Chickenman

Does the factory ECU or Transistorized Ignition box on a 1976 280Z have a built in Rev Limiter?

The more I look into this the more I like it. By keeping the factory Ignition box, I don't even have to play with the the switching of the dual pickup coils in the Dizzy. Plus I get MultiSpark, a Digital Sequential Rev Limiter and a High output Inductive spark with a nice long Spark duration.

That's exactly what I was wondering as well ( Multi Spark issue ). Edit: I guess it helps to read the Instructions... DOH. This couldn't be more simple. The HI-6S ( Inductive version ) solves the whole issue by keeping the original factory Transistorized ignition box. You remove all of the factory wires connected to the Negative coil terminal and connect them to the White trigger wire of the Crane box. It use the factory Ignition boxes grounding signal to trigger the Crane box. That way the factory injector triggering signal is still used and the Factory Tach signal is still used. The white wire is used for a Points trigger or Transistor trigger. Apparently you cannot directly trigger the Hi-6S with a Magnetic or Hall effect pickup. I'm used to the HI-6 model, which is the Capacitor Discharge model.That can be directly triggered by a Magnetic pickup or Hall effect pickup. And Optical pickup or points. In this case it looks like the Hi-6S inductive box is the easier choice. Everything from the distributor side right up to the coil Positive terminal remains stock. So the ECU, Factory Transistorized Ignition and Tach all get a factory signal. The Crane inductive box then takes the OEM ignition box output and converts it to the Multispark discharge at 450V on the Coil Primary side. So essentially it operates as a " Piggy Back " system in conjunction with the Factory Transistorized Ignition Box. Clever work around by Crane..... The Capacitor Discharge versions ( Hi-6, Hi-6R, Hi-6N ) , works as a complete stand alone or replacement Ignition box version rather than a " Piggy Back " like the HI-6S.

I'm planning on adding a Crane Hi-6S Inductive ignition box to my 1976 Datsun 280z. It has the twin pickup coil Federal Model dizzy. I've chosen the Crane inductive box for specific reasons and have been well pleased with the HI-6 CD version on other cars. Question is about install. Where specifically does the ECU get the injector Timing signal from? Is it from the negative terminal on the coil or from the Magnetic trigger in the dizzy? Has any one done an install of the Crane H-6S ( Multi-Spark inductive ignition ) on an FI 280Z and have any installation tips? TIA.

As others have stated. .080" plug gap is too large. While it may run better at idle, the big issue is crossfire in the dizzy cap. All of the High Energy systems made by Ford, GM and MSD etc, utilizing a gap over .050", are designed to be used with a large diameter distributor cap. This does two things: 1: It spaces the wire terminals farther apart so that you do not get cross firing. Depending on distributor rotor phasing, you could run into a situation at high RPM where the mechanical advance is locating the rotor tip close enough to the adjacent terminal, that cross firing can occur. That can cause massive pinging or detonation. On small diameter caps, keep the plug gap below .045" or better yet .040". 2: High energy systems, like an MSD, Crane or even GM HEI, create a lot of Ionization in the distributor cap. This increases the risk of cross fire. Later model Nissan Electronic distributors ( and Toyota and Honda etc ) had special distributor caps with vents to allow fresh air in and ionized air out. They also had special rotors with air vanes on the bottom to create a fan style venting system to get rid of the ionized gases inside the cap. Early distributor caps and rotors did not have these features. Running too large of a spark gap ( over .040" ) , with a CD Ignition and a small cap creates even MORE ionization. Large plug gaps ( over .040" or .045" ) stress ALL of the ignition components a greater amount and greatly increase the chances of cross fire or spark leakage. There is absolutely no need to run over .040" plug gap with any Z motor, IMHO.

Yes..that is more like what I was trying to say.

Devcon Plastic Steel Putty also works well. Used in Porting and polishing of Cylinder heads and manifolds to repair holes and modify port shape. It is not affected by Fuels or Oils. Make sure that you get the standard set time Putty. Do not get the 5 minute Epoxy or the 5 minute Putty. They are different formulations and I do not believe that they are as resistant to fuel and oil as the original Putty. http://www.itw-devcon.co.uk/index.php?/devcon_mro/epoxy_maintenance_repair_and_overhaul_systems/devcon_plastic_steel_putty_a/ Expensive, but worth it. http://www.amazon.com/Devcon-10110-Plastic-Steel-Bottle/dp/B00065TMTO/ref=sr_1_1?ie=UTF8&qid=1427214624&sr=8-1&keywords=devcon+plastic+steel Available in a 500g size as well. Part #10112, although it's a bit more difficult to find.

I can't remember exactly what that large vacuum valve above the left side carb is... but you don't need it. ( Some sort of Emissions device ) I also used to own a couple of early 240Z's. Both 71's with early style SUs. My street car had a local regrind ( Shadbolt M445 ) that is similar in specs to the Shnieder 274. 10 to 1 CR, Ported and Polished head, Cannon 2.5" exhaust system. Revved to 7,000 RPM. Idled just fine at 1,000 rpm, with a pretty heavy " rumpita rumpita " though. Sweeeet. . Took some distributor tweaking though. No AC however.... For the AC throttle kicker you may be better off get an Idle " kicker " solenoid off of a mid 70's or early 80's GM carburated car. These are an electrically operated solenoid that extends and retracts to raise the throttle speed. They are designed for a 100% duty cycle and are very reliable. Cheap too. Much easier and cleaner to install than all of the Vacuum diaphragm junk. Since the factory AC system uses an electrically operated Vacuum valve ( Called an FICD ) to actuate the " Kicker " vacuum diaphragm, you can just take the electrical wire that actuates that FICD valve and run it direct to the GM electric solenoid. Fabricate your own bracket and you have eliminated the most troublesome and unsightly parts ( vacuum parts ) of the AC idle " kicker " circuit.

Thanks, sometimes it is difficult to express in words what you are visualizing in your head. It's why talking face to face is such a better method of communication than E-Mails. You can immediately correct any mis-communications. BTW, I edited part of Post #6 as I made a confusing statement regarding the ECU reading of AFM values at WOT. It still senses them at 100% Flap opening, but of course they cannot rise above 100%. The ECU just reads this as a 100% Load value.

FW...kindly read my Post #15 again. You just repeated what I said in Post #15 and thought I had made abundantly clear in earlier posts. I never said ANYTHING about the fuel and air requirement remaining the same above 4,500 RPM. That is totally incorrect. Edit: AFM flap hitting 100% at 4,500 RPM ( approximately ) is a transition event that occurs when certain Parameters are met . I hope that makes it clearer. I just explained ( to the best of my abilities ) how the AFM senses load and VE. It's a COMBINATION of Factors that just HAPPENS to occur at around 4,500 ( sic ) RPM when engine is under FULL LOAD, WOT and Higher RPM's. Please forget all this light rpm cruise and driveway stuff. That is not what I'm talking about at all. I'll try one more explanation..... but it's getting late and I'm getting tired. 1: Vane style AFM's all lose accuracy as they near 100% opening. This is purely due to the mechanical limitations of the design. It is a well documented fact. Engineers who deal with instrumentality recognize that Analog measuring devices are always the most accurate in the middle sweep of their range. That is also a fact. 2: Because the engineers know that the Vane style AFM is not accurate enough near 100 % opening range, they have to design a work around. They also want good sensitivity at lower air-speeds to provide good drive-ability and fuel economy at part throttle and cruise. Therefor they design the AFM slightly on the small size, relative to the engines theoretical air displacement. This gives good resolution of AFM values at part throttle and cruise...just where they need it. 3: Once you get to 4,000 RPM ( approximately ) and go full power. IE: 3rd or 4th gear climbing a long hill at WOT... the engine wants a fuel curve of 12 to 12.5 to 1. This is a Full Power Enrichment Curve and it is pretty constant for any 4 cycle, normally aspirated Petrol engine. IE: So you downshift to 2nd and mat it to pass the Logging truck up the 15% grade. Wham.. 4,000+ RPM AFM meter flap goes to 100% open indicating 100% maximum engine load. TPS hits WOT contacts. ECU says to the Fuel injectors " Open the flood gates boys. We need to RICHEN things up big time and make some POWER!! " AFM stays at 100 % open and ECU maintains a Full power enrichment curve based on 100% load signal from AFM and adjusted per rising RPM. Now you're past the logging truck, pulling 6,000 rpm in 4th and you roll out of the throttle, but still maintain 6,000 rpm. As you roll out of the throttle the Volumetric Efficiency of the engine decreases dramatically due to the partially closed Throttle Blade and Airflow through AFM decreases. Hypothetically it may only be 70% open and WOT contact is now open. ECU sees this and reduces fueling accordingly, while still maintaining a safe AFR, as the engine is still twisting 6,000RPM. 4: Scenario 2; You have lots of space and leave it in 3rd to pass the Logging truck up the same hill. L28's have lots of grunt. 3,000 rpm, TPS indicates WOT but AFM only shows 60%. ECU says to injectors... Hey boys we need some more fuel...but don't go crazy yet. This stage is often called Partial Power Enrichment. As RPM's rise so does the AFM opening amount and the amount of Fuel required. Once the AFM hits 100%, the WOT switch is still closed and RPM's rise past a certain point, then the ECU will demand Full Power Enrichment based on a hard coded Full Power mapping. IDC will rise with RPM till Redline. . Tired now.. going to bed.

That is entirely correct. This is old technology and it does not have a a modern Digital feed- back system to control idle speed . There is no way for the analog ECU to compensate for extra load from imposed by things like alternator drag etc. The factory AC system uses an Vacuum " kicker " pot that mechanically raises the idle via a simple on/off switch. It is an archaic design... but that's what you have. Add to that a wider overlap cam, that may be slightly fouling plugs due to the " Tune " not being optimized for the Cam... and basically you have a Car that is affectionately known as having " Character ". It's going to have " quirks " and will never run like a box stock Honda... so don't expect it to. In other words... you may have to live with it. Now a sharp.... REALLY sharp... tuner may be able to stabilize the idle a bit more. But those type of guys are few and far between these days. Most of the really sharp Crab tuning guys are in their 60's now. It's a dieing breed...literally!! BTW.. I have a 1976 280Z running factory ECU and Factory AC. I have the equivalent of a Shneider 280 cam in it. The car idles pretty consistent at 1,000 rpm when warm... but it took a lot of tweaking. When the AC kicks in it's another matter. Still haven't got the stoopid AC vacuum kicker adjusted right. It's an archaic device. I just live with it.... until I get my MegaSquirt Pro system, with WB O2 sensor, and the Option for a modern GM style Idle air valve.

I get 28 MPG ( Imperial gallons ) on my 1976 with 3.90 gears and a ZX 5 speed. So you should be able to get a lot better than that. Personally I would send the stock injectors to a company like http://injector-rehab.com/shop/home.php and have them cleaned and balanced. If your " new " injectors are rated higher than the originals, then no amount of futzing about is going to correct things. That will throw the whole fuel curve out of whack. I'd also invest in a WB AFR meter such as an AEM. These are reasonably cheap and you get real time AFR mixtures with no guessing. Invaluable tuning tools.

Sorry, I've not made the basic premise and explanation clear enough. BTW, this is not all some " theory " I've made up by myself. It all documented in various Technical books and SAE papers on how Vane style AFM's operate. The Vane style AFM is a way of calculating engine Load or VE. Similar to what a MAP sensor does. Which incidentally, is why in the MR2 Turbo article the Vane Style AFM was replaced with a Device ( VPC ) that emulates a MAP sensor and why I included that article in the discussion. You're not understanding the 4,500 RPM (sic) limit correctly. When the AFM is said to " Max out " at 4,500 rpm... it is NOT maxing out purely because of any RPM limit . It's maxing out from AIRFLOW Limit because you ARE under WOT, Engine load is high and Engine RPM is high. The result of this " combination of factors " is that AFM Flap is open 100%. Thus indicating maximum engine Load. A Vane type AFM is a Load calculating device. Similar to a Manifold Absolute Pressure sensor. MAP's will indicate full engine Load well before maximum engine RPM. The Vane type AFM does exactly the same thing. It just so happens that these conditions occur at approximately 4,500 rpm.... Above that RPM , if you're still going up a long hill at WOT for example, the AFM will indicate 100% engine Load from 4,500 rpm all the way up to the Red Line. The ECU will calculate fuel accordingly. So if you keep your foot in it up the Hill, the ECU see's 100% Engine Load, increasing RPM and provides maximum fuel enrichment. The actual figure could be 4,500 rpm, 4,527 rpm, 4,6058 RPM, 4,800 RPM or any figure in between. 4,500 rpm is just the arbitrary figure given, that indicates when the AFM flap will hit the 100% value due to airflow, when engine is under high throttle and high load conditions. Of course the AFM is not going to Max out when you wing it in the Driveway with no Load. I thought that was well understood. I hope this clarifies things.

I think the ECU Bible or one of the articles by " Brapp " ( ??? ) mentions the frequency counter and voltage reference. Should be dead easy to incorporate into a circuit design. I believe that " Brapp " and the Bible also mention the 4,500 to 4,800 rpm limit for the Vane style AFM. I'll look in a couple of days for the link when I have more time.... I've got some books on modding Fuel Injection systems and one of the Project cars was a 1991 Toyota MR2 Turbo ( Factory stock ). Same style of Analog Vane AFM that we have. Seriously hard to modify when Boost is increased, but there are specialists who do it. One of the main issues ( On the Turbocharged) MR2 was that the ECU was Analog and it switched to Speed Density once RPM reached a certain point. AFM again was maxed out at around 4,500 RPM or earlier with more boost than stock. Analog is just so difficult to work with. You can't re-program Cells like a Digital ECU. It's all about tweaking resistors, Pots and other such nonsense. Much easier option is to go with a modern Digital Stand-Alone with Wide Band and fully programmable, but it was interesting to see just how much they could re-engineer the OEM Analog system. They did some pretty serious Mods to that poor Mother Board !! Modifications in article went all the way from Stock Analog ECU with Vane style AFM, to a VPC ( Vane Pressure Convertor ) that eliminates the restrictive and troublesome Vane style AFM to a MAP sensor style Piggy back with a built in Microprocessor that can be programmed to change the fuel curve. They even went as far as converting the original Analog motherboard with a Plug-in Daughter board to make the factory ECU digitally programmable. Eventually, after much fiddling and farting about and raising of Power levels...they ditched the whole mess and went to a Motec 48 stand-alone EMS... which is what they should have done in the first place, IMHO. It was an interesting read though.... 16 Stages that went from stock 165.2 RWHP to eventual 471 RWHP with a 2.1 stroker and Motec 48 EMS. And documented all the trials and tribulations.... all 21 pages!! Edit: Book is " How to Tune and Modify Engine Management Systems " by Jeff Hartman. ISBN 0-7603-1582-5 . A great technical book on Modding old and new EFI systems. It's a good read...

Even fairly modern systems such as the Bosch ME5.2 ( Narrow Band O2 sensor ) go into " Open Loop " at WOT above a certain RPM. The MAF sensor has no effect in " Open Loop " . It's a very common strategy in ECU mapping. Hitachi and Nippon-Denso do the same thing with Japanese ECU's. Narrow Band O2 sensors have a very limited range. They are only accurate in a narrow range close to Stoich ( 14.7 to 1 AFR ). The NB O2 sensor cannot measure mixtures accurately enough under hard throttle, high RPM's and Boost. The richer " Power " mixtures are outside of the sensors measurement range. So the ECU's just goes " Open Loop " and relies on a set fuel Mapping to calculate IDC. No input from the MAF sensor at all. My 1998 AEB engined Audi A4 1.8T does not even have a MAP sensor. ( Stock design ). It only has a MAF and NB O2 sensor. At WOT the ECU goes Open loop ( Speed Density ) by design and doesn't even use the MAF input. Yet it runs very happily to 7,200 rpm with about 14 lbs boost ( 18 lbs at 6,000 RPM ). And that's with only a Stage 1 chip. Drag Racers on some of the forums I frequent have made over 900 HP out of VW/Audi engines, using stand alone ECU management. Speed Density systems with no MAF sensors or AFM's at all. Modern F1 engines from the early 1980's through current 2014 have never used any type of Airflow Meter. All fuel maps are made based on MAP sensors, RPM's and TPS position. That's all the input they need. Race engines are nearly always at WOT. And WOT is very easy to calculate fuel flows. All using Speed Density systems.

It really doe's work that way FW. There is a correlation between the TPS switch and engine RPM. The TPS has WOT contacts and goes to a different Map ( Full Power rich ) when it sees the WOT switch close. Fuel injector duty cycle is relatively easy to calculate at WOT and varying RPM's. It's varying loads at part throttle and mid-rpm's that get tricky. Edit: Don't forget, at 4,500+ RPM you are nearly always in a WOT, hard acceleration condition. You don't cruise very often at 4,500 RPM or vary the throttle much. Anything above 4,500 RPM is a Full Power Mode and wants around 12.5 to 1 ( +/- .5 AFR ) and that is fairly constant. Everything works around BSFC and once you set that, you really do just increase the Fuel amount based on RPM. This on Normally Aspirated engines of course. Forced Induction needs Boost compensation as well. Edit 2: The AFM meter maxing out early will have no effect on supplying more fuel at high RPM's and WOT. The ECU ( on our cars ) will be in " Open Loop " under those conditions and will not be even reading the AFM values. Engines at WOT, heavy load and above approx 4,000 RPM all all need a Full Power Enrichment AFR ratio of about 12 to 12.5 under those conditions. A simple full power fuel map can calculate the IDC based on rising RPM's to maintain that calculated AFR. Vane type AFM's, on all cars, become less sensitive as the flap nears fully open. They start losing hysteresis. For that reason, manufacturers go to an RPM based Fuel/Timing Map once the flap reaches 100%, TPS indicates WOT, and RPM rises above a certain point. You can have VERY accurate fuel mapping done with just a TPS switch, Coolant sensor switch, and RPM sensing. Throw in a MAP ( Manifold Absolute Pressure ) switch into the equation and you have a Speed Density System which works very well on cars with big cams. GM used it successfully on it's 86 to 1989 TPI system. They only switched to a MAF measuring system around 1990. Don Devendorf developed 900 HP on the Electromotive 280ZX Turbos back in the early 1980's with a Speed Density System that used no Airflow meters. And that was on a Turbo with varying boost levels. A Normally Aspirated motor is much easier to calculate IDC and fuel curves than a Turbo motor. . Vane type airflow meters were never accurate enough at high airflow rates to safely calculate IDC by themselves. MAF meters with hot film sensors changed that and are a lot more accurate, but even then, at WOT and high RPM some fairly modern 1990's ECU's go into Open Loop with the MAF sensor and NB O2 sensor cut out of the loop and the ECU relies on a set " Power Map " for fuel and timing. MAF sensors ( Hot Film style ) and WB O2 sensors allow the ECU to stay in Closed Loop all of the time. Even then, some Manufacturers will still go to " Open Loop " at WOT. It's a primarily an Engine Safety Strategy.

And if memory serves me correct the AFM only provided mixture measurement and correction up to about 4,500 rpm. After that the ECU calculates IDC entirely based on RPM, TPS signal and CTS.

That statement is correct, as far as Spring Rate, but you may have taken it out of context in relation to how the Spring Load curve affects AFM flap operation. Spring Load is a factor of Spring Rate + Spring Pre-load + Spring Compression Height. Spring pre-load doesn't affect Spring Rate...but it does increase total spring resistance or Spring Load at a given point. Take a typical coil spring that is rated at 100 lbs/in and throw it spring a spring tester. At 0" compression height there is zero resistance ( no load condition ). At 1" of compression you should have 100 lbs of resistance. At 2" compressed height you should have 200 lbs of resistance. At 3" compression you would have 300 lbs resistance...and so on. Now add 1" of pre-load to the spring. Reset the spring height pointer to zero. At 0" indicated compression height you would have 100 lbs of resistance. At 1" compression height you would have 200 lbs of resistance. At 2" compression height you would have 300 lbs of resistance.... and so on. So increasing spring pre-load on your AFM spiral spring is going to change spring resistance or Load in a linear curve, throughout the entire sweep range.

Thanks for that. I'm about to put the 280Z back on the road after Winter hibernation and exhaust smells in cabin were a top priority. With new Tail light seals and the hatch panel seal, perhaps I won't reek of exhaust fumes after a drive!!

Yes, going from a 50 to a 60 idle jet is a pretty big jump. A single step is 5 numbers in size. Interestingly, on 44 mm Mikuni Solex carbs with 34 to 38 mm chokes, the #55 usually works out best from my findings. . The OER is based on the Mikuni Solex. I believe it uses the same Emulsion tubes and jets.

For idle, would adjusting the AFM air bypass to make the car run lean with zero extra resistance work?. Then you could add some fuel with the Pot to richen it and get Stoich or more at idle. Adjusting the AFM tension spring to make the car run lean throughout the mid-range and high end, then add fuel with the Pot should work . Or am I missing something?

The bible is correct. Early L24 engines had 33mm exhaust valves. and 42mm Intake Valves. Installing 35MM exhaust valves with a high lift cam requires slight bore notching for clearance. The valve center-line is offset to place the larger Intake valve closer to the center-line of the combustion chamber, so it normally clears the cylinder wall no problem. Installing 44 mm Intake valves and a .500" lift cam on an L24 will clear the cylinder wall " Physically " if my memory serves me correct. Bore notching on the Intake side is done purely for " un-shrouding purposes. DOUBLE CHECK that clearance...it's been a long time since I've assembled an L24!!! Best way is to install some lightweight checking springs on the valves and assemble with retainers. Bolt the head to the block with an old gasket, flip it over, then physically open and close the Intake and exhaust valves while looking down the bore. Confirm the valve to piston wall clearances visually. Use a dial indicator to measure valve lift. Give at least .090" clearance over maximum valve lift specs to allow for Valve float in the case of over rev. As I said. I'm reasonably sure that the 42mm and 44mm Intake valve clear the cylinder wall at all lifts. But check it to be sure. The 35mm exhaust valves do not. They can tag the bore edge. Of course you're going to check Piston to Valve clearance as well.... correct?

I'm in Canada, But my " guy " at Nissan says he can still get them from Japan. Still a good number and active for the 12033-A8620, the latest super-cede in Canada. I didn't check over-sizes. I have seen NOS of Nissan rings repackaged as some bizarre brand when I had my engine rebuilt in Portland. I'll try and dig up the name. They were definitely 100% Nissan rings. Or a bloody good copy, right down to the Nissan Cello bags and factory Nissan identification markings on the rings themselves. Something weird like " Dr Japanese " or something.... Edit: Doh... Just give Jock Rhodes a call at Bill's Datsun Shoppe in Clackamas Oregon. He has a huge stock of NOS Nissan parts. Depending on your engine year and model, he may have genuine Nissan rings sitting on his shelf. Not the Bizarro re-packaged stuff ... but genuine Nissan NOS. Jock Rhodes - Owner Bills Datsun Shoppe 16087 SE Evelynn St, Clackamas, Oregon 97016 Work; 503 656-0756 E-Mail: jockracing@comcast.net

Always go with the ring manufacturers specs. The rings could be made out of a different material that has a different expansion rate than the Factory rings. Ring material can be regular Iron, Ductile iron, Steel or Stainless Steel. And various alloy combinations in between. All have different expansion rates and different uses. Same with pistons. It's now 2015... not the early 1970's and technology changes.

Grant is a very common name in the Automotive Industry. They've been around since 1922. Very popular with machine shops that build " Meat and Potatoes " Domestic engines. Main stream rings generally for stock or Industrial engines. Nothin' fancy, but they've been around a lot longer than Manufacturers such as Total Seal. Hastings has been making Piston rings and other automotive parts since 1915. I don't like their oil control rings either. I normally use Sealed Power Moly rings on SBC's. Nissan rings on Nissans.