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2005 chevy trailblazer_lt_ext
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46 Posts
Discussion Starter · #1 ·
Does anybody know if PMCforless will max out the fuel injectors? I went to my local Performance shop and they wanted $500. for a tune... needless to say i decided to go with the PCMforless tune... But one thing i cant find any info on is wether they max out or adjust the amount of fuel going to the fuel injectors... The local shop said that it is something they would do if they tuned it... Anybody have any info on this?
 

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Northwest Chapter
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11,824 Posts
That sounds like they have no idea what they are doing...the whole point is to NEVER max out your injectors, what 100+% duty cycle means is the injector is staying open constantly and the spray pattern will not be optimal among other things. So no, PCM4Less and any good tuner will never max your injectors out. All tunes command the optimal pulse width to the injectors in order to deliver the proper amount of fuel under a given condition.
 

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2002 chevy trailblazer_lt
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388 Posts
Our trucks stock run on the rich side anyway, so if anything a tune would lean it out and run less of a duty cycle
 

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2002 chevy trailblazer_ltz
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58 Posts
Our stock tune is set for a commanded AFR of 14.6.

I believe that the injectors are the same as in our Colorado, but even then they rarely get above 25% duty if I recall- I know at idle they sit at 2%, and even revving to 4k doesn't get them above 8% in P/N. The logs that I have w/ our TB don't have duty cycle recorded, and mama has the TB right now, so I can't go out and scan what stock is.

I've heard a LOT of negative things about PCMforLess on the Colorado boards, and one member is having me re-tune him when he gets back from 'Asscrack-istan'. From what I've heard, most of the guys who've re-tuned one of their canned tunes found a lot of lean conditions more than anything, amongst other issues.
 

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2003 chevy trailblazer_lt
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425 Posts
they be talking the injector pressure. the higher the pressure the more amount of fuel injected into the cylinder in the same amount of time. i do not see why they you would have to upgrade to higher pressure injectors as our engines are not high compression, 500+ hp engines. maxing out an injector is bad this means it is "static" when this happens it means injector is too small for the needs of the engine. the biggest the duty cycle should be is 80%
 

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2003 chevy trailblazer_ls
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1,236 Posts
I'll lay odds that the same shop that wants to max out the injectors also thinks it is a good idea to pulse the injector shot to when the intake valve is open. That's about the only way they could get away with such a stupid statement as that.

Find another tuner...
 

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2005 chevy trailblazer_lt_ext
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Discussion Starter · #7 ·
hey guys thanks for the reply's
I went ahead and got the PCMforless tune and seem to be pretty happy with it so far.. I guess the "performance" shop was just trying to pull something over on me seing how im new to this and dont know any better... But thats what this site is for.. No i know not to take it to them for ANYTHING!! Thanks again.
 

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2003 chevy trailblazer_ls
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1,236 Posts
Just to note:

There are different perforance tunes for different purposes. If a local speed shop is all about the local drag or oval track, they'll be mostly thinking of tuning everything for WOT performance -- something that we REALLY don't want for overall street use.

Not to over simplify, but it is actually easier to tune a car JUST for WOT performance such as drag racing than it is to get it to idle at stop lights year around, no matter the weather conditions. That is something that a lot of speed shops just don't take into consideration. They get some software, a map of engine calibrations, and then just start ramping stuff up until it blows or fails to run. Hope that works out for them. For the rest of us, it is a tad more complicated than that.

The balancing act in a pre-06 TrailVoy platform with its manifold absolute pressure system of measure and tables is difficult at best. LOTS of variables involved.
 
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