Alvin is a very nice guy. I think he might be able to find it in his heart to forgive you , or, maybe he'll just reprogram your PCM to make your engine self-destruct MUAH HA HA HA HA HA HA what.

 

Well, after driving to work under my normal conditions and driving the way I always do, here are the NEW things I have found:

1) I didn't drive no 200 miles yesterday like I thought (I don't know WHAT I was on...) but only about 70 miles.

2) I tell you, I found myself continuously braking the entire time to work, not because it was stop-and-go so much, but because the normal amount of pressure I would use to press on the accelerator made it accelerate much faster then it used to. I kept creeping up on everybody's rear end. I'm surprised my rotors weren't glowing by the time I got to work There really is more pickup. I know there has to be more going on then just a boost in HP. There seems to be quite a bit more torque.

2.5) On the way to work and back, I'm usually in 4th gear most of the time, just because of the way traffic is on my expressway. There is a noticable difference in pickup in 4th gear. I don't even want to shift it into 5th because me likey the power

3) The engine is much smoother accelerating at low RPMs then it used to. When I was anything under 1750 RPMs and floored it to accelerate at higher gears, the engine would virbrate. Now, there is no vibration at all, and even when I am a little under 1500 RPMs and cruising down the expressway, I hit the gas and no vibration. It seems like the engine is not struggling as much as it used to.

4) A HUGE difference in upper RPM vibration. When I would get past 4500 RPMs, the engine would really start to vibrate alot, like I was pushing it too hard. Now, it doesn't vibrate AT ALL. It's SO smooth getting past that 4500 RPM mark. I used to literally feel like my engine was going to just vibrate right out of the engine compartment. Now, it's as smooth at high RPMs as it is at low. I don't know HOW the heck you did that little fix, but it's pretty awsome! I'm not afraid of blowing up my engine anymore! Is there something you did to make it smoother at the higher RPMs?

Since nobody here seems to have a Manual H3, I can't say you guys would feel or see the same effects that I do, but for me, I'm really impressed. It's such a bargain for $149. I don't know what the long term effects will be obviously, but so far, it's really starting to show some hidden power.

I have to say, I'm still VERY impressed by how much power this little I-5 engine can make, especially now. You have to give the GM engineers alot of credit for being able to pull off the H3 with this engine. I just wish they would have come tuned this way. It probably would have given them more selling power. The boost is enough for me to finally be content with the amount of power I'm getting.

Alvin: Thanks! I don't know what else to say You made me a happy driver.

(Yes I sound like a commercial, and NO I didn't get any kickbacks )

 

One other thing I forgot. I did two 0-60mph runs immediately before and after I swapped the pcm, timed with my watch and the speedo. First two were right at 15 seconds, second two after the swap were right at 12 seconds.

Not very scientific I know and also had my 35" tires on at the time so the actual times were probably a little less but a noticeable difference there.

I hope my buddies from the lotus forum don't see those 0-60 times.....[sm=happybounce.gif][sm=happybounce.gif]

 

Was that timed on a track or just you watching the speedometer and your watch

That sounds like something I would do! It doesn't take me no 12 seconds to get to 60! Damn I DO have it good with this 5 speed!!

 

The PCM learns three major engine items: fuel, spark, and idle. You can picture that the PCM is pre-programmed with fuel and spark info. As you drive the PCM looks at the oxygen sensor before the cat. converter and adjusts the air/fuel ratio to be 14.7:1. Learning is required because of tolerances in fuel pressure, MAF sensor, etc. The data the PCM learns about the fuel is stored in Trim cells (as in fuel trim not the other kind). So the PCM fine tunes the inital starting points. The data is retained until you reset it (using HPTuners, Tech 2, etc.) or when you disconnect power to the PCM.

Spark timing is similarily learned. The PCM starts with an upper and lower spark table (high octane and low octance). As you drive the knock sensor is monitored and timing is adjusted and ends up somewhere between the upper and lower table. This learning is reset under the same conditions with the fuel but also when you add significantly more gas.

Idle is learned as a function of engine temperature and gets reset the same way the fuel trims do. This learing is fuel, spark, and more importantly throttle position need to for the programmed idle RPMs.

There is other learning that the PCM does besides the big three that I mentioned.

 

When you say it learns the spark, what exactly does it learn? Does it learn how much voltage the spark plugs should get for the best combustion, or do you mean the timing of the spark? If you put something like Iridium spark plugs, or those Bosch Platinum +4's, how do things like that affect the PCM? Does it adapt to things like that, or does it always just use the first initial xxx miles of data for the rest of it's battery life?

Also, do those goofy 9 Volt battery adapters you buy at the store REALLY help keep your PCM's memory when you disconnect the computer? I can't see how that could work considering it's sending power opposite of what it's supposed to. Someone actually told me to use those things before thinking the computer's memory would be retianed when switching batteries. I'm a sucker though don't forget

 

It learns the timing. I don't think the PCM would notice the plug change unless the plugs were bad resulting in incomplete combustion or ran hot causing knock/dieseling.

I think the PCM only needs a few milliamps to hold its memory. I thought the these are suppose to provide memory hold power if you disconnect the battery. I don't know what would happen if you would open the door and the interior light drags the voltage down.

 

lol, its ok the guy from the SVT forum (me) caught you though! [sm=happybounce.gif]

I've stayed out of this thread because I don't really feel like I have much to contribute, but I do want to say that from the sounds of things I'm going to want to get a tune!

 

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Let me know if you have any questions or anything like that. I really feel like we have a great product for these Hummers. Our tune has got to be the absoulute best bang for the buck performance wise or mileage wise. They have been slow to take off but I sorta knew that was going to be the case as hummers are kinda on the rare side. I'm really eager to get a bunch of people to try the tuning.