Some performance/MPG mod info
 

Here is some early data (more to come) about the mods I have done and the impact:

1) K&N intake - with work done on the improve the transitions (much needed), improved the seal of the K&N divider from the engine compartment to breathe less engine compartment hot air. I tested 4 other air boxes too (one aftermarket and 3 progressive designs of my own)

2) B&B exhaust - from discussions with most of the exhaust manufacturers, all have about the same performance gain. The B&B doesn't have a resonator and has a flange in the back so that the B&B muffler can be easily removed (unbolted) and a custom muffler bolted on. I get complements on the sound, but I think the sound is just OK. Everyone has different tastes.

3) Ported/contoured throttle body ? the TB definitely needs some work ? worse than the LS1 TB. Worthwhile mod.

4) Using a fixed resistor in place of the IAT (air inlet temperature) sensor ? On previous GM OBDII PCMs a timing adder was based on IAT?s. Cooler air results in more timing. I?m telling the PCM that the incoming air is pretty cool to obtain more spark advance. Definite SOTP improvement and HP Tuners shows a timing increase.

5) Offset applied to the ECT (engine coolant temperature) - On previous GM OBDII PCMs a timing adder was based on ECT?s. Cooler engine results in more timing. I?m skewing the NOT temperature by about 10ish degrees ? cold ECTs are essentially the same to retain the stock cold engine starting timing and A/F ratio. I don?t know how much timing was added because of this ? some existing engines added timing and some didn?t for this amount of ECT change. This might not be worth the effort.

6) 38 ? 40 psi tire pressure ? seems to help some instead of 35 psi ? slightly rougher ride though ? even tire wear

So far no knock retard from the timing increase with 87 octane.

Performance ? definite performance gain ? I have preliminary real world dyno numbers, but I want to repeat testing and get 0-60 MPH before I post them. The engine doesn?t shift as much and holds fourth gear in lower RPMs (auto tranny). No ?blah? when you floor it from a standstill.

Fuel economy ? I make 95% ~3 mile trips with several hills. MPG was 12 and now after the mods is 14 ? 14.5. No highway MPG numbers.

I?m hoping to stir up some more tech discussion with this info.

Re: Some performance/MPG mod info
 

I've wanted to respond to this but haven't taken time until now. What mod's did you do to the throttle body? I have an Air raid TB. I have an SMA cold air Induction and a Cat back exhaust. The dealer ship installed all and said that it gave 41 more HP not sure about 41 but 20 would be closer to it I think. I drive 70-75 miles per day run mainly back roads and interstate I'm averaging 18.5 to 19.5. any help in HP or MPG would be great. I've been looking for tuner thru hypertech, superchip etc. response from them have been they dont have any thing.

Re: Some performance/MPG mod info
 

The back of the throttle body needs porting. The front of the throttle body needs some general shaping/polishing. Actually there is a lip on the intake manifold that needs work, but I was worried about dropping chips into the manifold.