basic forced induction tech questions
basic forced induction tech questions i have a couple questions i cant seem to find the answer to... if someone could fill me in, im sure it'll help others that have the same questions.
1. the stock FPR is based off atmospheric pressure... that would make the injectors seem smaller under boost.. whats the solution everyone is doing?
2. how are you handling fueling requirements over 1bar with the stock EFI system? other then HPtuners 2 and 3 bar Speed density tunes, im not finding much...
3. how do the "kit" systems compensate for fueling? i noticed some of them basicly said you're on your own, find a tuner...
. . . .3b: ok, i have HPtuners.. what do i do to compensate for fuel after 1bar? or am i just trusting that the MAP sensor "sees" all the extra air?
4. as much as i dont like FMUs, is it easier to just put one on the LS1 to compensate for boost? are they effective? would i have to zero out the injector table since the FMU would be manifold vac based? or can i leave it since the FMU wouldnt be changing anything at vac, only at boost...?
. . . .4b is there a way to run a FMU at the rear of the car, or am i just going to have to run a return line up to the front of my car, and use a conventional regulator and FMU there?
5. at sealevel, on a "avg day", how much air can i push into the LS1 before ive reached the peak of the stock (tuned) EFI system?
1. the stock FPR is based off atmospheric pressure... that would make the injectors seem smaller under boost.. whats the solution everyone is doing?
2. how are you handling fueling requirements over 1bar with the stock EFI system? other then HPtuners 2 and 3 bar Speed density tunes, im not finding much...
3. how do the "kit" systems compensate for fueling? i noticed some of them basicly said you're on your own, find a tuner...
. . . .3b: ok, i have HPtuners.. what do i do to compensate for fuel after 1bar? or am i just trusting that the MAP sensor "sees" all the extra air?
4. as much as i dont like FMUs, is it easier to just put one on the LS1 to compensate for boost? are they effective? would i have to zero out the injector table since the FMU would be manifold vac based? or can i leave it since the FMU wouldnt be changing anything at vac, only at boost...?
. . . .4b is there a way to run a FMU at the rear of the car, or am i just going to have to run a return line up to the front of my car, and use a conventional regulator and FMU there?
5. at sealevel, on a "avg day", how much air can i push into the LS1 before ive reached the peak of the stock (tuned) EFI system?
I would just install a rising rate regulator, thats the easiest way to do it, people mount them under the car where the T is located.
Personally, I am going to install some V6 fuel lines, a 1997 vette rail, and remove the regulator in the tank, when i go boosted. Zeroing out the IFR table for vacuum.
Many people just rape the calibration to compensate for the smaller injectors.
a FMU is just as bad as leaving it stock, instead of raping it to add you need to pull it out instead, altering the spark
Ryan
Personally, I am going to install some V6 fuel lines, a 1997 vette rail, and remove the regulator in the tank, when i go boosted. Zeroing out the IFR table for vacuum.
Many people just rape the calibration to compensate for the smaller injectors.
a FMU is just as bad as leaving it stock, instead of raping it to add you need to pull it out instead, altering the spark
Ryan
Last edited by slow; Apr 7, 2005 at 03:56 PM.
1. your stock IFR table is on a slant to compensate for this.. if it was flat you would be correct.. if you put a boost referenced regulator on the car you can make the ifr flat
2. until you go over your maf limit it will add fuel for any boost level.. depending on your year car you will have a different hp limit. without switching to map based as you mentioned you are left to only able to make crude adjustments to the pe enrichment afr table.. this will only work for one boost level at a time, every time you change boost/hp amount at a specific rpm you must retune.
3. some kits come with injectors, maybe a fuel pump..maybey tuning.. you get to choose what brand/type of these parts you want if you get one without it.. i wouldn't trust the 'tunes' that come with some popular 'complete' packages anyway.
4. fmu is a band aid for not enough fuel injector.. if you want to do anything like that just get a referenced regulator AND get the right injectors for your hp level. if you don't have enough fuel pump a fmu can hurt more than it can help.
5. a 98 pcm is good for about 450rwhp before you have to start cheating with the tune, a 99+ pcm is good for maybe 550rwhp. this does not count for a 2-3 bar modified pcm
2. until you go over your maf limit it will add fuel for any boost level.. depending on your year car you will have a different hp limit. without switching to map based as you mentioned you are left to only able to make crude adjustments to the pe enrichment afr table.. this will only work for one boost level at a time, every time you change boost/hp amount at a specific rpm you must retune.
3. some kits come with injectors, maybe a fuel pump..maybey tuning.. you get to choose what brand/type of these parts you want if you get one without it.. i wouldn't trust the 'tunes' that come with some popular 'complete' packages anyway.
4. fmu is a band aid for not enough fuel injector.. if you want to do anything like that just get a referenced regulator AND get the right injectors for your hp level. if you don't have enough fuel pump a fmu can hurt more than it can help.
5. a 98 pcm is good for about 450rwhp before you have to start cheating with the tune, a 99+ pcm is good for maybe 550rwhp. this does not count for a 2-3 bar modified pcm
Originally Posted by MIGHTYMOUSE
1. your stock IFR table is on a slant to compensate for this.. if it was flat you would be correct.. if you put a boost referenced regulator on the car you can make the ifr flat
ok, lets say im running the stock regulator/fuel setup..
the PCM is using the MAP sensor to see the current manifold pressure, does the lookup for the current injector size at that pressure, and goes on, right?
well after 1bar of pressure, it cant "see" past it right?
so at sea level (im at sea level) when i give it 3psi, it still thinks its at 14.7psi absolute, when its really at 17.7..... making the injector shoot less... aka "smaller"... right???
Originally Posted by MIGHTYMOUSE
2. until you go over your maf limit it will add fuel for any boost level.. depending on your year car you will have a different hp limit. without switching to map based as you mentioned you are left to only able to make crude adjustments to the pe enrichment afr table.. this will only work for one boost level at a time, every time you change boost/hp amount at a specific rpm you must retune.
the PCM runs off the stock algorithms until the MAF sensor is maxxed out.. after that, you can only add rough adjustments to the PE enrichment afr table.. but that enrichment is only so much, so if you set it to be perfect at boost level X, then it will have to be reset to match the now diffrent amount of air...
right?
Originally Posted by MIGHTYMOUSE
4. fmu is a band aid for not enough fuel injector.. if you want to do anything like that just get a referenced regulator AND get the right injectors for your hp level. if you don't have enough fuel pump a fmu can hurt more than it can help.
Originally Posted by MIGHTYMOUSE
5. a 98 pcm is good for about 450rwhp before you have to start cheating with the tune, a 99+ pcm is good for maybe 550rwhp. this does not count for a 2-3 bar modified pcm
example:
lets say i somehow manage to find a bigger maf and have a proper table for it.
now for XX frequency, it knows its this much more air... assuming i have enough injector to handle it, will that "raise the bar"?
if you change the maf to something rescaled that can work within the frequency window available you are golden.. but will lose some resolution. this is what harlan had done at one point with a mustang maf.
im not so clear on the speed density stuff... thats only been big the last year.. i dont know if you have to switch off to speed density at some point or if you dont have to run a maf at all.. but WITH the maf working in range... it doesnt matter what the map scale is.. thats only open loop or after maf fail freq(that you would move up) or something like that
im not so clear on the speed density stuff... thats only been big the last year.. i dont know if you have to switch off to speed density at some point or if you dont have to run a maf at all.. but WITH the maf working in range... it doesnt matter what the map scale is.. thats only open loop or after maf fail freq(that you would move up) or something like that
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one more question..
lets pretend i have the following done to my car:
new bigger injectors
walbro 255 pump
manifold pressure refrenced regulator
phamspeed budget turbo kit (or similar) supplying the boost
so i have the bigger injectors compensated for in the table (now constant across due to the new regulator)
other then that, at low boost levels where the MAF can still see it, theres no additional tuning REQUIRED to drive the car??
in otherwords, i could bolt it on, and putt around without worry of going super lean? i understand tweeking the timing and tweeking the fueling would help some, but its still going to be running "safe"??
or do i have to goto a diffrent spart curve, add fueling above a specific #, ect..... before its safe to drive?
lets pretend i have the following done to my car:
new bigger injectors
walbro 255 pump
manifold pressure refrenced regulator
phamspeed budget turbo kit (or similar) supplying the boost
so i have the bigger injectors compensated for in the table (now constant across due to the new regulator)
other then that, at low boost levels where the MAF can still see it, theres no additional tuning REQUIRED to drive the car??
in otherwords, i could bolt it on, and putt around without worry of going super lean? i understand tweeking the timing and tweeking the fueling would help some, but its still going to be running "safe"??
or do i have to goto a diffrent spart curve, add fueling above a specific #, ect..... before its safe to drive?
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Originally Posted by smokinHawk
yes you will need to tune the computer, just wont run optimal without a tune.
thats the answer to the question im trying to avoid asking.
ok, my 224cam car also wont run optimal without a tune......... but im not going to hurt the motor driving it like that until i slowly dial it in.
with a Trex, i cant even idle without a tune... and it wont drive at all, mega lean, ect..... it NEEDS it.
so my question being, will it hurt the motor running the stock tune... im not a tuning expert... i know the basics, but questions will pop up, and it will be a slow process.... while im doing that, or even before i start doing that, i would like to drive the car....
at low boost thats pushing air within the MAFs range, will the stock (injector corrected) tune hurt the motor?
i understand this isnt going to be a yes/no answer... im expecting "xxx" needs to be done... or at the very least somthing like "the timing will be too advanced" or "you need to take care of XXX"
well maybe I can help you out...do all the above...w/ larger injectors....the car will run....just might be giving up anywhere from 30 to 150 rwhp....HP tuners seems to be the best route I have seen for budget large boost.
the stock computer can adjust 25% either direction lean or richen part throttle.. you will be covered there and not 'hurt' anything.. now wide open theres really no gaurantees since with FI you need to run at a different a/f than what is on the stock tune... so i wouldnt reccomend that.