Boost valve question

[dmaxpilon]

Full service of all the fluids and filters. Ck balance rates on injectors and cp3 health. 50-100 hp tune, ditch the k&n if your driving in dusty conditions (stock air box supports over 500hp), 4” exhaust or stock is fine, boost and egt gauges, boost valve for stock waste gate.

If your power hungry start saving for a built transmission, 4500-5500 bucks.

Injectors will always be an issue on the lb7. Always be prepared to change all 8. Good Bosch remans will go 100k give or take. The new SAC style lb7 injectors should last longer but haven’t been out long enough to prove or disprove that theory. 2500 for injectors and the labor if you can’t do them yourself.

That’s my starter list. Is it a Cali emissions lb7?

What's your reason on changing out the boost value on the stock wastgate?

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[DAVe3283]

What's your reason on changing out the boost value on the stock wastgate?

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It's only necessary to add a boost valve if you're tuning it. The LB7 has a fixed vane turbo, so while the ECU can add extra fuel to support more boost, the wastegate needs some form of hardware mod to allow it. Replacing the whole wastegate (Banks Big Head, etc.) certainly works, but for a fraction of the money a boost valve does about the same thing.

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[dmaxpilon]

It's only necessary to add a boost valve if you're tuning it. The LB7 has a fixed vane turbo, so while the ECU can add extra fuel to support more boost, the wastegate needs some form of hardware mod to allow it. Replacing the whole wastegate (Banks Big Head, etc.) certainly works, but for a fraction of the money a boost valve does about the same thing.

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I have 5 duramax tuner tunes 5, 20, 60, 80, 100. I run the 60 90% of the time. A lot of the time the truck is towing or just out for a drive. With it being tuned you would recomend that I put in a ppe boost valve or changing out the stock wastgate spring to allow the truck to build past the 22 psi it is making now?

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[DAVe3283]

I have 5 duramax tuner tunes 5, 20, 60, 80, 100. I run the 60 90% of the time. A lot of the time the truck is towing or just out for a drive. With it being tuned you would recomend that I put in a ppe boost valve or changing out the stock wastgate spring to allow the truck to build past the 22 psi it is making now?

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A 100 HP tune might see some benefits from it. It would potentially lower EGTs a little, but on the smaller tunes they probably don't have enough fuel to make a difference.

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[TheBac]

Moved this question into its own thread.

 

[dmaxpilon]

A 100 HP tune might see some benefits from it. It would potentially lower EGTs a little, but on the smaller tunes they probably don't have enough fuel to make a difference.

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So on the tunes I have and the capability of the trans on these trucks ( without built trans) there would be no benefit of installing a ppe (or other brand) boost valve?

What about on a stock truck with no tunes?

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[DAVe3283]

On a stock truck, there is 0 benefit for the boost valve. With tunes, it starts having some benefits (lower EGTs and potential for more power with larger tunes). For a 100 HP tune, I probably personally wouldn't spend the money. Save the $30 towards a built trans, which will have a way bigger impact to the performance of the truck.

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[Mike L.]

On a LB7 why buy a boost valve when you can cut the hose, add a small pipe between hose ends and drill a 1/8 hole in the pipe.

 

[dmaxpilon]

On a stock truck, there is 0 benefit for the boost valve. With tunes, it starts having some benefits (lower EGTs and potential for more power with larger tunes). For a 100 HP tune, I probably personally wouldn't spend the money. Save the $30 towards a built trans, which will have a way bigger impact to the performance of the truck.

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Okay so I'm not seeing the reason for adding the boost valve, the trans can barely hold up to 80 over tune ( I have limped mine twice). So if the only benefits from doing this is over 100hp tunes, by that point wouldn't you be changing the turbo set up regardless?

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[dmaxpilon]

On a LB7 why buy a boost valve when you can cut the hose, add a small pipe between hose ends and drill a 1/8 hole in the pipe.

Why would you drill a hole in the pipe? Isnt the purpose of those boost valves to slow down the amount of pressure going to the wastegate, to up the boost going through the turbo? And by adding a hole in the new pipe not let more air out? (I understand that 1/8 is quite small)

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[DAVe3283]

On a LB7 why buy a boost valve when you can cut the hose, add a small pipe between hose ends and drill a 1/8 hole in the pipe.

Why would you drill a hole in the pipe? Isnt the purpose of those boost valves to slow down the amount of pressure going to the wastegate, to up the boost going through the turbo? And by adding a hole in the new pipe not let more air out? (I understand that 1/8 is quite small)

What MikeL just described is making your own boost valve. As you said, the point is to reduce the pressure seen by the wastegate. So just putting a restriction in line won't do it. That would cause the wastegate to open more slowly, but eventually the pressure would equalize, and the wastegate would open, dropping the boost back to stock. So you would get a spike to high boost that fell off shortly after. By drilling a small hole on the wastegate side of the restriction, it lets a small amount of boost to the wastegate, and a small amount of boost out to the air, so the pressure never comes up all the way.

IMO the PPE boost valve is cheap enough that it is worth just picking up, and not having to worry about the size of holes you drill. But MikeL is right: you can just make one.

Okay so I'm not seeing the reason for adding the boost valve, the trans can barely hold up to 80 over tune ( I have limped mine twice). So if the only benefits from doing this is over 100hp tunes, by that point wouldn't you be changing the turbo set up regardless?

Once the trans is built, the LB7 can make a lot more power with the stock turbo & fuel systems by just adding the boost valve and a lift pump. For example, this is the tune I wrote & run on several stock-motor LB7s: No Logic 3.0 (+175 HP)
A 100 HP tune is pretty small for a LB7. Even the 175 HP tune I wrote is totally safe, and I even tow with it. Just add a pyrometer and watch your EGTs on long hill climbs.

IMO save your time/money on the boost valve, and save up for a built trans. Then you can really wake up your truck with some hotter tunes.

 

[Mike L.]

^^^^^^^^^^^^^
Well written.

 

[TheBac]

PPE boost valve(or the other copies of it) wont hurt a thing on a stock truck. Put a good tune to the truck, though....it allows you 32-33psi from the stock turbo.

 

[Mike L.]

Correct Tom.

 

[77cruiser]

The most I got was about 27 post IC just enough to give an over boost code.

 

[dndj]

I've seen 30 psi peaks (pre-IC) with 50-60 degree ambient temps and a 100-120hp Efilive tune. Stock LB7 IHI turbo w/PPE boost valve.

 

[dmaxpilon]

What MikeL just described is making your own boost valve. As you said, the point is to reduce the pressure seen by the wastegate. So just putting a restriction in line won't do it. That would cause the wastegate to open more slowly, but eventually the pressure would equalize, and the wastegate would open, dropping the boost back to stock. So you would get a spike to high boost that fell off shortly after. By drilling a small hole on the wastegate side of the restriction, it lets a small amount of boost to the wastegate, and a small amount of boost out to the air, so the pressure never comes up all the way.

IMO the PPE boost valve is cheap enough that it is worth just picking up, and not having to worry about the size of holes you drill. But MikeL is right: you can just make one.


Once the trans is built, the LB7 can make a lot more power with the stock turbo & fuel systems by just adding the boost valve and a lift pump. For example, this is the tune I wrote & run on several stock-motor LB7s: No Logic 3.0 (+175 HP)
A 100 HP tune is pretty small for a LB7. Even the 175 HP tune I wrote is totally safe, and I even tow with it. Just add a pyrometer and watch your EGTs on long hill climbs.

IMO save your time/money on the boost valve, and save up for a built trans. Then you can really wake up your truck with some hotter tunes.

Thanks for getting deeper into with topic with me. I'm sure this will help out others as well, when deciding to install or not install a boost valve on there truck. To sum it up, for stock trucks there is no huge gain to have a boost valve installed, it would be a better used on trucks with bigger tunes (say 100hp or more)?


And for the secound part. (I haven't opened the thread yet) In the thread you listed does it talk about a trans and supporting mod to go with that 175 hp tune?

I've talked to @Mike L. A few years ago about building a trans for a 1000hp+ but its big $$$. Is there a way to start towards that 1000hp+ trans that wont break the bank but make it capable of handling the 175hp tune safely?

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[TheBac]

Dont know what a boost valve is for, but want a trans built for 1000+hp. Oooookay......

There are no shortcuts to "get around" holding higher power tunes, especially on a 5 speed Alli. You have to pay to play.
Sure, you can build it yourself if you use a quality kit like Evan's...but you better know what youre doing.
Most people dont know how, so they have theirs built by a reliable, experienced shop like Mike.

 

[dmaxpilon]

Dont know what a boost valve is for, but want a trans built for 1000+hp. Oooookay......

There are no shortcuts to "get around" holding higher power tunes, especially on a 5 speed Alli. You have to pay to play.
Sure, you can build it yourself if you use a quality kit like Evan's...but you better know what youre doing.
Most people dont know how, so they have theirs built by a reliable, experienced shop like Mike.

Yea I get that. Was thinking maybe with doing a converter and bullet input and outputs and trans tunes it would hold up for a year or 2 tell I'm ready to spend the 10k

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[TheBac]

Why do it twice? Get a concrete plan together for what you really want to do, whether its 500hp or 1000, then save your money and wait til its time. Make sure you talk to your trans builder beforehand about your goals so the build can match your plans.

BTW, a normal trans build (like most of us have) with converter shouldnt be over $6000. Those billet parts you list do add to the price, though.