VP44 defuelling

N

nate

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Apr 6, 2008
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Bear with me, I don't know a whole lot about performance stuff on these trucks.

I think it's what you'd call de-fueling.

I got a TST CE and when I run the higher #s and get on it a bit (like 25%-30% throttle) and let off, the truck bucks HARD. Bad enough that thought I broke something in the trans or rear end the first time it did it.

I wasn't sure if it was a the torque convertor unlocking hard, so I manually locked it and it's not the problem for sure.

On #9, I have to very very lightly feather off the throttle or it will do it.

Is this something I have to live with or is something not right? I can do it even on #6 when I get on it fairly hard.


BTW this thing is nuts other than that. I accidentally hit 45psi on the stock HX35:aiwebs_029::eek:
 
You aren't talking about turbo barking are ya? I don't know if a stock turbo will bark when fueled hard or not. I don't drive a auto so I don't know about the tranny. Defueling is typically when your performance chip or stock ECM module figures out that you are dumping more fuel that you should and starts cutting back. If it fuels ok while your foot is still in it and only does it when you let off hard, it shouldn't be "defueling" that is your problem. Any other symptoms that you can describe?
 
I can bark the turbo real bad if I let off hard, but this is different.

Picture the rear end locking up solid like something broke and then unlocking...about 5-6 times. That's what this feels like. The truck bucks HARD!
 
That's the famous TST competition shudder. On the higher levels it's overtaxing the pump and when you back off it's shuddering the pump. The best numbers for power are level 6 or 7. I usually ran with it on level 1 and the smarty on level 5.
 
Yeah I will really have to mess with all the settings between the Smarty and the TST when I get the sticks in there and the turbo.

Thanks for the help on this BgBlDodge. I'm glad it's not something that only my truck does, cause then I start worrying!
 
No problem. Let me know if there's anything else. I ran a TST/Smarty combo for a couple of years and have a feel for how they work together.
 
I think what you are getting is surging. This happens when the timing and fuel delivery dont like each other.
 
It's not exactly timing and fueling fighting each other. The TST does very, very, very little timing. The rest of it is in the smarty. What's happening is the TST is demanding more than the VP can give and when you back off of it the VP spazs for a sec or two and catches up.
 
BgBlDodge said:
It's not exactly timing and fueling fighting each other. The TST does very, very, very little timing. The rest of it is in the smarty. What's happening is the TST is demanding more than the VP can give and when you back off of it the VP spazs for a sec or two and catches up.
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Yep. It can be violent.
 
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