LS swap 1999 c3500 single cab lb

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Supercharged111

Truly Awesome
Joined
Aug 20, 2015
Messages
12,614
Reaction score
15,239
What kinds of issues were you guys seeing? If I were to redo that elbow setup I could back the sensor up to the plastic tube leading to the TB which would straighten airflow in front of the sensor. And maybe uncork it a little.
 

CarolinaOBS

ZIP TIES AND PB BLASTER
Joined
Nov 11, 2015
Messages
269
Reaction score
447
Location
North Carolina
Closed loop with MAF. I did OLSD years ago and AFRs changed with the weather. It also didn't deal with elevation changes at all. This truck is around 24 degrees at 110kpa which seems to be about the knock threshold.

I tried doing maf with boost and it never wanted to work right. Went to SD and it varies slightly with temperature swings but I adjust the IAT table and it keeps it pretty close with the fuel trims. I have no elevation change here so it works.
 

CarolinaOBS

ZIP TIES AND PB BLASTER
Joined
Nov 11, 2015
Messages
269
Reaction score
447
Location
North Carolina
What kinds of issues were you guys seeing? If I were to redo that elbow setup I could back the sensor up to the plastic tube leading to the TB which would straighten airflow in front of the sensor. And maybe uncork it a little.

maf signal would be jumpy and inaccurate. Best working place is farther from the throttle body in a straight piece of intake tubing if possible.
 

Supercharged111

Truly Awesome
Joined
Aug 20, 2015
Messages
12,614
Reaction score
15,239
The thing I can't wrap my head around is that the factory table uses airflow but the COS uses MAP for boost. If you peg the MAF table you're stuck in no man's land, which I believe is the reason most people go SD. Seeing how you can skew IFR/VE/MAF though you can gain headroom. Only thing there are 2nd and 3rd order effects, i.e. stuff that relies on calculated torque.
 

RDF1

I'm Awesome
Joined
Apr 3, 2018
Messages
1,184
Reaction score
976
Location
MS
maf signal would be jumpy and inaccurate. Best working place is farther from the throttle body in a straight piece of intake tubing if possible.

Yep the Hz readings would jump around and thus the AFR was all over the place.
The air would run the larger radius of the 90* bend and depends on how you orient the MAF is how much airflow it was detecting.
 

RDF1

I'm Awesome
Joined
Apr 3, 2018
Messages
1,184
Reaction score
976
Location
MS
The thing I can't wrap my head around is that the factory table uses airflow but the COS uses MAP for boost. If you peg the MAF table you're stuck in no man's land, which I believe is the reason most people go SD. Seeing how you can skew IFR/VE/MAF though you can gain headroom. Only thing there are 2nd and 3rd order effects, i.e. stuff that relies on calculated torque.

Ive never tried to understand it that far in depth.
I started out with mine (Turbo 5.3) trying to tune it with the MAF and maxed it out and AFR went dumb. So learned how to tune it with COS3 on EFI Live and Speed Density, never looked back. Later on i swapped in a LQ4/80E with bigger 75mm turbo, retuned with larger injectors and W/M. Towed trailers heavier than the truck was rated for thru Texas, Louisiana, Mississippi, Alabama, Tennessee, and Kentucky. Never had a issue with AFR with weather or altitude changes. BUT, i was using Windshield Washer Fluid thru the Water/Meth injection system. I tuned it without W/M and then kinda tuned it with W/M but not rely on it in case of a failure. It stayed in constant boost (6-8psi) for a long time on some of those trips thru the hills of north Alabama towing 8500#. I put almost 300,000 miles on that setup with the turbo and only tweaked stuff such as Spark in the IAT table for the Methanol and shift points. Once i got the fuel dialed in and adjusted it a little for the W/M i let it be. Towed like a dream and turbo whistle got old after ahwile but oh well.

All i know is after tuning 12 Turbo charged and 2 supercharged LSx with a LS1B PCM's, MAF always gave me fits. COS3 or COS5 Speed Density was easy and worked great. There are IAT and ECT corrections for fuel in there. Also turning off the engine while fueling up let the PCM take a Baro reading before starting so it slightly adjusted for Altitude changes.
 

CarolinaOBS

ZIP TIES AND PB BLASTER
Joined
Nov 11, 2015
Messages
269
Reaction score
447
Location
North Carolina
The carnage....

You must be registered for see images attach
You must be registered for see images attach



Ive never tried to understand it that far in depth.
I started out with mine (Turbo 5.3) trying to tune it with the MAF and maxed it out and AFR went dumb. So learned how to tune it with COS3 on EFI Live and Speed Density, never looked back. Later on i swapped in a LQ4/80E with bigger 75mm turbo, retuned with larger injectors and W/M. Towed trailers heavier than the truck was rated for thru Texas, Louisiana, Mississippi, Alabama, Tennessee, and Kentucky. Never had a issue with AFR with weather or altitude changes. BUT, i was using Windshield Washer Fluid thru the Water/Meth injection system. I tuned it without W/M and then kinda tuned it with W/M but not rely on it in case of a failure. It stayed in constant boost (6-8psi) for a long time on some of those trips thru the hills of north Alabama towing 8500#. I put almost 300,000 miles on that setup with the turbo and only tweaked stuff such as Spark in the IAT table for the Methanol and shift points. Once i got the fuel dialed in and adjusted it a little for the W/M i let it be. Towed like a dream and turbo whistle got old after ahwile but oh well.

All i know is after tuning 12 Turbo charged and 2 supercharged LSx with a LS1B PCM's, MAF always gave me fits. COS3 or COS5 Speed Density was easy and worked great. There are IAT and ECT corrections for fuel in there. Also turning off the engine while fueling up let the PCM take a Baro reading before starting so it slightly adjusted for Altitude changes.

did you tune any on dyno or all on the street? Also whenever I get it back together and start tuning again would it be alright if I pmed you questions?
 

RDF1

I'm Awesome
Joined
Apr 3, 2018
Messages
1,184
Reaction score
976
Location
MS
The carnage....

You must be registered for see images attach
You must be registered for see images attach





did you tune any on dyno or all on the street? Also whenever I get it back together and start tuning again would it be alright if I pmed you questions?
Why you gotta be so mean to them ring lands?
99% street. Only tune on the dyno when it's traction limited. Think 25 psi on a 6.0 and street tires.....
Na man hit me up whenever you need to. I might be slow to respond but I'll help where I can!

Sent from my HiDiNg PlAcE
 

CarolinaOBS

ZIP TIES AND PB BLASTER
Joined
Nov 11, 2015
Messages
269
Reaction score
447
Location
North Carolina
Why you gotta be so mean to them ring lands?
99% street. Only tune on the dyno when it's traction limited. Think 25 psi on a 6.0 and street tires.....
Na man hit me up whenever you need to. I might be slow to respond but I'll help where I can!

Sent from my HiDiNg PlAcE
Oh yea abused pretty bad. Going with some forged slugs now. Thanks man, I seem to have a grasp on the fuel and idle tuning just fine just having a hard time figuring out how to log and when and where to adjust the timing....you see where ballparking and half assin it got me lol
 

Supercharged111

Truly Awesome
Joined
Aug 20, 2015
Messages
12,614
Reaction score
15,239
Aren't those the El cheapo forged slugs already? I have the same in my spare LT1. For timing, I bring it in sooner than stock. I bump globally until I see knock, then start reshaping it. Adding more down low helps a lot with loafing along in OD. The thing I suck at is blending.
 
Top