tricking computer by running bigger maf/injector without tune?
08-19-2014, 02:46 AM
#1
tricking computer by running bigger maf/injector without tune? I know tricking the pcm isnt the best idea but im curious about this topic.
Back in my supra days we used to drop a lexus maf with 550cc injectors.
the idea was the fuel and air was both increased 20% while the computer think its still stock #. it may not be exactly 20% but its close enough that it runs just like stock would.
this allowed us to run more boost as it raised the fuel cut and increased fuel all while still having a "nuetral" maps.
So out of curiosity would it work on the fbody aswell?
Im thinking 85mm z06 maf paired with 32# injectors.
air will be an increase of 12% while the fuel is 11%. very close.(1998 is 28.6#)
so in theory the pcm will act like it would normal wouldnt it?
what I mean is any unmetered air is matched very closely with unmettered gas?
Back in my supra days we used to drop a lexus maf with 550cc injectors.
the idea was the fuel and air was both increased 20% while the computer think its still stock #. it may not be exactly 20% but its close enough that it runs just like stock would.
this allowed us to run more boost as it raised the fuel cut and increased fuel all while still having a "nuetral" maps.
So out of curiosity would it work on the fbody aswell?
Im thinking 85mm z06 maf paired with 32# injectors.
air will be an increase of 12% while the fuel is 11%. very close.(1998 is 28.6#)
so in theory the pcm will act like it would normal wouldnt it?
what I mean is any unmetered air is matched very closely with unmettered gas?
08-19-2014, 01:08 PM
#3
Short answer: There is no point. The stock maf and injectors are enough to support over 400rwhp. By the time you need to upgrade either, you will need a tune regardless. There is no HP gain to be had by changing either one of them.
Longer answer: Also I seriously doubt the math is that simple. The mm rating point for the MAFs doubtfully fully take into account the airfoil, screen (or lack thereof), etc.
There are a lot of different tables pertaining to the injector flow rate that must be addressed when they are changed. Also the volumetric efficiency table needs cleaned up after changing them. Same goes for the MAF scaling table.
Also a mail order tune is cheaper than a maf or injectors anyway and will net performance gains.
Longer answer: Also I seriously doubt the math is that simple. The mm rating point for the MAFs doubtfully fully take into account the airfoil, screen (or lack thereof), etc.
There are a lot of different tables pertaining to the injector flow rate that must be addressed when they are changed. Also the volumetric efficiency table needs cleaned up after changing them. Same goes for the MAF scaling table.
Also a mail order tune is cheaper than a maf or injectors anyway and will net performance gains.
08-21-2014, 09:49 PM
#4
air will be an increase of 12% while the fuel is 11%. very close.(1998 is 28.6#)
Injectors without a re-tune for the right size is going to washout your engine real quick.
08-23-2014, 10:24 AM
#6
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Actually you thought it worked well, but it did not. The only reason supra engines don't blow is because they are tough as hell, you were not asking for that much more power, and the oem maps are pretty conservative.
If you had an AFR gauge, you would have seen how fueling was all over the place; an EGT probe would have also showed how timing was not right at all either. You did not have the tools to see there was a problem, that is a huge difference.
It somewhat would work out if MAFs had a linear output (which they don't, that is why MAF systems use a VE/VQ map to convert the MAF output to something linear), if the injector size / airflow change ratio would be exactly one, and if both injector sets had the same latency (which they never).
If you had an AFR gauge, you would have seen how fueling was all over the place; an EGT probe would have also showed how timing was not right at all either. You did not have the tools to see there was a problem, that is a huge difference.
It somewhat would work out if MAFs had a linear output (which they don't, that is why MAF systems use a VE/VQ map to convert the MAF output to something linear), if the injector size / airflow change ratio would be exactly one, and if both injector sets had the same latency (which they never).
