Mark IV BBC LS2 Cam Sync and Crank Trigger Solution

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wikd69
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Mark IV BBC LS2 Cam Sync and Crank Trigger Solution

#1 Post by wikd69 » Sat Oct 08, 2016 7:36 pm

I'm shifting entirely over to an EFI and distributorless ignition setup (LS2 style) on my new build and it's been a real learning experience over this last year. I still have several months worth of work left to finally get the Camaro back on the street, but I've made great progress so far. I'm hoping to get to dyno by mid to late November.

Old school Mark IV BBC's don't lend themselves to this sort of new-era LS2 build. Crank triggers have been around for a long time but there's not a lot of options available which provide the cam sync signal required by the ECU for DIS. Various options are available to convert your distributor to provide a cam sync for the ECU, but I'd really like to lose the distributor altogether. For one thing, it's a make-do solution and would be in the way down the road if I needed to move up to a 12-71 or 14-71 blower. A distributor style unit is definitely not compatible with that scenario.

There is a new timing cover available for Mark V BBC's which incorporate both the cam sync and crank trigger sensors, but they do not work with my old style block. There's a company which sells a distributor-type unit which provides a dual-sync signal, but again, this is not compatible with my plans to possibly hang a bigger blower on the motor.

So, I'm working on a home-grown cam sync and crank trigger solution. I'm still not convinced it's going to work. If not, I'll fall back to other options to meet the need. If this does work out, it'll be pretty cool :mrgreen:

I came up with an approach which uses dual HE sensors mounted through my upper Comp Cams timing cover plate. I designed and had a local CNC shop machine out the new dual sync plate that mounts on the upper timing gear. The plate is both doweled and secured to the timing gear with flush-mount machine screws and uses high-temp neodymium magnets in combination with hall-effect sensors to provide both cam sync and crank trigger signals to the Holley ECU. There is a wedge of space just below my electric water pump which exposes just enough of the timing cover to allow sensor placement. I timed and located all of the magnets to align with this location. If this does work, all of this will be out of sight from above and I won't need to run a conventional crank trigger on the snout. The sensors I'm using are MSD 2348 HE sensors which have an integrated LED indicator. This makes it pretty handy to check timing for the digital rising/falling index points.

Image

The photo above is the 1/4" plexiglass mockup I'm currently playing with. In this view I'm indexing the hall-effect sensors to the dual sync magnets. The precision required in placing the trigger points and sensors is pretty significant. Given the cam sensor layout actually represents 720 crank degrees, my 3.25" trigger circle yields about .014 travel for each degree of crank rotation. My current challenge is getting the sensors placed in the right locations and ensuring the end state provides a reliable, consistent and predictable timing scheme for the ECU. The per-cylinder crank trigger signal is used by the ECU to initiate all sequential injection and spark timing events. This is not a place I can afford to screw up - this is why I've spent so much time laying this all out. The solution is designed around a CNC-produced trigger plate, a bit of machine work to mount it to the cam gear and uses off the shelf wiring harnesses and sensors. If this does work it'll be easy to duplicate for future builds.

What do you guys think of my approach ?
1969 ProStreet Camaro RS Best 9.75@139 1.46 60'
Blown 427 BBC, TH400 w/Brake, Back-Half Ladderbar
Narrowed 12-Bolt, 4.10 Gears, Spool, Moser 33 Spline

http://www.marsh-racing.com/harrys_camaro-1.htm

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Re: Mark IV BBC LS2 Cam Sync and Crank Trigger Solution

#2 Post by mytmouz » Sun Oct 09, 2016 10:55 pm

I like. A modified crank trigger wheel and a different sensor was the first thing I thought of. I assume you went with a cam wheel for packaging reasons?
Trucks are for haulin...

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Re: Mark IV BBC LS2 Cam Sync and Crank Trigger Solution

#3 Post by wikd69 » Mon Oct 10, 2016 1:32 pm

mytmouz wrote:I like. A modified crank trigger wheel and a different sensor was the first thing I thought of. I assume you went with a cam wheel for packaging reasons?
Yeah. I figured since I was going to the trouble of hanging a cam sync on the front of the cam I might just as well include a crank trigger solution as well. The design was pretty straight-forward after I got my head around what this new Holley Dominator ECU wants for triggers and timing events.

I had a narrow wedge of space available below the water pump to physically locate the sensors through the timing cover (see photo below). The cam sync and crank trigger points on the new wheel are clocked independently of one another because of the need to closely co-locate the two physical sensors. I had to sit and study that scenario for a while before I finally started laying out the design.

It also took a while for my brain to finally fold around the fact that the cam operates in a 720 degree universe (1 cam degree equals 2 crank degrees) while crank events take place in a 360 degree window for individual cylinder timing. This is all elementary on the surface - it's after you start trying to get a live, working model spinning in your head that reality starts to warp. I did get there, but I still find myself tripping over the forward and reverse ATDC and BTDC degree numbering scheme on my timing wheel lol...

I just got the sensors located and installed in the top timing plate late last night. Next up is to get down to the shop to get some permanent bungs tigged in place for the sensors. Right now they’re just tapped and threaded though the quarter inch aluminum cover plate. My target for placement was 60 degrees BTDC for the crank trigger and 195 degrees BTDC for the cam sync. I actually hit 61 degrees on the crank and 197 degrees on the cam sync. Not bad for Kentucky windage and the old mark one eyeball :mrgreen: As I mentioned elsewhere, each degree of crankshaft rotation equates to approximately .014 travel on my cam trigger wheel circle. I did lots of mock-up trial and error before I got to the right place.

Image

I’ll follow up with another more technical post about what I’ve learned about Holley injection stuff. I swear, the folks in industry who write the technical material released with some of these new products had to have been raised on a different planet. They seem to go out of their way to confuse the reader. :scratch:
1969 ProStreet Camaro RS Best 9.75@139 1.46 60'
Blown 427 BBC, TH400 w/Brake, Back-Half Ladderbar
Narrowed 12-Bolt, 4.10 Gears, Spool, Moser 33 Spline

http://www.marsh-racing.com/harrys_camaro-1.htm

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Re: Mark IV BBC LS2 Cam Sync and Crank Trigger Solution

#4 Post by John_Heard » Mon Oct 10, 2016 4:05 pm

Don't you need a way to adjust the sensor position for timing adjustments?

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Re: Mark IV BBC LS2 Cam Sync and Crank Trigger Solution

#5 Post by ytnova » Mon Oct 10, 2016 4:46 pm

Interesting idea, I like it. For my BBC setup in the mustang, I was just going to run the pickup in the distributor for the cam signal and a standard holley crank trigger. I have to run the distributor in order to drive the oil pump as mine is staying wet sump, but I see where you are going and your needs.

As for being able to adjust them, not really, in the software, there is a camshaft offset so you can sync them that way, you just have to get it close enough to run so you can use a timing light and + or - the event in degrees. You also can choose at what time in the engine cycle that you what the injector to fire. If you are choosing to batch fire the injectors, like if the injectors are above the blower, there is no real reason to sync at all.
I am not really sure what the question is, but I am pretty sure the answer is Big Block.

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Re: Mark IV BBC LS2 Cam Sync and Crank Trigger Solution

#6 Post by wikd69 » Tue Oct 11, 2016 11:27 am

ytnova wrote:Interesting idea, I like it. For my BBC setup in the mustang, I was just going to run the pickup in the distributor for the cam signal and a standard holley crank trigger. I have to run the distributor in order to drive the oil pump as mine is staying wet sump, but I see where you are going and your needs.

As for being able to adjust them, not really, in the software, there is a camshaft offset so you can sync them that way, you just have to get it close enough to run so you can use a timing light and + or - the event in degrees. You also can choose at what time in the engine cycle that you what the injector to fire. If you are choosing to batch fire the injectors, like if the injectors are above the blower, there is no real reason to sync at all.
What EFI box are you running ? Holley ? And if so, which one ? The Terminator and Dominator ECU's are the same basic ECU, the Dominator just has more available I/O ports, natively handles a second O2 sensor and allows control of electronic transmissions. Otherwise they're pretty much the same box.

As to driving the oil pump, I bought the MSD stub unit which drops down in the distributor hole and serves that need. I though about adapting that unit and adding a dual sync mechanism to in, but having the sensors on the front site of the motor had more appeal. If I do this correctly, I can hide all of the plug wires, harnesses and coil packs out of sight and with the exception of TPS, IAT, etc., wring, have a very clean top end. That wasn't the true goal with all this, but it'd sure be cool to do :mrgreen:
1969 ProStreet Camaro RS Best 9.75@139 1.46 60'
Blown 427 BBC, TH400 w/Brake, Back-Half Ladderbar
Narrowed 12-Bolt, 4.10 Gears, Spool, Moser 33 Spline

http://www.marsh-racing.com/harrys_camaro-1.htm

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Re: Mark IV BBC LS2 Cam Sync and Crank Trigger Solution

#7 Post by ytnova » Tue Oct 11, 2016 4:29 pm

Holley HP and yes, the engine management side of them is all the same including the software. So far the HP has suited my needs and I have not had the need for the additional I/O stuff, trans control, or DBW, especially since I have done the digital dash which allows some additional I/O options. Once the replacement power plant is completed, I will update to the newer version 4 software, I didn't want to mess with it prior to dragweek. I also plan on doing the same and relocating the coils off the valve covers and putting them down along the oil pan rail in order to clean it up some. Keep us posted on your idea, I'd like to see how it turns out.
I am not really sure what the question is, but I am pretty sure the answer is Big Block.

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Re: Mark IV BBC LS2 Cam Sync and Crank Trigger Solution

#8 Post by wikd69 » Tue Oct 11, 2016 7:09 pm

ytnova wrote:Holley HP and yes, the engine management side of them is all the same including the software. So far the HP has suited my needs and I have not had the need for the additional I/O stuff, trans control, or DBW, especially since I have done the digital dash which allows some additional I/O options. Once the replacement power plant is completed, I will update to the newer version 4 software, I didn't want to mess with it prior to dragweek. I also plan on doing the same and relocating the coils off the valve covers and putting them down along the oil pan rail in order to clean it up some. Keep us posted on your idea, I'd like to see how it turns out.
What coil packs did you use ? I'm going with the Holley SmartCoils. They're spendy but at this point it's a spit in the ocean, cost wise lol...

As I understand it, the Holley SmartCoils are just a spiffed up version of the IGN-1A's.
1969 ProStreet Camaro RS Best 9.75@139 1.46 60'
Blown 427 BBC, TH400 w/Brake, Back-Half Ladderbar
Narrowed 12-Bolt, 4.10 Gears, Spool, Moser 33 Spline

http://www.marsh-racing.com/harrys_camaro-1.htm

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Re: Mark IV BBC LS2 Cam Sync and Crank Trigger Solution

#9 Post by ytnova » Wed Oct 12, 2016 10:16 am

I am using the OE stock round truck coils with the external heat sinks. I have had it up to 22lbs so far with no issues, it is usually around 20lbs of boost with .025 plug gap. I would steer clear of the Chinese replacement ones unless you can verify the build specs on them. Pay attention to the coil dwell settings in the software, most of the issues guys were having was do to incorrect dwell settings in the software that guys were not aware they could change. The holley forums have a good amount of info on what to set them at depending on what coil you are using. I like the smart coils and feel it is a worthwhile upgrade, just have not pulled the trigger on them yet, I have other things I would like to do first.
I am not really sure what the question is, but I am pretty sure the answer is Big Block.

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Re: Mark IV BBC LS2 Cam Sync and Crank Trigger Solution

#10 Post by wikd69 » Thu Oct 13, 2016 6:48 pm

John_Heard wrote:Don't you need a way to adjust the sensor position for timing adjustments?
MAJOR DISCLAIMER: I don't have access to software code inside the Holley ECU - the methods and processes I speak to below are what I expect the Holley software designers have utilized. One thing I've learned from doing IT for 35 years is this: There are only so many ways to skin a cat. The approach I've described below is how I've done similar things - not ignition management but I've designed and coded many similar solutions doing time slicing to determine transaction rates over time, etc. I would be extremely surprised if my assumptions here are very far off the mark.

There, now I feel better. I didn't want to come across like I had insider knowledge of internal Holley ECU code.

Addendum: This is the third time I've edited this content - hopefully my description makes better sense this time around. My brain must have been in orbit the last two times I tried this.



Okay, I promised a more technical commentary on this setup, so here goes. Bear with me if my technical layout is not exactly correct. I’ve had to infer and assume quite a lot in arriving where I am.

For the purposes of discussion, let’s use my build as an example. All degrees referenced below are crankshaft degrees.

My build uses a Holley Dominator ECU and a distributor-less ignition setup with individual coil packs. I use Cam Sync and Crank Trigger mechanisms to anchor and bootstrap ignition event timing. All timing events are managed by the Holley ECU, including the ability to set and change ignition timing events during execution, even down to the level of changing timing for individual cylinders on the fly. All of this is controlled by the ECU at run time. All of the Best Practice settings below are for an 8 cylinder build. 4, 6, 10 & 12 cylinder builds have their own separate recommended settings.

After the Cam Sync and Crank Triggers are set in place to tell the ECU when and where to initiate management of ignition events the physical positions of these sensor points will never change. All future timing settings are done via the ECU software config screens.

Because of the physical placement of my trigger wheel magnets and Cam Sync / Crank Trigger sensors, we know the:

• One Cam Sync event occurs at 195°BTDC for Cylinder #1 (Holley Best Practice recommendation)
• Crank Trigger events occur at 60°BTDC for each Cylinder (aka 'IRA', see below) (Holley Best Practice recommendation)

• Cam Sync events occur 1 time for each full cam rotation (two full crank rotations).
• Crank Trigger events occur every 90 degrees of crank rotation.

Among other settings within the ECU, we set the following:

• Engine Firing Order to 18736542 in the ECU configuration screen (yep, I'm using a 4/7 swap)
• (IRA) Ignition Reference Angle at 60° in the ECU configuration screen (this is the fixed Crank Trigger degrees BTDC)
• Ignition Timing at 34° in the ECU configuration screen (this is the degrees BTDC when I want the plug to fire)

There are many other settings within the ECU, but these are the ones which apply to our overview here.

Remember that the ECU is just a computer and is running software which does lots of different things at the same time. My overview below is a very simplified assumption of how (I surmise) the box does what it does. My first assumption is that we need to bootstrap and sync the ECU with the #1 Cylinder crank trigger event.

The following is what (I surmise) happens within the ECU at initial startup and afterwards:

1. The starter motor spins the crank
2. The ECU begins looking for the Cam Sync Trigger event
2. The Cam Sync Trigger event is seen (we're at 195° BTDC for #1)
3. The ECU begins looking for Crank Trigger events (this begins the ignition bootstrap sequence)
3. The 1st Crank Trigger event after Cam Sync is seen (we're now at 150° BTDC for #1)
4 . The ECU saves the current system clock time
5. The 2nd Crank Trigger event after Cam Sync is seen (we're now at 60° BTDC for #1 - aka 'IRA')
6. The ECU subtracts saved clock time from current clock time to get total elapsed milliseconds
7. The ECU divides elapsed milliseconds by 90 (degrees) to determine milliseconds per crank degree
8. We're sitting at IRA (60° BTDC for #1). Ignition Timing is defined as 34° BTDC.
9. The ECU counts down the equivalent number of milliseconds to allow for 26 degrees of crank rotation
10. The crank should now be at 34° BTDC. The ECU fires the coil pack for #1 cylinder
11. The ECU repeats the mSecs-per-crank-degree calculation for each Crank Trigger event, firing cylinder coils in firing order sequence

This repetitive recalculation of milliseconds-per-crank-degree allows the ECU to adjust for changes in engine RPM in real time.

As I stated, I surmise this is how the Holley ECU manages ignition timing events. The derived IRA window (in my case, the 60 degrees between IRA and TDC) is where all ignition events are performed. This magic is what allows you to vary spark timing on a per-cylinder basis, *each time* a cylinder plug fires, based on other things which are monitored or taking place at the same time. Sequential injection events occur at different times within each individual cylinders 4-stroke cycle but they still occur based on the Crank Trigger IRA and the derived TDC for each cylinder.

John Heard: This is what took me so long to understand, because I came into this with the same question you posed. After having seen how folks deploy conventional crank-triggers by lock-phasing their distributors, my question too was “How do you change ignition timing with this new EFI/ECU box ?”. The magic is the fact that there’s a very fast CPU watching events and managing all sorts of stuff. You provide the ECU with routing instructions (firing sequence) and event anchor points (Cam Sync & Crank Trigger IRA) and the onboard CPU & software takes care of the rest. All logging, I/O collection and distribution, all changes to timing or injection events, triggering multiple stages of nitrous or water/methanol injection, controlling electronic transmissions, dual drive-by-wire throttle assemblies and monitoring and reporting on engine state metrics (Inlet Air Temp, Coolant Temp, Throttle Position, Idle Air Control, Engine RPM, Fuel & Oil Pressure, AFR states, etc., etc., etc.) all are done on a continuous basis and used at your discretion to report on and control lots of things during operation.

If you’re a really geeky systems guy like me, this is beauty :smt003

And note: The above is for a simple LS2 style build. The Holley ECU can accommodate lots and lots of variants in how you put your stuff together. My approach is intended to emulate a factory LS2 build and if I don’t screw things up, it should be pretty clean. I'm also going to run 16 injectors in 2 banks of 8 injectors each, and someday perhaps, simultaneously drive trim injectors down at the individual cylinder intake runners. Depends on how geeky I want to get. :-P

Hopefully my description is pretty close to how the Holley system does its thing. As a long time software developer, my description above is how I would do this. I welcome any critiques or corrections from folks who know the Holley system better than I do :) :nutkick: (Edited to add the major disclaimer at the top, correct some assumptions and comments about injection events as related to the IRA 'window', and to rewrite the ignition bootstrap method descriptions).
Last edited by wikd69 on Wed Nov 16, 2016 1:34 am, edited 5 times in total.
1969 ProStreet Camaro RS Best 9.75@139 1.46 60'
Blown 427 BBC, TH400 w/Brake, Back-Half Ladderbar
Narrowed 12-Bolt, 4.10 Gears, Spool, Moser 33 Spline

http://www.marsh-racing.com/harrys_camaro-1.htm

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Re: Mark IV BBC LS2 Cam Sync and Crank Trigger Solution

#11 Post by John_Heard » Thu Oct 13, 2016 10:18 pm

I get it, just didn't realize the Holley took care of advance and retard. I assume you get where things are initially with a timing light, tell the computer where it's "at" then it can adjust from there. Wonder if you have to spin it over on the starter with plugs out to find your initial timing reference.

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Re: Mark IV BBC LS2 Cam Sync and Crank Trigger Solution

#12 Post by wikd69 » Fri Oct 14, 2016 1:00 am

John_Heard wrote:I get it, just didn't realize the Holley took care of advance and retard. I assume you get where things are initially with a timing light, tell the computer where it's "at" then it can adjust from there. Wonder if you have to spin it over on the starter with plugs out to find your initial timing reference.
If you look at the first photo I posted with the plexiglas mockup, you can see the sensors I'm using have LED's built into them - thats one of the benefits of magnetic vs ferrous sensor targets. Ferrous targets require a minimum speed as they pass the sensor to register a signal. The magnetic sensor lets me dial in the sensor positions at zero rpm on the engine stand with a lot of precision. Slowly roll it over on the stand by hand, watch the LED change state and then note the degrees on the degree wheel. My fixed IRA is close to 62 degrees BTDC - I'll use that IRA number in the ECU along with 34 degrees of timing. First time I fire the motor I'll check the timing with a light and then adjust my IRA in the ECU settings with the difference to correct it. Thereafter I'll never need to fool with the IRA setting, even after an engine teardown, etc. It's fixed and immutable.

To your point, I just took a timeout and did a bit of reading in the Holley help files. I found you can set a cranking timing value that applies below an RPM level you specify. Above that RPM the standard ignition timing is used. So you guys with mondo max compression ratios can get things rolling a bit easier.

If you're curious about the settings available on the Holley system, you can download and install the software for free on your laptop. You don't actually have to own one of the systems to play with the software. Install it, play with it, it's really really comprehensive and the help file that comes with the software is pretty good. The way they set it up is stupid - you can't play with the screens while you have help open. So, you have dig into where the software installs and find the 'Holley.chm' help file and open it directly. Then you can cruise around the ECU config screens with help open in a different window.

One really cool thing is the ability to alter timing +/- degrees on one or all cylinders based on real-time conditions. The ECU will also drive multiple (2 ?) stages of nitrous and you can alter timing to coincide with that I believe. And if you're using fuel injection, you set up a dry nitrous plate and increase your injection amount to compensate for the nitrous flow. Lots of really cool stuff with this box :smt003
1969 ProStreet Camaro RS Best 9.75@139 1.46 60'
Blown 427 BBC, TH400 w/Brake, Back-Half Ladderbar
Narrowed 12-Bolt, 4.10 Gears, Spool, Moser 33 Spline

http://www.marsh-racing.com/harrys_camaro-1.htm

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