I've read most of the links in the scan/tune section and other online sources for tuning. I've read the FSM's pages for drivability and emissions. And I've worked on every car/truck/bike I've ever owned and I still am at a loss to figure out how or if some of the performance modifications work.

AFPR: It seems to me that with a stock computer, that if one were to adjust the fuel pressure up that he would see a rich condition in open loop. But once the computer closes the loop it would detect the rich condition and lean out the FAR by shortening the injector pulse.

24# injectors: Same as above. Open loop = rich. Closed loop = normal. Except that I wouldn’t think larger injectors would not make their optimum spray pattern at standard fuel pressure.

Larger Throttle Body(TB): Again it seems that unless the stock TB is restrictive that increasing its size could actually yield a lower intake velocity and hurt performance.

Larger MAF: Same as TB but if the comp is getting bad data, isn’t it going to return to normal operation once it relearns the BLMs?

MSD ignitions: CFI-EFI and I discussed this in a thread in the legacy forum. I can’t speak for him, obviously, but I seem to remember the consensus was that a working stock ignition works just fine until modifications get into forced inductions or high compression ratios. The installs I’ve seen of these are very hit and miss. Some look like hacked jobs and some look like they were factory installs. Some people have also bitched endlessly about them crapping out on them. Since they weigh more and draw more electricity, I suspect they reduce power and increase ETs. Has anyone ever done a dyno run before and after a MSD install? What about ¼ mile times?

If tricking the computer into making different choices is the goal of some of the above modifications then why don’t people put in trick O2 sensors that will always read lean or engine coolant temp sensors that will always read cold?

Years ago I read an article that said one should always take a comprehensive approach to performance tuning. The idea of one thing changing the performance was shunned and the idea of custom chip/bin was put forward as the only way to make sure that the common modifications will yield actual results. Otherwise, it’s just pulling the yarn of a sweater.

I’m not saying that what I’ve written here is how things are. I’m just saying that’s how they seem to me. What am I missing?

Quote:YEP! That is an analog solution to a digital problem. The computer keeps the A/F ratio correct for the 95% of your driving, but allows the mixture to go rich when you go into the open loop PE mode at WOT. The higher pressure can cause a better atomized spray from the injectors, but proper programming can accommodate the injectors and the fuel pressure you really need.

Quote:As you said...Same as above. Depending on the level of power that can be produced, the BMFC of your engine will tell you how much fuel and what size injectors will get the job done.

Quote:The engine is an air pump. If the TB isn't a restriction you can leave it alone.

Quote:Same as TB.

Quote:Most after market ignitions are capable of putting out more power than the stock ignition. But since a stock or mildly modified engine will never meet or exceed the capability of the stock ignition, the fancy, expensive stuff is a waste. Remember a coil won't put out any more voltage than necessary to jump the plug gap, regardless of the potential. I would argue that a good ignition system would reduce power or hurt ETs, but they won't help in most cases, either.

Quote:That is the wrong way to approach the subject. Don't try to fool the computer with false input. Program the computer to do what you want with true, correct input. Otherwise, you will soon be tricking and out smarting, yourself.

Quote:And all the modifications should be carefully coordinated to work together toward a single performance objective.

RACE ON!!!

Then there is the guy who mods his engine, lots of HP and Torque, so then he snaps axles, ujoints, dirveshafts, or whatever is the leakest link in getting the power to the ground. The entire vehicle must be taken into consideration as each change affects something else. OOPS--don't forget the brakes, gotta stop at the end of the track????