Engine Lag During Aggressive Acceleration...

[rodie81]

Wanted to get some feed back from other XB12 Owners...

I have an '08 XB12XT with just over 10k on the clock. The bike is set-up 'stock' (i.e., no exhaust, intake, or ecm mods).

I purchased the bike used and have put approx. 1000 miles on it. During this time I've noticed that under heavy acceleration I experience a momentary lag in throttle response. That's to say that my throttle input initially feels directly linked to acceleration (very linear) until I hit a half-open (approx.) throttle position... At this point the engine momentarily stops its linear acceleration (for a fraction of a second, just long enough to notice) even as I continue to roll-on gas... Then (almost as if a switch has been turned on) the engine continues to accelerate to redline and/or gear change. This is most noticeable when rolling-on throttle aggressively: accelerating from a stop, jumping from low rpm (idle) to high rpm, etc.

I'm wondering if I'm 'feeling' the interactive exhaust valve opening (and thus re-routing exhaust flow) as my engine hits some critical rpm, exhaust pressure, etc.

Any thoughts out there in Buell land? Anyone experience similar acceleration characteristics with their late-model Xb12's? I appreciate any feedback... Thanks guys!

 

[Stevenc150]

Mine used to have a hesitation, sometimes hiccupped, when twisting to full throttle - but only occasionally. I did 2 things that made a Noticeably big difference, so I'm not sure which made the bigger impact.

I switched plugs to NGK Iridiums (DCPR9EIX) from some basically Brand new HD OEM plugs.

And I did the Breather Re-route w/ Pics.

Maybe one or both of those will help. Also, I guess you're already you're running high octane gas.

 

[LeFox]

- breather re/route
- tps reset
in that order...

this should help reduce the lag. if you want more, you should get your ecm tuned.

 

[rodie81]

OK...

The breather re-route is at the top of my 'to-do' list. I'm running brand new (OEM) plugs, might try the NGK Iridiums. And yes, running 91 octane.

Back to the re-route... I didn't think it would have any substantial effect(s) at higher rpm... I thought it was primarily targeting off-idle/slow-speed 'choppy' engine characteristics associated with re-cycling spent exhaust gases..Yes/No?

I eventually want to tune the ecm. I would like to wait until after I fit my bike with an aftermarket exhaust..

My Uly is still under warranty, so I may take her to the dealership, see what they have to say.

Thanks for the feedback guys! This is a great forum for Buell owners!

 

[LeFox]

hold on...

are you still running the bike in? cause then it will get better.

a tps reset isn't an ecm tune, it's just a re-calibration.

 

[rodie81]

No, the bike is an '08 model with with just over 10k miles on the clock. (I'm the second owner, I purchased it with just over 8.5k). I still have warranty coverage thru the spring of next year...

And, yes, I realize that TPS Reset and ECM Tune are not the same thing... I don't want to mess with ecm mapping (if at all possible) until I mount an aftermarket exhaust.

Back to your re-route suggestion... you think this could help engine performance at higher rpm?

Thanks LeFox.

 

[LeFox]

yea, it helps with a smoother burn along the complete rpm range.

you just feel it more in lower rpm, like every fibration.

 

[isogear]

[up]
Thank you to all that helped with the breather re-route info.
As is said, it's the easiest and cheapest mod. to make. Makes technical sense too.
Did it to my 08 Uly . Routed the line down the front with breather about 1 foot above a pet-cock valve.
26K miles in 13 months. Best ride ever.

 

[okey]

rodie81 are you talking about if you are riding along at low rpm's then go wide open throttle is it then that you experience the lag?

 

[dallasb]

Wow how do you guys find these old threads

 

[isogear]

I have same issue with my 08 Uly XT. Lag from 4K to 4.3 K while asking for major acceler.

It comes and goes. I have done breather re-route, Use Iridium plugs, 91 oct. TPS reset, and even ECM code update from dealer ( they called it re-flashing, as if they are using EEProms. etc. etc. and it still happens.

But not all the time.

So, I'm convinced it's a result of the 'air/fuel mix versus load' learning pattern that the ECM uses while riding.

I've narrowed down to keeeping at lower RPM's , with low loads, for say over 20 minutes, to get the 'Learning curve for the ECM' to begace that way, and air temp. is a factor too.

For those of you confused about the real-time ECM learning algorithum....I have to say look up one of the posts on it. All I know is that it exists, and it does affect big accelerations at big throttle openings, in that narrow rpm band.

I just live with it, by anticiapting a need for full torque at those rpm's, and accelerate at the appropriate speeds.
hope that helps

 

[KRUSHERXX]

I had the same problem with the hesitation upon acceleration. I cleaned the throttle body. Problem solved.