Recently, I installed V&H dresser duals, Ventilator elite air filter, and SE race tune. The shop dyno turned the bike, however, the throttle seems to be very different. Does the tuning change throttle response? Since the tune, the throttle seems "jerky". In other words, slight moments of the throttle equal large changes in fueling.

 

If the VE tables are NOT synchronized correctly you can definitely feel it in the throttle with flat spots along with the jerking as you said. This is one reason we always sync the VE tables before the throttle sensitivity is set.....! So to answer your question ''will a tune up change the throttle response'' a good tune up will enhance your response, a bad tune will make it jerky.
Doc

 

Hi Doc, do you mind if I ask what you mean by "Synchronised"? Others just talk about mapping them out ...you sound a little more purposeful there. cheers

 

[QUOTE=Gordon61;15314880]Hi Doc, do you mind if I ask what you mean by "Synchronised"? Others just talk about mapping them out ...you sound a little more purposeful there. cheers[/QUOTE

The Harley doesn't have a MASS AIR FLOW SENSOR as our cars and trucks do, so we as tuners have to program the ECM or tell the ECM how much air is flowing through the motor. We use the VE tables to do this edit....we raise the VE values to get more fuel and lower the VE values to take fuel away. So how is this done.....the simplest way I can tell you this is first we program the ECM to give us a AIR FUEL RATIO (AFR) of 13.5 across the board in the FUEL TABLE, now that the ECM knows we want 13.5 it will try it's best to deliver that 13.5 AFR. We use the Dyno to sample the AFR by making runs in the THROTTLE POSITION and RPM break points that map has designated. We install an 02 sensor in the pipe, either by a sniffer or one installed in the pipe bung, to sample what the AFR is coming out of the engine. If the sample isn't the 13.5 I requested the ECM to give me then I will adjust the VE Table, at the RPM and THROTTLE POSITION break points the map has, to achieve the 13.5 AFR I requested by taking fuel away in the rich spots by making the VE values smaller and adding fuel in the lean spots by increasing the VE values. After this edit has been made we sample the AFR again using Dyno.......if I am getting the 13.5 across the board then I was successful, if not I will make another adjustment to the VE table until the 13.5 requested is actually coming out of the pipe 13.5. So if I asked for 13.5 AFR and 13.5 AFR is sampled the fuel is now synced to the VE tables....at this point I could ask the ECM for 14.5 in Cruise and the ECM will deliver 14.5, I could ask the ECM for 13.0 at wide open throttle and the ECM will deliver what ever I request.
I as I said this is the easiest way for me to explain Synchronizing the VE tables....2007 and up Harleys have added Adaptive Fuel Values that allow us tuners to Sync VE tables using the stock 02 sensors which makes the process much faster, however the bottom line is the VE Tables HAVE TO BE Synchronized so the ECM knows how much air is flowing through the motor at any RPM and Throttle position before the tuning tables are are touched. The VE Tables effect EVERYTHING....if they are wrong EVERYTHING is wrong....they are the MATH of the map.
One thing I see at most tuning shops and dealers is the operator never checks his o2 sensors to see if they are reading correctly. If the 02 sensor isn't reading right then your out come will NOT be what you are requesting......tuners are ONLY as good as their 02 sensor are. If you ask a tuner when the last time he checked the accuracy of his 02 sensor and he says its the same one the dyno came with get the heck away from him as fast as you can. I check the bikes 02 sensors before I tune it, if they are lazy, or not reporting correctly I address them before I do the tune up.
Doc

 

^^Thanks Doc

I thought you were maybe hinting at the front and rear VE's needing to be "synchronised" or within a certain percentage or something, or even hinting at the need to tune CDE/EGR.

That jumpiness I found could still happen after the VE was mapped properly (ok so I don't have a dyno but autotune said it was right anyway) because of large steps in VE between adjacent cells, especially noticeable in the low revs/throttle area.

I wish we had more tuners in the UK

 

Gordon
When the VE are done correctly like I explained 99.9% of all drivability problems are GONE, along with decel popping too. One other thing Gordon and I don't mean to pop your bubble BUT there is NO such thing as AUTO TUNE....it's snake oil.
Doc

 

You're not popping any bubble there with me Doc, right there with you on that one

My reference to autotune was simply in regard to what the little box said it was doing.

Nice to see Mr Wizard start a thread on that very question - these thing might do something in an automatic fashion, but tuning your bike properly, is definitely not it. Oh, and while we are at it, canned or calculated maps are hog's wash as well.

 

It may well be a change to a setting available in your tuner.
SEPST gives the option to change something called throttle progressivity using HD's terminology. But it equates to throttle response.
In standard trim the amount of degrees you open your throttle grip does not correspond to an equal amount at the electronically operated throttle plate. So for an approximate example if you twist the throttle grip to 5% open the throttle plate would open 2.5 %...at 10 % it would open lets say 5% and it continues in this vain until you are at much larger throttle positions where it get's much closer to a 1 to 1 throttle. This gives a very controllable and soft feel to the throttle and is done for a few reasons.


It is likely that your throttle progressivity has been set to open fully so that now you get your 5% at the throttle body when you open the throttle 5% etc.
This gives a much more direct and jerky feel compared to the softer feel in standard set up which sounds like the sensation you are getting. Some like it, some don't.


It would be worth asking them if they've done this and get them to put it back to where you were happier, or set it lower than a full 1 to 1 throttle.


https://www.hdforums.com/forum/touri...with-this.html


hope this helps.

 

Yo ucan change the Throttle table all you want with the tuner you mentioned but its a waste of time.....that tuner only allows the table to be effected in neutral .....it's a joke at best.

 

I wasn't mentioning this as some kind of debate as to its merits but rather trying to answer the original poster's question as it appears that they are using that tuner and it could cause the symptoms he is suggesting if by "fueling" they meant throttle response.


"Since the tune, the throttle seems "jerky". In other words, slight moments of the throttle equal large changes in fueling."


Depending on a rider's own ability to feel changes would result in a considerably different throttle feeling from the original stock setting and then going to 1 to 1 throttle.


This option operates at all times whilst riding and not just in neutral.