How does the LB7 wastegate actuator work?

[markrinker]

I have yet to even pull the top plastic cover off my Duramax, but wondered if someone in the know could explain how the wastegate actuator works?

A quick glance today looks like it picks up boost from near the intake manifold and opens up the wastegate at a predetermined pressure to bleed off boost.

Wow...the 6.5 engineers sure overengineered boost control...(vacuum, sensor, solenoid...)

I bought a cheap boost valve that goes inline to fool the actuator. Must be a restrictor of some sort?

[Tough Guy]

Yes, the wastegate is pressure actuated...Kennedy has a nice little gizmo that "fools" the wastegate actuator.

The 6.5L truly is a engineering "gem"... :rolleyes:


Chris

[DmaxMaverick]

In spite of the engeering nightmare, the 6.5 wastegate control is far better, when working properly.

The LB7 wastegate will bleed off exhaust pressure as manifold pressure rises. This wastes energy, and causes a falloff of peak pressure.

The 6.5 wastegate control, on the other hand, will hold the wastegate closed until the trigger pressure is reached, then dumps the exhaust pressure to maintain it. On/Off. Way better. This is what JK's boost valve does, on the LB7, and it's adjustible.

Active control is almost always better than a passive control that relies on spring load, but the simplicity factor can win out.

[markrinker]

JK how does your LB7 boost valve work? Is it a restriction to the factory line, or does it employ a check valve and spring to bleed off boost and maintiain peak as described?

[mcmonroe]

How is boost controlled on both the LLY and the LBZ? Via wastegate as well?

Mark

[DmaxMaverick]

Originally posted by Mark Monroe:
How is boost controlled on both the LLY and the LBZ? Via wastegate as well?

Mark LLY/LBZ doesn't have a wastegate. The exhaust pressure is controlled by the VGT. The exhaust gasses are directed into the turbine by vanes, which are controlled by the PCM.

[Kennedy]

Originally posted by Mark Rinker:
JK how does your LB7 boost valve work? Is it a restriction to the factory line, or does it employ a check valve and spring to bleed off boost and maintiain peak as described? You really need to get around a bit more:

http://www.thedieselpage.com/reviews/jkboostvalve.htm

[markrinker]

I read that long ago - have you sold your million of 'em yet?

The $28 Ebay purchase I made is simply a restriction to the line. Not adjustable. I may relist it and buy one of yours after testing to see what pressures I get with this one.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=8027811615&rd=1&sspagename=STRK%3AMEWN%3AIT

What would you say the effective range of peak pressures are - with your adjustable unit - with stock fuel rate, exhaust, etc. ???

[ 02-04-2006, 07:28 PM: Message edited by: Mark Rinker ]

[Kennedy]

From little/no change to mid 30's which is too much for the stock turbo.

Adding the boost valve to the stock program/fueling will not give much if any power increase. You need the exhaust heat and throughput to make the boost come up. Put a little fuel on it with an Edge box and watch it do it's magic!

[markrinker]

My propane tank should be here this week and mounted/filled by week end.

The plan is to put all hardware, and software and your electronic EGT/boost gauge in place, and take the following measurements:

1) Stock EGT and boost - as a baseline
2) EGTs and boost with propane - MSD factory settings
3) EGTs and boost with inline restrictor

The next few weeks will be used to detail the mileage and power affects of running propane over diesel while towing. Hope to capture lots of statistics.

JK I may become an EFI Live customer if my testing leads me to modifying the OEM fuel map for the LB7. I am interested in reducing diesel and increasing propane proportions while in tow/haul mode ONLY. Is this possible?

[Kennedy]

With the EFI Live DSP2 you have the ability to toggle between 2 programs (A and B) as well as use a programmable output that can be triggered by RPM, Boost, ECT, or Throttle position.

[markrinker]

Sounds like the ticket. When I get all the testing done in 'Phase I' I may be over to do some detailed tuning on your dyno for a 'power setting' and for an 'economy setting'...

[dieseldummy]

So what makes JK's better than the $28 variety besides adjustability? I was planning on trying the $28 one to see what it does with stock and performance programing. If it's not worth trying I'll have to rethink that though.

[markrinker]

On first examination, the 'cheapie' unit is well machined, but technically crude. Simply a pressure restrictor - via a tiny machined hole. I thought it would employ a spring and check valve for a predetermined 'optimal' LB7 boost level. Nothing even close.

Kennedy's is not only adjustable, the result would be a completely different boost curve by holding back all pressure until your setting is met, then letting pressure past to the wastegate actuator. The resulting boost curve would look much steeper, with a square (flat) top at your target pressure.

The cheapie would have a more gradual curve, with a rounded top. This means less boost down low. More boost up high after you want to cap it. I don't want my turbo barking with propane blowing through it.

I am sure that testing will show that the adjustability and square curve is well worth the extra cost.

[DmaxMaverick]

Originally posted by dieseldummy:
So what makes JK's better than the $28 variety besides adjustability? I was planning on trying the $28 one to see what it does with stock and performance programing. If it's not worth trying I'll have to rethink that though. Two different animals. The $28 item just slows down the airflow between the compressor housing and wastegate actuator. It only delays activation. Effective for a short burst, useless on a long grade. It can also cause an overboost condition with some mod conditions, and even in stock trim under the right circumstances, like very high altitude (less pressure on the other side of the actuator).

JK's valve closes the connection between the compressor housing until a specified pressure is reached, then releases it to the actuator to allow the exhaust gas to bypass. Once the pressure drops back into the envelope, it closes off again, and bleeds the pressure from the actuator. If you overboost, it's because you set it that way.

I don't usually endorse any products, but JK really has the only device that does this. The other device is trouble waiting to happen, IMO. "Post it on Ebay, and they will come...."

[dieseldummy]

So the $28 unit is very similar to "boost elbows" used on cummins engines. I've often thought that there is something flawed with the theory of "bleeding" boost off... Looks like I need to save another chunck of cash.