I am on holidays right now, driving through the mountains in lower british columbia. Truck is running great,,,,,, EXCEPT,,,, if I am in overdrive,,, it will pull like crazy,, just beautiful, until the rpms get down to around 1850. Then my turbo just starts barking,, violently. it will do it in any gear if I am at about that rpm and pulling hard.


A little about what I am running,,, 03 dodge, sps 6280 turbo running around 39 psi, full race tranny and tourque (all billet) 4" mbrp afe intake, Juice w/ attitude @level 5 , bully dog pp at level tow. I am pulling a 13000lb jayco trailer.

I have tried running 1 or the other (juice or bullydog) various levels of both,, to no avail. any ideas on this would be greatly appreciated. Also why cant i seem to pull much boost when I am just running the bully dog pp?/

 

You really need to visualize a turbocharger's compressor performance map to understand what's happening. A turbocharger uses a centrifugal compressor - this is a dynamic as opposed to a positive displacement air compressor. In a dynamic compressor, the only thing that keeps the flow from reversing (the cause of surge or "barking") is the ability of the compressor to maintain enough flow to sustain the head (Pd minus Ps) across the impeller.

When engine RPM drops, the swallowing capacity of the engine drops - it can't move as much air through the engine at a lower RPM. Yet your compressor discharge pressure is still up at 39 PSIG. Referring to the compressor performance map, head is still high but flow is decreasing - which walks the turbo right across the compressor surge line.

The solution is to increase flow (downshift to increase engine RPM) or to decrease head (back off the throttle or adjust the wastegate to reduce boost pressure).

By the way, any air filter or other intake restriction increases head since it lowers Ps.

Rusty

 

Great info Rusty.


One more thing to add is the fuel backdown on your Juice. This got me once this summer on my first big pull. I forgot I was messing around with the defuel and had it set at 1250. Once I reached it the truck started to bark and surge something fierce. I realized what I had done and set it higher. I had no other problems the rest of the year.

 

wow, that was a very impressive post by an individual that obviously knows his topic. I was just gonna say take it out of overdrive for the hills. But I learned from the post as well. great job rusty

 

Nice post Rusty thats some great info, and easy to understand.

 

thanks rusty for the info,, now if I read this right it means that I probably have 2 big of a turbo? Cause it sure sucks to drive right now,, (to fast for out of overdrive, not fast enough for the turbo) or is there settings that I can change that might help this?

Thanks again

 

i'm not sure since you have an aftermarket turbo....but with a bullydog on a stock turbo you will not have any more boost than stock since the Bullydog doesn't do boost fooling. The Edge Juice will increase boost 5-7psi on stock turbo.

so i guess your shop wasn't correct in saying "just add more power"....its a boost issue. hmmmm, but still thats a great trick they tried "Add more hp to fix your problems and be sure to buy from us!"


great informative post, rusty!

 

I thought that there was no need for boost fooling on a 2003? Am i miss informed?

 

Yes, the larger turbo is sized for higher flow at a comparable or slightly higher head. Whereas a stock turbo could handle a relatively high discharge pressure at this lower flow, the larger turbo cannot. This gets into a concept known as the turndown capability of the compressor - a subject for discussion some other time.

Not being a 3rd gen owner, I'll leave any performance controller settings discussion to those who know.

Rusty

 

I had the same problem on my SPS66. I had to swap down to a SPS62 in order to retain my towing capability. It really made it miserable to drive. Since i have done the swap, I am so much happier wiht my truck.

 

Towing with the J/A lvl 5 which has timing and Bully Dog which has timing is probably not a good Idea.....fun for drag racing....deadly for cylinder pressures at high torque levels such as the peak of your torque curve 1850 rpm. I'd immediately turn the J/A down to boost fooling only if not completely off or go back to stock with the BD. 39psi towing is awesome but your pushing it for vacation time. That violent barking is adding wear to something, guaranteed. Your are as Rusty has stated, off the compressor map. In the mountains air density is less and most of the downloaders and boost foolers manipulate boost in one way by telling the ECM that you are at a higher altitude than you really are. You might be driving on Mount Everest as far as altitude goes. What codes do you have? ks

 

Just keep the RPM's up...over 2200 and you will be fine...no more bark/surge.

I tow at 39 psi all the time.

 

CQ, I don't doubt it one bit....but do you do it on vacation.

Would a BD turboguard help this situation. ks

 

it pulls like crazy till i go under 2000 rpm,, which of course is 100 kmh (60mph) which is pretty much what i need to run at,, if i shut off the o/d unit it then over revs, and will just gain speed like crazy,, no matter how big the hill. very inconvienent. Oh and you would have to go on holidays with me to understand,,, lol,, I like to be able to keep up with the traffic so to speak,, lol

 

I only have the normal 602 and 603 which are normal with the bully dog,, and a 700 which is a tranny controller error. I am confused by this boost fooling thing.. can you explain this a bit farther??

thanks in advance