Truck bucking

[ruben121]

So I've always had a little miss, I would noticed it with my edge jammers 150s with the comp on level 5 at WOT, not bad enough for me to worry about.

 

But I upgraded to a quadzilla and also got 7x.013s , the miss turned into a very aggressive buck, it's literally breaking my dash.

 

I notice that with the quad on level 0 it doesn't do it but with the quad on at any other level it does it, the more aggressive fueling the worse and it even does it on level 2 with less power than stock , as soon as I put it on level 0 I have no buck on my throttle.

 

Any ideas would be appreciate it to help me tackle this some of the mods are SO pump, t3 66/74/14 , 7x.013s, fass 90, fmvb 47re.

 

[Me78569]

What tune are you running?   Bucking is normally too much timing for the setup.  what rpm's does it buck?     

[ruben121]

6 hours ago, Me78569 said:

What tune are you running?   Bucking is normally too much timing for the setup.  what rpm's does it buck?     

Quadzilla, it does it with multiple tunes I’ve created , and I even bought a tune and it does it too. Like I was saying it only does it with the quad on level 1+ .  Level 0 it’s normal. 
 

IT does it at all Rpm’s , seems that the more fuel and rpm’s I give it , the worse it bucks . Even when I’m cruising in town the truck starts jerking and it makes my foot on the pedal jump too . 

[Me78569]

try this for timing settings on any of your tunes. 

 

  This trick uses ecm timing as the base and adds on top with the values at each rpm band.      

 

Timing:

Fuel Load Timing: 0

Low PSI Timing Reduct: 0

Timing Reduct Scaling: 0

Light Throttle Timing Adv: 0 

Light Throttle Timing Load Limit: 0

 

Timing vs rpm

1500: 1

2000: 2

2500: 3 

3000: 4 

Timing Max: 5

[ruben121]

I tried this and wow , I think it’s going and the truck if fueling like crazy when it’s not cutting out . I currently don’t have lockup but I have a new converter heading my way . I will try it with lockup when my converter gets here and let you know . So what can I do for timing now . I mean to try and squeeze the most out of it . As of right now it’s staying like this because it is the best it has acted out of all the tuning I’ve tried . I’m getting ready to take it to the 1/8 in April so any advice to squeeze the most power without bucking like crazy would be noted . 
 

thank you for your help , you’ve helped me a lot.

[Me78569]

Post up your old tune settings and we can adjust now that's e know it was bucking because of too much timing

 

[ruben121]

Here ya go . This is the tune I changed , all I did is changed the timing to what you said . 

[Me78569]

I'd prob bump low psi timing reduct to 5.0*

then do your rpm curve like htis

 

1500: 14

2000: 18

2500: 23

3000: 28

max: 30

[ruben121]

Thank you I’ll try it , if the bucking comes back I’ll just go back to the rpm 1,2,3,4,5 and reduct back to 0 , I rather have a smooth rpm . 

[Mopar1973Man]

Bucking is usually a sign of over advancement. Typically occurs because cruise timing is use and stacking added timing on at a low RPMs. Pay attention to RPMand ti.ing when it bucks. 

[ruben121]

Thank you, 

[ruben121]

11 hours ago, Me78569 said:

I'd prob bump low psi timing reduct to 5.0*

then do your rpm curve like htis

 

1500: 14

2000: 18

2500: 23

3000: 28

max: 30

So I tried this and the aggressive bucking was back , when doing a hard pull and then let off the throttle it would buck super aggressive so I stopped on the side of the road and then adjusted the settings back to low psi timing reduct doing it or the rpm curve.

 

1500: 1

2000: 2

2500: 3

3000: 4

max: 5 

 

then problem was instantly gone .

 

I'm going to leave it like this for now but I can't understand if its the 

 

[Me78569]

Super odd 

[ruben121]

Just now, Me78569 said:

Super odd 

Tell me about it , when I get my new pump I’ll turn the timing back to what I had it and see if it still does it 

[Me78569]

Some trucks are picky about timing.   Watch your timing at 2750+ rpm if you rev that high. You injectors are big enough you should be maxing timing by 3k rpm for max power.

 

[ruben121]

44 minutes ago, Me78569 said:

Some trucks are picky about timing.   Watch your timing at 2750+ rpm if you rev that high. You injectors are big enough you should be maxing timing by 3k rpm for max power.

 

Yeah I hit redline every gear when I’m playing with it around 3500 plus , but it’s just weird I don’t get it . 
 

at least we got it acting right with the timing trick you gave me . I appreciate it sir 

[Me78569]

ensuring your timing hits 30 * at 3k will help with that hard pull up top.  

 

you might need something like this

 

1500: 1 

2000: 2

2500: 3.5

3000: 5

max: 6.5

[ruben121]

1 minute ago, Me78569 said:

ensuring your timing hits 30 * at 3k will help with that hard pull up top.  

 

you might need something like this

 

1500: 1 

2000: 2

2500: 3.5

3000: 5

max: 6.5

Perfect I’ll play with it , and let you know . 

[wil440]

I have a problem with bucking too,  injectors on my truck are ready for replacement as my idle is 850 or so warm and load wanders between 4 and 8, tried various tunes, the one I use now was written by @Me78569 for a stock truck and it's the best as of yet but still bucks until it's really warm ?

I recently spoke to a diesel shop near me ( Midlands UK) about injectors as I had a JCB head skimmed there and have used them for quite a few years, 7x10's at 320bar would be £80 each no cores and due to the £ to $ shipping and duty from the USA thats a steal.

While I do see the reason of setting injection pressure at 320 bar or lets say "over stock"  to be better atomization the trained mechanic in me just see's a whole lot more work that the VP needs to do to build that extra pressure.

reading the previous posts I might change the cruise timing rpm as if a stomp it it stops bucking

I wish I wasn't sooooo busy  not

 

[Mopar1973Man]

293 Bar is the lower limit.

310 Bar = 4,500 PSI

320 Bar = 4,641 PSI

Max limit is 327 Bar according to the Dodge FSM. Adding the extra 10 Bar improved the spray starts super easy in the cold. Then it extends the life span of the injectors since when you dip below 280 Bar you'll start to see misfire at hot idle.

 

Remember VP44 could produce pressures as high as 20,000 PSI at wide open.