Any feel like having a tuning discussion?

[ChevyHighPerformance]

Originally Posted by H3slate

So it improved HP and torque? What about mpg? I am also interested in a legitimate way to get a little more from my engine.

I haven't run through a full tank with my normal driving yet. I've been taking a few highway trips which is going to skew my normal 100% city MPG high. So far, every other tuner I spoke with stated an increase in MPG.

[H3PAC]

I would assume that the expert engineers at GM would have already programmed the vehicle to perform optimally - i.e. the best combination of power/fuel efficiency/emissions, etc. I see programming devices advertised for sale to the conusmer and I wonder, why would an amateur playing around with these settings be able to do a better job than an entire professional team? Please don't misunderstand me - I don't mean to be disrespectful, I'm just trying to understand what the goal of reprogramming is. Can anyone please clareify this?

[ChevyHighPerformance]

Originally Posted by H3PAC

I would assume that the expert engineers at GM would have already programmed the vehicle to perform optimally - i.e. the best combination of power/fuel efficiency/emissions, etc. I see programming devices advertised for sale to the conusmer and I wonder, why would an amateur playing around with these settings be able to do a better job than an entire professional team? Please don't misunderstand me - I don't mean to be disrespectful, I'm just trying to understand what the goal of reprogramming is. Can anyone please clareify this?

First of all I really like GM, and I never bought anything other than a GM vehicle.

I some cases I agree with your thoughts. However, the amount of testing on the C6 Corvette&Z06 was way more extensive than the H3. So the tuning of the Corvete is much closer to optimal than the H3's, in my opinion. I feel GM has limited money/resources which limits development. Also, GM has to design to some extreme conditions such as temperature, fuel grades, etc which dictate the amount of conservatism in the tuning. For example, I think there is a TSB for the I5 for rough idle requiring a PCM reflash. So there is one example of where the experts didn't take everything into account the first time. OK, so everyone makes mistakes.

For example, if you have good quality gas and you don't operate in extreme temperatures, you can re-optimize you programming to your environment. Ask any tuner what the optimum A/F ratio is for best power and you'll get something like 12.8 - 13.1:1. However, GM has a 11.3 commanded A/F ratio for wide open throtle (WOT) for max power. Why? 11.3 is more conservative and provides more margin in case of problems. However, if you have a custom tune you can get the optimal A/F for more power. The same can be said for the timing or torque managment.

It's not that GM doesn't know how to optimise performance (look at the C5R), but is forced to for manufacturing tolerances, warranty issues, etc.

So a custom tune is one made for your vehicle - kinda like a custom suit.

[Hal]

Feel free to give those of us who are interested, but by no means experts, links to any refrences where we can learn more about this stuff.

Keep the info coming, I like this topic

Like I always run premium gas, have a 5-speed and live in a hot southern climate... I never thought about optimizing an engine for things like this.

[ChevyHighPerformance]

Originally Posted by Hal

Feel free to give those of us who are interested, but by no means experts, links to any refrences where we can learn more about this stuff.

Keep the info coming, I like this topic

Like I always run premium gas, have a 5-speed and live in a hot southern climate... I never thought about optimizing an engine for things like this.

Here is a link to LS1TECH that has other links about tuning.
http://www.ls1tech.com/forums/showthread.php?t=287094

I really haven't read through the stuff listed here but it came highly recommended.

[ChevyHighPerformance]

Just an update. With the new increase in low end torque, I modified the auto tranny shift speed table. This table shows at what MPH and throttle position you want the tranny to upshift or downshift for each gear. I lowered the MPH at which the tranny up shifts and I moved out where the tranny down shifts - I added more hysteresis. So when you are doing 60 MPH and you press on the throttle slightly the tranny doesn't down shift to 3rd right away. I get into 4th gear much quicker now and the acceleration in 4th is fine for small-medium grades. If I need more acceleration, I just blip the throttle more and the tranny will downshift. The stock shift tables can cause you to downshift (4th to 3rd) if you increase the throttle by as little as ~12%.

For low throttle positions I upshift quicker for better (hopefully) MPG. When you need the acceleration the new shift table doesn't hold you back.

[ChevyHighPerformance]

Another update. I've tweaked the tranny shift table several times. Not very scientific but - now it feels like the H3 floats/coasts. Before it always seemed like I always had to press on the throttle just to coast around town (as if I was dragging something behind me).

Also, in my plan the speed limit is 25 (lots of kids) and my plan is pretty hilly. Before I had to press the throttle to climb a hill but to keep speed going down the other side I would just let off the gas and I would maintain speed. Now, I have to press the throttle less to climb the hills and when I go over the peak, I let off the gas and I accelerate down the hill and have to use my brakes.

I know its not scientific, but now the H3 seems "lighter".

[f5fstop]

Originally Posted by ChevyHighPerformance

It's not that GM doesn't know how to optimise performance (look at the C5R), but is forced to for manufacturing tolerances, warranty issues, etc.

So a custom tune is one made for your vehicle - kinda like a custom suit.

I agree with Chevyhighperformance on this one; GM does have to produce a calibration that is designed for all factors, where a custom tune can increase performance. I had one on one of my Vettes, and it worked well. This was a custom tune loaded by a LS1 program, not a standard tune off a hypertech type device. Most of the standard tunes on the hypertech type devices are not much help.


As for testing, I understand that no tuner does long term testing prior to releasing a tune; the purchaser becomes the tester. What I was implying is your statement that there was a durability fault with the existing program (and which one, there have been at least two different updates since introduction, and there might be more, I haven't checked in a few months), and GM has quite a few production vehicles out there with high mileage; and some very early mules with tons of mileage, and no major durability problems I know of have been found. Those that were found, were updated with a new calibration, and then nothing really fixed in the new cals with durability.

[ChevyHighPerformance]

Originally Posted by f5fstop

As for testing, I understand that no tuner does long term testing prior to releasing a tune; the purchaser becomes the tester. What I was implying is your statement that there was a durability fault with the existing program (and which one, there have been at least two different updates since introduction, and there might be more, I haven't checked in a few months), and GM has quite a few production vehicles out there with high mileage; and some very early mules with tons of mileage, and no major durability problems I know of have been found. Those that were found, were updated with a new calibration, and then nothing really fixed in the new cals with durability.

I see two types of tune: performance and luxury. For the Corvettes, Silverado SS's, and F-bodies, performance is the goal and I'll shoot for a 12.8-12.9:1 A/F at WOT. For the H3 (first luxury tune), MPG is primary then performance and I'm shooting in for a 12.2:1 A/F under WOT. From what I remember on a 350 HP LS1 a 13:1 produced about 3-4 more HP at the wheels than a ~12:1 A/F. So for the H3 at 220 HP, the extra 2-3 HP at 13:1 isn't worth running closer to the edge.

As I go through with a tune, I try to identify the vulnerabilities - where is the engine stressed the most and how much relative stress. I shoot for having the most stress at WOT. However, some tuners leave voids and if you operate the engine in this region the engine stress is excessive.

I've done some tuning and published articles on how to tune, but I don't consider myself a pro like Bryan Herter or Steve Cole. That is one reason why I started this thread to solicit opinions from other people who are tuning.