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HKS DLI questions


Ian C

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I've got one, fitted, but I can't work out what it does and how it's supposed to work. Which annoys me :innocent: So, techie discussion time - what does it do and how does it work? :)

 

Sub-discussions of what the difference is between the DLI and DLI II would be good as well.

 

It's got eight wires - one gnd, one +12v (taken from the igniter pack) and 6* lines that go off to the wires between the coils and the igniter pack. This is the switching side of the coil rather than the power feed side which I find odd, and you also don't have to wire a specific DLI lead to a specific coil - any to any will do.

 

Any thoughts? First person to copy and paste the meaningless advertising blurb will get moderated :D

 

-Ian

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Guest Usmann A

Well I spoke to a few guys over in the US, I dont thnk it actually amplifies the spark as we know, but yet rather keeps the coil packs charged for longer, or charged heavier.

 

I was told its a tad bit complex on how it works.

 

Its something like that, theres not alot of info on this component detailed, but it does work.

 

Thats all I found out, but it does seem to do the job well.

 

 

 

:)

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Originally posted by Usmann A

Well I spoke to a few guys over in the US, I dont thnk it actually amplifies the spark as we know, but yet rather keeps the coil packs charged for longer, or charged heavier.

 

I was told its a tad bit complex on how it works.

 

Its something like that, theres not alot of info on this component detailed, but it does work.

 

Thats all I found out, but it does seem to do the job well.

 

 

 

:)

 

Spot on U,. It keeps a charge longer in the coil packs:thumbs:

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Originally posted by Ian C

I've got one, fitted, but I can't work out what it does and how it's supposed to work. Which annoys me :innocent: So, techie discussion time - what does it do and how does it work? :)

 

Sub-discussions of what the difference is between the DLI and DLI II would be good as well.

 

It's got eight wires - one gnd, one +12v (taken from the igniter pack) and 6* lines that go off to the wires between the coils and the igniter pack. This is the switching side of the coil rather than the power feed side which I find odd, and you also don't have to wire a specific DLI lead to a specific coil - any to any will do.

 

Any thoughts? First person to copy and paste the meaningless advertising blurb will get moderated :D

 

-Ian

 

I once tested a MKIV with this gizmo on it against a stock one, looking at HT voltages and couldn't see any difference. I concur it may just hold charge longer, but I doubt it does a lot. I think I would look to remote coils and leads if I was building a big HP engine, and run a proper capacitive discharge ignition pack. I think Motec does one.

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This is my thinking. Unless it somehow steps up the 12v rail to a higher voltage and shovels that into the coil?

 

But it's on the ground side of the coil so how does that work!?

 

Could these things be snake oil?

 

Mark: I've d/loaded that vid, I've just gotta ship it home, ta for the DVD stuff :thumbs:

 

-Ian

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I've been reading up on inductance and back-EMF, and the only factors that seem to effect this are the inductance of the coiland the rate of change of the current in it. Since you cannot change the inductance of the coil, it's this rate of change that intersests me, since it is the time taken for the current to drop to zero (i.e. the time taken for the switch to go to ground and the current to drain out through the igniter).

 

Could it be possible that the DLI offers a lower-resistance path to earth, or some kind of super-fast switching?

 

The other possibility could be that the unit somehow increases the current in the coil by increasing the supply voltage, as Ian suggested. If you increase the initial current but keep the time to switch to ground the same, then you still get a higher rate of change, and hence a bigger back-EMF.

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Does the DLI not act as a secondary coil in itself and fire at the same time as the primary coil giving a bigger shot?

 

Hey Chris, AEM also do some CDI units now, a 4 channel and 8 channel which will prob be alot cheaper than the motec units.

 

There are a couple of supras running either in the states and I believe there is one over here as well using the 8 channel.

 

I have the HKS DLI on mine as the AEM uses wasted spark instead of the stock direct fire setup, without the DLI you cannot run more than .6 bar on stock turbos as there is not enough spark with the DLI its been tested to over 1000ushp.

 

:thumbs:

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In my experience I've taken off the DLI in favour of a proper CDI system.

 

The supra we did yesterday misfired badly no matter what plugs, plug gap or ignition advance we had.

 

Un plugged the CDI and it got 50% better.

 

Removed the CDI and fitted the AEM C2DI which charges the coils at 540V and with the secondary to primary winding ratio this gives one hell of a kick! to the spark. Candle to Lightning comes to mind.

 

It then ran 1.6 bar on Optimax (with an AEM EMS) at 769BHP at the wheels. Watch out for this one soon when we get 2.0 bar on race fuel!

 

In my opinion I've always found the DLI caused more problems than it was meant to solve, often working better without it.

 

Pete

 

We fitted Richard Beaumonts super fast 200SX with the C2DI from AEM to cure his misfires.

Be warned this kit will kill you if you touch it, it's that powerful.

ALWAYS take the advice on the packaging and heed all warnings.

 

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Originally posted by THOR Racing

In my experience I've taken off the DLI in favour of a proper CDI system.

 

Removed the CDI and fitted the AEM C2DI which charges the coils at 540V and with the secondary to primary winding ratio this gives one hell of a kick! to the spark. Candle to Lightning comes to mind.

 

It then ran 1.6 bar on Optimax (with an AEM EMS) at 769BHP at the wheels. Watch out for this one soon when we get 2.0 bar on race fuel!

 

In my opinion I've always found the DLI caused more problems than it was meant to solve, often working better without it.

 

This is interesting Pete, I know that if you have the incorrect dwell time configured in the AEM the DLI will not work correctly, I have spoken with AEM regarding this as the dwell time should not make any difference as the supra has a smart ignitor but if you play with this setting it does make a difference.

 

I have mine set to 20 which I beleive is the same setting everyone with AEM and DLI is now using without issues.

 

Paul Whiffin was also using this setup on his beast.

 

:thumbs:

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Wez,

Umm. Interesting about the dwell time. I did have a fiddle but didn't seem to do much, I'll have a look into it. Thanks.

I did then change to CDI and swap the Coil packs at the same time. Still, you cannot ignore the oomph the CDI gives you :)

 

Chris,

 

The CDI can be fitted to ANYTHING!

So long as there is a reference signal. So it'll work on say an MR2 with a distributor right up to an 8 cylinder V8 or something.

 

One thing though.

 

If you have the AEM EMS then you can get away with only using the 4 channel CDI as it uses a wasted spark system.

 

If you want CDI on a Supra or Skyline running 6 cylinders on the stock ECU then you need to upgrade to the 8 channel CDI unit.

 

Don't be fooled. If you fit an 8 channel CDI to a car with AEM EMS then it's wired up like a 4-channel anyway! So you just wasted your money.

 

Also be careful as you MAY need to knock some ignition advance OFF at low rpm with CDI.

 

Regards

Pete

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The CDI info is good stuff, thanks - any prices, just in case?

 

But has anyone figured out exactly how the DLI is supposed to improve matters, how it actually works? I don't like having something in the car that I don't understand...*

 

-Ian

 

*apart from female passengers of course

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4 channel CDI is £206 incl

8 channel CDI is £311 incl

 

I thought the DLI was just a piggy-back unit which...

 

Senses when the ignitor is firing the coil and then discharges it's own capacitor. Then a short while later it fires another (based on the time it sees between cylinder firing)

 

The discharging capacitor voltage is higher than 12V and boosts the coil charge. Hence when the coil discharges the multiplication inside causes a better spark. I do not know by how much the coil is boosted. I can see the dwell time having to increase for the DLI using the AEM EMS only because the AEM uses wasted spark and hence fires two coils at once. I guess the DLI on it's own doesn't have enough oomph to fire two plugs without increasing dwell (charge) time.

 

 

The CDI on the other hand is wired in series and takes over control of the spark. It uses the ignitor as a reference and charges the coils with 540V (not 12V). The secondary to primary winding ratio then multiplies this voltage up to a very large value and wires the coil. It has a BIG sticker that warns of serious injury or death if you piss around with the CDI. Be warned it's a pokey ole fella!

 

It is also able to multiple fire the coils at low revs. So you get good clean fuel burn on large injectors as it fires up to 8 times per cylinder.

 

You can turn the multiple firing off to chedk timing etc or if you don't want it.

 

Pete

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Righto, so going back to the whole theory behind the ignition system, I thought the spark was caused by the low tension coil being charged, and then the igniter pack removing the charge suddenly, and this causes the field between the low and high tension coils to collapse and that causes the high tension coil to dump it's stored charge out via the spark plug gap.

 

So, the spark is caused by *removing* the power on the primary circuit, but the power of the spark is determined by how much it charges up the low tension coil before the spark is needed. If the DLI boosts this charging somehow by dumping a capacitor charge into the low tension side before it has to spark, that would be sorta plausible, but how does it know when to do it?! Or have I got all the ignition stuff wrong?

 

That CDI thing sounds like the business if all else fails - does it use stock coil packs though? How long would they survive under that sort of load?

 

-Ian

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Originally posted by THOR Racing

I thought the DLI was just a piggy-back unit which...

 

Senses when the ignitor is firing the coil and then discharges it's own capacitor. Then a short while later it fires another (based on the time it sees between cylinder firing)

 

The discharging capacitor voltage is higher than 12V and boosts the coil charge. Hence when the coil discharges the multiplication inside causes a better spark. I do not know by how much the coil is boosted. I can see the dwell time having to increase for the DLI using the AEM EMS only because the AEM uses wasted spark and hence fires two coils at once. I guess the DLI on it's own doesn't have enough oomph to fire two plugs without increasing dwell (charge) time.

 

Surely by the time the circuitry senses the coil firing then it's all over? Even if it isn't then by re-applying a voltage to the primary coil during the spark you will destroy the field around the coil (admittedly immediately replacing it with a second, even bigger one). Unless I've got the whole spark thing wrong and it doesn't work on back-EMF at all.

 

Maybe the HSK DLI simply does the "double firing" trick? It sounds a lot simpler than guessing when the next plug needs to fire based on the time between sucessive spark events.

 

Also, what is the effect of putting a bazzillion volts into the primary coil, when it's only designed to take 12?

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I've just skim-read the spark ignition chapter in the Bosch handbook and it looks like the charging and discharging of the coil isn't as instantaneous as I thought.

 

At 7000RPM, each coil will be firing at 17ms intervals. The Bosch book reckons it takes about 2ms for the coil to discharge completely. If the spark cannot form properly then it will take longer.

 

Maybe there is time to squeeze in a second spark, or to sense the first and boost it, but I doubt that the burn will be optimally timed with the DLI when it takes only 4ms for the piston to move from TDC to BDC on the power stroke (at 7000RPM)!

 

*edited to remove uneccessary words and for general sense-making*

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I suspect the hks dli system puts a coil (inductor) either in series with or in parallel with the existing coil pack earth return,thus changing the overall inductance/capacitance this will have the effect of lengthening the spark spark duration,but at a reduced spark voltage-cos you cant get something for nothing- a simpler way to increase the spark is to increase the input voltage to say 18 volts but this would have to be matched with the coil pack inductance to increase the the spark duration.

-also i think spark frequency will come into it - the v12 jag had to resort to 2 coils to aid high rpm sparks- then again i could be wrong - ill look into it and come up with a definative answer

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  • 12 years later...

Stumbled across this thread and thought I'd post a test that my friend made with a 2JZ stock coil. You can see on the video when the HKS DLI is switched on and off, the spark on the plug is a lot stronger with the DLI on:

 

 

[video=youtube;Rzr310-qFk0]

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