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2004 gmc envoy_sle
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43 Posts
Discussion Starter · #1 ·
I want to improve the performance on my '04 Envoy I-6. My vehicle is very sluggish and doesn't shift well. I think I need to look into whether my cat clogged, but even so, I still want to improve the power and performance more. I've been doing a quite a bit of research here on Trailvoy for three things: Custom CAI, performance catback exhaust, and PCM for less tune.

I think for sure, I am going to order a tune from PCM. That mod is consistently getting good reviews for improving the problems I listed above.

I've read through a lot of threads on CAI and performance catback exhausts, and I'm not clear if either of those would be worth doing if my main goal is to improve hp, and acceleration. I also tow a bassboat. Any suggestions on what I should do, if anything, besides the PCM tune?
 

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2007 chevy trailblazer_lt
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756 Posts
iv'e got k&n cai and just deleted the resonator.. i wasn't expecting to get anything from removing the resonator besides better looks and lil different sound. cai didn't do much at all either.

now as for the pcm tune i also got that done and man can i say that it is def worth it for sure. much better pick up and overall shifting is much better. worth the $$. i can't really say the cai is worth what it cost tho and i couldn't justify spending upwards of 600 bones on an exhuast either.:m2:
 

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2003 chevy trailblazer_lt_ext
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967 Posts
From everything I've read, the tune is the best bang for the buck. If you do an exhaust and CAI, you'll want to customize your tune to take advantage of those.

As far as shifting, the tune will help that. But I've owned 3 other GM trucks with the L460E transmission, and they all shifted the same. They tend to "hang on" to 1st gear unless you are really pressing on the gas hard.

I just changed the CAT on my TB. More on that here: http://forums.trailvoy.com/showthread.php?t=60198
 

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2003 chevy trailblazer_ls
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1,236 Posts
I'll echo what the guys said above. There are not huge gains just laying around for the 4.2 like there were for de-tuned Chevy 350s. The 4.2 is already twisted pretty tight by the factory, and all we can really do -- apart from opening up a new Platinum Master Card -- is to optimize the airflow in and out.

Other gains can be made apart from upping engine horsepower, however, and these are not often talked about in threads looking to bump power.

1) Reduce weight -- cutting weight from the platform is the same as adding horsepower. Weight savings can come in a number of ways, from removing un-needed seats, spare tire, jack and tools, heavy exhaust components, lighter wheels and tires, etc.

For instance, this calculator:
http://www.ajdesigner.com/fl_horsepower_elapsed_time/horsepower_elapsed_time.php
Shows approximate vehicle horsepower based on quarter mile times and vehicle weight. Plug in factors like a 16 second quarter mile with a 4500 pound vehicle and the calculator spits out about 217 rear wheel horsepower -- a fair approximation of our 4.2 Trailvoy machines.

Drop the weight by 200 pounds and see what comes out of the calculator.
Play around to try and hold the horsepower steady, while manipulating weight, and you'll see how much improvement you can make in the times from just this mod.

2) Areodynamics -- let's face it, our trucks are BRICKS. Lowering, reducing drag (mirrors, roof rack, trim pieces, wipers, air management under and in front of vehicle, etc.) all make a difference in terminal trap speed in the race -- or just plain acceleration on the street. Shave it, slam it, de-badge it, tuck it, polish it -- all helps.

3) Rolling resistance -- Off-road AT style tires are not the best rollers out there. Make tires lighter for quicker gain in wheel speed (also helps overall vehicle weight as above). Don't get wild with overall diameter -- 24s SUCK power! Wider also robs power, but there is a balance between getting rubber on the road and rolling resistance. Use synthetic oils in the drive-train. Make sure things like brakes are not dragging.

4) Gearing -- this is perhaps the best and easiest avenue for performance increase! Swap in a set of 4.10 (or 4.56) gears and get an instant multiplication of available horsepower that will make a big difference.

Do what you can on the engine -- tune is AWESOME -- get the transmission shift sorted out -- then attack the other stuff on the list and go faster than the other guy.
 

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2004 gmc envoy_sle
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43 Posts
Discussion Starter · #5 ·
Thanks for the responses.

I have to agree, my Envoy is definitely a brick right now. It doesn't help that I switched from a V-8 Grand Cherokee either. Anyhow, I did a lot of research, all on this great site. I decided to go with the True Flow CAI, same as yours, glfredrick! The price on Amazon made the choice a lot easier. I also ordered a tuned PCM from PCMforless. I'm really looking forward to seeing the results after I get everything installed. :)
 
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