How to tune the LSJ or any car for that matter.

[Twincharged]

First thing is first. You need to know what a STOCK car's ECU wants to see.
You need to datalog all the sensors of the stock car under different operating conditions. I use an OBDII scanner for my laptop and datalog all of the sensors and ignition timing. I scan it under normal cruising, idle, WOT, Decell, partial throttle accell. You need to pay attention to MAF sensor peaks, MAP sensor peaks, and ignition timing peaks.

Now you want to go fast but your ECU doesn't. What to do what to do? Well for one is to trick the ECU. Put the ECU in it's happy place. Make it think that everything is OK when the truth is you are boosting the hell out of it. YOu need to reproduce it normal operating conditions by emmulating it's normal sensor outputs. Go no higher than the normal MAF sensor fequencey. No more voltage than what the MAP sensor would normally produce. You need to cap or clamp these sensors off. You need to do it to all of the sensors.

Add boost add fuel. Do not attempt to do anyting to your car with out being able to monitor whats going on. YOU NEED A WIDEBAND O2 before you change boost or attempt to tune anything.

Larger injectors. You want to run larger injectors and pull back on the MAF frequency to make it idle and run right. Well in this situataion you can take the MAF out of it's normal operating scope and result in changes of normal engine operation. (more ignition timing). You can get away with this if it is a narrow margin. Tune in the air fuel ratio that you are looking for then compair the MAF readings with your stock reading. Try and compromise with the tune and meet in the middle. I really don't recommend this method and in the end on the LSJ YOU CAN"T ADD ENOUGH FUEL to make up for the the last few 100 RPMs of the map where the ECU pulls boost.

The best way to tune is to be able to manipulate all sensors that the ECU reads. Tune your so that you do not exceed the peak Grams per second reading on the MAF and KPA on the MAP sensor. By doing this your car thinks that everything is normal. Well how do you get more fuel for the boost? You need to add extra injectors. These injectors are going to tie into your current fuel system and need to be driven off a piggyback that has Pulse Width Injection. You can inject the fuel totally seperate of the factory ECU.

You see the ECU has no idea what is going on. You can get away with Murder this way

[Sp00ner]

Great write up TC...

[jmc007]

Here are my opinion, please guys correct me if I'm wrong.

The MAF sensor is implied in several calculations by the PCM. It's related to the RPM and also the MAP sensor #1 (the one BEFORE the supercharger). I think (and have experimented) that tricking it will only permit to tune the air fuel ratio within a small range, thus affecting the ignition timing in a not optimised way.

I DO NOT suggest the Apexi S-AFC II for our cars. Ray from Revitup clearly said that he didn't been able to get it work properly on his wife's supercharged Cobalt SS.

For the air fuel tuning, the service shop manual clearly says that the injector pulse width is controlled by the rpm, the intake air temperature, the engine coolant temperature and the load. With a small pulley (smaller than 2.8") the LOAD factor here is the more important factor to take care of. That's why tricking the Mass air flow signal is not as effective as tricking the MAP (manifold absolute pressure signal; that's the pressure after the supercharger). Fooling the mass air flow signal down let the PCM thinks it's less loaded, so he runs more timing, resulting in knock retard.

About the MAP signal, you're choice is to clamp it or to scale it. I will myself try soon to scale it, since I think to clamp it (especially when you run a pully smaller than 2.8") will not be as effective.

There is at least two device to do that. First is the Perfect Power SMT-6 piggyback (as used by Twincharged or in the former PSI-FI kit or the current Revitup Kit) or the second device is the Split Second PSC-1 controller.

Both have advantages and disadvantages. SMT-6 is very great and can controll and fool mainly every parameters on a car; that's impressive. But one problem is that the version sold to us (customer) is a box with wires, with no ability for us to program it, so we have to buy it with the calibration provided by (or ask to) the seller. There is a SMT-6D (developper series) that is sold only to dealers and can tuned by a laptop.

About the Split Second PSC-1 controller, it's a bit cheaper, it's only able to scale the map signal and is programmable by a laptop.

Hope this could help ...

[BigBrother]

Good basics. HP Tuners suite will be available soon, so you can save yourselves a lot of trouble and focus on optimizing real tables, lol!

[Oddjob]

At what stage in my performance mods would I need to think about getting a maf translator or a mini afc?
Thanks.

[jmc007]

Which year is your car and what are your current mods ?

[Oddjob]

Its a 04 with gm manifold, 3 inch exhaust, sms throttle body, NKG spark plugs, BF 2.9 pulley, bypass mod, I am getting gm stage one.

[goofyguy]

Originally Posted by jmc007

There is at least two device to do that. First is the Perfect Power SMT-6 piggyback (as used by Twincharged or in the former PSI-FI kit or the current Revitup Kit) or the second device is the Split Second PSC-1 controller.

Both have advantages and disadvantages. SMT-6 is very great and can controll and fool mainly every parameters on a car; that's impressive. But one problem is that the version sold to us (customer) is a box with wires, with no ability for us to program it, so we have to buy it with the calibration provided by (or ask to) the seller. There is a SMT-6D (developper series) that is sold only to dealers and can tuned by a laptop.

About the Split Second PSC-1 controller, it's a bit cheaper, it's only able to scale the map signal and is programmable by a laptop.

Hope this could help ...

I just wanted to drop this in here. If anyone needs larger injectors and say a smt6 that completly unlocked I can get them. If it works out I can make a package out of them. Regardless I can get them for about 400 shipped to you. Thats fully unlocked unit you plug it in and tune it that way you want.