LB7 low RPM "bog"

L

Luvss350

New member
Aug 25, 2017
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silverton OR
Hi This is my first post here and i think im in the right spot

My dad has a 04 duramax LB7 we just did head gaskets and 20 over injectors and installed a fast 150 lift pump and now the truck has a bad bog leaving intersections. We cant figur out why it bogs so bad The bog hapens stock tuned(100% factory) or with the edge chip in it or with efi live in it (what little i know about tunning diesels) i corrected the injector polse width and tryed other stuff i read on here i thought would help but nothing did.

The bog is from idle to about 1800-2000 rpm then the truck black smokes and takes off (my dad dose not want black smoke) if you let off the throttle and get in to it agian and rpm are above 2000 no bog it only hapens if the rpm drops below 2000

Other mods the truck has is a air aid air filter and intake and changed the wastgate and a bd disel stage 3 tranny and i think thats everything


Any help would be grate we are going on a long trip next week and need to get it figured out
 
Awenta

Awenta

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Sep 28, 2014
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Take a complete log of a few runs and post them up


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Dozerboy

Dozerboy

Well-known member
Jun 23, 2009
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Tq referance, rpm, throttle position, rail pressure actual and desired.

You are doing your own tuning right?

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DAVe3283

DAVe3283

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Sep 3, 2009
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I would log MAF value as well. If it is doing it on the stock tune, that points to something mechanical. 20% over injectors shouldn't be enough to mess with the stock tune at all.

Which brand injectors did you go with? I presume they are VCO, since SAC injectors start at 40% over or so.
 
wilsondiesel

wilsondiesel

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Nov 11, 2015
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DAVe3283 said:
I would log MAF value as well. If it is doing it on the stock tune, that points to something mechanical. 20% over injectors shouldn't be enough to mess with the stock tune at all.

Which brand injectors did you go with? I presume they are VCO, since SAC injectors start at 40% over or so.
Click to expand...

What should MAF read? I'm having a similar issue with a ZF6 truck. Builds up to 15psi of boost but very slow in low rpm and takes a bit to get wound up. No shaft play in turbo, no boost leaks, holds rail pressure just fine. Replaced MAF with a known good one and the pigtail also. Stock tune, stock injectors with a couple with high balance rates..
 
DAVe3283

DAVe3283

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Sep 3, 2009
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wilsondiesel said:
What should MAF read? I'm having a similar issue with a ZF6 truck. Builds up to 15psi of boost but very slow in low rpm and takes a bit to get wound up. No shaft play in turbo, no boost leaks, holds rail pressure just fine. Replaced MAF with a known good one and the pigtail also. Stock tune, stock injectors with a couple with high balance rates..
Click to expand...
It has been so long since I had a stock motor, I don't know anymore :joker:

With MAF and RPM, you can do a calc PID that does cylinder air, which will let you see if the engine is constantly on the MAF limiter table, which is what you really want to know. If it is constantly on the MAF limiter for a stock truck, something is wrong. If it isn't on the MAF limiter, something else is limiting power. It just lets you know if you need to address an airflow issue, fuel pressure issue, etc.
 
Dozerboy

Dozerboy

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Jun 23, 2009
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We can't just tell you what the maf should read. That's totally dependent on rpm, fuel, and engine load. Between 13-30psi IIRC is the limit of the sensor. I look more at the curve of how the maf builds, but I've only played with vvts not fixed turbos.


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L

Luvss350

New member
Aug 25, 2017
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silverton OR
Dozerboy said:
Tq referance, rpm, throttle position, rail pressure actual and desired.

You are doing your own tuning right?

Sent from my SAMSUNG-SM-G900A using Tapatalk
Click to expand...

Yes im doing my own tuning and im still learing efi live and up untill now i have not done diesels so im learing a lot and reading a lot of the threads on here.
 
L

Luvss350

New member
Aug 25, 2017
9
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silverton OR
DAVe3283 said:
I would log MAF value as well. If it is doing it on the stock tune, that points to something mechanical. 20% over injectors shouldn't be enough to mess with the stock tune at all.

Which brand injectors did you go with? I presume they are VCO, since SAC injectors start at 40% over or so.
Click to expand...

They are from lincoln diesel specialties
 
wilsondiesel

wilsondiesel

Member
Nov 11, 2015
190
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Sedalia, MO
DAVe3283 said:
It has been so long since I had a stock motor, I don't know anymore :joker:

With MAF and RPM, you can do a calc PID that does cylinder air, which will let you see if the engine is constantly on the MAF limiter table, which is what you really want to know. If it is constantly on the MAF limiter for a stock truck, something is wrong. If it isn't on the MAF limiter, something else is limiting power. It just lets you know if you need to address an airflow issue, fuel pressure issue, etc.
Click to expand...

I've got a log I could email and see what you think. Its not on the MAF limiter the way I'm understanding it. Only reaches limiter once in the log. I feel like something else is limiting the power but just don't see what when it builds rail psi just fine...
 
DAVe3283

DAVe3283

Heavy & Slow
Sep 3, 2009
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Boise, ID, USA
wilsondiesel said:
I've got a log I could email and see what you think. Its not on the MAF limiter the way I'm understanding it. Only reaches limiter once in the log. I feel like something else is limiting the power but just don't see what when it builds rail psi just fine...
Click to expand...
Yeah, post up a log and I can look when I get a chance. Might be a few days though for me. If you post it here, anyone with time can help out.

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L

Luvss350

New member
Aug 25, 2017
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silverton OR
So i have not had time to get the log but now the truck is dieing at when i stop at a light and is hard to start sometimes im thinking fuel pump?
 
IOWA LLY

IOWA LLY

Yes, its really me
Feb 23, 2007
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So It didn't do it before, and now it's randomly dying....

Fix whatever you screwed up while doing the Headgaskets and injectors! Why would the pump just magically go bad?

This fits right in with the "built not bought" thread going on right now. And is a prime example that some things are better left to professionals.


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