Zmanco

Here's my situation: L28 block recently rebuilt with flat top pistons Mild cam (Delta cams regrind .480" 284/284) 6:1 header and exhaust stock EFI intake manifold with 60 mm TB Megasquirt N42 head My thinking so far has been that to get much more power I'm going to have to begin spending some big $$$ on head work and intake manifold. My inclination has been to stop here with the L28, focus more on my driving skills on the track, and when I eventually decide I need more power, go LS1 and T56 (more bang for the buck). But... I can't run full max spark advance (35 degrees) because of the poor quench characteristics of the open chamber N42 head and high compression. I enjoy wrenching I have a hard time leaving well-enough alone So I'm wondering if maybe I should pull the head and do the following: - replace the valve seals (they could use it, but they're not a problem yet) - unshroud the valves - do some very mild porting of the intake/exhaust passages I've been watching a lot of the threads here on porting and believe I have a good idea of the basics. I have a scrap head to practice on, but don't have a flow bench. My questions to the experienced head porting guys are: 1) Does what I'm describing sound like a stage 1/stage 2 port job? 2) Roughly what kind of additional power am I likely to see? 5-10 HP? more? 3) What is your sense of how much unshrouding the valves will lower the CR? I'd like to get to the full 35 degrees of advance I see others running. (I remember a great thread where the topic of which was more important: CR or spark advance was discussed, and BRAAP made a strong case for advance over CR.) 4) Am I going to see enough of an improvement to make this worth it? Or should I stick with my original plan to work more on my driving skills? I'll stop here and wait for some feedback. TIA!

Mine has had a half-cap on it for more than 5 years now (installed by the PO) and unless you look closely, it's easy to miss the seam and think the dash is stock. Not really a repair, but easy to do and reasonably priced. And apparently durable too.

With SUs the mixture is determined by the profile (taper) of the needles. With a more aggressive cam the profile of the stock needles is no longer going to match the mixture requirements across the rev range. Tuning that would be done by replacing jets on Mikunis or Webers is done instead by grinding the needles. I found that once I had a good mixture at WOT at high revs the mixture at idle became too rich. This was the main reason I gave up on the SUs - it was too hard to tune across various engine conditions for a non-stock cam. That said, I suspect the stock SUs would flow enough air for just about any reasonable L28 built for street use. There's a famous story of Norm who used to run 12's with SUs... I'm sure he was a master at grinding needles.

It looks like it's a Canadian show. Anyone know how/where to find it in the US?

Some humor for a Friday ... http://youtube.com/watch?v=Bd876iqGdT4

Ha! I hope that it's at least faster now!

I initially mounted through the radiator fins, but a year later had 2 of the tubes leaking from the top. After the repair I fabricated this setup. The fans are held flush against the radiator without putting any stress on the tubes. I had to cut a little of the lower bracket for a few inches where it passes in front of the AC compressor. Without AC it wouldn't have been an issue, but without AC, I could have used the Taurus fan and saved time and $$$. BTW, the biggest drawback to this approach is the lack of a fan shroud. I suspect that's why the temp goes up in traffic with the AC on. The air is only passing over the fins directly in front of the fans. Even with 2 fans, there is still a lot of the radiator that has very little air flow over it when the car is moving slowly. Without the AC compressor there would have been enough clearance to mount the taurus fan offset to the driver's side. If you don't have AC, I'd strongly suggest you consider this approach. Plus, IIRC, the taurus is a 2 speed fan so you can set it up to run on the lower speed most of the time, and still have an option for high speed when needed.

Most of the aftermarket efans don't move as much air as the taurus fan. But on my 73 with AC, the taurus fan was too deep to fit so I couldn't use it. So I went with 2 x 12" from ebay mounted side by side. I've had this setup for two summers now and it works great with one exception: can't drive in stop/go traffic in the summer with the AC on without the temp climbing too high. Oh well... it's not a daily driver anyway. FWIW, I'm using the 4 row MSA radiator. Edit: I went with the 2 x 12" instead of a single 16" for three reasons: 1) they weren't as deep so fit better. 2) the motors are offset from the center of the radiator so don't come as close to the spinning studs on the water pump that used to hold the fan clutch. 3) In case one fails, at least I still have some cooling. Edit #2: You may want/need to upgrade your alternator. The stock alt on an early Z won't put out enough current at idle to run the fans and headlights without having the battery "contribute". On your later ZX it might be better, but be prepared to upgrade if it isn't.

I suspect it's real too, although I'm bothered by the scenes where he turns off the main roads and is going through narrow streets. He is often running through the gears into 4th gear which at the top of the rev range has to be in the 75mph or greater range. I find it hard to imagine that is how fast he is traveling in those narrow streets. Or maybe he was just especially brave that day - balls of steel ...

Just keep in mind that there are very few performance brake pads available for the S12+8 caliper. With the S12W, you can use 300ZX pads and grind off the tab. This opens up a lot of choices for track pads that don't exist for the S12+8. (Remember, these calipers came from a Toyota 4x4 truck and the pad materials available reflect that.)

It might simplify things, but I don't think you'll have enough rear brake bias as the rotors for the 280zx rears are smaller in diameter than the 240sx. I can't help you with bracket drawings as I bought mine from Ross at Modern Motorsports. Everything bolted on as expected.

The more brake you have up front, the more you need in the back. In fact, you really want to land up with the rears locking up a little before the fronts, so that you can then tune that out with an adjustable prop valve ultimately resulting in the fronts locking up first. I went with the Toyota 4x4 vented up front and 240sx in the rears and the only way I was able to get enough braking in the rear was to go with a pad material in the rear with a higher coefficient of friction than the front.

Jon, do you think there would have been a problem if the wires had been in good condition? I'm wondering if the primary issue is wires with worn insulation?

Does anyone have any objective data that supports this concern (that bundling the wires together will cause problems with coupling of the spark to other plugs)? I'm familiar with the phenomenon's affects but wonder if enough energy is coupled to the unintended wires to actually cause a large enough spark to cause ignition at the wrong time in another cylinder. I'd be curious to see data that shows this to be an issue with real ignition systems (as opposed to the theoretical discussions we had in my physics and EE classes). BTW, I'm NOT saying this isn't a real issue (sorry for the double negative), but so far all we have are a few anecdotal examples that claim it can be a problem, and also a few claiming that bundling wires doesn't cause a problem at all. In the spirit of hybridz, can we get some objective data? And in case anyone is wondering, yes, I have spacers on my wires

Matt, that's progress at least! If you have access to a spare relay, swapping it would be the easiest/fastest to confirm that the relay is bad. I will say that I've never seen a relay fail such that it shorts to ground, so I'm suspicious that the problem might be with the wiring between the relay and the horns. You could test the relay if you have a DVM. Measure the resistance across the contacts (from the diagram I posted it looks like it should be the contacts that correspond to the green and green/red wires on the socket). With the relay removed the resistance should be infinite. Then measure the resistance across the coil (should be the other 2 connectors on the relay). It should be somewhere in the neighborhood of 100 ohms. You could also check continuity from the green wire at the socket to the connectors at the horns. Also, with both horns disconnected and the relay out of the socket, measure resistance from the green wire at the socket to ground. If it's anything other than infinite, there's a problem in the wiring between the relay socket and the horns - probably something has cut through the insulation and grounded it. I could go on with scenarios, but if you look at the wiring diagram, you can easily come up with a bunch of scenarios to test that will eventually isolate where the fault is. Keep at it - I'm very curious to hear what you find!

I've never had to trouble shoot mine so don't know where it is. I'd start with the relays under the dash on the passenger side, just ahead of the door opening.

I grew up in the Bay area, got married, and had my daughter there. When she was 7 I was offered a relocation to the Denver area by my company. I took it and don't regret it at all. BUT .... What I didn't consider was what my job prospects would be when I left my employer, which I did about 2 years later. Since then (about 7 years now), I have yet to work for a company based in Colorado. I've been fortunate to find jobs that didn't require me to relocate, but my choices were much more limited. My skills (technology sales and marketing) are best suited for areas like the Bay area, and I was a bit surprised at how few opportunities there were for me at my level of experience in the Denver area. From your post I suspect you're earlier in your career than I was when I moved, and hence you'd likely have more choices for jobs if/when you left the one you'd be moving for. I can't tell you if you should move, but you should look closely at what types of jobs are available for you in Reno TODAY in the event that the worst thing happened and you found yourself looking for a new job after you moved. If you don't see much opportunity, then Reno might not be the right place for you. Good luck!

I don't think the white wire is the issue as it is just providing power from the battery to one side of the fuse. Earlier you said that the fuse blew as soon as you put it in, even with the horns disconnected (make sure BOTH were disconnected). Find and remove the horn relay. If the fuse still blows, then focus on the wiring between the fuse block and the relay. If it doesn't blow, then focus on the wiring between the relay and the horns. I suppose the relay itself could be bad as well - let me know what you find out and we can go from there.

Sorry, I missed that you found it from the datalog Have you gone back to the datalog and looked at all the other signals such as MAP, O2, CLT, batt V, etc? If the MS unit itself is functioning properly, then one of the other parameters should be changing at the same time as the PW. Just a thought, are you running the latest version of MS firmware? You might reload it anyway. I've seen posts on the MS site where people have solved this type of random issue with a reload. I'm a bit skeptical that this would help, but if you run out of other ideas, it's something else to try. Good luck!

I would suggest you datalog it, and then look at what else is changing when the PW jumps up. For example, noise on the MAP signal might make MS think that you've suddenly go a lot more air flowing into the engine.

A poor ground connection or not grounding everything to the same point can lead to noise. A bad alternator could do the same as well. This is a hard one to trouble shoot without a lot of trial and error. But if you're not seeing resets and the PW and ignition advance values are consistent when you feel the miss, then I don't think you're going in the right direction. Think about it: to oversimplify things, MS is just telling the injectors when and how long to fire, and the ignition systems when to fire. If the logs don't show any anomalies with them when the miss occurs, then it's likely coming from something else. My own experience with misses (different from hesitations) is they are usually spark related. Often one of the spark plug wires has an intermittent open (broken conductor) that's not visible because it's covered by the insulation. It sounds like you only experience it after driving for an extended time. As the wires heat the insulation will expand and could intermittently allow the open to drop the spark. You'd notice it most when accelerating hard. Do you have a spare set of wires to put on? What is the condition of your distributor cap and rotor? Like I said above, my own experience is that these are the more likely culprits, not to mention they are a lot easier to check.

If your battery voltage gets noisier as revs increase, then something isn't right. You'll have some amount of noise no matter what, but if it's tied to engine speed, then I'd check all my power and ground connects. There's a lot of good info on wiring at http://www.msefi.com. I suppose you could try putting a noise filter inline with +12V to the MS box, but if the rest of your wiring is good, you shouldn't need it. But with regard to your miss, if the MS is resetting, your datalogs will show it. If they aren't, and the PW and timing values are staying consistent when you feel the miss, then I'd continue looking elsewhere.

I took your file and converted it to excel and then hid some unused columns to make it easier to read. I also highlighted in yellow the PW and RPM columns. On this pull, I don't see any significant drops in PW that would cause you to feel a miss. I did notice one event where your Batt voltage dropped to 9V (highlighted in red). Did you have a reset there? That would feel like a miss alright! FWIW, above 5k your rpm doesn't look any rougher (noisier) than my NA. Above 4k rpm the MAP reading seems to jump around a lot, but perhaps that's normal for a turbo? A suggestion: run a datalog with megatune. As soon as you feel a miss, hit the space bar on your laptop. That will mark the spot in the datalog where it occurred - offset by the time it took you hit the space bar of course. Then use megalogviewer to go back and find the marked event. Look for a reset, or anything out of the ordinary with PW, O2, and Battery readings. That might give you a clue. If everything looks good, you might need to look elsewhere. I'd check ALL my wiring for anything that could be intermittent. With the engine idling wiggle all your connections listening for anything that affects the idle speed, even momentarily. If none of this helps, I'll suggest something else: consider changing plug wires. I had my MS working pretty well with the exception of occasional resets when running at WOT for extended periods. I decided to stop using the MS PWM and instead added resistors to the injector circuits. I found I didn't get resets at WOT throttle anymore, but instead began to get them more often all over the rev range, even at idle. After a lot of research on the MS site, I decided to change to Magnecore wires since they seem to have the best suppression of RF energy. Since I installed them ~500 miles ago, I haven't had one reset. I'm not saying this is what's happening in your situation, but if you find the "miss" is really a "reset", then this is something to consider. 2nd gear pull.zip

Matt, a few things: - what do you mean by your comments about some fuses have the battery running through them? - Even though I have a 73, I just found a 72 wiring diagram which I've attached. It shows there's a relay for the horn. I'd try removing it and seeing if the fuse blows. - I must be blind because I can't find the horn switch (on the steering wheel) on this diagram to see if it's powered by the same fuse. Besides the relay, the horn switch is a moving part and hence a likely candidate to fail due to age, etc. Also, have you done any work around the steering wheel recently? Stay on it - the horn circuit isn't that complicated so you should be able to find the problem. 72_240z_wiring.pdf

By "miss", do you mean loss of power? What does the injector pulse width look like when it occurs? If the PW from the log is reasonable, then it might be a fuel delivery or ignition issue.