Menu
What's new
By:
Filters

Hesitation WOT

DanijelTodic

DanijelTodic

Active Member
Joined
Oct 17, 2019
Messages
109
Location
Amsterdam, The Netherlands
He guys!

I have a question regarding the throttle response on my flashed 2015 S10.

The bike sometimes lacks power when WOT from around 3500 to 4500 rpm. This is only if i open up the throttle without rolling on. Just snapping it open. The strange thing is that it's random. Most of the time she takes of real quick but sometimes she seems to be holding back. Like she is being limited. Weird.

Hope you guys can shine a light on this
 
Alexander

Alexander

Active Member
Joined
Mar 8, 2020
Messages
83
Location
Kansas City
In my experience (tuning high-horsepower forced induction cars with aftermarket ECUs for 15 years), this is purely a fueling issue. The hesitation/stumbling you're feeling is due to a lean spike caused by the rapid increase in airflow without a matching increase in fuel injector pulsewidth.

The aftermarket computers I work with have specific tables to combat this, separate from the primary fueling tables -- often called "acceleration enrichment," the digital equivalent of an accelerator pump -- which are used to dump in extra fuel based upon the rate of TPS% change or MAP or a blend of both. Most engines like to have a LOT more fuel under rapid throttle changes, like pig rich 10:1 that would freak most people out, but you have to tune this by feel rather than by targeting a specific AFR like usual. I could elaborate at length, if you're interested, but it's more information than most people care to read.

I notice this problem myself on the stock tune with throttle blips, and it annoys me, but Yamaha has to deal with emissions and fuel economy constraints, and the stock ECU might not be the most advanced thing ever.
 
Last edited:
DanijelTodic

DanijelTodic

Active Member
Joined
Oct 17, 2019
Messages
109
Location
Amsterdam, The Netherlands
Thank you for this very thorough explanation. So what happens is that simply said the fuel is not able te keep up with the amount of air when snapping the throttle open...? It does make sense but I am surprised that the guys who flashed the ecu did not address this.
 
Don in Lodi

Don in Lodi

Well-Known Member
Founding Member
2012 Site Supporter
2013 Site Supporter
2014 Site Supporter
Joined
Feb 1, 2011
Messages
5,780
Location
Lodi Kalifornia
Are you always in the right gear for the speed? Slapping a whole bunch of throttle at 35mph in sixth gear ain't gonna do much.
 
twinrider

twinrider

Well-Known Member
Joined
Sep 28, 2011
Messages
1,882
Location
Yokohama
DanijelTodic said:
He guys!

I have a question regarding the throttle response on my flashed 2015 S10.

The bike sometimes lacks power when WOT from around 3500 to 4500 rpm. This is only if i open up the throttle without rolling on. Just snapping it open. The strange thing is that it's random. Most of the time she takes of real quick but sometimes she seems to be holding back. Like she is being limited. Weird.

Hope you guys can shine a light on this
Click to expand...
Not all flashes are equal. Get in touch with Chris Steedman at CJS Racing in the UK and he can sort you out. http://www.cjsracing.co.uk/

He sent me a flash via a shop he works with in Japan and it is awesome. Zero issues, loads of performance.
 
StefanOnHisS10

StefanOnHisS10

Converting fuel into heat, noise and a bit motion
Staff member
Global Moderator
Joined
Apr 8, 2020
Messages
2,168
Location
The Netherlands, Friesland.
@twinrider . Could that work without going there? I mean can he do a flash via my own PC or something? That he sends the file and we update it to the ECU via a cable? Maybe a stupid question... @DanijelTodic and I both live across the pond. That would be interesting!

stefan.
 
WJBertrand

WJBertrand

Ventura Highway
Joined
Jun 20, 2015
Messages
4,528
Location
Ventura, CA
If you're cruising along at part throttle at speed, the velocity of the intake air, through the small throttle opening is pretty high. Suddenly snapping the the throttle open, at the same RPM/ air flow rate, causes the intake velocity (not to be confused with volume) to suddenly drop and momentarily disrupts cylinder filling causing a loss in power. I don't know if a direct injection engine would behave the same way, but as our engines are port injected, that sudden loss of intake velocity disrupts both air and fuel delivery to the combustion chambers momentarily. I suppose a more sophisticated EFI system, with an intake flow sensor, might better compensate for this by limiting throttle opening electronically, but our bikes don't seem able to do that.

What tune are you running? I noticed this effect with the Flash Tune canned tune, but haven't tried it with Anthony's tune.
 
DanijelTodic

DanijelTodic

Active Member
Joined
Oct 17, 2019
Messages
109
Location
Amsterdam, The Netherlands
StefanOnHisS10 said:
@twinrider . Could that work without going there? I mean can he do a flash via my own PC or something? That he sends the file and we update it to the ECU via a cable? Maybe a stupid question... @DanijelTodic and I both live across the pond. That would be interesting!

stefan.
Click to expand...
That would definitely be interesting. I could send the file to the company that flashed my ECU.
 
DanijelTodic

DanijelTodic

Active Member
Joined
Oct 17, 2019
Messages
109
Location
Amsterdam, The Netherlands
WJBertrand said:
If you're cruising along at part throttle at speed, the velocity of the intake air, through the small throttle opening is pretty high. Suddenly snapping the the throttle open, at the same RPM/ air flow rate, causes the intake velocity (not to be confused with volume) to suddenly drop and momentarily disrupts cylinder filling causing a loss in power. I don't know if a direct injection engine would behave the same way, but as our engines are port injected, that sudden loss of intake velocity disrupts both air and fuel delivery to the combustion chambers momentarily. I suppose a more sophisticated EFI system, with an intake flow sensor, might better compensate for this by limiting throttle opening electronically, but our bikes don't seem able to do that.

What tune are you running? I noticed this effect with the Flash Tune canned tune, but haven't tried it with Anthony's tune.
Click to expand...
This sound pretty plausible. If i just roll on the throttle a bit she flies off. But even after the flash she is quickest around 5000rpm and up when accelerating. Is that the same with your bike?

I am running a tune that is flashed by a Dutch company called Carmo.
 
twinrider

twinrider

Well-Known Member
Joined
Sep 28, 2011
Messages
1,882
Location
Yokohama
StefanOnHisS10 said:
@twinrider . Could that work without going there? I mean can he do a flash via my own PC or something? That he sends the file and we update it to the ECU via a cable? Maybe a stupid question... @DanijelTodic and I both live across the pond. That would be interesting!

stefan.
Click to expand...
I'm in Japan. He sent it to a shop he works with in Japan and they uploaded it to my ECU. So he could send it to that shop that flashed your ECU if they were willing to do the upload for you. Mine is also a 2015 EU spec so you could use the same flash he sent me. Tell Chris that Jim in Japan recommended you contact him about that flash he sent me.

Btw. I can whack the throttle open at any speed and the motor instantly responds.
 
Last edited:
You must log in or register to reply here.
Top