LBZ: terrible mileage, lots of smoke

LWATSON

LWATSON

future trans limpers
Jul 30, 2008
2,587
1
36
55
Scotland Neck NC
I have a friend with an LBZ he just had a mild build done, cut lb7 pistons and kept his Lbz rods. It has a 366 charger, 60 over exergys and a exergy sportsman pump. His mileage is now down to 12- 13 mpg before the injectors and pump it was normal, I guess around 18? My first thought was during the install maybe the MAF sensor was damaged or installed backwards. We've confirmed the sensor is in correctly so now maybe thinking it could be dirty or damaged. Any more ideas on the excessive smoke and poor mileage? Also need to mention hes running the exact same tunes I am and my truck smokes less on acceleration and I'm running a S475. We both got the 60's about the same time and Dustin pretty much loaded the same file in both our trucks with no changes, so I'm pretty sure its not his tuning.
 
Burn Down

Burn Down

Hotrodder
Sep 14, 2008
7,092
28
48
Boise Idaho
I'm sure he has checked simple stuff like air filters... I would look at fuel pressure. Ramp up the rail at idle and make sure the pump and injectors can at least make full pressure at idle. Maybe log it and watch what the fuel system does under normal driving at some wot runs. It could have a bad pump or injector/s...
 
IdahoRob

IdahoRob

New member
Jun 5, 2007
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I agree testing a different MAF is in order but may be a boost leak. Are the boost/egt/drive pressure numbers in line with what the set-up should be doing?

If all that checks out, then I'd start pulling the maf scaling back. Sometimes too much fuel cools egts in low rpm and will hurt spool up. Less low end fuel may really bring it alive if everything else checks out.
 
LWATSON

LWATSON

future trans limpers
Jul 30, 2008
2,587
1
36
55
Scotland Neck NC
Max boost is where it should be but he said his boost goes up and down at cruising speed from 1-4 psi, up and down. I'm thinking he has a combination of issues. He cleaned his MAF sensor yesterday and said he thinks that helped allot. His DIC actually shows better mileage now even though we all know this is not accurate when tuned. I'm thinking what Rob said about scaling is something that really needs to be looked at.
 
LWATSON

LWATSON

future trans limpers
Jul 30, 2008
2,587
1
36
55
Scotland Neck NC
No telling, he's getting a pvc plug to rig up a test piece. We will see, I predict MAF needs rescaling as per Rob, MAF sensor needs to be replaced, and boost leak lol.
 
O

onebaddmaxxx

Active member
Feb 22, 2009
1,212
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Cecil County Md
an s366 would likely run a 4" intake requiring different MAF tuning that your s475 that probably has a 5" intake. Tell him to log it and see how many gram/s his MAF is reading at idle engine running. Needs to be around 40
 
LWATSON

LWATSON

future trans limpers
Jul 30, 2008
2,587
1
36
55
Scotland Neck NC
Dustin is aware and could probably help more if he had the truck in his possession. He cleaned the MAF and is running a tank of fuel through it now and he feels pretty good about what he's seeing. And he also has a 5" intake so the only difference between our trucks is the charger. He does have an exergy sportsman pump but I don't see that effecting fuel mileage?
 
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