[CHIEFTAIN]

hey guy's what the optimum boost for a 1998 12v? I'm not sure what turbo it is just whatever is stock.

 

[illflem]

If you exceed about 35 psi the stock turbo starts losing efficiency.

 

[CHIEFTAIN]

That's what I thought but wasn't sure. I don't know much about turbo's My brother's truck pegs his 35# gauge. I believe it's probably pushing 40#. Thanks

 

[plvaulter06]

yep past much past 35lbs and you've got yourself huge hair dryer. It doesn't take much on them to get up around 35 lbs. Also if your flowing a bunch of fuel they are basially impossible to regulate with the waste gate. I tried making a boost controller for mine but it was about impossible. Even if i hook my waste gate back up to stock (opens at about 20lbs) the thing will still build well over 30 lbs. I hated it though because it was laggy as anything and blew the mother load of smoke. I just prefer to have it completely blocked off and foot regulate to keep it down under 40lbs

 

[Dual K20s]

The stock wastegate only vents the back three cylinders ..............


How does the wastegate setting have an effect on spool time? :kick:

 

[plvaulter06]

dual k's, well... what i meant was that when i had it hooked up normal (opens at like 20# or whatever) that it would build 35lbs but it would take forever to get from 20 to 35 with the waste gate open; it would probably take 3 or 4 seconds to climb the last 15lbs up to 35 flowing full fuel and blowing tons of smoke. whereas with the waste gate disconnected it will jump up to that much boost almost instantaneously, and without nearly as much throttle imput probably about 3/4 skinny pedal

 

[Dual K20s]

Thats cause its only three cylinders pushing the last 15psi. The drive pressure in those cylinders was probably crazy. Boost creep means youre wastegate is way to small ......
20lbs is what I would have considered the WG setting and max boost

 

[plvaulter06]

i realize this... but how could the wastegate only be venting 3 cylinders, that doesn't make any sense. the exhaust of all the cylinders are routed through the exhaust manifold down into one, and into the exhaust housing, when the waste gate opens it allows some of the gasses to bypass, it cant choose what cylinders to use and not.

 

[yzgaret]

Dual K don't leave us hanging! This is a very interesting thread. Please tell us more.

 

[Cummins35.9]

probably because the manifold is split into 2 holes and so is the turbo. front 3 and back three. while the system is open and connected the divider kinda directs the exhaust gas. thats my guess

 

[Dual K20s]

probably because the manifold is split into 2 holes and so is the turbo. front 3 and back three. while the system is open and connected the divider kinda directs the exhaust gas. thats my guess

DING DING DING! We have a winner!

The manifold is divided in an effort smooth the exhaust pulses in a way that they don't fight each other. Turbos are designed to match this design. Holset only drills the wastegate passage into the rear passage.

An undivided spacer, removing the divider in the turbine housing, drilling the wastegate passage threw the center divider or using an external wastegate are good ways to vent all cylinders.

 

[Smokinrebel]

what happens if you close off the wastegate?

 

[Dual K20s]

With enough fuel the drive pressure goes through the roof and if you have enough pressure it will shove the compressor wheel into the housing. Not to mention the power loss from excessive DP and superheated air.