Upgrades?????

[Field Scout]

very nicely put

[shlprk]

Thanks, So Hadden are u suggesting that the only upgrade out there for this particular vehicle is the catback system? ( I would only put the catback on my vehicle, only way to go) I've read so many posts that they can c improve ments with the pcm4less upgrade. I was under the assumption that with the ecm upgrade that it would do all that, to improve shift points, mpg, and torque. You obviously know what your talking about, so is the pcm4less false with there advertisment and a waste of time?
Well if you cangive me more 411 I would appreciate it Thanks in advance.

[Wisha Haddan H3]

I honestly don't have any experience with PCM upgrades, but here's why I'm skeptical. Anyone who's actually chipped their H3, feel free to correct me.

Why people chip:

1. To move the powerband into a specific RPM range.

On engines with fixed valve timing, the timing doesn't change from low to high RPMs. The engineers had to decide not only where to optimize the powerband but also how to make the rest of the powerband acceptable while balancing power and fuel economy.

Aftermarket PCMs eliminate the power/economy trade-off and optimize timing in a specific RPM range (usually high-end for racing or low-end for towing and off-road). The trade-offs are poor performance in the off-range and engine stress from a combination of power in the optimized range and neglect in the rest of the band. Some companies offer an in-cab controller so you can pick your powerband for racing, towing, cruising or whatever.

2. To change the shift points (automatic trans)

This changes the RPM where each gear shifts up or down ... the same concept as the Power/Economy button on some cars. For maximum economy, you shift sooner to keep the average RPMs as low as possible. For maximum power, you stay in each gear as long as possible to stay in the powerband. Plus, when you shift, you're right below the power band and ready to accelerate through it.

3. To firm up the shifting (automatic trans)

This completes each shift faster. The thinking is that the faster you get into the next gear, the quicker you can get to the powerband in the new ratio. But it isn't as smooth between shifts and puts more stress on the drivetrain.

4. Correct the speedometer

If you change your tire size, you can usually correct it by chipping.

Why I wouldn't chip (even if I had an automatic):

1. The I-5 has VVT (variable valve timing)

VVT dynamically changes valve timing across the RPM band. Since GM didn't have to sacrifice power or durability at particular RPMs, they could optimize it from top to bottom. This partly explains the I-5's flat torque curve, providing almost as much torque at 2800 as it does at 5600 RPM. Basically, the RPM optimization is already done. There might be some wiggle room to trade economy for power, but you would really have to know what you're doing for minimal gains imo.

2. If you're driving hard, you're already flooring the pedal

... which keeps the transmission in gear through the power band for free.

3. Firmer shifts? Cool, you saved 0.5 seconds

4. Ok I admit it ... correcting for 35" tires would be cool.

5. Why risk voiding a 100,000 mile warranty?

6. Gas is expensive. It costs too much to lose a lot of fuel economy for marginal power gain.

7. Seat of the pants dyno? Come on ... The few people on this board who have tried chipping or programming the PCM said they "felt" a difference, but provided no convincing evidence. Give me dyno results, track times, and mpg measurements.

8. Time in the shop. I know a guy who chipped his truck. He won't shut up about the power gains, but it's always in the shop with engine and tranny problems. But then again it is a Dodge ...

So yeah, I'm skeptical, but I'd like to be wrong here. I want more power same as everyone else.

[ChevyHighPerformance]

I'll add my 2 cents.

The PCMs aren't chipped they are flashed through the diagnostic connector.

1) There are two areas to improve power: fuel and timing.

Timing - The PCM uses two 2D tables of data for timing - a high octane table and a low octane table. The tables provide the timing based on RPM and cylinder airmass (g/cyl). You can add timing where ever you want/feel. Optiminal timing improves both power and fuel utilization (fuel economy). These tables are optimized based on the octane fuel you want to use.

Fuel - There is a part throttle A/F ratio set at 14.7:1 to minimize emissions and improve fuel ecomony. During WOT (wide open throttle) there is another table that essentially provides the A/F ratio as a function of RPM. At high RPMs the stock WOT A/F is set at 11.3:1. To make better power and use less fuel you want this A/F to be about 12.5:1 for this type of vehicle.

2) Auto tranny shift points - There are tables that show at what speed to upshift and downshift as a function of throttle position. I have mine set up so that when you are just putting around the tranny upshifts sooner than stock to improve fuel economy. When you give it some throttle I have my tranny shift at higher speeds to improve acceleration. Properly picking tranny shift speeds can improve MPG.

3) Shift firmness is comprised of two elements: torque management and shift pressure. Torque managment is basically the reduction of timing when shifting to minimize the load on the drivetrain. Shift pressure is kinda how hard the tranny shifts gears. Increasing shift pressure doesn't necessarily reduce tranny life.

4) VVT - The PCM uses 5 VE (volumetric efficiency) tables to accomodate the VVT. My opinion why the 3.5L torque curve is flat is that the engine runs out of air at the upper RPMs. The 3.7L with VVT has its peak torque much higher than the 3.5L.