Another successful LS1 coil swap

Post by **WhatsADSM** » Mon Jul 06, 2009 7:38 pm

Yea dwell is the amount of time that the builds up a charge in the coil before firing it.

For those looking into the swap. This is a spreadsheet that Darius and I put together. I listed my (conservative) dwell settings that I used for my AEM. These settings are for normal 13v-14v battery voltage.

This should cover the PFC which (to my understanding) uses dwell degrees. And the AEM which has a few look up tables but is calculating everything is mS.

For the AEM you will need everything except dwell degrees.For the PFC you can just use the highlighted yellow RPM and dwell degrees cells. If you want to see the conversion from time to dwell degrees it is in the spreadsheet.

PDF screenshot of the spreadsheet:http://www.murlynna.com/Car/LS2Dwell/LS2_dwell.pdf

Spreadsheet:http://www.murlynna.com/Car/LS2Dwell/LS2_dwell.xls
Modified by WhatsADSM at 10:48 PM 7/6/2009

Post by **240z4u** » Tue Jul 07, 2009 1:55 am

You guys are so smart at math! Looking at the chart it makes sense how you created the table. Very cool, thank you for sharing.

Evan

Post by **Darius** » Tue Jul 07, 2009 2:47 am

Oh yah, that's right. The AEM uses a battery correction factor, but I didn't include that in the calcs for the PFC because it does not appear to have one. It could be built into the software calculation, but IMO that would be stupid not to be transparent about that input.

Basically, the conversion from degrees to mS is directly proportional (1:1). So if you want to increase the dwell 50%, multiply the existing values by (1+0.50) and you're done. I have some time tonight so I'll tinker with it.

Think of dwell like a sneeze. The longer you have to inhale air into your lungs, the harder you typically sneeze. If it sneaks up on you leaving less time for inhalation, it is a less aggressive sneeze.

The same goes for capacitors. The longer you give them to charge, the higher the likelihood of them reaching their full charge before they are called upon by the ECU to discharge (fire). If there is too much dwell, the coils can overheat and be damaged because they are sitting for too long at full charge. Too little dwell and the spark power won't grow large enough to fire the cylinder off.
Modified by Darius at 7:52 AM 7/7/2009

Post by **240z4u** » Tue Jul 07, 2009 3:42 am

Darius wrote:Oh yah, that's right. The AEM uses a battery correction factor, but I didn't include that in the calcs for the PFC because it does not appear to have one. It could be built into the software calculation, but IMO that would be stupid not to be transparent about that input.

Basically, the conversion from degrees to mS is directly proportional (1:1). So if you want to increase the dwell 50%, multiply the existing values by (1+0.50) and you're done. I have some time tonight so I'll tinker with it.

Think of dwell like a sneeze. The longer you have to inhale air into your lungs, the harder you typically sneeze. If it sneaks up on you leaving less time for inhalation, it is a less aggressive sneeze.

The same goes for capacitors. The longer you give them to charge, the higher the likelihood of them reaching their full charge before they are called upon by the ECU to discharge (fire). If there is too much dwell, the coils can overheat and be damaged because they are sitting for too long at full charge. Too little dwell and the spark power won't grow large enough to fire the cylinder off.

Modified by Darius at 7:52 AM 7/7/2009

Props for a disgusting yet effective analogy. I suppose I never thought of increasing dwell that way, easy enough. I just happened to find my notes so I can list the control in wires for the coils. This is for S2 RB25DET ONLY as far as I know.

1 - Black/Pink2 - Pink/Yellow3 - Pink4 - Pink/Blue5 - Pink/White6 - Pink/Green

Post by **240z4u** » Tue Jul 07, 2009 4:47 am

According to actual testing, going beyond 1.9ms of dwell does not improve spark at all! Food for thought before really cranking it up.

http://forums.hybridz.org/show...42616

Post by **WhatsADSM** » Tue Jul 07, 2009 5:29 am

240z4u wrote:According to actual testing, going beyond 1.9ms of dwell does not improve spark at all! Food for thought before really cranking it up.

http://forums.hybridz.org/show...42616

Hmm that is really stange. In the MS version of the testing (http://www.megamanual.com/seq/coils.htm) they suggest using significantly more dwell than 2ms?! In any case you can always start with a constant 2ms dwell and if you get some spark blowout try increasing the dwell to 4ms or so and see if you get real life better results or not. Another great idea would be to put a scope of a stock LSx engine and see what GM does.

Keep us posted on what you find.

BTW,

I was just thinking about it and I think the PFC is fully direct fire ignition (i.e. not wastespark), so honestly even at the worst case 8000 RPM 4ms dwell is peanuts and still gives the coil quite a lot of cooling time.

8000 RPM = 7.5ms per rev. Because direct fire it is 1 ignition event per 2 revs, so 15ms per ignition event.

4ms/15ms = 26.6% coil duty cycle2ms/15ms = 13.3% coil duty cycle

Post by **240z4u** » Tue Jul 07, 2009 6:03 am

Fair enough, might as well do 4ms especially if there is that much cooling time. I wonder if he got that result using the wolf system because the coils were getting hot or the internal ignitor was trying to protect them.

Post by **Carl H** » Tue Jul 07, 2009 6:50 am

im not gonna lie but i am kinda jelous of the setup...the ability to blow thru 9:1 afr charges is nice.even with splitfires, should the charge even get close to 10:1 it will NOT ignite the charge and causes a nasty hickup.

Post by **legit240sx** » Tue Jul 07, 2009 7:00 am

looks tight man, in doing the coil swap i get that there is better spark, are there any downs falls to it?

Post by **240z4u** » Tue Jul 07, 2009 7:10 am

Carl, sell your splitfires if your really "jealous" lol. This setup is pretty cheap overall and I am sure you could basically recoup all the costs. The LS2 coils are the ones to get BTW.. even higher spark energy.

It was awesome, the car was pulling smoothly but black smoke about the color of a locomotive exhaust was pouring out the back!

Evan

And, because it has been asked twice... THERE ARE NO DISADVANTAGES from a performance stand point. They aren't as pretty, however if I have a coil crap out I go to autozone and you place a call to an importer. Changing plugs is less than half the work too.

As a tip, if you do this be sure to get plug wires with a 45 degree boot.. the 90s are not a good fit.

Post by **legit240sx** » Tue Jul 07, 2009 7:52 am

got it thanks

Post by **rb25det250sx** » Wed Jul 08, 2009 10:48 am

WOW perty imprssive info. good to know there are people to do that kind of detailed work. Thanks guys, this will deff help in the future. nice job with the swap to BTW!!

Post by **Sil240** » Thu Jan 28, 2010 1:59 pm

http://forums.corvetteforum.co....html

Here are the Dwell tables for :

2001 C5 Corvette LS2

2004 Silverado 5.3 LS2 Truck coil

Post by **Darius** » Thu Jan 28, 2010 2:20 pm

Nice find!

Post by **Sil240** » Tue Mar 23, 2010 4:50 am

Darius- Or anyone else running LS2/LS2 Truck coils

Could you please post up your Dwell Tables???

Carl is burning a chip for me and he needs the Dwell table.I've already sent him the Tables for the Silverado that I posted earlier.Not sure if he needs RB with LS2 coil Dwell tables???

Post by **240z4u** » Tue Mar 23, 2010 4:52 am

I haven't touched the dwell yet.

Post by **Sil240** » Tue Mar 23, 2010 5:54 am

Oh yeah...

What were the specs of the T3/To4E you were running?

In another thread you said you were having surging problems?

Website · Post by **meet07** » Fri Mar 26, 2010 12:21 am

Sil240 wrote:http://forums.corvetteforum.co....html

Here are the Dwell tables for :

2001 C5 Corvette LS2

2004 Silverado 5.3 LS2 Truck coil

So what does this dwell chart mean? I know the longer they charger the better the spark.

Post by **Sil240** » Fri Mar 26, 2010 2:46 am

To tell you the truth, I don't exactly know.

But from what I've been reading and been told.It seems its the table of how much time (Milliseconds) the coil has to charge up before it fires at "X" Voltage vs "Y" RPM

I'm guessing that as RPM goes up, you have less time to charge.As voltage goes up, you'll need less time to charge

If that's wrong, someone please correct me!!

Post by **240z4u** » Fri Mar 26, 2010 2:50 am

You are over simplifying when you say "longer charge = more spark". This is true to an extent. Generally there is a plateau where the spark doesn't get any stronger and then you are basically just heating the coil up. Not good. Shortened lifespan of the coil is the result.

Yes, dwell is charge time for the coil listed in MS.

There is less time at higher RPMs to charge them (obviously, as you stated).

Post by **raremotive** » Fri Mar 26, 2010 6:57 am

That posted thread is a sad read really. There's zero recognition of charge developed during dwell time and it's release as the good info givers have given, the whole thread has been trashed.

Website · Post by **meet07** » Fri Mar 26, 2010 11:12 am

Rare_f8 wrote:That posted thread is a sad read really. There's zero recognition of charge developed during dwell time and it's release as the good info givers have given, the whole thread has been trashed.

I disagree!! This thread has not been trashed?

Post by **Sil240** » Fri Mar 26, 2010 11:21 am

I would assume that he's talking about the thread that I posted.The GM Chevy thread.

Post by **raremotive** » Fri Mar 26, 2010 4:47 pm

meet07 wrote:
I disagree!! This thread has not been trashed?

Sil240 wrote:I would assume that he's talking about the thread that I posted.The GM Chevy thread.

,

sorry I was not clear/distinctive.
Modified by Rare_f8 at 7:59 PM 3/26/2010

Post by **OutToWinPAHC** » Fri Mar 09, 2012 6:27 am

Okay reading this, I am new to power FC... And I need help setting the dwell in datalogit. Does anyone have their setting for truck coils for this?

Post by **240z4u** » Fri Mar 09, 2012 10:27 am

I am still running stock dwell actually, I never changed it!

Post by **OutToWinPAHC** » Fri Mar 09, 2012 11:15 am

Yeah I just dont know how to use the info from the table above to convert to what this image says. I dont now the formula or correlation.

This is not my screenshot

Post by **240z4u** » Fri Mar 09, 2012 12:59 pm

I haven't had any spark problems at stock dwell, so I am not gonna mess with it.

Post by **OutToWinPAHC** » Sat Mar 10, 2012 7:36 am

Yeah but all these are is transistors and I would like to make the gate signal timing correct. I was hoping someone can help me witht he conversion to what power FC uses.

Post by **lexcrob** » Wed Jan 30, 2013 9:22 pm

dead thread sorry BUT OMFG YOU GUYS ARE FRIKEN WIZARDS

I have new respect for rb owners reading all that makes me want to stick with mine now. Just when I was gonna sell out new motivation.

Another successful LS1 coil swap

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