Captain Obvious

You're right Jeff. I currently have the N47 head and it sounds like I've got round exhaust ports unlike what I said above. My desired plan on the exhaust manifolds would be to keep the 83 manifold on the new engine and use the O2 sensor location for a wideband some time in the future as suggested earlier. The reason for the engine swap? My current engine runs fine, but has dubious quality: My oil pressure is good but not great. My compression is good but not great. I think I've got a minor head gasket leak. I've got a couple stripped valve cover bolt holes from an overzealous PO. I've got a stripped distributor mounting hole on the timing cover from a PO. I've found one or two glass beads coming out of the oil pan on two successive oil changes. Bottom line is there's a bunch of small stuff wrong with it, none of which is known to be insurmountable at this time. But I'm figuring that if I'm going to invest time and money in a motor, I could start with a better base. Of all the items above, I'm most worried about the head gasket (and the glass beads). My PO did a head gasket right before I bought the car and I think I've still got issues. I've seen pics of hairline cracked N47's and I'm thinking that might be what's going on with mine. I know the different head/block combos have been talked to death and I know the answer to the question I'm about to ask is available out there if I were to search for it, but... Off the top of your head, do you know what compression ratio I would end up with if I were to plunk my current N47 on my new F54 block? Assuming the head isn't cracked of course...

Cool. I like the idea of the injector driver chip. Assuming the availability is stable, I think they'll make for a better end result. So, if you would like another set of eyes on the schematic and/or board layout, I'd be happy to have a peek. I'm probably not previously familiar with any of the parts you're using, but that shouldn't stop me. PM me if you're interested.

You guys have pretty much nailed my thoughts... All things considered equal without any other input, my plan would be to strip down the 83 and redress back up looking like a 77. A little simpler, a little lighter looking, and certainly more authentic for a 77. But I'm happy to give up on looks if there are tangible reasons such as performance to do otherwise. My 77 is square exhaust port, but I'm running a header that the PO installed. I was planning to switch back to a cast iron manifold of some sort as part of this job, so in other words... I know I've got some exhaust work to be done no matter what route I proceed on. I don't like the exhaust work from my PO and I was planning to rework everything anyway. So it sounds like there are some fitment issues with the ZX intake in the earlier years, and no known performance gains to be had by using the webbed manifold? Zed Head, I'll take a look at that intake manifold taper you mentioned and the location of the throttle body. I didn't notice either of those. There are six years of technological advancement possible between my 77 and the 83... You would sure hope that there were some improvements, right?

Way cool. Never seen anyone cut into a gas tank before. Thanks for the view!!

Nothing? All these people building engines and nobody has any ideas? Wrong forum? Is this a hybrid Z kind of question?

Bluetooth? IR? Seriously though... I would just put the connector anywhere on the unit your board layout will allow. Anyone who knows enough to mess with their engine in depth enough that they need a custom tuning set-up better be able to take the kick panel off to get to the connector. Drive around for a little while until you get the tune just right? Seems like a small price to pay.

I'm going to replace the motor in my 77 Z with one from from an 83 ZX and I'm trying to figure out what parts I should use from the 77 and which parts I should use from the 83. Two of the specific areas of decision making are the intake and exhaust manifolds... The 83 intake manifold is webbed while my 77 is not. Anyone know why Datsun started webbing the intake manifolds? Is that for heat? Strength? Something else? Given a choice, which is better? The 83 exhaust manifold has an O2 sensor while my 77 does not. Are there performance gains to be had by switching over to the ZX fuel injection controller that uses the O2 sensor or does it not really matter? Basically I'm trying to build the best motor from the two and I would like to keep it looking like a 77, but if there are compelling reasons to use 83 specific parts beyond block, head, timing cover and oil pan, then I'd like to hear about it.

I'm going to replace the motor in my 77 Z with one from from an 83 ZX and I'm trying to figure out what parts I should use from the 77 and which parts I should use from the 83. Two of the specific areas of decision making are the intake and exhaust manifolds... The 83 intake manifold is webbed while my 77 is not. Anyone know why Datsun started webbing the intake manifolds? Is that for heat? Strength? Something else? Given a choice, which is better? The 83 exhaust manifold has an O2 sensor while my 77 does not. Are there performance gains to be had by switching over to the ZX fuel injection controller that uses the O2 sensor or does it not really matter? Basically I'm trying to build the best motor from the two and I would like to keep it looking like a 77, but if there are compelling reasons to use 83 specific parts beyond block, head, timing cover and oil pan, then I'd like to hear about it. Should I be asking these questions in the first gen or second gen forums? Maybe I should post in both...

I know it adds no technical value to the thread, but there sure have been some very creative and entertaining additions to the fish/wife/girlfriend/pole conundrum discussion. Thanks for the chuckles!! :laugh:

I don't know if the whole assy's swap, but I do believe there was a design change to the electrical switch part of the assy that resulted in two non-interchangeable versions of the electrical switch. Are you trying to fix an electrical issue, or a mechanical issue? (Or both?)

No, I think he was suggesting that the fish give his girlfriend a pole and then.... Uh... No, that can't be right either.

Check out the venturis on that beauty!! :kiss:

The nipple on the top of the float bowls is a vent, not an overflow. Yes, in the event of a float valve malfunction, a properly connected tube would direct overflow gas into the air cleaner box instead of spouting straight up making a dangerous flammable mess, but that's not the intent. The intent is that the float valves do not malfunction. However, there is still a need to vent the upper part of the float bowl even when the float valves are working properly and venting it to the clean side of the air cleaner is the proper location for it. Problem is (as you have discovered) that the 260 air cleaner backing plate doesn't have nipples specifically for those vent tubes like the 240 base does. There should be a smallish nipple about middle top of the 260 backing plate. Used to go to the throttle opener. Use a "T" there and port to both carbs. If you aren't using the throttle opener deceleration system anymore, that port is surplus. Question though... The 260 air cleaner doesn't naturally even bolt up to the round top carbs... Are you using adapters?

Haha!! Finally!! That took way longer than it should have! (It was 38 by the way... :laugh: )

How many drops is this for you, Lieutenant? Me too. And I don't use the clutch to take it out of gear. Once you slow down to the point where the gear train is unloaded it slips out easily.

That's neat stuff. I've wondered about that. I like your conclusions as well. Makes sense for some small amount of additional mixing and smoothing of transients by the time gasses reach the light of day, but it should still be FIFO for the most part. Cool!

I found the first generation Integra (85-89) headlight chime to be quite polite. Not the key in the lock warning, but the headlight chime. The key left in lock is your ubiquitous "beep-beep-beep-beep", but the headlights are this very polite "bing-bong" thing. Sounded like they even used mechanical bells struck by a clapper of some sort instead of it being electrically generated. Don't know if you can buy the module aftermarket, but if you're junkyard hopping, it might give you another alternative to try. Might also be on later modules as well, but I don't know for sure.

Yeah, the original ECU is a highly trimmed black box full magic and voodoo. I didn't do a lot of reverse engineering either, but I did get through the output stage and the "After Start" enrichment section. Tough part is there are three IC's in there and I have no visibility into what's inside the cans. They predate DIP packages, and there's no discernible standard like "opposite corners are power and ground". So for the sensor inputs, I've traced the circuits up to the IC's, but once they connect to one of the IC's, I hit a wall. I hooked the ECU up on the bench with a scope and a sig-gen and tried to get it to speak, but no luck. I just stuck in fixed resistors for the sensors, but I must have missed something because I couldn't get any injector pulses. Then I ran out of time on that project and moved on to something more pressing. My car runs well so it was an academic investigation only. But think about this... All analog. Instantaneous continuous response. Smooth transfer function. And has been bulletproof reliable since 1977.

All that stuff I said about big current not flowing through the fusible links? Forget all that... I bet one or more of your fusible links fried. You should double check them to be sure. (Glad you found it!!)

I don't know anything about the supply side as I'm jut datasheet shopping. Never actually tried to buy any of the injector drivers. From fuel injection to industrial chicken skinner... You'll have to walk me through that one over drinks sometime. FYI, the original ECU used a pair of NPN Darlington BJT's to drive the injectors. Three injectors per driver pulled to ground. They segregated the ground for these drivers from the rest of the circuitry so the switching currents didn't mess with the analog front end. Separate analog and digital grounds inside the ECU.

In theory, shorting the battery post right to ground through the hold-down bracket should not have put any current through any of the fuses or fusible links at all. The loop would be: positive battery post to the body through the hold down bracket body into the harnesses through all the ground wires connected to the body the ground wires back to the battery negative post through the negative batt cable and/or the FI ground connection Of the two ways to get back to the battery negative post the negative FI connection is clearly the weaker link. I'd start there and at the body to block ground tie connections. I bet you burned up a ground wire or one of your FI components that connects to ground. If stuff got hot enough that you got smoke, there should be visible damage somewhere. Look at the smaller ground wire off the battery that goes to the FI system. If it's not there, you should probably seek the assistance of someone in your area who really really knows the FI system because it's probably gonna be a tricky hunt. I didn't look hard, but quick scan shows the FI main relay, thermotime, fuel pump relay, fuel pump control relay all connect to ground. On edit... I see that lenny types faster than I do!

Haha! If you weren't so far away, I'd put em back on for ya. I bet I could convert you to the dark side...

Wow... The temp was at "E"??? You must have been really flying!! :laugh:

Fortunately??? Wuss.

Makes sense. Moore's Law historically has been as accurate as Murphy's Law, and if memory space and processor cycles are cheap enough to burn off, then why not, right? However, for this application my plan for all assy wasn't driven so much by cost or speed, but for reliability and predictability. I wanted to know exactly what was in all the registers at all times. I'm out of touch and I'm comfortable with that. I always wrote the low level interface code for the stuff I designed, but I've never been a software jockey. I've done just enough to be dangerous. You're clearly going a lot more complex than I had planned to do. I was thinking just model the transfer function of the original ECU and that's it. Let's see... Of your vars above, the only things I need to know are AFM, IAT, CLT, TPS, and Pulse_Width. Everything else was for phase II. So I don't want to hear about it when your interrupts hiccup once every few days and you can't track it down. Are you sure you main loop will be able to keep up at 100ms worst case update at redline? You got a pulse width module timer in that beast so you don't have to babysit digital output pins to drive the injectors? About the battery voltage... The original ECU tweaks the injector pulsewidth WRT battery voltage. Higher voltage opens injectors faster and all that. However, if I were doing this, I would probably switch to one of the pre-canned injector driver IC's that has the voltage correction built in. That would be one less thing to worry about and would be much more consistent than the stock system or trying to make that adjustment yourself. If you use something that has the fast opening peak/hold current control as well, then you can get rid of the injector resistors and run Vbatt right to the high side of the injectors. The PIC stuff was intriguing. I did maybe three projects with them, and it sure was a paradigm shift from the Motorola stuff. It took a little sideways thinking to figure out that branching stuff, but once I got a handle on it, I really liked it. It's like Whaaaat? Skip the next instruction? What the crap is that? You have to use goto's? I was always taught that goto's were evil. You need to embrace the goto. But guess what... The newer bigger PIC stuff has conditional branches just like Mot. Feels like home.