GMC Truck Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
703 Posts
Discussion Starter #1
my nelson tune that's on the way is an 89-91 tune and i plan on running 89 most of the time, but just to ask the question...what would happen if i ran regular 87?
 

·
Registered
Joined
·
1,816 Posts
chances are that it would knock, then the knock sensor would hear the knock, and the computer would step back the timing till the knock goes away, and you may loose a bit of power.
 

·
GMFS slowest truck :read:
Joined
·
5,501 Posts
i wouldn't do it...pingin is bad on the motor...just stick with 89 or have nelson send you one for 87 instead...
 

·
To hell with BHO!!
Joined
·
2,645 Posts
Even non-audible knock is bad. If hes tuning it to run 89, hes giving it quite a bit mroe timing. Dont run 87, in the long run it wont be good. If the PCM senses long durations of knock it will fall back to the low octane timing table while pulling timing. I thought if the PCM sees a buttload of knock it threw an SES light and went into reduced power mode but I could be wrong. If my memory serves me corectly the max the PCM can pull is 8*.
 

·
Registered
Joined
·
378 Posts
you can run 87 octane as long as you arent going to be racing it. hahahaha,. that usually doesnt happen. i have ran 87 on a trip but as soon as i went to pass a slow car she would knock. you need to run at least 89 since he has raised the timing in the lower tabels to accomidate the performance. but the pcm can correct for bad gas. oh yay the pcm can pull up to 20* timing.
 

·
To hell with BHO!!
Joined
·
2,645 Posts
02denali said:
you can run 87 octane as long as you arent going to be racing it. hahahaha,. that usually doesnt happen. i have ran 87 on a trip but as soon as i went to pass a slow car she would knock. you need to run at least 89 since he has raised the timing in the lower tabels to accomidate the performance. but the pcm can correct for bad gas. oh yay the pcm can pull up to 20* timing.
Did your custom Westers come set up to automatically pull 20* when it got to a certain TPS%??? I just opened up Edit on my laptop and the spark retad limits are set at 10*.
 

·
Registered
Joined
·
703 Posts
Discussion Starter #8
02denali said:
you can run 87 octane as long as you arent going to be racing it. hahahaha,. that usually doesnt happen. i have ran 87 on a trip but as soon as i went to pass a slow car she would knock. you need to run at least 89 since he has raised the timing in the lower tabels to accomidate the performance. but the pcm can correct for bad gas. oh yay the pcm can pull up to 20* timing.
Well I better just run 89 then becuase im used to having a Gen I vortec with a single chamber and the Gen1's just dont have the awsome smooth sounds when the peddle is down like my new Gen2. With this being said i cant go a tank of gas without gettin on it every once and awhile :head:
 
1 - 8 of 8 Posts
Top