To tune or not to tune....

[Riktar]

That is my question. I know it should improve my MPG (albeit slightly) and provide better drive-ability but here's the thing:

On a recent road trip down to North Carolina I was able to get 23.5 mpg by keeping the speed below 70 and keeping the AC compressor off. Even driving 70 - 75 with the AC running I was getting 21.5 to 22.1 MPG. Driving around home (mostly rural) will get me in the high 18's MPG if I take it easy.

My driving environment is rural so usually am going between 45 - 60 mph. The only performance I am concerned with is passing ability at these speeds. Compared to my Pontiac G6 (3.5L) I feel the performance is "adequate" when passing. Not as fast as the G6 (The G6 will jump to nearly 90 mph when making an "extended" pass at 55 - 60. The TB will be damn near 80 in a similar scenario) but not that far behind. And since my driving "style" is casual, I am not too awful worried about the 0-60 performance area.

So I am left wondering if I would see any (noticeable) increase in MPG or if I could close the gap in performance (to my G6) while passing.

And I should note that (according to the former owners records) a "firmware update/adjustment" was done to "improve drive-ability and MPG" by a local shop in the area. So maybe this was an actual PCM flash/tune that has already been done?

 

[Mooseman]

Usually, we get a tune to eliminate annoyances and issues with the stock tune and smog equipment, like the SAIS and electro-viscous fan clutch, and to improve other things like shift firmness and torque management. MPG improvement, to me, would be a bonus. That being said, my MPG actually went down but I am still investigating this as a slight misfire could be responsible.

A tune is the single most popular and satisfying mod done to our trucks.

 

[Riktar]

I guess I bought into the marketing hype I see on some of the sites. IE: 10-12hp gain! Better MPG! Fresher breath... ;-)

I will still do some digging into this. Interestingly enough, PCM of NC is only 45 minutes from where some of my brothers and sister lives! And I was just down there a couple of weeks ago. UGH....

Maybe on my next visit down South....

Thanks for the reply!

 

[Mooseman]

One thing they don't offer but can be done is TCC engagement to 100% instead of slow PWM. Lime-Swap does it, which works great. Same effect as a shift kit.

 

[AzTruckGuy]

I'll let you know this weekend....I got my loaner from Lime-swap on Monday and I will be installing tomorrow...How youre getting 23mpg on the freeway boggles my mind? I had to put so much into my Trailblazer just to get back up to working conditions and the best city I get is 15MPG. I got the tune to remove the slow turtle feel of the throttle when Im driving on the freeway and hoping the slow transmission shifts will be gone as well

 

[Riktar]

Bear in mind I do NO city driving where I live. Rural roads by me have nice long stretches. I can drive almost 10 miles without ever having to stop. And I time my stops by way of coasting as long as I can before I have to hit the brakes for a stop sign.

I am sure that if I were to drive around the Milwaukee area on a regular basis my mileage would be right around your 15 MPG figure.

As for the highway, I was VERY (and pleasantly) surprised when I got my first fill-up and the math verified the 23+ MPG on the first tank. Also consider that the majority of that tank was driving through Indiana which is a very flat state. That helps quite a bit. Also keeping the speed below 70 MPH kept my RPM's well below 2000 on the tach. While the 3.42's I have in the tail might not be the best for acceleration off the line, they do pay dividends at Highway speeds.

 

[Kelly@PCMofNC]

Obviously I'm biased, but I think it's one of the best bang for the bucks you can do on just about any GM truck. Gets rid of lag, better performance and mileage, cleans up the transmission...really no downsides to it!

 

[AzTruckGuy]

Obviously I'm biased, but I think it's one of the best bang for the bucks you can do on just about any GM truck. Gets rid of lag, better performance and mileage, cleans up the transmission...really no downsides to it!

I would say and no, my own personal experience. The weight is a huge issue in the Trailblazer at 4,616 lbs any tune would be just for freeing up power, but it wouldn't be notice due to this weight. I don't have a spare tire, removed the trash can muffler, bought tires due to the weight to decrease the weight. Realized that the heavy ass frame is 90% of the weight on Trailblazer, had GM put these vehicles at about 1,000lbs less, everything would be better MPG, Power ratio, hell even a tune at that time would really out the Trailblazer

 

[djthumper]

You are one out of hundreds of people that have had their PCM tuned. I really think that you have more issues that is causing the issue with the tune. You put a tune on a 14 y/o vehicle that you have not owned the entire life and worked on numerous items.

 

[HARDTRAILZ]

I would never own one of these without a tune to be honest. All of them I have owned have been tuned. Best mod i think I did to my truck.

 

[jsheahawk]

One thing they don't offer but can be done is TCC engagement to 100% instead of slow PWM. Lime-Swap does it, which works great. Same effect as a shift kit.

Sorry for my newb-ness on this, but what exactly does that do?

 

[AzTruckGuy]

You are one out of hundreds of people that have had their PCM tuned. I really think that you have more issues that is causing the issue with the tune. You put a tune on a 14 y/o vehicle that you have not owned the entire life and worked on numerous items.

Been in the family since 35k miles I got it at 95k miles, I know the history of it. It has been worked out and even with replacing parts that didn't need replacing it still gave an error code. You are right it’s a 14yr old vehicle that has a rudimentary pcm, how much can a tune really do? Like I said before in other post, the tune got rid of 80% of the sloppy shifting delay it had, but I can still feel it. For a 4660lb vehicle I’m lucky to feel the pedal. It feels smoother, but is it what I expected? No and that’s my opinion.

 

[Mooseman]

Sorry for my newb-ness on this, but what exactly does that do?

On the stock tune, when the PCM is commanding the TCC to lock, it will do so slowly using Pulse Width Modulation (PWM) to slip the clutch so that you won't feel it. The tune can change that to 100% engagement so no slip.

 

[Shaw520]

Mooseman,...When bangin around town (never over 45mph),..I find that leaving the trans in 3rd position keeps the TCC out of lockup,...Ive already noticed better throttle response and hopefully with the added benefit of less trans wear going in and out of lockup,...sound true?

 

[Mooseman]

Nope. The TCC still locks up in 3rd while cruising depending on speed. Probably don't feel it because of PWM.

 

[AzTruckGuy]

Mooseman,...When bangin around town (never over 45mph),..I find that leaving the trans in 3rd position keeps the TCC out of lockup,...Ive already noticed better throttle response and hopefully with the added benefit of less trans wear going in and out of lockup,...sound true?

I agree with in the better feel in 3rd . I drove like this in town for a while but would hit over 50mph and realized I shouldn't be driving like that so I went back to the D driving

 

[jsheahawk]

On the stock tune, when the PCM is commanding the TCC to lock, it will do so slowly using Pulse Width Modulation (PWM) to slip the clutch so that you won't feel it. The tune can change that to 100% engagement so no slip.

Sorry but why is instant lockup preferred?

 

[Mooseman]

The main one is usually to eliminate the slippage and shudder from a worn valve in the valve body caused by the PWM. Then, without slippage, reduces wear on the TCC and heat generated. And it just feels better to have that positive engagement.

 

[jsheahawk]

The main one is usually to eliminate the slippage and shudder from a worn valve in the valve body caused by the PWM. Then, without slippage, reduces wear on the TCC and heat generated. And it just feels better to have that positive engagement.

Copy. Thanks for the explanation.

 

[Locksmith]

Obviously I'm biased, but I think it's one of the best bang for the bucks you can do on just about any GM truck. Gets rid of lag, better performance and mileage, cleans up the transmission...really no downsides to it!

Will be sending my pcm on Jan 2nd 2018 ! Take care of me Brother!