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Location:
Lost in the K hole
Registered:
May 2002
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going from low to high impedance injectors??
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Sun, 14 December 2003 12:49
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im looking at doing a mild injector upgrade (from 280 to 315cc/min).
the stock injectors are 3.x ohm low impedance (peak and hold?) type, and the 315's im looking at using are high impedance (saturation?) type.
now i know the low impedance are better functionally (or at least thats what im lead to believe) so am i doing anything 'bad' by upgrading to the high impedance, saturation type just to gain a few cc's ??
(also, remind me if im woring, but doing a straight swap from low (stock) to high impedance using a stock toyota computer etc is ok??)
cheers
ed
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: going from low to high impedance injectors??
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Sun, 14 December 2003 14:12
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do the stock low-impedance injectors use a resistor pack?? if so, then the computer sees them as high impedance anyway.
the peak and hold, or saturation methods of powering injectors is totally different. you can swap high impedance injectors for low impedance with a resistor pack, but you can't swap the other way (if the low impedance do not use a resistor pack)
the main difference between the two is in the opening and closing times. thsi can affect idle quality, and also affect the calibration of the actual open time, due to the high impedance taking longer to open, and longer to close.
idle quality is really only an issue when you have short idle pulsewidth, and mostly only on turbo cars using high volume injectors relative to the engine size.
more of a concern is if the tuning of the stock computer for the larger injectors will actually be what the motor is wanting....
Cya, Stewart
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Location:
Lost in the K hole
Registered:
May 2002
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Banned user
Location:
ADELAIDE - The Drift City
Registered:
July 2002
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Re: going from low to high impedance injectors??
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Sun, 14 December 2003 14:37
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find out what resistance the low imp ones are and then the high ones, might be worth playing around with some simple resistors from dicksmiths.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: going from low to high impedance injectors??
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Sun, 14 December 2003 14:40
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well, to start, measure the resistance of the resistor pack 
the 4KE resistor pack i have has 2 injector outs, and each is about 3.8ohms. each injector is 2.4ohms. i can't remember how to work out current flow thru each branch of a resistor network, so i'll leave that to you 
a 12ohm injector with 12V will have around 1amp running thru it.
a low impedance injector will have maybe 2 or 3amps to crank it open, and then a hold current of maybe 25-50% of this.
on megasquirted cars, ppl are successfully using resistor packs with low impedance injectors, and using saturation method.
10 ohms is a pretty big difference to the ECU...as you are considering how many amps the ECU is grounding.
since power is supplied to the injectors, and the ECU just grounds them, you can work out roughly the max current that flows thru the ECU (assuming it just shorts the injectors) by working out total resistance of injector and resistor pack, depending on how many injectors there are for each circuit of the resistor pack.
if the high imp inj's have more resistance than the sum of the low ones with the res's, then the total ECU current will probably be lower, and might be ok..
you also need to consider the 'flyback current' generated when the injector closes, as high imp flyback is bigger than low imp flyback (maybe due to larger inductance???)
there is a possibility that the flyback spike can take out the injector drivers....
anyhoo, a few things to think about...
oh and have a look at this page, they discuss what size resistors to use with low imp injectors, which you may be abl eto use to back calculate stuff
http://members.shaw.ca/megasquirt/manual/minj.htm
Cya, Stewart
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: going from low to high impedance injectors??
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Sun, 14 December 2003 14:42
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oh, and if you want to play with resistors, remember to use big arsed ones.. at least 25watt, and 1 resistor per injector... the resistors dissapate a lot of energy, and the more the better.. particularly if you have a single injector failure... it gets all bad
Cya, Stewart
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Banned user
Location:
ADELAIDE - The Drift City
Registered:
July 2002
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Re: going from low to high impedance injectors??
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Sun, 14 December 2003 14:51
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see... theres someone who knows more shit then m about electrics
*not surprised*
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: going from low to high impedance injectors??
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Sun, 14 December 2003 14:57
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LOL  nahh i've just been reading the Megasquirt list for about 2 years, and have heard and researched many things about adapting EFI stuff... from 8hp B&S motors to quad turbo 8L V8's using TBI (HUUUGE flyback probs, but what do you expect with such massive injectors) and Ricks infamous 600hp hayabusa land speed car
even just the Megamanual is worth a read for anyone interested in EFI.
Cya, Stewart
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Location:
sydney
Registered:
March 2003
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Re: going from low to high impedance injectors??
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Sun, 14 December 2003 21:47
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dont waste time with resistor packs and stuff
just go get an aftermarket ecu
the factory ecu is tuned to the standard injectors
so if u fit the bigger ones yr mixtures will be way out all the way thru the rev range
why not just get a new ecu and it will save the hassle
if you are [planning to do more mods to the engine just bit the bullet and buy and aftermarket ecu now
and dont waste time and money trying to get bigger injectors to work on standard ecu
u hear it every day
someone tryin to do things cheap
i always say do it right the first time
it will save u money in the long run
if u cant afford to do it right then dont touch the bloody thing
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Location:
Lost in the K hole
Registered:
May 2002
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Re: going from low to high impedance injectors??
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Mon, 15 December 2003 07:16
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| sideshow wrote on Mon, 15 December 2003 08:47 |
if u cant afford to do it right then dont touch the bloody thing
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*bit*
*chewed*
*attempted to swallow*
*started choking and is now asking for water...*
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Location:
Brisbane
Registered:
February 2003
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Re: going from low to high impedance injectors??
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Mon, 15 December 2003 08:02
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Ed, do you need Heimlich maneuver http://www.americanheart.org/presenter.jhtml?ident ifier=4605 ?
seriously: i've got an unbuilt Megasquirt. would control your fuel and if you dump aux-air valve control (or use something not requiring ECU control) then it can also also run spark to a locked dizzi- plus either way you get to dump the AFM! needs laptop to tune, all DIY, mostly open-source software... is my 2nd-standby unit.
anyway... might be cheaper than selling your arse/house/2nd-child/DNA to buy Haltech or Wolf or EMS or ...
charles.
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Location:
sydney
Registered:
March 2003
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Re: going from low to high impedance injectors??
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Mon, 15 December 2003 08:51
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sorry for being so harsh
main thing i was tryin to get thru to most people
is save abit more and get the good big mods done
instead of done all the small ones
in the end if u spend 500 to 1000 more on an aftermarket ecu at the start
then in the long run it could end up cheaper
whenever u get a mod done all u need is ecu retuned rather than tryin to get yr mixtures right on a std ecu each time u do a mod
i have been workin on rally cars and race cars most of my workin life so spending abit extra to get the good stuff is what ive grown up on
and after workin on afew cars that are total heaps of shits
then spending the extra money is well worth it
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Location:
Lost in the K hole
Registered:
May 2002
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Re: going from low to high impedance injectors??
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Mon, 15 December 2003 12:12
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nah, thats cool sideshow, i know exactly what youre saying, and offer the very same advice to others...
just had something in mind  albiet dodgy, i think it wouldve worked...
no need to now tho anyway
cheers
ed
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