Captain Obvious

How about a couple pokes for input (in no particular order)? @Chickenman, @duffymahoney, @jonbill @blodi, @JSM, @conedodger

Yeeesh. Too much black magic and voodoo in that ECU for me to ever consider doing something like that. If you ever succeed with this, I will drive my Z to your house and loudly proclaim in public that your kung fu is the best.

Current owner... Albert Hammond?

I want an A/F ratio meter like many of you other guys have so I can make a run with the car while logging the fuel ratio details. My short list is "I want to do data logging, and I prefer an analog display over digital." If I pulled the trigger today, it would be for Innovate's MTX-AL (analog). Why? Because I know nothing about such devices and Innovate is a big player in the market, and hopefully produces quality stuff. Any input about Innovate's logging and analysis software? If I don't like it, are there other third party offerings that I could use instead? Any other recommendations about brand or style? * I thought I had asked some of these questions in the past, but I just can't remember or find it if I did. So apologies if I'm rehashing something I've already done.

Well beyond the scope of the thread, but... The theory behind that is that the voltage from the coil will ramp up rapidly until it reaches the point where it ionizes the air in the gap and jumps that gap. By adding that additional second gap, the voltage will rise further before it finally jumps the gap. This is because the effective gap distance is greater and a greater gap takes a higher voltage to jump. By riding the voltage curve higher and holding off the spark a little, you can get a higher energy spark. It's also helpful when there's a carbon trace buildup. The carbon trace could provide enough of a path to dissipate the coil discharge without having to spark at all. With that second gap and riding further up the voltage wave before discharge, you can sometimes burn out the carbon traces. Assuming, of course, that your coil has the nuts to consistently jump a gap that big. There are plenty of risks, but (as you found) in the old days, it could sometimes get you home in a pinch.

Simply because I had all the parts handy, I took fresh measurements and ran some numbers: 280 throttle butterfly - 50mm diameter. This provides 1964 mm square area. The Sentra (96-98) throttle body as well as the 280ZX are also the same as the 280Z Carbs butterfly (both round and flat tops) - 46mm diameter. This provides 1662 mm square area. Now interesting (to me) is that the 1964 sq mm for the throttle body is shared between six cylinders, while the 1662 sq mm for the carbs is shared only between three cylinders instead of six. So for the fuel injection, it works out to 327 sq mm per cylinder and the carbs work out to 554 sq mm per cylinder. The carbs provide significantly more butterfly area per cylinder than the fuel injection. Now I'm sure Nissan did their research and found 50mm diameter for the EFI was good enough, but the difference is still striking. Working backwards from the carbs 554 sq mm per cylinder, you would need a 65mm diameter throttle body to get the equivalent area per cylinder. I'm no in any position to draw any conclusions from the above, but I was moving some stuff around today and had all the parts handy at the same time.

Damn your eyes!!

LOL. All the rest of that material keeps squirrels out of your bell housing. Haha!! Racer X, I bet everyone at every level of racing bends some rules and stresses others beyond the limits of bending. Your secret is safe with us. All 30,000 of us. Haha!

At that level of detail, my stainless plate is (nominally) four thousandths (.004 in) thinner than the plated original. So I guess it's a performance increase too. Not sure how much weight difference that would result in, however.

Hmmm. As simple as the question seems, I'm not sure what you're asking. Are you asking "Is there a weight difference between my new stainless piece and the old triangular holed carbon steel piece? If so, then (ignoring miniscule differences in density between stainless steel and carbon steel) the answer is "No, they are the same." But if you are asking "Is there a weight difference between my new stainless piece and the older 240 version with the round hole?", then the answer is "Yes, mine is lighter because the hole is larger." Here's a pic of a rusted up older 240 design with the round hole in the middle:

As a recent project, I had a new rear plate made for between the engine and the transmission. It's laser cut out of 304 stainless, and it turned out fantastic! Just the thing for bling! Since I'm putting it on a 280, I modeled it after the later version with the triangular shaped hole instead of the earlier 240 version with the round hole in the middle. The parts fische says the manual trans 240s used P/N 30411-E3000, while everything after that used P/N 30411-A8600. Also note that the 240 version was superseded by the 280 version, so according to that documentation, they are interchangeable. Here's the new shiny stainless bling plate next to the original with the failing plating: Mounted on the back of the motor: Pic of the front of the transmission to see where the holes are: And here's the plate up against the tranny face. Just hanging in place with bolts and drill bits: Any interest in having more of these made and offering for sale?

I'm saying that I don't remember the exact locations of all the parts involved and it's possible that the throttle opener may be mounted lower on the 240 balance tube. If that's the case, the throttle opener device itself may be identical between 240 and 260, but they may have put it in a different spot between the two. Same goes for the throttle stop you're hovering above on the balance tube. That little stub of throttle linkage may be significantly different between the two. I just don't remember. I know lots of people have done flat top to round top conversions and have overcome these hurdles and I bet there are pictures out there on this forum that would answer some of those questions.

Glad to help. Hope it saves some time. You may find that the holes in my plate are a tight fit on the mounting bolts with the geometries and tolerances involved. The holes in the throttle bodies I've messed with here use larger holes than what I put in that plate. In fact, they used two different hole sizes on the diagonal. Two of them are really sloppy, and the other two are tighter, but still not as tight as what I did. Anyway, you may find that you need to open those holes up a little bit to get it to fit without interference on the mounting bolts. Depends on the accuracies of all the parts involved. On the factory floor, they just want things to fit without a fight and they made the mounting holes sloppier to guarantee that happened.

Well if you're going to make it two pieces, you really don't have to clock the throttle body if you don't want to. You can use flat head screws or counterbored bolts to hold one piece to the manifold. Screw that into place first. Then use flat head screws to hold another plate to the first and have threaded holes in the new pattern on the second plate. Not really a good description..... Anyway, here's my sketch of the original throttle body mount. Let me know if you can't read the dimensions and I'll edit the sketch to make them more readable: I made a spacer plate for the Sentra throttle body. The mounting pattern is the same, but the linkage interfered, so I had to move the throttle body out away from the intake by 1/4 inch. Here's a spacer plate made to the dimensions above: And here it is next to the intake hole:

That vacuum servo that is giving you troubles is called the "throttle opener", and it's job is to hold the carbs open a tiny bit under very high intake manifold vacuum conditions. Essentially it is supposed to prevent the manifold vacuum from going above a certain level. It's in the same category as the anti-backfire valve. And to answer the question about the linkage... No, that adjustment screw is not supposed to be floating in air a half inch away from the linkage. I assume that it's all caused by incompatibilities between the 260 bits on the balance tube and the 240 bits below. Last answer... Yes, that is a round top style piece between the two carbs. So for now, you can just leave the throttle opener disconnected and get the car running well. Then once you're over the basic hurdle, you can get yourself a round top balance tube and throttle opener maybe.

Did the car run reasonably well with the flat tops on it? First thing would be to make sure it's a decent running motor in the first place. Start by getting rid of the vacuum leaks. Just to test things, you can cap off the entire anti-backfire system. You can also pull and plate off the EGR just in case it is sticking open a little. Other things maybe? You've got a rubber vacuum line connected to the front manifold right behind the carb. This is the line that splits and goes to your throttle opener and AB valve. Well there's another nipple (broken off) right next to that one. What's up with that? Is that a leak? And the throttle linkage doesn't look quite right to me. The stop up by the EGR valve is nowhere near making contact. And the connection nut on the rear carb looks like it's bent and/or loose? Is that an attempt to mitigate the "too short" linkage piece between the two carbs?

Describes me too, so I guess it fits. Haha!! Seriously though, about the only time I miss having a more highly featured phone is when I travel. For finding local attractions like food or entertainment, and directions to such places. Other than that, I'm still satisfied. It makes and receives calls and rudimentary texts. I'm good. And yes... I only have to charge it every couple of days. I see people sitting in public places huddled around the wall outlets charging their devices and sometimes quarrelling about the use of the outlet. My criteria for my phone goes like this: Makes and receives calls and texts. Small as possible. Long battery life. No external call activating buttons and cannot (not just "unlikely", but CANNOT) pocket dial by accident, even if I'm in there playing with myself and push a couple buttons by accident. That's about it.

OK, I'll look for my sketch. So I've got some questions about this adapter plate you're planning... With the mounting holes being "close, but not close enough", there is significant overlap between the original pattern and the scheme for the 350Z. That overlap presents a set of difficulties in making an adapter plate. It would actually be easier if the patterns were radically different instead of just a little different. Are you planning to make this thing from multiple pieces and sandwich them together? Are you planning to spin the 350Z throttle body a little (clock it 45 degrees or something) so that none of the holes interfere with each other? Something else? Sorry... I'm just having trouble picturing this plate.

Glad you quieted it down and got it running better. So you didn't mention it, but I'm assuming you also fixed the injector O-ring leak while you were in there? Yes, vacuum leaks large and small are the cause of many of the problems with the fuel injection system.

We have a "somethingCast" (Chrome maybe) and something else newer. Two dongles hanging off the back of the TV. Someone in the house surely knows how to use them. I don't use either of them because my flip phone won't talk to them.

Haha! Nice glitch. So this 2-D drawing for inlet face of the stock plenum... I don't have anything in electronic form, but I have a pencil sketch around here somewhere. Would that help?

Not sure why it would do that, but I think it's just the idle air whistling. What happens if you close off your idle air screw completely? You might have to keep it running by manually holding the throttle open a little bit while testing. The reason I ask is because I've messed around with a couple different throttle body options and one of them would whistle like that if the idle air passage was being worked too hard. I made the noise go away by opening the throttle plate a little, which allowed me to close down the idle air passage. More air past the butterfly and less through the idle bypass and it quieted down.

And thanks for the pics Jim!

Congratulations Jim!!

Haha!! I remember that scene (now that you mentioned it). I wonder if one of the TV systems we have in the house will get that for me... I think I need to watch that movie again to refresh my memory. If only I knew how to work the TV systems. We have Netfax and Disney Puss or something like that? I'll need a navigator.