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Twin cam head for the L6 from Derek at Datsunworks


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Getting a little tight in there!

 

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Got the plug tubes done. Decided to dry fit the rocker assembly. The nice thing about the K20 was the cylinder spacing was shorter than the L6. This meant things were easier to fit. In order to take up the space between the rockers and towers I decided to machine some washers out of 6061 aluminum in 3 thicknesses and I also purchased some .002" shim washers.

 

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Was bit tedious but really went pretty quickly. Here is a shot in application.

 

 

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Had a little free time yesterday and decided to make my own oil cap. I'm really happy with the results.

 

This is right after machining.

 

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It looked nice but it was a little too blingy for my taste so I gave it a little time in the vibratory finisher. Looks more appropriate for the build style I'm using.

 

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Getting to the end of it. Only a couple more things to make and I really need the cams for that.  

Edited by Derek
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This is all Tony D’s fault:)   Hi everyone. Some of you know me from my  DIY EFI manifold project http://forums.hybridz.org/topic/63445-making-my-own-efi-intake-the-first-casting/ &#

Machine work finished!   I can relax a little:) Just got done with their first bath. Still need de-buring and edge finishing but the majority of the work is done.    

Yes, the exhaust port 'could' use some work, the as-cast cleaned intake is flowing within 10cfm of a 4 hour port job on an OS Giken head.   Those numbers outflow most max ported SOHC heads

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Okay, who's the "Best Man" of this "soon to be" marriage. And what do I need to bring (besides a fat a$$ wallet) to the start up party?

 

All kidding aside. Been a lurker for quite some time, and my compliments to you sir for your due diligence in this endeavor.

 

Patiently waiting like others to hear it come alive. Beautiful work....

 

Daniel

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Running the L28ET optical dizzy has always been a solution but most people runing sequential fuel and/or spark are going to want to clean up that huge lump hanging off the side of the block. Having the cam cores drilled and tapped to mount is definately a bonus. If we could settle on a cam sensor that is commonly found and readily avaliable would be a major bonus. I know you will be running a distributor for R&D purposes but I can't imagine spending $10k + putting a modern EFI head that will run under high compression or boosted applications and not running sequential spark. Sequential spark is more precise in timing and provides a hotter spark required with higher pressure combustion.

Edited by FricFrac
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I know you will be running a distributor for R&D purposes

 

Actually I'm running EDIS but I get your point.

 

 

 

 

if we could settle on a cam sensor that is commonly found and rediliy avaliable would be a major bonus

 

 

I'm all ears:)  That's whats causing me to hedge. When I made the EDIS adapter kits, at the time it was the dominant choice. I don't see that for the cam fire. Optical requires clean and sealed. That means it must reside outside the valve cover. Since it has to reside outside the valve cover there is really nothing for me to add as there is plenty of wall thickness to accomplish most any kind of mounting. And if not then an adapter plate could be added. Even if there was an internal solution there really isn't a lot of room inside to do it.

 

Personally I don't see not having a cam driven solution out of the box as being a problem. Having a way to attach to the cam is the biggest issue. After that it's a mater of some fabrication. It's a problem that will solve itself when the first person that wants it makes it happen. People spend a lot more on an OSG and they run a dizzy.

 

 

 

 

Those Honda lash adjusters are great, super easy to use. Hopefully there is ample clearance to the fuel lines to get a feeler in there, hard to tell from that angle.

 

It looks a lot closer than it is.

 

Thanks I'm really happy. I'm still waiting on the shoe to drop and I have ugh oh moment. Fortunately Tony has caught a few. Some a little later than I would have preferred :)

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Well, I guess you could make your own, or don't buy this one...

 

I don't need to buy or have the intention of buying something to point out a part of the project that I feel could use some more love and attention on the next go-around.

 

This is a discussion forum. We discuss things here. If that's not the case, then why are hundreds of people posting in this thread? Are they going to buy it too? Why are you so offended by my opinion, anyways? Are you buying?

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Running the L28ET optical dizzy has always been a solution but most people runing sequential fuel and/or spark are going to want to clean up that huge lump hanging off the side of the block. Having the cam cores drilled and tapped to mount is definately a bonus. If we could settle on a cam sensor that is commonly found and readily avaliable would be a major bonus. I know you will be running a distributor for R&D purposes but I can't imagine spending $10k + putting a modern EFI head that will run under high compression or boosted applications and not running sequential spark. Sequential spark is more precise in timing and provides a hotter spark required with higher pressure combustion.

Actually,sequential spark is NOT more precise, nor does it necessarily provide a hotter spark than a wasted spark setup using only a crank trigger wheel like Derek offers in his EDIS kit. Such a setup will be MORE precise than any setup run off a cam or distributor mounted trigger wheel.

 

As Derek implied, EDIS is not the best way anymore, but the trigger and sensor themselves are still current. Maybe a 60 tooth wheel instead of 36, but that's it.

 

A single tooth cam trigger can be run directly off a cam lobe, or any bump up there. There are threaded sensors out there that would require only drilling and tapping, admittedly precisely, the valve cover once. Presto, full sequential everything!

 

But in the meantime, among just the products Derek offers, you can achieve the highest timing precision possible. You'll just be achieving it twice per cycle!

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Isn't comparing "wasted spark" to "sequential" the wrong comparison?  It should be wasted spark versus coil-on-plug (COP).  Tried to find a simple internet reference but everyone compares wasted to sequential.  But it seems like you should be able to run wasted spark in sequential mode.  You only get half coil capacity (as noted above).  Maybe EDIS doesn't do sequential.

 

Sequential goes away in most systems above a certain failry low RPM number anyway.  It's mostly an emissions fix, isn't it?  And it seems like the "trigger" is where the precision and accuracy are generated.  The 360 little holes are for that purpose.

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Isn't comparing "wasted spark" to "sequential" the wrong comparison?  It should be wasted spark versus coil-on-plug (COP).  Tried to find a simple internet reference but everyone compares wasted to sequential.  But it seems like you should be able to run wasted spark in sequential mode.  You only get half coil capacity (as noted above).  Maybe EDIS doesn't do sequential.

 

Sequential goes away in most systems above a certain failry low RPM number anyway.  It's mostly an emissions fix, isn't it?  And it seems like the "trigger" is where the precision and accuracy are generated.  The 360 little holes are for that purpose.

It sounds like you are thinking of sequential injection, as opposed to ignition.  They are two separate and independent things.  In both cases you double the amount of time between events, but the advantages take place on opposite ends of the RPM range.

 

For sequential injection the advantage takes place at low rpm, where the doubling of time between events means that you also get to double the injector pulsewidth.  When you are running large injectors and require really low pulsewidths at idle and cruise, this becomes pretty much essential to get any kind of part throttle driveability.  As RPMs rise this becomes less of a big deal due to generally higher loads, but it's still helpful. As far as I know, there would be no reason for it to revert to non-sequential at higher RPMs.

 

For sequential ignition, the advantage is at high rpm, where the doubling of time between events allows more dwell time for the coils to reach their full energy potential.   Waste spark systems have been used successfully to some very high (10,000+)  RPMs, though, so the advantage for this application is debatable.

 

While you could do a single point timing pickup using cam or distributor timing, as Brady pointed out, that would be a step (probably several steps) backwards in timing accuracy.  Most setups that I have seen for this use a crank trigger for the actual timing, supplemented by a cam/distributor trigger to tell it which 360 it's on.  In this setup the inaccuracies of the cam trigger are not an issue, as it essentially just needs to fire somewhere within the correct 360 degrees.  

 

A potential problem with this setup is that you now have a second sensor that must be working in order to get the sequential feature to work.  For sequential injection, this isn't a big deal, since being 360 degrees out of phase on injector events still works, and probably isn't even a noticeable thing.  For sequential ignition it's a much different story - being 360 degrees out is kind of a bad thing.  For this reason I would prefer using a modified distributor mounting for the cam timing, as it is a much less harsh environment for the sensor than trying to get it to live inside the valve cover.

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Yes NewZed and Bradyzq I suppose I wasn't specific enough with my statement. By removing the mechanical slop from a setup such as the distributor by directly interfacing to a cam/crank you can get a more precise measurement.As you can imagine under acceleration to and from deceleration you will move through the range of "slop" giving you potentially degrees of error.

 

A COP/CNP gives a hotter spark GENERALLY speaking. There are thousands of different coils and wiring and combinations thereof so I'm speaking in generalities here. A wasted spark with a typical EDIS setup uses a dual tower coil pack which means your spark has to jump across TWO spark plug gaps. You are unnecessarily wasting half your energy across a second plug. The EDIS system was a technological step from a distributor to a distributorless ignition system as it is a less complicated system and was easier to implement when it was first conceived. You can run COP/CNP in a wasted spark configuration and avoid the energy lost in a twin tower configuration but remember you are doubling the duty cycle of your coil packs.

 

GM uses a lump on the cam and a hall effect sensor. That would require having a lump added to the cam which I suppose is an option.

 

You can use any sensor method you like. In all the military equipment I've worked on the most precise is to use a syncro. The next most common (and becoming more common) is an optical encoder. I've never seen a variable reluctance setup on any rotation sensor used on military equipment. Remember that a variable reluctance setup is sensitive to both the angle and gap of the sensor. It also produces an ugly analog signal that needs to be reconditioned into a digital signal. An optical encoder produces a digital signal without requiring reconditioning. The 1981 1/2 280ZXT used a variable reluctance setup (CAS) for Nissan's first ever turbo engine. That to the best of my knowledge was the end of the CAS for Nissan. They went to an optical encoder in 1982 and have been using optical encoders since then.

 

Measuring from the cam is most precise way to measure cam timing otherwise you will be measuring the gear and chain lash at the very least from the cam to the front of the crank. That is why modern EFI systems use both a crank and a cam sensor to measure how much out of phase the crank and cam are in reference to each other.

 

For most of us L28ET guys the precision of the optical dizzy is good enough but this modern head will be used to a much higher performance level than our typical L28ET build. I think some builders will be concerned with that precision.

Edited by FricFrac
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A wasted spark with a typical EDIS setup uses a dual tower coil pack which means your spark has to jump across TWO spark plug gaps. You are unnecessarily wasting half your energy across a second plug. The EDIS system was a technological step from a distributor to a distributorless ignition system as it is a less complicated system and was easier to implement when it was first conceived. You can run COP/CNP in a wasted spark configuration and avoid the energy lost in a twin tower configuration but remember you are doubling the duty cycle of your coil packs.

This is a common misconception.  The "waste" gap is on the exhaust stroke and as such is a MUCH easier gap to jump than the one on the compression stroke.  FAR lower pressure and higher temperatures results in a far less dense atmosphere for the spark to jump through.  There is some energy lost vs not having the waste gap, but it's more like a few percent, certainly _NOT_ 50%.  

 

As I mentioned the main advantage here is the increased dwell time for the coils, but you have to go pretty high in the RPM range to see big advantages.  Granted this head should still make power at 9000 rpm, but there are waste spark systems that can still go that high.

 

 

 

Measuring from the cam is most precise way to measure cam timing otherwise you will be measuring the gear and chain lash at the very least from the cam to the front of the crank. That is why modern EFI systems use both a crank and a cam sensor to measure how much out of phase the crank and cam are in reference to each other.

 

I'm pretty sure that the cam sensor is only being used to determine which 360 you are on.  This is certainly true on any aftermarket systems that are likely to be used with this head.  OEM Direct Injection systems _might_ me able to use cam/crank phasing info to some advantage, but I think its safe to say that nobody is going to be doing direct injection with this head.

Edited by TimZ
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In two posts I learned more about injection and ignition timing than I ever knew. Thanks. 

 

I don't need any of that for this build. I think if I was going to do it for a customer i would cut a U shaped chunk out of the back of the valve cover. I would mount a sub plate to the back of the head that matches the U shaped cutout and mount my sensors there. Especially if it's an encoder or shaft driven sensor. Trying to keep a shaft driven item properly aligned on something like a valve cover that is removed frequently is problematic. Better to have it on a fixed plate.

 

As long as the back of the cams are drilled and tapped there really isn't anything other than clearance between the valve cover and firewall stopping someone from implementing any of these things. The stock Honda K20 has 2 sensors in the rear reading 2 wheels bolted to the cams. They are part of the end cam tower and the valve cover seals against it.

 

I have people interested in this head that want the ultimate high HP L6 build. And I have others that want one because it looks so freeking cool. Best not to loose sight of that. 

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This is a common misconception.  The "waste" gap is on the exhaust stroke and as such is a MUCH easier gap to jump than the one on the compression stroke.  FAR lower pressure and higher temperatures results in a far less dense atmosphere for the spark to jump through.  There is some energy lost vs not having the waste gap, but it's more like a few percent, certainly _NOT_ 50%.  

 

As I mentioned the main advantage here is the increased dwell time for the coils, but you have to go pretty high in the RPM range to see big advantages.  Granted this head should still make power at 9000 rpm, but there are waste spark systems that can still go that high.

You are correct in saying that it's not 50% of the energy wasted on the exhaust stroke but a few percent is also incorrect. I'm sure we could do the math based on the pressure in the combustion chamber and figure the differences in potential required to jump the gap. This is a simple series cicuit. The current through the circuit will be the same. The voltage dropped across the gaps will be different but it still takes over 10kV to jump the gap on the wasted spark. This is absolutely more than a few percent wasted. Twin tower coils are typically higher output to compensate partially for this.

 

I agree with regards to dwell time being a major advantage of a sequential system at higher RPM.

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In two posts I learned more about injection and ignition timing than I ever knew. Thanks. 

 

I don't need any of that for this build. I think if I was going to do it for a customer i would cut a U shaped chunk out of the back of the valve cover. I would mount a sub plate to the back of the head that matches the U shaped cutout and mount my sensors there. Especially if it's an encoder or shaft driven sensor. Trying to keep a shaft driven item properly aligned on something like a valve cover that is removed frequently is problematic. Better to have it on a fixed plate.

 

As long as the back of the cams are drilled and tapped there really isn't anything other than clearance between the valve cover and firewall stopping someone from implementing any of these things. The stock Honda K20 has 2 sensors in the rear reading 2 wheels bolted to the cams. They are part of the end cam tower and the valve cover seals against it.

 

I have people interested in this head that want the ultimate high HP L6 build. And I have others that want one because it looks so freeking cool. Best not to loose sight of that.

 

Since its based off a Honda configuration why not set it up the same way the Honda Cam angle sensor is set up and use the Honda sensor?

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The Cam towers are rotated 180 degrees so the number 5 (rear) tower is in the front and the sensor plate is machined off to clear the timing chain. But you could use the Honda sensors I suppose. But that's not my department:)

Edited by Derek
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TimZ: Yes, I was referring to a single tooth on the cam only to sync which 360, not 6 teeth on which to trigger spark events. 6 teeth would be a huge step backwards indeed!

 

FricFrac and TimZ:You don't need a twin post coil to run wasted spark. You can use 6 COP or CnearP coils and fire them in pairs. You can even use 6 coil drivers instead of 3, if the coils don't have them built in.GM LS style coils come with built-in ignitors and will still be loafing (40% duty cycle or so assuming 2.5ms dwell) along at 9000RPM in wasted spark.

 

If you need extra dwell for boost at 9000RPM, well, you're in the 1%, and if you can't figure out a way to get a cam sync trigger (VR or Hall is what pretty much all the OEM use) in there, you probably shouldn't be building a 9000RPM turbo twincam Z!

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TimZ: Yes, I was referring to a single tooth on the cam only to sync which 360, not 6 teeth on which to trigger spark events. 6 teeth would be a huge step backwards indeed!

 

FricFrac and TimZ:You don't need a twin post coil to run wasted spark. You can use 6 COP or CnearP coils and fire them in pairs. You can even use 6 coil drivers instead of 3, if the coils don't have them built in.GM LS style coils come with built-in ignitors and will still be loafing (40% duty cycle or so assuming 2.5ms dwell) along at 9000RPM in wasted spark.

 

If you need extra dwell for boost at 9000RPM, well, you're in the 1%, and if you can't figure out a way to get a cam sync trigger (VR or Hall is what pretty much all the OEM use) in there, you probably shouldn't be building a 9000RPM turbo twincam Z!

Re-read my post. I said you didn't need to run wasted spark with twin towers but that is the common configuration....

 

It's not about being able to figure out how to implement the sensor. This is the design phase of the head so now is the time to consider how to implement those items into the design.

Edited by FricFrac
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It sounds like you are thinking of sequential injection, as opposed to ignition.  They are two separate and independent things.  In both cases you double the amount of time between events, but the advantages take place on opposite ends of the RPM range.

 

I did blend my sequentials.  Was trying to figure out why FricFrac was talking about "sequential" ignition and got messed up.  I assume it was as opposed to wasted spark, but there must be a more clear term for it.  "Normal" ignition, maybe?  Single coil, wasted spark, coil-on-plug?  Even wasted spark is sequential where it matters so that doesn't seem like a distinction..

 

If ignition timing is based off of crankshaft position, as an indirect measure of piston position, and if lash in the system is important to be accurate, why would a cam sensor be better than a crank-mounted sensor, or even a distributor?  Both of the latter two have lash inherent. Focusing on ignition alone, no cam timing control, or injection.  Just the timing of the spark.  That's accuracy, having the sensor tied to the crankshaft, no chain or gear lash to deal with.

 

Precision might require an optical device, the more signals the better.  So, an optical device on the damper pulley seems like the ticket.  For most accurate ignition timing, regardless of coils.

 

Just trying to break it down to the basics.  There are many combinations a person could put together.  Anyway, as Derek pointed out, the buyer can put whatever system on that they want.

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