LT5 Ignition Systems Question???

[Blue Flame Restorations]

Hey guys, let's get Ron Wozniak involved here.

Here's the ???

How can we update the ignition system for a coil to plug (LS) type system?

It would be nice to update the technology with modern day parts that are accessible and may help to aid in HP gains.

Here you go, Ron!!!
Thanks!
Brett

[Tyler Townsley]

Can a Northstar dis module be used in place of the LT 5 dis module? Can the LT 5 dis module be rebuilt? If so how do you get it apart. I understand you have a lt 5 module with the cover off? Can you post a picture of it?

Tyler

[LGAFF]

What was the DIS system used on the two motors that were built to solicit potential business from Bentley/Rolls Royce? My undestanding was that it utilized a crank trigger system.

[LGAFF]

Well since the engine is gone, I will let the cat out of the bag. If you recall a motor being sold in MI recently....well a few weeks after it went up for sale, I bought the Thunder at Stillwater video. Amazing there was the gloss black engine shown during the plant tour, grey plug wires and all. I contacted a workers at Mercury and it was a test engine for a possible outsourcing of the LT-5 to Rolls, there was one other built with a crank trigger, and that was it.

Engine has apparently sold

[XfireZ51]

I found a more recent posting explaining the cop conversion on the 4g63. Just a little food for thought.

http://www.dsmtuners.com/forums/articles-electrical-wiring/290665-coil-plug-wiring-install-pics.html

Were it only that simple.

[tomtom72]

:o I know I really don't belong posting in this thread because I don't understand this ignition stuff. I would like to ask a couple of questions. I'm sorry to clutter up this thread. :o

Why do we need to consider reconfiguring our OEM ignition system? Strictly because our parts are NLA, and no one is able to repair our OE DIS boxes?

Does a COP system allow tuning latitude specifically for ignition events? Our system does not allow any type of ignition tuning, right?

See how much I don't know! Sorry guys.

TIA
:cheers:
Tom

[tomtom72]

Thank you Rob. :thumbsup:


I am a bit less in the dark now. I wonder if in the LT5 application that our system was easier and less expensive to do than a COP system. I'm wondering if combustion chamber design, our vs the LSx motors', indicated that an LT5 could get away with using a waste spark system and not suffer?

Okay, I ask too many questions because I don't really get electronics at all. Sorry all.

Thank you for helping me to gain some knowledge!:cheers:

[Hog]

There are some SAAB CNP(Coil On Plug) setups that look like the setup above which do not use high tension plug wires.
The GEN III (LS1/6) use a CNP(Coil near Plug) ignition which use short high tension wires.

The only shortcoming I see with the LT5 system(if there is 1) is the length of the high tension plug wires.

The Northstar uses a wasted spark setup as well.(plug fies both on the power stroke and the exhaust stroke).
Getting away from the distributer was the big step in GM ignitions which was used in the 2002 L31 Vortec SBC350 in the trucks. Timing advance was PCM controlled, but as coil voltage goes up, cap/rotor wear increases. The L31 uses a 4x reluctor wheel on the crank.(4 pulses per crank rev. and a 1x camshaft sensor in teh ditributer body-1 pulse per camshaft rev)
There was a Vortec 454 BBC that uses the same distributer as the L31 Vortec 350 SBC and the same coil(which is the same coil the LT4 engine uses) as well it uses the same 4x crank and 1x camshaft position sensors.
In 1998 GM took the L29 Vortec 454, installed a CNP ignition along with a 24x crank reluctor/1x cam sensor and used an ETC(electronically controlled throttle) and called this the Vortec L21 454. This was the 1st GM truck engine to use CNP ignition. The camshaft position sensor(CMP sensor) is the same sensor as was in the older distributer body which was driven by the camshaft gear, except instead of the typical ditributer cap, a plastic cover is used. The only purpose of this cam gear driven unit is to drive the oil pump, and to give the PCM a 1x signal.
This engien was used in HD truck applications like the Kodiac meduim truck, P30 vans and motorhomes. The conventional Vortec L29 454was used in3/4 ton and 1 ton trucks.

In 2000 GM went from the L21 454 and the L29 454 to the Vortec 8.1(496) which used a full CNP ignition with a 24x reluctor crank reluctor and a 1x camshaft position sensor. For the new engine, the cam driven ditributer was needed as the PCM got its cam sensor info right off of the cam sprocket reluctor from a sensor mounted in the front timing chain cover.

Sorry for the book, but thats illustrates the ignition evolution for GM trucks. This has made it possible for more modern PCM's like the 411 PCM along with a SBC version of the L21 24x crank reluctor to convert conventional SBC's to run LS1/L21 style CNP ignition. It has also made it possible to run LS1/L21 styke CNP ignition on LT1/4's, eliminating the Optispark system.
The 411 PCM is GM p/n 12200411, it uses dual 80 pin connectors, and is a 512 kb OBD2 PCM.
If you can feed the 411 PCM a 24x signal, you could use is to fire an LS1 GEN 3 SBC CNP 8 coil ignition. Also feed it the TPS and MAP data, you coudl also control its fueling. No morew chips, say hello to flash memory and OBD2 tuning products. But it can only control 8 high impedance injectors, and wouldnt control the secondary throttles. I assume if someone really wanted to, they could eliminate the secondary throttles, and even the secondary injectors.

I dont see much if any gain (powerwise) from using a Northstar coil pack, as the LT5 uses pretty much the same setup IIRC. There would be soem advantages so far as parts availability goes.

Sorry for the book.

peace
Hog

[XfireZ51]

Rob,

I was commenting on the article for comverting the Toyota motor you posted.
The issue that I and several others found is that the LT-5 ignition module acts more like a. co-ECM. It has it's own processor. Remember that the LT-5 ECM code is really a modified L98 code. Do with 8 injector drivers, they adapted it to run 16 by powering the secondaries thru the secondary injector relay. The primary injector provides the firing signal and so they fire in tandem. The L98 code assumes a distributor. That's why the crank signal feeds the ignition module and not the ECM. So we believe that parameters like coil dwell time are managed by the ignition module. The LSx coils have the PCM providing that control. These are the things that have me excited about LT5Ignition coming on board.

[tomtom72]

Thank you Hog. :thumbsup: On the length of the secondary wires, couldn't you just go up a few mm to compensate for voltage drop?

A little more light for the mushroom!
I'm going to ask one more dumb Q in a "what if" vane....the Ford GT motor has two injectors per cylinder and COP ignition ( I think it don't have a distributor? ) and a blower. I wonder how they drive two injectors and could their ECM and ignition control box ( if it even has an ignition control box? ) be adapted to an LT5?

The way I see it if you want only one injector per cylinder in an LT5 you need the whole top end of the second design motor. It only had one injector per cylinder. Hummmm, I wonder what they used for an ignition system?

Thank you both, Rob and Hog, for putting up with my ignorance.:cheers:

[XfireZ51]

Rob,

I was commenting on the article of COP conversion for the Toyota motor not on what you plan on doing. eficonnections provides a complete conversion for both early and opti-spark motors for conversion to CNP.
The LT-5 ECM code is a derivative of the L98 code. So no secondary injector drivers, no ignition coil controls. That's why the secondary injectors have their own power thru the 2ndary injector relay and are triggered by the primary injector. The L98 assumes a distributor. So it handles timing but not much else. The LT-5 is a more intelligent ignition module acting almost as a co-ECM.
That's why the crank signal goes to the IM and not the ECM. The IM has it's own processor. So we believe parameters like coil dwell are embedded in the IM firmware. That's why I am excited to have LT5Ignition on the forum. Maybe he can shed some light on this whole topic.

[Tyler Townsley]

. It would still be a batch fire, but would allow changing the control module. .

It is not a batch fire system. The efi is sequential and spark is wasted spark.. The lt 5 ecm/dis is a little more advanced than you give it credit for. The ecm code is not just modified l98 code, it is far more flexible and with Tod Ps definition files there is no need for any other ecm system up to about 600 rwhp. The turbo applications use an additional fuel injector with a link setup but it is fuel only. There is no reason to change out the waste spark method. Besides if you go cop you clutter up the best looking underhood engine out there.

The issue is the dis module. It is sensitive to heat and if installed without the correct grease it will overheat and fail. I have 3 dead modules and if we could get a rebuild capability it would sure help those who discover the hard way that the correct grease matters.

With Moats tuning aids and current software you can tune on the fly.

Tyler

[tomtom72]

Tyler, the FSM says if you r&r the DIS to use di-electric grease as the heat sink interface. What is the correct grease to use?

I was thinking that the same grease that is used to bed a PC's processor to it's heat sink would be a better choice than di-electric grease?

TIA
:cheers:
Tom

[Tyler Townsley]

I never said the injection was batch fire. If you read my post you will see batch was thrown in with wasted spark talking about the ignition. In some circles you will hear batch thrown in with wasted spark, which is why it was placed there, but I never once said the injection on this motor was batch.

The system may be more advanced than credit given I suppose, but it is also overly complicated, and does nto seem very flexible, imho.

So you are saying there is no benefit from an upgrade to the ecu in this car?

Batch fire applies to fuel, it means all the injectors fire at once, it does not apply to spark. So when you used it I assumed you were refering to fuel. EFI is inherently complicated or sophisticated depending on your point of view. A lt 5 in stock or modified form to about 550 rwhp will not benefit from another fuel/spark system. You need the right tools and an understanding of the tuner definition files, no small task but there are a couple of folks on the forum who have mastered this tuning and can do a calibration quickly and accurately.

Tyler

[Tyler Townsley]

Tyler, the FSM says if you r&r the DIS to use di-electric grease as the heat sink interface. What is the correct grease to use?

I was thinking that the same grease that is used to bed a PC's processor to it's heat sink would be a better choice than di-electric grease?

TIA
:cheers:
Tom

There was some discussion about this in the past and I think we decided you are correct. We felt the FSM referred to the wrong stuff. What is needed is a substance the conducts heat to the plenum where the incomming air cools the plenum base and indirectly the module.

Tyler

[Tyler Townsley]

Once this car is complete I am taking it down for a day with Corey, and we are going to test it in a lot of different configurations. We are going to test it from stock all the way down to the plenum, tb, and airhorn to ported plenum, ih's, tb, air horn, headers, etc. I have a egt in each runner, as well as multiple temperature sensors. It should result in some useful information, no matter which side of the fence you are on.

If you get the chance take a tuning ride with Cory in a stock ecm car and his tuning equipment and software. I believe he used the stock setup in the Bonniville car and did not run into problems until trying to get the last 2/3 mph to break the record. I think it was about 650-700 rwhp at 7900-8000 rpm where the ecm momentarly reset for some reason we still do not understand.

EGTs are good but a wideband is better.

As a side note Jerry Watts said they had an efi system in the early 80s that had the same afr for all cyl but a new manager did not like its looks and stopped development and went to the 'tuned port' setup that never achieved what they were able to do with the earlier setup.

Tyler

[Blue Flame Restorations]

I just emailed Ron Wozniak. I'm in Little Rock, traveling from SW TX. Picked up a 35 Auburn Botattail Speedster to retsore this year.

Hopefully, Ron will login to this discussion.:cheers:

[Hog]

If you get the chance take a tuning ride with Cory in a stock ecm car and his tuning equipment and software. I believe he used the stock setup in the Bonniville car and did not run into problems until trying to get the last 2/3 mph to break the record. I think it was about 650-700 rwhp at 7900-8000 rpm where the ecm momentarly reset for some reason we still do not understand.

EGTs are good but a wideband is better.

As a side note Jerry Watts said they had an efi system in the early 80s that had the same afr for all cyl but a new manager did not like its looks and stopped development and went to the 'tuned port' setup that never achieved what they were able to do with the earlier setup.

Tyler
I believe there are other parameters other than WOT power that could benefit from a more modern processor. Driveability being one. The LT5 was ahead of its time so far as part/WOT transitioning, esp. controlling the 8, then 16 injectors.

I do agree that there is not much to be done ignition wise, or fuel wise when talking about WOT power. The WOT tuning is the "easy" part.

I am wondering if you could eliminate, the secondaries (easy enough) then simply plug the injector holes in the injector housings and fuel rails. The use a larger injector to compensate, with a more modern ECM/PCM, heck you could even incorporate a MAF.
These MAF react better to mods than speed-density does.
I'm just thinking aloud.


EGT's are just another way of determining the a/f ratio of a cylinder. I would rather have a thermocouple in each cylinder's exhaust than a wideband O2 sensor in each bank, esp. if I have a means of adjusting a/f ratio's on a cylinder per cylinder bases.


Todesengel, I understood what you were meaning about the "batch fire" ignition comment.

peace
Hog

[Tyler Townsley]

Tyler,
I have two wide band's, and two narrow band sensors placed in the headers as well, at the collector area. The haltech can use this information to adjust the afr to keep it's set target. The egt sensors are to give me a cylinder by cylinder breakdown of what is happening throughout the process. This will illuminate the design flaws, if any, with both the stock, and dropped/siamiesed plenum. I am interested to seewhich cylinders are getting more airflow depending on plunum used. I plan to use this information to fabricate my own plenum when I go tt.

I have the same. According to the Lotus engineers the most compromised part of the stock plenum is the placement of the injectors. Cory relocated/changed this on the Bonniville car and should be able to give you valuable pointers on what changes work and which do not. You want to make a plenum? Take a Mustang GT 500 s/c and graft it to the lt 5 plenum THAT would be real HP improvement.

My current project is putting a 2001 lightning motor in a 65 fairlane. Got it positioned and it will require some slight hood modification.LOL

Tyler

[Tyler Townsley]

I think we are all on the same page now. I do not mind being slapped around when I cannot articulate myself properly. I am typically rushed when I post, and my brain runs faster than my fingers can type. :handshak:

Sorry if I was a bit short. These posts are read by a lot of people who do not have a grasp on the correct terminology and it was more an attempt to keep it straight in thier minds. I agree with your assement of MAF vs MAP.

Tyler

[todesengel]

Sorry if I was a bit short. These posts are read by a lot of people who do not have a grasp on the correct terminology and it was more an attempt to keep it straight in thier minds. I agree with your assement of MAF vs MAP.

Tyler

Tyler, no apology needed. I can see where my post may have created confusion. We are all on here to learn, and share. I have a LOT left to learn, and do not mind being corrected when I am outright wrong, or just need simple correction. :cheers:

[LT5 Ignition]

Hey is there a time limit for once you start writing? I just wrote about 5 paragraphs trying to help answer some of the questions and when I hit submit it said I was logged out and I lost the message.

Here is a shorter version:
If someone wanted to go to a coil per cylinder system like a Gen3 small block LS1, here are some challenges I can think of. The LT5 ECM is designed to receive a 4 ppr digital input REF for engine position sensing. It outputs a single 4 ppr EST signal that is pulse width controlled for coil on time (Dwell time) and phased for spark timing control. The ignition module is the go between that receives the 9 tooth VR signal and creates the REF signal.
It also receives the EST signal and splits it into 4 coil primary current drivers.

The Gen3 small block ECM receives a digital crank position signal and outputs 8 separate EST signals directly to Coils with internal drivers.

[LGAFF]

I think it is an internet setting on your computer....I recall a similiar issue

[ScottZ95ZR1]

Hey is there a time limit for once you start writing? I just wrote about 5 paragraphs trying to help answer some of the questions and when I hit submit it said I was logged out and I lost the message.

Happens to me often. When you are presented with the message stating you've been logged out, if you immediately enter your login information and log back in your message will post and won't be lost. But, if you hit your browser's back button your post will be lost. I've found that to be the case for me, anyway.

[Blue Flame Restorations]

Glad to have you involved, Ron!! Is it even possible to update the igntiion system by using a module compatible with a crank positioning sensor?

[LT5 Ignition]

Thanks,
Some more ignition stuff:
I believe the 1990 LT5 engine was released prior to Northstar. One difference between Ignition modules. Northstar ignition used 2 VR crank sensors with 24 pulses (or was it 32 ?) per revolution rather than the 1 sensor and 9 pulses of LT5.

The ignition module uses suface mount components and is potted. Than a lid is sealed over. Typical sealing of igniton modules of the time not designed to be serviced. A serious electronics expert may want to try. Another thing it contains is a Motorola processor with EEPROM. If it lost its memory I do not know what one would do.
the whole module was made by Motorola who supplied it to Delco Remy who supplied it to the Chevrolet group. It does have a back up mode that allows ignition output if communication is lost from the ECM.

I would be happy to help discuss some after market system ideas such as MSD?
I'll check back Wed.

[LGAFF]

Any comment on the trigger system that was used on the two bentley motors?

Here is a note on internet settings, be sure to check remember me...and
check cookies settings:

The privacy settings for your web browser may be set too high to allow the message board cookies to be set on your computer. We have noticed that when users are being upgraded to Internet Explorer 8 the privacy settings are being reset to a higher level. You may need to lower those settings. For Internet Explorer browser go to Tools > Internet Options > Privacy and set the slider to low.

[XfireZ51]

LT5,

The approach that I took in adapting LSx coils was to try using the IM as the sequencer. Rather than have the IM actually fire the coil through ground signal, we built a circuit that converted the ground into the triggering signal used for the LSx coils. I built separate power and ground circuits for the LSx coils. They suck up quite a bit more power than is provided LT-5 coils. Each side of LSx coils needs a 20amp fuse. I was using the 2nd gen LSx truck coils which are the ones all the C6 guys rave about due to the 120k volt spark it throws.The motor would "start" but I suspect that the IM could not complete the timing "hand-off" after reaching the 400rpm threshold. I was able to achieve a Start to On transition several times with the 1st gen truck coils I had. The first time it ran, I found that I had two of the coils reversed in terms of sequence causing it to run rough. Once the coil sequence was corrected, motor started and idled smoothly but then came to a halt after blowing the 10amp fuse in the secondary injector circuit which powers the LT-5 coils.
I then built harnesses to completely separate the power and ground circuits for the LSx coils from the LT-5 circuit. In this configuration, the motor would only Start but not transition to On.

[-=Jeff=-]

The ecm code is not just modified l98 code, it is far more flexible and with Tod Ps definition files there is no need for any other ecm system up to about 600 rwhp.

With Moats tuning aids and current software you can tune on the fly.

Tyler


Moates stuff is readily available but how/where do we get Tod Ps definition file that was mentioned?

[XfireZ51]

Jeff,

And just to expand on your point, there are multiple def files for the LT-5 that differ year to year. Even within each year, there is a mid-year mod made to each def file. Gotta know which one you're using or the motor starts to run funny if at all. I once mistakenly saved my cal using the $D0 mask but the cal was actually formatted for the $D0A mask. Car ran but very rich.

[Tyler Townsley]

Moates stuff is readily available but how/where do we get Tod Ps definition file that was mentioned?

On this board you will be timed out so do long posts in notepad and paste it in the message.
OK. On the def files by Tod. He has hundreds of hours in reverse engineering the GM calibration code. It has several HUNDRED different calibration points. I have the GM listing in english of the calibration but both of us are rather guarded in release of the information. I would email Tod directly about his TDFs. He might point you to specific points you are looking for.
Tuning software for OBD I
In addition to Tunercat:
http://www.tunercat.com/
there is Tunerpro:
http://tunerpro.net/v5whatsnew.htm
Moats stuff is here:
http://www.moates.net/
The above is for those who choose to stay stock ecm/ignition. For those who want to stray and REALLY want to get into DIY EFI there is the following:
BE PREPAIRED TO INVEST SOME TIME IN READING.
http://www.bgsoflex.com/megasquirt.html
http://www.diyautotune.com/
I know there are several commercial systems out there but they are beyond my pocketbook.

The iginition side of the tuning software is pretty straightforward but there are some real gotchas in the fuel side due to the way the calibration handles the fuel for the dual injectors.

Unless you are a real glutton for work the stock system is more than able to contend with normal to modded motors.

Tyler

[XfireZ51]

LT5_Ignition,

Need to ask if the ICM shuts down if it doesn't see coil current. As this is what we were thinking is the issue.

[LT5 Ignition]

After looking at this thread more carefully I can see there is a lot of knowledge on engine controls. I can see it will take awhile for me to catch up. My hobbies are sailing, skiing, woodworking, etc. It's about time I did something engine related after work except running a chainsaw !!

The Ignition module should not shut down if it does not see coil current. It does have current limiting control much like a Gen3 LSx coil driver that is built into the individual coil. One reason for not allowing a shut down is that it would be a harsh penalty for the failure mode of one loose coil connector or failed primary coil winding. Letting the customer run on 6 cylinders is usually better than none for a short time. A way to test this idea is to unplug one coil while the engine is idling. Probably not much room to do that! But I am curios and do not have my own LT5.

Side note: There are little energy losses in clean spark plug wires. The exhaust spark on a DIS is a greater loss. I agree with the writers saying you should not see a difference between a coil per cylinder or a DIS system on a stock LT5. Wet, salty wires contribute to loss of peak secondary voltage necessary for very cold starts or WOT transients but I can imagine that ZR1 owners keep their wires clean and do not start much below freezing.

I would like to discuss some of the other questions later.

[LGAFF]

Ran across this guy looking for parts.....

Hi Lee, sorry about slow reply
I would think it easy to convert
the only issue I see is driving 16 injectors, but I believe most reasonable aftermarket systems will drive 16.
The ignition is quite easy, as it has the std GM 4 wire interface to ecu, which I why I chose it
Also , so does the Cadillac Northstar, but this has a different trigger setup, the LT5 is easier.
There is a program called Big Stuff 3 which I have used on Big Block Ford which uses individual coils same as Gen 3
This will drive 16 injectors.
Depending on what your application is, if you are still using it in Corvette, I would stick with what you have.
It is simple, and the only trouble you should ever have is the ignition module itself.
The coils are dime a dozen, pickups are common and basic, so I would buy spare modules if they are getting rare
I dont know much about the ecu with these, but would be surprised if someone like Tuner Cat or TunerPro dont do software for them to retune them if you hve made mods
I would love one of these in my 32.......

Regards
Al Gibbs
www.kalmaker.com.au (http://www.kalmaker.com.au/)

[XfireZ51]

LT5_Ignition,

"...I agree with the writers saying you should not see a difference between a coil per cylinder or a DIS system on a _stock_ LT5."

Interesting comment and I note you underlined the word stock. Why would you say there would be no discernible difference on a stock motor, and secondly would you have a sense on the power level where the Gen3 ignition would have an impact?

I can understand the IM continuing to operate with 1 or even 2 coils going out but what if it sensed ALL four coils out?

[carter200]

The coils are dime a dozen, pickups are common and basic, so I would buy spare modules.


Where are these modules sold? Thanks.........

[Blue Flame Restorations]

I just bought an extra module off Ebay. I'll probably buy a few more over time just to make sure I have extras.

[carter200]

I just bought an extra module off Ebay. I'll probably buy a few more over time just to make sure I have extras.

What wording would one use to look one of these up on Ebay?

[Blue Flame Restorations]

What wording would one use to look one of these up on Ebay?


I just typed in "ZR1 module" and found more than one at the time. About two weeks ago.

[LGAFF]

I picked up one for $76

[mike100]

do the ign modules have different part numbers for different years, or are they all the same? I want to know if I can keep a spare from a 90 for use on my 91.

[zr1don]

For LT5 Ignition: My LT5 continues to run w/two spark plug wires pulled. I inadvertantly left #'s 1 & 3 off and failed to plug them back in when I started it. It ran rough, but continued to run in that condition.

[A26B]

do the ign modules have different part numbers for different years, or are they all the same? I want to know if I can keep a spare from a 90 for use on my 91.

Depends on which 90 DIS module. The first 500 90 models used PN 1103737.

[LT5 Ignition]

ZR1don,
thanks for the info on the secondary wires. The IM does not sense or control the high voltage side of the coil (transformer). Therefore it should continue to operate all the coils with secondary wires off ( Be careful with the loose wire 40,000 volts !!)
XfireZ51,
If all 4 coils stop working it is more likely that the IM is the cause of them not working since it is the source of their power. In addition to checking the resistance of coil windings, you can connect a spark plug across the secondary towers and momentarily touch 12 volts across the primary. You should see a nice blue spark.

[LT5 Ignition]

XfireZ51 ref. post #35,
There are 3 operating points to challenge an ignition design.
1 idle requires higher energy ( longer, fatter spark ) to ignite the poorer mixture due to low air velocity across the injector. LT5 has high velocity across the primary injector at idle because the secondary runners are closed.
2 Peak torque has the highest cylinder pressure to ignite so you need the most secondary voltage to jump the gap. After the initial arc not much energy is required because the dense gas contains a lot of energy from heat and compression.
3 at high speed you start to run out of time to charge the coil or coils. Big problem with distributors on an 8 cylinder. 4 coil DIS helps because two coils can charge at a time.
I know the system has some margin for more power. but I have not tested it beyond stock power. I would be interested if some Forum members have.

[carter200]

Depends on which 90 DIS module. The first 500 90 models used PN 1103737.

Jerry,
Do you have a number for a 95?

[tomtom72]

Hi Ron, I think that all the larger displacement LT5's, like the 368, 400, 415 and the 441 and 427's which range in hp from 500+ rwhp to past 650 rwhp still use the OEM DIS ignition.

I would hasten to add that I am not fluent in making any of these bigger inch LT5's...it's just that the ignition system is never mentioned as having been supplanted by another system other than the OEM system on these motors.

:cheers:
Tom

[XfireZ51]

LT5-Ignition,

If you were responding to my question of all 4 coils. not working, I was posing that condition where rather than grounding the coil, that ground signal was used as a trigger for the LSx coil. I believe the IM fires the appropriate coil by grounding that coil. Now what if the IM was grounding the coil was simply converted to an ~.4v trigger signal sent to the corresponding LSx coil pairs.
There would be very little load to the IM. And now that happens for all coils. Also, what is the dwell set for the LT-5 coils and where is it controlled? CN it be adjusted?

I hope that I am being clear and would be happy to try to clarify further if I can. But think of it as the IM being converted to simply a sequencer for the LSx coils. And using what was originally the trigger ground for the LT-5 coils and converting that into a compatible trigger signal recognized by the LSx coils instead. Much less voltage. As I see it, GM took the ignition module functions and divided those functions between the coils themselves and the ECM thereby eliminating the need for the IM.

[-=Jeff=-]

F.A.S.T. use to (might still) make an eDIST. it would eliminate a distributor and would sequence LS Coils.. it needs a Crank and Cam Sensor.. cam for position and Crnak for firing, but the Crank sensor had 4 notches not 9..

I would think that connected to our ECM might work, but the main challenge would be the Crank sensor

[-=Jeff=-]

eDIST threads I found:

http://www.thirdgen.org/techboard/diy-prom/220101-edist-distributorless-ignition-system.html

http://www.turbobuick.com/forums/performance-ecm-upgrades/30786-fast-amazing-lt1-w-distributorless-ignition.html

[A26B]

Jerry,
Do you have a number for a 95?

PN 1103841

[carter200]

PN 1103841

Thanks Jerry :cheers:

[todesengel]

Here is my ATI setup with a 60-2 tooth trigger wheel for the haltech standalone. he missing two teeth are under the crank sensor when the engine is at 60* BEFORE TDC. (Techincally it CAN be anywhere, but putting it at 60* BTDC give you a tooth offset of 0 and trigger angle of 60*)

http://i13.photobucket.com/albums/a260/chaosrob/ati2.jpg

http://i13.photobucket.com/albums/a260/chaosrob/ati1photo.jpg

[LT5 Ignition]

LT5-Ignition,

If you were responding to my question of all 4 coils. not working, I was posing that condition where rather than grounding the coil, that ground signal was used as a trigger for the LSx coil. I believe the IM fires the appropriate coil by grounding that coil. Now what if the IM was grounding the coil was simply converted to an ~.4v trigger signal sent to the corresponding LSx coil pairs.
There would be very little load to the IM. And now that happens for all coils. Also, what is the dwell set for the LT-5 coils and where is it controlled? CN it be adjusted?

I hope that I am being clear and would be happy to try to clarify further if I can. But think of it as the IM being converted to simply a sequencer for the LSx coils. And using what was originally the trigger ground for the LT-5 coils and converting that into a compatible trigger signal recognized by the LSx coils instead. Much less voltage. As I see it, GM took the ignition module functions and divided those functions between the coils themselves and the ECM thereby eliminating the need for the IM.

I think understand. The LSx coils are controlled by their ECU with a 5 volt high to 0.2 volt low signal (EST signal). When the signal is high, the coil turns primary current on and when it falls the coil turns off current rapidly causing the spark. The high time (dwell) is typically around 3 to 4 ms. So, like you say, you can convert the 0.4 low state dwell time to a 5 volt high state time with a buffer chip. You feed 2 LSx coil pairs with this signal and you still have a DIS.
I can not remember the typical dwell time of a LT5 IM. I think it is shorter than 3 ms. Perhaps a Forum member knows. Is it in the service manual?
I do not think there would be a performance benefit to using LSx coils. The larger diplacement engines should not need more secondary voltage unless they are also increasing cylinder pressure at time of spark. ( increasing torque/litre (Brake mean effective pressure) ).

[XfireZ51]

I think understand. The LSx coils are controlled by their ECU with a 5 volt high to 0.2 volt low signal (EST signal). When the signal is high, the coil turns primary current on and when it falls the coil turns off current rapidly causing the spark. The high time (dwell) is typically around 3 to 4 ms. So, like you say, you can convert the 0.4 low state dwell time to a 5 volt high state time with a buffer chip. You feed 2 LSx coil pairs with this signal and you still have a DIS.
I can not remember the typical dwell time of a LT5 IM. I think it is shorter than 3 ms. Perhaps a Forum member knows. Is it in the service manual?
I do not think there would be a performance benefit to using LSx coils. The larger diplacement engines should not need more secondary voltage unless they are also increasing cylinder pressure at time of spark. ( increasing torque/litre (Brake mean effective pressure) ).

From examples I have seen of LSx coil conversions, 5ms dwell appeared to be the optimum. Any idea where the dwell control resides and if its programmable. If the dwell is less than 3ms, it might explain why motor would run but then shut down. Perhaps not enough energy for the LSx coils to fire at less than 3ms dwell.

[LT5 Ignition]

The LT5 ignition control is similar to the L98 distributor system in that when you are cranking the ignition module provides the dwell and it is longer than run mode to handle the transient voltage and speed during crank . The engine is going to slow to worry about overheating the coil. Once you are above about 400 rpm, the ECM takes over dwell control with a shorter, probably <3ms dwell. I do not believe the ignition module is programmable but I will try to investigate. The ECM is. That would make sense why an LT5 may stall right before it hits idle on a crank to run transition using one of the following coils. '92 GEN 3 LS1 small block uses coils with around a 4-5ms dwell. The Gen 4 small block (~96? intro ) uses coils with around 3-4ms. I am curious why there is an interest replacing the DIS coils with a LSx type?

[XfireZ51]

LT5,

We started investigating the LSx coils with the potential of eliminating the IM which appears to be unique to the LT-5 ( and expensive). I have also followed conversions in a number of other car lines, including the LT-1 and GN Buicks, utilizing the LSx coils. The coils represent an opportunity to bring a hotter spark, faster spark for the LT-5. Altho it would maintain "waste spark" each cylinder would have an individual coil dedicated to it, again allowing greater energy for spark. With the higher rpm range of the LT-5, having a hotter, more intense spark would produce better power at top end. It is also suggested that the LSx coils are partly responsible for the power that LS motors and heads develop. With the LSx coils being independently powered, this would remove some of the "heat" from the IM.

[tomtom72]

Ron,

If you search the P/N 1103841, IM or as we call it DIS box, it is NLA at GM.

Obviously not a great situation if you need to replace it. I also don't know of too many places that even repair our ECM's, let alone a DIS box.

I have a spare IM in my parts stash. I think that a failure of some of an LT5's electronic control "black Boxes" is a greater fear than if you were to spin a rod bearing. That my be hyperbole on my part. It does appear to be easier to replace internal motor parts than to get some of the LT5's black boxes replaced or repaired.

:cheers:
Tom

[Blue Flame Restorations]

We need a source for someone to repair electrical ignition components OR an alternative to the current system. There's $$$ to be made for a repair source for our IM's, for sure.

[XfireZ51]

LT5,

In post #45 you stated that "at high speed you start to run out of time to charge the coil or coils. Big problem with distributors on an 8 cylinder. 4 coil DIS helps because two coils can charge at a time." One of the reasons I thought then 8 coils are better than 4 since each coil has more time to charge even at higher rpms.

If this is true, then wouldn't the coil dwell need to be under ICM not ECM control?

Also, with 2 coils charging at the same time, does this also mean there was "overlapping dwell". And if there was, it is of a benefit.

[LT5 Ignition]

I can now appreciate the concern with the IM availability. Also, I apoligize I got my dates mixed up on LS introductions in post 56. It was the Gen 2 small block LT1 in 1992 (ABITS). The Gen3 LS ~ '97 and Gen 4 ~ '05. I agree that if you can keep the IM module from sinking the primary current it will run cooler.
Now, if someone can come up with a way of turning the 9x VR signal into into a 4x logic signal and also take the single EST signal from the ECM and steer it to the 4 coil pairs in firing order it seems the IM can be eliminated. For sure the LS systems have dwell overlap starting around 4000 RPM. Perhaps the Lt5 does too. In the run mode the IM could have been designed to follow the falling 4x EST signal from the ECM for end of dwell spark timing but control the start of dwell ahead of the rising EST pulse. I can not remember if it actually was. Would it be worthwhile to put a couple of current probes and a scope on the coil primaries to see if the dwell overlaps on a LT5 at higher speed? I wish I had one!!

[POWERBRAKEBOB]

Does anyone know if the MSD DIS-4 box will replace and remove the factory DIS Box?

[XfireZ51]

Does anyone know if the MSD DIS-4 box will replace and remove the factory DIS Box?

Nope. Just an amplifier.

[POWERBRAKEBOB]

I'm still chasing this "cranks but won't fire" problem on mine. I have changed the IM, the CPS, tested the harness between CPS and IM, all fuses, tested the ECM and Jet chip, new battery, coils are new MSD 6 months old, all new injectors, have key on power to the coils, IM, and computer. NO trouble codes. Had the plenum off a dozen times.. Checked for bent pins on the IM. really causing me some problems. Any OTHER ideas?

[Tyler Townsley]

Fuel pressure? No spark across the plugs when cranking?

Tyler

[XfireZ51]

I'm still chasing this "cranks but won't fire" problem on mine. I have changed the IM, the CPS, tested the harness between CPS and IM, all fuses, tested the ECM and Jet chip, new battery, coils are new MSD 6 months old, all new injectors, have key on power to the coils, IM, and computer. NO trouble codes. Had the plenum off a dozen times.. Checked for bent pins on the IM. really causing me some problems. Any OTHER ideas?

Have you installed a stock chip? When you turn KEY ON, does the SES light blink once? You won't get trouble codes till the motor runs. Are the pumps coming on?

[POWERBRAKEBOB]

I set a plug out on the engine with wire and cranked. NO spark. NO flash of the noid light. Sec light flashes, then goes out by turning key to ON. Key on, pumps run two seconds. Cleared door alarm. I did find a fuse burned out under the right dash. It looks to be marked "conx" or "cone" . I replaced ALL fuses on the right side of dash. VATS by passed. It was running when I parked it one night, next day, nothing. I bought a used IM from Brett. Replaced CPS, which did test "open". Tested the harness from CPS to IM for shorts. None. I'm sure it's something simple, but I can't find it, and my FSM's are buried in storage. Frustrating, and I need the car. It does have 268,000 miles on it, which I am sure is a record. No one has ideas on when things fail at what mileage.