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Discussion Starter · #1 ·
Some advice respectfully sought from the fuelling / tuning experts ...

Took the DB killer out of my Yoshi R77 for a ride this weekend that includes a good section of twisties. I also loaded the stock PCV map for running without the DB killer.

Highway and town riding was fine but there was noticeable hesitation exiting corners when getting back on the throttle around 5/6,000 rpm. I've ridden that bit of road many times with stock exhaust/fuelling, Yoshi with DB killer in/stock fuelling, Yoshi with DB killer in/PCV custom map/Dynojet stock map (all with stock air filter) and have never experienced any hesitation.

Am I right in thinking this is likely indicative of a momentarily lean condition caused by sharp throttle input? If that's the case, then would enabling the PCV Accel Pump feature be the way to go? If I can't sort it then it's back to DB killer in because I found the hesitation a real pain. I may put the DB killer back in anyway because without it's bloody loud without it!

Thanks in advance ...
 

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Discussion Starter · #2 ·
I should also have asked: "If it is a momentary lean condition, is it happening without the DB killer in because there's greater airflow through the engine and while the PCV stock map is adding fuel, it's not adding it fast enough at immediate throttle roll-on so just richening the map won't help?"

As I'm sure is obvious from these posts I'm no expert.
 

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It's either lean or rich. You are saying 5-6K RPM but how much throttle input? 20%? 40%? Try hard accel vs slow accel throttle...

My ECU is flash and honestly had to use neg number in A/P fuel trim. It was a bit too rich roll on throttle. On top of my head my settings are 3% throttle, 15 rev and -6% fuel.

Eyeball how much throttle you are adding when the problem occur then use that has a throttle value. Go up in fuel trim until the problem is fix... or down in value.

Now I also want you to keep in mind the PCV maps are generic map. Many factors can influence a tune... like elevation, temperature, humidity, gas used... Most map done here might be with E10 gas in the USA. Meaning with 10% Ethanol added... Corn fuel! So basically if you are experiencing some issues, might consider a custom tune from a reputable tuner in your area.
 

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Discussion Starter · #4 ·
It's either lean or rich. You are saying 5-6K RPM but how much throttle input? 20%? 40%? Try hard accel vs slow accel throttle...

My ECU is flash and honestly had to use neg number in A/P fuel trim. It was a bit too rich roll on throttle. On top of my head my settings are 3% throttle, 15 rev and -6% fuel.

Eyeball how much throttle you are adding when the problem occur then use that has a throttle value. Go up in fuel trim until the problem is fix... or down in value.

Now I also want you to keep in mind the PCV maps are generic map. Many factors can influence a tune... like elevation, temperature, humidity, gas used... Most map done here might be with E10 gas in the USA. Meaning with 10% Ethanol added... Corn fuel! So basically if you are experiencing some issues, might consider a custom tune from a reputable tuner in your area.
Thanks Marthy. I should have said that fuel is invariably regular 95 (that's the only non-ethanol fuel we can get here in Thailand). All the other variables have been pretty much constant (temp, humidity, altitude). I've also got basic PCV without Auto Tune.

I also should have made clear that it's only noticeable with sharp throttle inputs. Smooth input, no problem.

So sounds like it would be a good idea to try the Accel Pump feature?

BTW I'd LOVE to get a a custom tune from a reputable tuner in my area … but in the great metropolis of Bangkok there are, as far as I am aware, only two tuning outfits, neither of which really fill me with confidence.
 

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Ok. Try my AP settings and go up or down in fuel trim. But before check what your AT fuel trims are... AT can help as much as shoot you in the foot! Before doing anything... reset the trim and turn AT off for a ride. Find a good base map and keep the AT fuel trim set at (+/- 5%) 40% throttle & over... over 6K RPM.
 

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Discussion Starter · #6 ·
Thanks Marthy. I don't have AutoTune but sounds like playing with AccelPump settings is the way to go. Will be interesting to see what happens. Unfortunately I'm off on a 3-week trip day after tomorrow so will have to wait till I get back :(

I'll report back i.d.c.
 
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