i know our truck dont have these, but is there a conversion kit we could run.

bd power makes one but it is not cheap , $650 . unless you are running a big hp tune most likely you wont need one .

There's mine on my Aurora 5000

bd power makes one but it is not cheap , $650 . unless you are running a big hp tune most likely you wont need one .

OK, stupid question here.
What is the difference betwen a blow-off valve and a wastegate?

wastegate controls the amount of boost the turbo will build to ,(some are adjustable) , a blow off lets that pressure off the system as soon as you let off the throttle, thus you dont have @ 35 lbs of boost with no where to go but back on the turbine impeller thus creating ,whats known as turbo bark, which is bad on the turbo

OK, stupid question here.
What is the difference betwen a blow-off valve and a wastegate?

Plus they are on opposite sides of the turbo. Wastegate diverts exhaust gasses to control drive to the compressor. Blowoff is on the compressor side to blow off excess boost to the engine when load is suddenly decreased.

exactly what CAP and idle chatter said

There's mine on my Aurora 5000

Ryan I assume you're running head studs, no?

nope, 75+ sled hooks and 35 drag strip passes with the aurora and stock studs.

nope, 75+ sled hooks and 35 drag strip passes with the aurora and stock studs.

:eek: :eek: :eek:

How much booost?

makes ya feel al warm and fuzzy now BEN , dosent it !!!!!!!!!:hug: :chevy: :drop_mout

53-56psi

53-56psi



:eek:

53-56psi

i love duramaxs. my 6.0 powerstroke couldn't handle 35.:ro)

do the lb7's have a BOV? if not, why not?


at what point is a BOV needed on a duramax?

with big turbos and high boost the immediate let off the compressor wheel will fight the air in the system and bark the turbo , usually the higher the boost the more likely the need for one , they are big in the pulling circuit, as they have lots of immediate let offs, you can feather off the pedal with out a bark but they do help

do the lb7's have a BOV? if not, why not?


at what point is a BOV needed on a duramax?

None of them have one - it's an aftermarket add-on. Stock LB7s have a pressure-actuated wastegate and rarely bark. The stock LLYs have the VNT turbo and you can hear most of them bark on some of the pulling video clips here on the Place. Just as they stop the pull and chop the throttle. (Makes a strange "whoop-whoop-whoop" sound). Like CAP said, only a problem in certain special situations - made worse if you've got a big turbo on there and pushing big boost.

Mine barks on TC lock up at 30/32 LBS of boost that I backed down from 40 that would bark the shifts.I aint got Ryan's :eek:

Or a turbo :)

why do they chop the throttle like they do?

why do they chop the throttle like they do?

Well, you're pulling a sled with every ounce of power your truck can develop until it just can't pull any more. At that point stress has been building and has reached a maximum deadlocked against the weight of the sled. If it's stopped moving, you want to relieve that stress as quickly as possible before something in the engine and driveline snaps! No time to feather it down.

ok so it just adds a small amount of stress to the parts to let them come down from being worked so hard gradually. gotcha

why do the lly's bark? i thought the VVT used it's vanes to not need a bov, or are they just not that great at doing it?

i just reread your explanation on why they chop the gas when they let off and i guess i misunderstood it. if you want to relieve all the pressure at once, then what's the point of adding MORE stress by giving it more gas at the end?

im missing something

I think so, by chopping the throttle I mean suddenly getting OFF the throttle. You are feathering the throttle up and up during the pull to control wheelspin as the sled gains weight until you are at full throttle and the sled stops your truck. Then you GET OFF the throttle as quickly as possible to stop the tremendous strain on the engine and driveline. This results in a sudden stoppage of fueling to the cylinders, a precipitous drop in exhaust flow and turbo drive and pressure surges on the intake side of the turbo caused by the highly compressed air in the intake. In essence, you suddenly reverse the pressure across the turbo drive - from high exhaust flow driving the compressor to pressure on the compressor trying to reverse the spinning turbo. That's the bark and whoop whoop whoop. The popoff dumps off the intake pressure to prevent the "backdrive" forces on the turbo.

Thanks for the explanation:

Now another question, what activates the BOV? Does it monitor Throttle Position and/or Boost, and what parameters are used for engaging the BOV?

I think so, by chopping the throttle I mean suddenly getting OFF the throttle. You are feathering the throttle up and up during the pull to control wheelspin as the sled gains weight until you are at full throttle and the sled stops your truck. Then you GET OFF the throttle as quickly as possible to stop the tremendous strain on the engine and driveline. This results in a sudden stoppage of fueling to the cylinders, a precipitous drop in exhaust flow and turbo drive and pressure surges on the intake side of the turbo caused by the highly compressed air in the intake. In essence, you suddenly reverse the pressure across the turbo drive - from high exhaust flow driving the compressor to pressure on the compressor trying to reverse the spinning turbo. That's the bark and whoop whoop whoop. The popoff dumps off the intake pressure to prevent the "backdrive" forces on the turbo.

It it boost actuated. Normally, you might run 45 psi of boost, but when you chop the throttle, the turbo can't spin down as fast as the engine can, and it's still making boost that the engine can't use. This extra compressed air needs to go somewhere, so when the pressure builds (we'll use 60 psi for an example) it either has to go back out the way it came in (past the turbine blades, bad for the thrust bearings...) or out of a BOV or surge valve, which is vented to the atmosphere. The pressure that the BOV activates at is dependent on the spring holding it shut, and is usually adjustable.

Great explanation guys.

So what triggers the blow-off? Boost drop? Throttle position? Something else?

I have a blow-off for the BD Turbo (not installed yet) and I thought it had a throttle position input. If so, then does it "blow off" when you come off WOT? I also get turbo bark occationally now with the stock turbo on partial throttle acceleration in tow-haul, and was wondering if the blow-off addresses these barks too. The reason I bought it was for sledpulling, when you can bark the turbo for 5 seconds easily at the end of every pull.

Doug

Great explanation guys.

So what triggers the blow-off? Boost drop? Throttle position? Something else?

I have a blow-off for the BD Turbo (not installed yet) and I thought it had a throttle position input. If so, then does it "blow off" when you come off WOT? I also get turbo bark occationally now with the stock turbo on partial throttle acceleration in tow-haul, and was wondering if the blow-off addresses these barks too. The reason I bought it was for sledpulling, when you can bark the turbo for 5 seconds easily at the end of every pull.

Doug

Generally, it's just the increase in the pressure of the intake tract (post turbo), that triggers the blow-off. When the intake tract pressure increases over the threshold of what the spring on the valve can hold, it blows off, and continues to do so until the pressure in the intake is less than the spring pressure of the BOV. I've not dealt with diesel BOVs, so I suppose there could be a throttle input, but I have no idea.

it should blow off anytime you chop the throttle, not just at wot and 60 psi.

I think some of them can be "armed" to pop at zero throttle. That would be good for pulling, you hit the arm button as you start the pull and it pops as soon as you get off the throttle. That would be a good activated action for the "extra" wire on EFILive DSP2 - when you select your sled pull tune, the wire activates your popoff valve at zero percent throttle.

by chop i meant the extra stab of the throttle at the end of a run

i always see these cummins guy do a great pull, then let off the gas, the 1 second later i see another puff of black smoke - telling me that he stabbed his go-pedal real quick.

it may just be a macho-thing, though

by chop i meant the extra stab of the throttle at the end of a run

i always see these cummins guy do a great pull, then let off the gas, the 1 second later i see another puff of black smoke - telling me that he stabbed his go-pedal real quick.

it may just be a macho-thing, though

I think those guys have manual trannys (Dodge auto couldn't survive pulling!) The "chop" you refer to is after they are clutched or in neutral and it is a "macho blip."

If you want to hear what a bark sounds like

1. Push down hard on the brake pedal, no harder than that
2. Put it in drive
3. Push down hard on the Diesel pedal, no harder than that
4. When the truck starts to move or the tires break loose or the torque converter is stalled pull your foot off the Diesel pedal very quickly.

The barking you hear is the extra compressed air you created with the turbo, trying to enter the engine but can't because the rpm's of the engine dropped sudenly but the turbo's rpm's haven't yet,so the compressed air has to go somewhere and it does, back out the turbo and air cleaner it just came in thru, so now your turbo went from spinning 100,000 rpm's forward to 0 rpm's and the bark is actually the sound wave of the air in the turbo blades.

The Blow off valve will let this extra air (which has gone from say 30 psi boost up to 50 psi boost all of a sudden) escape thus not damaging your turbo.

Now when you drive normal or even race as long as you let your foot of the Diesel pedal gradually you won't have that happen because the system can equalize itself quickly.

But the bigger tune you have and the faster you let off the pedal while racing or pulling the more chance you have of doing damage.

DD

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PS Try the bark at your own risk, it has been known to kill. :)

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