adaptation is limited.
• Custom Tune: If all else fails, a dyno tune tailored to your bike might sort it out. The T800+ is convenient, but a custom map can nail the AFR for your exact conditions.

My Take
This doesn’t sound like a major issue—more like an annoyance that’s fixable. I’d lean toward the UpMap’s cold-start fueling being the culprit, given the O2 sensor is out of the equation. It’s not "normal" to stall like this, but it’s not uncommon either with aftermarket setups. Start with the easy stuff (longer warmup, verifying the map), and if it persists, consider a dyno run or reaching out to Termignoni/UpMap support for advice on your specific config.

wow, what a reply. Thanks for the detailed info.
After a couple of minutes it is totally fine and have never stalled at the lights etc.

I'll go through the tinks you sugest.

Thanks!!!

carldickson said:

Hi, I have the arrow slipon on my V2 and everything is fine when warm, but on a cold start if I do a tiny blip of the throttle after a minute of idleing it stalls and then is hard to start again.

Im running the t800+ UpMap. I have disconnected the O2 sensor as well.

Is this normal?


Thanks

Click to expand...

The cold enrichment is incorrect. They didn't compensate enough for the exhaust. The O2 sensors are not active until the bike warms up. Everything runs a map before the O2 sensors come online. So it has nothing to do with that.