Turbo 6.0, 5.3 or 4.8
08-02-2013, 01:51 PM
#21
Adding a turbo isn’t going to make much of a difference on the MPG.
08-02-2013, 02:51 PM
#23
I have been working on the tune for a long time, have tried olmaf and olsd, two different cams (226/234 and 219/224), replaced wbo2 sensor, resealed header collectors, checked over everything numerous times, read spark plugs, etc and I can't seem to find anything wrong besides deciding the ls3 heads are simply way too big to have any kind of torque at cruise rpm.
While logging I have seen a best instantaneous mpg of 18mpg at 50mph, 15.7:1 afr and about 1400rpm. at 80mph 2000rpm it gets 14mpg instant. once I average in a tank, I'm getting about 11-13mpg. This is a S10, not a bread truck.
I have tried cruise timing up to 38*, afrs from 14.7 to 18, i went to a 185* thermostat from 160. All of the PCMs assumptions (IFR, AFR) match up with what is happening in the real world, so I don't think there is anything weird happening like bad injectors, fuel pump, bad o2, etc. The truck rolls easily so its not sticking brakes as far as I can tell.
Idle vacuum is 16", cruise vac is anywhere from 14 to 17"
The truck is a beast under power so it doesn't seem like its any kind of major mechanical issue, just too much cylinder head for the application.
With all the differing success of the ls3 head swaps I knew I was taking a gamble and it seems like the heads are just not fit for my goals.
When I had the 226/234 cam, I couldn't cruise below 2000 rpm. with the smaller cam it now cruises ok at 1400, but it is obviously not doing it efficiently.
I will post my latest tune and log tonight when I get home from work.
While logging I have seen a best instantaneous mpg of 18mpg at 50mph, 15.7:1 afr and about 1400rpm. at 80mph 2000rpm it gets 14mpg instant. once I average in a tank, I'm getting about 11-13mpg. This is a S10, not a bread truck.
I have tried cruise timing up to 38*, afrs from 14.7 to 18, i went to a 185* thermostat from 160. All of the PCMs assumptions (IFR, AFR) match up with what is happening in the real world, so I don't think there is anything weird happening like bad injectors, fuel pump, bad o2, etc. The truck rolls easily so its not sticking brakes as far as I can tell.
Idle vacuum is 16", cruise vac is anywhere from 14 to 17"
The truck is a beast under power so it doesn't seem like its any kind of major mechanical issue, just too much cylinder head for the application.
With all the differing success of the ls3 head swaps I knew I was taking a gamble and it seems like the heads are just not fit for my goals.
When I had the 226/234 cam, I couldn't cruise below 2000 rpm. with the smaller cam it now cruises ok at 1400, but it is obviously not doing it efficiently.
I will post my latest tune and log tonight when I get home from work.
Having that lean of afr at cruise can hurt your mileage. I have played with lean cruise alot over the years and every vehicle is different I havent seen any get the best mileage with an afr of 18. You need to only change one variable at a time to see if your making any progress. I would get your fuel tables dialed so so your fuel trims are +-3% when commanding 14.6, then start adjusting timing 1 deg at a time +-. Its very time consuming but its about the only way to rule out its a tuning issue. There are tons of LS2's out there with LS3 top ends from GM. Post your current tune and I'll take a look.
08-03-2013, 01:00 PM
#26
TECH Fanatic
Thread Starter
Having that lean of afr at cruise can hurt your mileage. I have played with lean cruise alot over the years and every vehicle is different I havent seen any get the best mileage with an afr of 18. You need to only change one variable at a time to see if your making any progress. I would get your fuel tables dialed so so your fuel trims are +-3% when commanding 14.6, then start adjusting timing 1 deg at a time +-. Its very time consuming but its about the only way to rule out its a tuning issue. There are tons of LS2's out there with LS3 top ends from GM. Post your current tune and I'll take a look.
I have been having a hard time adding more timing at cruise without affecting part throttle acceleration.
08-04-2013, 10:05 PM
#27
Looked over your tune, the 3 biggest things I see that would definitely hurt your fuel economy:
1. VE table
2. High Octane Timing Table
3. Commanded Fuel vs RPM
The 4th thing would be always in OL with no O2 sensors. Until you fix at least the first 3 you will always get terrible economy on your current tune. I would fix all 4 if it were mine.
1. VE table
2. High Octane Timing Table
3. Commanded Fuel vs RPM
The 4th thing would be always in OL with no O2 sensors. Until you fix at least the first 3 you will always get terrible economy on your current tune. I would fix all 4 if it were mine.
08-05-2013, 01:06 PM
#29
Hey man, just took a quick glance at your tune and there's so many changes that I'd just start over with a stock bin and go through the efilive tutorials on dialing in the VE. You're going to want to run the 02's front for fuel trim and you might like to run a MAF as well. Do all that and you should see a vast improvement in fuel economy!
08-05-2013, 01:45 PM
#30
Hey man, just took a quick glance at your tune and there's so many changes that I'd just start over with a stock bin and go through the efilive tutorials on dialing in the VE. You're going to want to run the 02's front for fuel trim and you might like to run a MAF as well. Do all that and you should see a vast improvement in fuel economy!
Thats what I was going to type, I agree with you.
08-05-2013, 05:57 PM
#34
Is it possible to fill me in with something a little more specific about what is wrong?
Just starting over and redoing the same thing I have always done is obviously not going to be the answer.
I have run the truck OLSD and OLMaf with similar results. I get the VE and MAF tables to within about 1-2% across the board, I am not sure how this is something that needs to be wiped out to redo again. I also have not been able to get my NBO2s to function correctly. they read 400-420mv no matter what so I gave up and just disabled correction. Should it even matter if the VE tables are within 2%? Is there a difference between 14.7 at OL and 14.7 at CL?
Just starting over and redoing the same thing I have always done is obviously not going to be the answer.
I have run the truck OLSD and OLMaf with similar results. I get the VE and MAF tables to within about 1-2% across the board, I am not sure how this is something that needs to be wiped out to redo again. I also have not been able to get my NBO2s to function correctly. they read 400-420mv no matter what so I gave up and just disabled correction. Should it even matter if the VE tables are within 2%? Is there a difference between 14.7 at OL and 14.7 at CL?
08-05-2013, 06:05 PM
#35
TECH Fanatic
Thread Starter
so if i have a TT 317 headed 6 liter and a TT 5.3, how big of a difference will the fuel economy be?
Last edited by TrendSetter; 08-05-2013 at 06:11 PM.
08-05-2013, 06:22 PM
#36
No way to know, hundreds of possible variables. Fuel economy and twin turbo dont go together BUT with fuel injection, ls motors and tuning its just a BIG bonus that you can get really good fuel mileage with high horsepower combos. The same combo that can get 28mpg on the highway with cruise control can easily get 10mpg in town playing around. Cam choice, intake,exhaust, trans,gearing, tire size, etc all affect fuel economy. The best thing to do is build your combo to reach your power or et goals and then whatever fuel mileage it gets is just a bonus. If your tuning isnt correct none of them will get the best fuel mileage.
