just put on a 2# upper (6#'s total now). on the way back from the dyno, I hit it on the highway. at about 4500-5000 rpm, (3rd grear), the truck started lurching, or bucking... hard to explain. I am guessing detonation due to the increase in boost, but it was less like I heard it, and more like I felt it.

Any help is greatly appreciated,
Aaron

 

I realize this question is asked frequently, but come on...
help me out please!

 

I have never heard of detonation causing bucking. I always thought it was just something you hear. how was your a/f on the dyno?

 

I'm not trying to be a smart a$$ or anything but have you changed your fuel filter in the last 5,000 miles. Of what you are describing, sounds like to me it's a fuel problem.

Ryan

 

detonation from what I understand sounds like a taping metal on metal kinda like a knock....

never heard of it bucking though... I'd check the fuel or fuel filter

 

Doesn't sound like detination to me. I would look elsewhere for the cause of lurching and bucking.

 

top of third gear??!! Someone was doing more than the speed limit.........


Still calling to get that race gas number, i'll call when i find out.

 

Sounds like you toasted a plug or three.
Thats exactly what it does when you toast them (been there done that) BTW, What plugs are you running ?

 

Rob, I really hope not. I'm running Denzo IT-20's. I realize that I need to change to 22's, but I left the dyno thinking I was still pretty safe (under 12).

After the incident, the truck ran fine all the way home (taking it easy of course). If I toasted even one plug, wouldn't I know it?

BTW, my fuel filter has been changed within about 5,000 miles, and this problem occured right after I cranked the boost up two pounds. I don't think it's a fuel delivery issue, but probably an air/fuel or timing issue. I also retarded my timing 2% with the Predator... I thought I was pretty safe

 

here's the dyno sheet. Does that seem like a nasty drop in fuel at about 5000 rpm?

 

is that 17:1 in the beginning accurate? That seems a bit lean even for just cruising. I thought you wanted to be nead 14 at cruise.

 

It might be. I know I should've had my tuner build a custom tune for the extra 2#'s before I brought it to the dyno, but I figured I would have enough adjustability to compensate for it via the Predator. Like I said, I thought I was still pretty safe in the mean time until my truck started pulsating at 100+ mph. I'm more concerned with the spike near 5 grand. My fuel curve with the 4#er and custom tune was real nice and flat.... not like this last one

 

HELP!

 

THERE IS NO DIFFERANT TUNE
4lbs and 6lbs is the same tune

Would it drive ok you ask ? YES
When it happen to me, I must have first toasted just one plug
and never knew it. I drove the car around for days and had this weird bucking but only when I got into it, I couldn't figure it out ?
It drove perfect other than a slight weird idle and the bucking when I got into it. Well me being me, where else better to find out but the track, so that weekend off to the track I went

Truck was running great (or so I thought) Burnout went well,
dusted a Z-06 off the line, but with in seconds all hell broke lose,
I guess the other two toasted that time and it was pure detonation like I never want to hear again. I shut it down rolled into the pits and was ready to cry. Weirdly enough I started it up and again it was running great (or so I thought) so off the to tree I headed again Again the Burnout went well, lined up against a Tundra, (is that what they call them?) light went green and it was pure detonation again. Lets put it this way, somewhere in this world there's a Tundra that THINKS he whooped a Lightning.

I drove around for a few more days after that still nto knowing what it was, and believe it or not the truck ran great as long as I didn't get into it too much.

 

My truck at the time had like 5200 mile on it, so I never thought about the Fuel Filter, schitt I've gone 100K in a family car without changing a fuel filter. USA Hooters and RWTD (James) figured it out over the phone and told me to go change my Fuel Filter, Cut it in half and take a picture
BOY WAS I SURPRISED TO FIND THAT AT 5K


Afterwards the prob was still there so I knew what was next
(plugs only had 500 miles on them too )@%$(@$%@$@$)


You would truly be amazed on how good it ran with 3 plugs looking like that as long as you didn't go ape schitt on it

I MAY BE WRONG BRO, your A/F #'s are fatter than many we see,
but a clogging fuel filter may have caused a plug to melt, IF THATS WHAT IT IS ??? Remember on a Dyno they take it up slowly, then only get into it a few seconds, so if your flowing a little less than needed, it may not show up for another second or two.
Hopefully I'm wrong

AND CONGRATS ON THE AWESOME #'s
Using STD #'s, your officially in the 400/500 club, WOO HOO