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2004 chevy trailblazer_lt
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Discussion Starter · #1 ·
Well guys I had my pcm upgraded to premium gas by pcmforless(awesome guys,gals) and installed it today. I did just alittle bit of driving and response seems to be noticable and fun to drive. My other tune according to pcmforless was done with efi live and the speed limiter sometimes will not shut off with that program. I found that out one day when a jeep cherokee decided to keep riding my bumper so I floored it and left him in the dust and reached 105 mph and wham it just stopped climbing. Pcmforless has redone my pcm with hp tuner so it should be off, Im not planing on going that fast anytime soon but its hard not to get into it with all these open roads in NewHampshire and Maine :)


My current mods:

pcmforless tuned- premium

Airaid cold air intake

throtte body spacer

Magnaflow dual exit catback system

Magnaflow highflow catalytic converter (on the bench at work,soon to be installed)




http://www.youtube.com/watch?v=-6q3RK4EDRg&feature=channel_page
 

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2003 gmc envoy_slt
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7,190 Posts
What was the PCM set-up for before the change? I'd be interested in what kind of difference the 91 octane makes in mileage.
 

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2005 chevy trailblazer_ls
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Well guys I had my pcm upgraded to premium gas by pcmforless(awesome guys,gals) and installed it today.
I'm curious as to the reason for upgrading to premium gas. The purpose of the higher octane in premium gas is to prevent the compressed fuel from exploding in the cylinder prematurely (detonation). Unless you modified the engine to increase compression in the cylinders (e.g., milled head, restroked crank, etc) running higher octane serves no purpose. The hydrocarbon and oxygen content of premium is the same as regular. There's no increase in potential energy output, hence no effect on power or mileage.
 

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2004 chevy trailblazer_lt
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Discussion Starter · #4 ·
I'm curious as to the reason for upgrading to premium gas. The purpose of the higher octane in premium gas is to prevent the compressed fuel from exploding in the cylinder prematurely (detonation). Unless you modified the engine to increase compression in the cylinders (e.g., milled head, restroked crank, etc) running higher octane serves no purpose. The hydrocarbon and oxygen content of premium is the same as regular. There's no increase in potential energy output, hence no effect on power or mileage.
The higher octane allows more room for timing advance which helps in HP and responsiveness..... Plus when I found out my speed limiter was not disabled I figured why not get what I can get out of my engine even if its minor.


Honestly guys, and I am not trying to sound like an ass but I really do not need a lesson in gas and engines. I am a 20 year veteran auto technician that just likes to tinker around with my vehicle and I know its not a race car but I can assure you this grocery getter has beaten a few V8 vehicles. I just posted to show what I have done since there is always someone asking about what mods are done to the limited 4.2L I6.


For the one that asked what tune did I have before the premium... it was set for 87 octane


Thanks guys, Preston
 

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Discussion Starter · #6 ·
Thankyou, and now that it has been on for a few months its louder and deeper then the video. I will have to do a new video after I install the magnaflow catalytic converter
 

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2002 chevy
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The higher octane allows more room for timing advance which helps in HP and responsiveness.....

I did just alittle bit of driving and response seems to be noticable and fun to drive.

For the one that asked what tune did I have before the premium... it was set for 87 octane

:iagree: Ive been trying to tell people this and they dont believe me. I had 87 a while ago and it was slow off the line plus it kills gas real fast. When i switch to premium (Including the tune) its just exact how you describe it, its fast and doesnt kill gas as much as 87.
 

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2004 chevy trailblazer_lt
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Discussion Starter · #8 ·
:thx someone who agrees with me :thx


After driving it around today the gas needle did not drop as far as it normaly did (i feel some better fuel mileage is coming and this thing does haul azz) :thumbsup:
 

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Discussion Starter · #9 ·
I know this is a exhaust update but figured since I started a thread here I would let you guys know that I have installed the magnaflow direct fit catalytic conveter(now I have a full magnaflow exhaust). I will have to let ya know what if any difference is felt in a few days of driving and letting my new pcm program learn itself alittle more since I just installed it the day before.


(this video is before the "cat" change)

http://www.youtube.com/watch?v=-6q3RK4EDRg&feature=channel_page
 

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2002 chevy
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I know this is a exhaust update but figured since I started a thread here I would let you guys know that I have installed the magnaflow direct fit catalytic conveter(now I have a full magnaflow exhaust). I will have to let ya know what if any difference is felt in a few days of driving and letting my new pcm program learn itself alittle more since I just installed it the day before.


(this video is before the "cat" change)

http://www.youtube.com/watch?v=-6q3RK4EDRg&feature=channel_page
I have the same thing. to me didnt notice any performance. it felt the same as the oem except that its stainless steel.
 

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Discussion Starter · #11 ·
yeah I figure it will be minimal if any....but it looks nice seeing all that stainless steel :woot:
 
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