Racetronix, question about how your injectors are designed to work
Thread Starter
Joined: Mar 2003
Posts: 8,319
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From: North Carolina
Racetronix, question about how your injectors are designed to work OK, well I got an email back from Ken at HP Tuners and my corrections were going the wrong way, this is what he said.
"The problem with increasing the injector size on a stock motor is the injectors will start to misfire in the idle range.
All injectors have a minimum allowed pulse width based on flow rate and fuel pressure.
Going below this limit will cause the injector to not open"
From my logs, this makes sense. The more fuel I take out of the car, when the o2s read rich for too long, the car stumbles. I take it the pulse width is getting too low. Now do your injectors have any kind of minimum pulse width where there could cause some issues? If I would have known this a while back it would have helped. The thing is everyone is telling me they should beable to run on the stock engine. I think the way I had my older tunes set up, not running so rich at idle, could have effected this seeing everyone else runs some higher negative numbers at idle -10 or -8 where I was at about -2. So maybe after the cam install, and a higher demand for fuel, I can get the pulse width to be high enough so this wont happen? Does this make sense or no?
"The problem with increasing the injector size on a stock motor is the injectors will start to misfire in the idle range.
All injectors have a minimum allowed pulse width based on flow rate and fuel pressure.
Going below this limit will cause the injector to not open"
From my logs, this makes sense. The more fuel I take out of the car, when the o2s read rich for too long, the car stumbles. I take it the pulse width is getting too low. Now do your injectors have any kind of minimum pulse width where there could cause some issues? If I would have known this a while back it would have helped. The thing is everyone is telling me they should beable to run on the stock engine. I think the way I had my older tunes set up, not running so rich at idle, could have effected this seeing everyone else runs some higher negative numbers at idle -10 or -8 where I was at about -2. So maybe after the cam install, and a higher demand for fuel, I can get the pulse width to be high enough so this wont happen? Does this make sense or no?
http://www.racetronix.com/
i scrolled down till i found the 60# high Z injector:
http://www.racetronix.com/L107FM.html
and i found this:
i donno what "offset" means... but id imagine that if the turn on time is 1.14 and the off is .85, id imagine 2ms would be the absolute min time for them... but im not a expert.
i did read on here somewhere that if the injector pulse goes too low, the PCM will group them together so that it has a larger pulsewidth...
so i just loaded up HPtuners and took a look... there is a min pulsewidth table.
try changing it to atleast 2ms, and see if that helps:
heres a pic of where i found the table:
i scrolled down till i found the 60# high Z injector:
http://www.racetronix.com/L107FM.html
and i found this:
Offset: 0.055ms, Turn on time: 1.14ms @ 14VDC, Turn off time: 0.85ms @ 600KPa
i did read on here somewhere that if the injector pulse goes too low, the PCM will group them together so that it has a larger pulsewidth...
so i just loaded up HPtuners and took a look... there is a min pulsewidth table.
try changing it to atleast 2ms, and see if that helps:
heres a pic of where i found the table:
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
Dynamic Flow Rate @ 43.5PSI (300kPa) = 8.63 gm/pulse - 2.5ms pulse width and 10ms repetition rate
i found that on the 38#ers, if i can figure out what to change and exactly what to do that would help. thanks for that information, it helps a lot. looking at my injectors right now they were running 1.8 to 2.0 ms at idle. now if someone here can anylize this information and let me know the proper changes to make i would love it
i really am not too clear on making changes to these tables so i dont want to test it if you know what i mean.
i found that on the 38#ers, if i can figure out what to change and exactly what to do that would help. thanks for that information, it helps a lot. looking at my injectors right now they were running 1.8 to 2.0 ms at idle. now if someone here can anylize this information and let me know the proper changes to make i would love it
i really am not too clear on making changes to these tables so i dont want to test it if you know what i mean.
i wouldnt hesitate to change them... its only the min injector pulse.. and this is exactly the problem you're having.. put in a 2.0 or even a 2.1 across there, and see if it idles better... if it does, great... if it doesnt, you can always set it back..
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
ok so maybe u understand this talbe more than me, since its at 1.277 do i change both to tables? the min and default? raise this up to tell the computer "hey these injectors cant go this low"? and what about the others short limit and adder? do you know anything about these?
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Originally Posted by WS6FirebirdTA00
ok so maybe u understand this talbe more than me, since its at 1.277 do i change both to tables? the min and default? raise this up to tell the computer "hey these injectors cant go this low"? and what about the others short limit and adder? do you know anything about these?
i dont have the injectors in hand right now, athough these are the ones going into my car... so im very intrested in it.
its only 30seconds to flash, so id change just the min injector pulsewidth first... and see if it corrects itself by not going below the "minimum"...
its one of thoes try and see things i suppose...... also one of the reasons id love to have a injector swap database... because theres more to them then just one table..
Originally Posted by WS6FirebirdTA00
ken had said something about making sure the injectors arent misfiring, do you or anyone know any information on this?
think about this:
to make a injector flow more, you make it bigger... well bigger weighs more... so it moves slower... it cant react as fast.
at the tiny pulsewidths that worked fine for the tiny stockers (tiny in comparison) the injectors are becoming irratic.. not behaving as designed...
you cant give them a pulsewidth that low.. peroid.... so tune around it... have the PCM give the fueling with a longer pulsewidth, less often.
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
so what it sounds like is when i take too much fuel out of the car, it doesnt inject as much fuel. so when it reads its rich it pulls fuel to the point where the injectors "misfire". adjusting the low pulse would keep them from dipping this low but i would still be left with my rich condition at idle, if this is true and is the case then adjusting the pulse limit would keep it from going too low but would leave me rich how i am now, i would have to demand more fuel at idle, ie cam and heads, for them to work right down low?
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
nope not yet i have some dynamics hw i have been working on it is prob gonna have to wait til this weekend, hopefully racetronix will reply too. i will post up as soon as i do it though
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
i havent even got to go on a ride yet so i havent been able to try, i adjusted the tune with the pulse widths the same and my car is idling fine now, i just have to see if its rich, then i have to adjsut the pulse widths, i dont have my license so i cant just go and test lol wish i could though
Thread Starter
Joined: Mar 2003
Posts: 8,319
Likes: 1
From: North Carolina
im gonna try and change it and let it run outside and see if it chagnes, the only time i can get accurate data is when its been driven but ill try something