Turbo Tuning

[scotts90ranger]

The only time any engine needs to go into open loop is when the exhaust temperatures start to get past the safe point where you need to start adding fuel to cool the exhaust. That has nothing to do with it being forced induction or not, forced induction engines can just flow more air and fuel to heat up the exhaust easier than a N/A engine. I agree things get different depending on the control scheme... About a year ago I was tuning on a supercharged 6.2L engine at work to meet emissions and everything. It is for jet boat applications so I limited the engine to 5000rpm, I was able to keep it in closed loop control through about 3800rpm if memory serves and about 60% load. The engine ended up making 509hp at 5000rpm and I limited it down to that which was at about 7psi boost, if I went for more power I started having catalyst temperature issues along with emissions issues, and I think back pressure and valve temp issues... I don't think many people will use them at that point though as the fuel usage is kinda ridiculous .

 

[Blown]

Uh I disagree. Forcing Open loop fuel earlier gives you the ability to control the AF ratio via the base fuel table with the strategy these Rangers use. Closed loop fuel is about keeping it clean for emissions at 14.64:1. That is way to lean for boost, creates heat, and preignition. Engine go boom!

 

[scotts90ranger]

Ok, I'm used to modern stuff then... with what I work with we have two full spark tables, one for low octane fuel and another for high octane fuel, along with knock sensors adapting between the two and taking out spark when needed, also while tuning we run with thermocouples at all exhaust ports watching exhaust temperatures. With all of that, there is no need to run in open loop until it is necessary to keep the port temps in control... If I get a chance tomorrow I will have a look to see how long I kept that 6.2L LSA in closed loop, but my guess is somewhere over 300hp while still in closed loop... but this is a low boost application (somewhere around 7psi) on an aluminum block and headed V8. I have control over the base fuel table, power enrichment, acceleration/deceleration fueling, idle control, when the engine is in closed loop, how the O2 system controls fueling, spark (including knock control), throttle If the strategy on the Ranger engines is different that's fine, as far as I remembered from back in the day they went to open loop at 3000rpm or over a certain throttle position or something. I'm able to do all of what I do while keeping the engine running smooth and responsive, meeting emissions and getting as good of fuel economy as possible from keeping it in closed loop.

Ok, I'll stop going off topic... I imagine there isn't as much control on what the OP is dealing with compared to what I'm used to...

 

[Blown]

Ok, I'm used to modern stuff then... with what I work with we have two full spark tables, one for low octane fuel and another for high octane fuel, along with knock sensors adapting between the two and taking out spark when needed, also while tuning we run with thermocouples at all exhaust ports watching exhaust temperatures. With all of that, there is no need to run in open loop until it is necessary to keep the port temps in control... If I get a chance tomorrow I will have a look to see how long I kept that 6.2L LSA in closed loop, but my guess is somewhere over 300hp while still in closed loop... but this is a low boost application (somewhere around 7psi) on an aluminum block and headed V8. I have control over the base fuel table, power enrichment, acceleration/deceleration fueling, idle control, when the engine is in closed loop, how the O2 system controls fueling, spark (including knock control), throttle If the strategy on the Ranger engines is different that's fine, as far as I remembered from back in the day they went to open loop at 3000rpm or over a certain throttle position or something. I'm able to do all of what I do while keeping the engine running smooth and responsive, meeting emissions and getting as good of fuel economy as possible from keeping it in closed loop.

Ok, I'll stop going off topic... I imagine there isn't as much control on what the OP is dealing with compared to what I'm used to...

I appreciate your knowledge. But, Yup this is old stuff, no closed loop fuel table in my 2001 tune. It is a constant 14.64:1 In my older 96 Bronco there was a closed loop fuel table you could adjust, in stock form it had 14.64 in all the cells in the table. Hear ya on closed loop for mileage and emissions with the HEGO's doing the work.

 

[Billman]

Closed loop is also great for idling, just off idle and cruise. Just so happens that that is where my problem lies. There are no tables labeled VE. As stated earlier in this thread the engine runs great and fuel trim is good under boost. In fact if I could get boost at idle all would be great. Any load under 25% the engine stumbles and bucks (fuel trim at ~42%) I need a remedy...

 

[Billman]

Update... The Base fuel table has been found... It is in: Fuel/Base fuel calculation/Base fuel table... it is in lambda and load vs RPM. I have modified the table and proud to say the problem is fixed. Now at low loads the fuel trim is ~8%! Thanks to all who posted. This problem was exasperated by my very tight schedule. Many days I was able to read the posts but had no time to experiment with the software. SCT needs to post some kind of instruction manual for their program.

 

[Blown]

Update... The Base fuel table has been found... It is in: Fuel/Base fuel calculation/Base fuel table... it is in lambda and load vs RPM. I have modified the table and proud to say the problem is fixed. Now at low loads the fuel trim is ~8%! Thanks to all who posted. This problem was exasperated by my very tight schedule. Many days I was able to read the posts but had no time to experiment with the software. SCT needs to post some kind of instruction manual for their program.

Awesome!

SCT wants to sell tunes, not support DIY, then there are snob tuners to deal with. As you just found, it is not that difficult to tune. I was able to learn to tune my trasnmission as well withthe info I found out there for the Tweecer and on EECTuning. I got it shofting firmer, faster, and a bit later as well as downshifting sooner in my Performance tune. Then I got a much more mellow Mileage getter tune......................................

The base fuel table is for bigger moves, you can fine tune by adjusting the amount of air flow in the MAF Transfer. Add air it will richen and vice versa.