SySt666

iTrader: (4)

How many amps will an ignition coil and injector require at the max (redline) on an LS1? Basically, is an 18 AWG wire good enough to give voltage to one bank of coils/injectors on an LS1?

xEtherealx

I'm wondering the same thing. Has anyone done this? I haven't been able to find average current draw for injectors or coils so I have no idea what the overall draw and wire size requirement is.

pantera_efi

iTrader: (1)

Hi, as a Coil Manufacturer/Designer, an EMS Manufacturer, Wiring Harness Manufacturer, I too face this question often with my customers.

Lets follow OHM's Law :

The LS injector is 14 Ohms = 1 AMP at 100% Duty Cycle (14 Volts) = 4 AMP each side.
The coils are NOT the same for LS engines as there could be five different choices.
THAT "batch" is common with 10 AMP draw each X 50% Duty Cycle = 20 AMP each side.

NOW the 18 Gauge Wire is rated at 20 AMPS THOUGH that same wire is DE-RATED by the Length.

MY method is each coil/injector using 18 Gauge TXL Crosslink, about a foot long.
Those eight wires per side are then "ganged" to a 14 Gauge wire, TXL Crosslink insulation.

Lance

xEtherealx

I'm dubious about 10A draw of the coils, I've seen 2A peak quoted and scoped, and keep in mind that average draw (not peak) should be used for this purpose. Also where'd you get 50% duty cycle because I couldn't find that info last time I looked. MSD does quote their ignition box

That said, keep in mind that your circuit would need to be fused for the current capacity of *the smallest wire* in it -- the 18ga. According to this table that's fine since 18ga is good to at least 24 amps for a 1' strand. That seems high to me, but that's what Tessco says.

I've banked my ignition by grouping the coils and injectors on each side, as I've seen this done a bajillion times with a 15amp fuse. If each side was really pulling 24 amps a 15A fuse would blow in short order.

stevieturbo

Depends what coils. Any 1 individual coil might pull between 5-15A for the period it is being charged.
Obviously all coils will never be charged at the same time though....indeed only 1 at a time will ever be charged depending on your setup.

Most Injectors pull very little current

I would always supply coils separately though anyway

xEtherealx

I'm going to have to disagree, again I saw 2A *peak* for square truck coils and there's just no way that a coil would draw 15A, so I'm thinking you just randomly chose those numbers.

"Most injectors pull very little current" -> We know for sure that they pull 1A each.

Also more than one coil is active at a time, as they need to charge up before discharging.

stevieturbo

The lowest current draw seem to be the old LS1 square coils at around 5A max.

I've tested 585's and 514's and they pulled around 13-14A max ( dependent on dwell time of course ) when wired as wasted spark as I run, so thats around 7A max each coil

So no, go test them with a current clamp and oscilloscope and you will see for yourself. And different types of injector will pull different amounts of current, and fuel pressure used can also have an effect.

The 660's I use pull less than 1A each, around 0.8A. but I did only test at idle. I dont think it would change much under higher loads though.

So no, I didnt pluck anything from fresh air, but it would seem you are doing so. Exactly how did you get a figure of 2A for the coils ? as that is very low unless you're running a very low dwell time for the test.

xEtherealx

See the link I posted in #4 of this thread

stevieturbo

Test I did a couple of years ago, at this dwell they're pulling around 23A peak so 11-12A each coil.

Obviously at lower dwells this will be lest as can be seen from the ramp rate.

I have injector traces somewhere, but cant find them just now. Could easily test again though

stevieturbo

And as you can see he's using old coils and charging them for a fraction of what they normally see. At his 1.9ms the coils are still charging, they have not flatlined
So it's no surprise he's seeing such low currents.

Not really sure why he thinks the coils are full charged when it's clear to see they are not.

stevieturbo

And for IGN-1A coils under same conditions

Pretty sure I dwelled them around 4200us for this test. The scope software doesnt display correctly on the home PC so cannot measure the time period easily. Would need to go back to the laptop

But same again 1v is 10A so the coils wired as pairs are pulling around 13-14A peak. So around 7A peak each.

And again on these tests it's clear to see these coils are still charging. With the test in post #9 you can see the coils are fully charged as the current line plateaus.

xEtherealx

I think he is fully charging -- look at his Measurement #3, in which the current is clipped. I'm not sure if it's his ECU doing this or the coil itself.

Is there a way to test the coil current draw without a scope? I can simulate a signal with my arduino pretty easily, just need an accurate measurement. Not that I doubt your numbers, but I'd like to verify on the particular coils I have since I'm seeing different results.

stevieturbo

The only coils that are known for premature firing that I am aware of are the D585's It's well known never to run these at more than 4500us dwell.

There are varying reports that some are ok up until 5000us, but the only safe number to ensure they do not self fire seems to be 4500us.

I havent heard or seen anyone talk of any other LS type coil behaving like that though.

Although of course whilst the charge time is a static number here....whether it is affected by duty cycle or not is another matter. They may fire more prematurely at higher duty cycles where there is less off time to recover or it may be a fixed number they dont like.

I only tested some 585's on a friends car for current, but never had any to test the self firing problem myself