Carbureted RB Engine? (put away your pitchforks!)

[CowboyZbop]

Hear me out, put away your torches and pitchforks for a second!

At this point in time, I'm using what I have available. I'm not tearing apart a RB turbo engine and trying to make it carb'd. I already have available to me a stock NA RB. I've read all the other post that regard carbing an RB. People get upset, OP gets bashed, people argue, that's not what this is about. I get it man, I'm on your side! Someone is still going to chime in with their 2 cents haha. But like I said I have mostly what I need in front of me. I'm not all about HP and I'm not going through the hassle of going the turbo route at this point in time. This will be a hassle, too, but I can't imagine as much. 

Now on to the problem. Everything seems self explanatory as far as a RB swap into a Z car but I can't wrap my head pairing the carburetors with the ignition system of a RB. What are the ways around this?  I've read some posts but they don't go into much detail of it. And a lot of dead links. I guess I'm more of a fabricator than an electrician. Not much of the former either, to be honest. I know people who do carb swaps on LS1s can just pick up a MSD ignition system and everything is plug and play. I'm sure there isn't anything like that for this. Why would there be, you know? 

Would my best bet is to break out the wiring diagrams and find an aftermarket ignition system to wire it to? Would a Nistune or something similar allow me to do what I need plugging into the existing harness? What is everything that controls ignition timing on an RB? (AFM, TPS, MAF, O2 Sensor, Air Temp Sensor). Any extra hurdles if I'm working with a Neo RB25? I've been researching this topic for awhile and I'm getting to the point where I can't tell if I'm under thinking this or over thinking this. Basically, looking for the easiest route (aren't we all) into tricking the ECU, if possible. This is all being put in a 260z. If too tricky, I will have to play with the idea of just keeping it fuel injected. 

Just here to refresh the brain, bounce some ideas back and forth, and get flamed in the process.

Thanks!

[GTSBoy]

The effort spent on forcing it to work with carbs would certainly be better spent just putting an EFI pump and some fuel line into the car.  Seriously.

If you really would prefer to go carb, and you are happy to have a single air feed to however many carbs (be that 1, 2 or 3) then all you need to do is put the AFM into the air inlet and just run the ECU. The ECU will run the sparks and will try to run the injectors, but as there will be no injectors and fuel will automagically find its way into the engine via the vintage tech, you will no doubt get combustion and power. There will be hassles. The ECU will be expecting a TPS signal it can work with for idle, and it will be wanting to do idle speed control via IACV and also messing with the timing - and guessing that you won't have an IACV, it will definitely end up screwing with the timing.

As I said, going EFI would be easier.

If you can go further afield than using a (Nistuned) original ECU then you could use an aftermarket ECU that can run off MAP and you won't need the AFM and you might find it easier to side-step some of the idle hassles, etc.

[KiwiRS4T]

You don't really say why you want to do this. Is it just because you have a carburettor lying around? You have an RB engine ...the bits you need to make it work are readily available (second hand if necessary) as is all the info.

If you are a masochist or you just want to be different go for it.

[WMDC35]

Could look for details on RB24S, was supposed to be carb

[Ben C34]

There are ignition only standalone Ecu's, that would be the reasonably obvious choice for ease of use.

[hattori hanzo]

unsure why people get so mad when its going into a z car, interested to follow how you go about it! 

 

 

[CowboyZbop]

14 hours ago, GTSBoy said:

The effort spent on forcing it to work with carbs would certainly be better spent just putting an EFI pump and some fuel line into the car.  Seriously.

If you really would prefer to go carb, and you are happy to have a single air feed to however many carbs (be that 1, 2 or 3) then all you need to do is put the AFM into the air inlet and just run the ECU. The ECU will run the sparks and will try to run the injectors, but as there will be no injectors and fuel will automagically find its way into the engine via the vintage tech, you will no doubt get combustion and power. There will be hassles. The ECU will be expecting a TPS signal it can work with for idle, and it will be wanting to do idle speed control via IACV and also messing with the timing - and guessing that you won't have an IACV, it will definitely end up screwing with the timing.

As I said, going EFI would be easier.

If you can go further afield than using a (Nistuned) original ECU then you could use an aftermarket ECU that can run off MAP and you won't need the AFM and you might find it easier to side-step some of the idle hassles, etc.

This is has been a helpful post. Thanks for taking the time to scratch the itch. I think I'll be cramming just about as much air in the cylinders with this carb setup. But running it the way you mentioned within your second paragraph is exactly the nightmare I wanted to avoid and if that was the case, I'd 100% go EFI. And I still might. It's a dual carb so I can't imagine what I'd have to do with the AFM sensor..

BUT

If an aftermarket ECU can bypass those things that is something I would like to look into. I have been looking at a couple already, just didn't know if it could go as far as into "bypassing" or better put side-step, like you said, a lot of those little things like TPS or IACV.

I don't necessarily have my heart set on anything I just wanted to try to get an idea of what would be needed. When you don't see things like this done, it's usually for a reason. I know I'd be far better off with keeping it EFI and it most likely will happen. But there's still that voice..

[CowboyZbop]

13 hours ago, KiwiRS4T said:

You don't really say why you want to do this. Is it just because you have a carburettor lying around? You have an RB engine ...the bits you need to make it work are readily available (second hand if necessary) as is all the info.

I don't quite understand this post. The bits I need to make it work are readily available? Keeping it fuel injected, yes. It's mostly wiring and changing fuel delivery which has been documented. Going carb'd, no. As the info? Also none that I can find. 

But the reason behind it is pretty much what you said, I have decent carbs lying around. I can spend the money to change fuel delivery which and stick to all the benefits of EFI. It would be the cost efficient way to go short term and long term. But read below.

14 hours ago, KiwiRS4T said:

If you are a masochist or you just want to be different go for it.

Now THIS I understand and you're probably right! haha

[CowboyZbop]

13 hours ago, WMDC35 said:

Could look for details on RB24S, was supposed to be carb

I poked around at these and I think there may have been some RB30's out there that were carbed on some Nissan Patrols or something, as well?? Big question mark on that.

But from what I seen they were all built with mechanical distributors which doesn't help me much in this case. 

[CowboyZbop]

12 hours ago, Ben C34 said:

There are ignition only standalone Ecu's, that would be the reasonably obvious choice for ease of use.

As I mentioned to GTSBoy and my original post this is a route I would like to happen. I just wasn't sure if standalone ECU's would side-step all those little things that keep the motor running nicely such as TPS, AFM, IACV, etc.

Good to know!

 

[CowboyZbop]

4 hours ago, hattori hanzo said:

unsure why people get so mad when its going into a z car, interested to follow how you go about it! 

 

 

I agree entirely. In my situation I'm not deflowering anything valuable, hacking away at anything where it can't be reversed. Also I kind of like the idea of that (kind of) period correct vibe going on. I knew what I was getting myself into posting this but they're going easy on me! haha

I'd be sure to follow up if I end up going that route! Thanks!

Edited May 19, 2019 by CowboyZbop

[GTSBoy]

If you have 2 carbs, then I would argue that they are not decent. There's probably no justification in having carbs on an L6 unless they are triple Webers. A pair of twin SUs is not really a "performance" situation.

Multiple carbs make for a grumpy annoying existence. Injection takes away so many of those annoying cold weather cold start throttle pumping experiments, etc etc. The driveability benefits alone are worth it.

I would also argue that the time, effort and money spent on getting the ignition working without full engine management is not going to equate to "cheaper and easier" than just running the RB the way Nissan intended.

Don't get me wrong - I love the sound of open carbs - I spent years driving around an ALFA with trumpets and sock filters.  But I wanted to inject it to get away from all the carb hassle. That's ultimately why I bought the Skyline.

[CowboyZbop]

I'm not saying what I have is going to create a performance application. I do have a set of Ztherapy carbs that I have ran for years with no issues on an modified L series and should be able to handle an RB with little to no modification in terms of internals of the carbs.

I'd argue that some flat tops make more of a headache than round tops. But that's just from my personal experience though. I can crank up a carbed L series engine of mine on the first key turn every time. But let's not get off topic.

I do want to state that you put "cheaper and easier" in quotations and from my posts I don't think I ever used the word "cheaper" as that is not the point of this. I apologize if I did. Easier I know I did say. As in I will pay extra, IF there was something that would make this an easier and more reliable install. If a certain aftermarket ECU could achieve that then I would as least like to look into it.

Like I said before I'm not stuck on the carb thing. Just wanted a discussion of what could make something like that work. I understand the benefits of not going carbed. I love EFI, just as much if not more than carbs. I couldn't count the dead brain cells or how often I had bloodshot eyes fiddling with carbs over the years. Maybe it's starting to show haha. I would probably put all this to the side and grab a Skyline myself if it were possible.

 

Edited May 20, 2019 by CowboyZbop

[niZmO_Man]

Nah Skylines are overrated, except R31s

 

N/A doesn't sound too shabby. You can grab yourself an RB20DE NEO and make it rev to 9,500 rpm.

[CowboyZbop]

Was there supposed to be an example of a car in that video? All I see is a girl in a bikini! 

I assume an RB25DE NEO would rev just as well? Any input on if an aftermarket ECU would allow it to run reasonably?

The video looks to be running ITB's which allows all of the stock wiring to stock sensors to be kept with the LINK ECU they are using? Or am I wrong about that?

[hattori hanzo]

7 hours ago, CowboyZbop said:

I agree entirely. In my situation I'm not deflowering anything valuable, hacking away at anything where it can't be reversed. Also I kind of like the idea of that (kind of) period correct vibe going on. I knew what I was getting myself into posting this but they're going easy on me! haha

I'd be sure to follow up if I end up going that route! Thanks!

Its a Z, the vibe is critical to maintain with carbs! 

[GTSBoy]

6 hours ago, CowboyZbop said:

I assume an RB25DE NEO would rev just as well?

No, not quite. The 20 has a shorter stroke so the piston speeds are noticeably lower. You still need to take care of the other things that can get in the way of revs (lifters/shims, springs, etc) but there are plenty of RB20s that have been turned to nearly 10k. Very few 25s ever get turned that fast.

6 hours ago, CowboyZbop said:

The video looks to be running ITB's which allows all of the stock wiring to stock sensors to be kept with the LINK ECU they are using? Or am I wrong about that?

Well......it depends on what you mean by "all of the stock sensors". Of course it's injected, so it has full management (although why she put a bloody F-CON on there along with a Link ECU, I'll never know!). Having ITBs on an aftermarket ECU is easier than trying to do it on the Nissan ECU. You have freedom to do whatever is necessary to get a TPS onto it, whereas with the Nissan ECU you'd be trying to use either the original TPS or something else OEM Nissan that looked the same to the ECU.

Everything else needs to be what the ECU requires. The F-CON / Link must be running from MAP because there's nowhere for an AFM to be installed on that engine. You still need water temp sensor, but with non-Nissan ECUs it could be any water temp sensor. The CAS must stay, unless replaced with expensive crank triggers. That's about it to make it run properly.

6 hours ago, CowboyZbop said:

I do want to state that you put "cheaper and easier" in quotations and from my posts I don't think I ever used the word "cheaper" as that is not the point of this. I apologize if I did. Easier I know I did say.

Easier often comes with cheaper. It's not really true in either case with this decision though. Going carbs will cost more in time, effort and money than keeping the injection. If you put carbs on it you're going to have to come up with an inlet manifold and solve all the other issued I've raised. If you keep injection, the inlet manifold comes for free, the management problems go away. You only need to add the fuel system (which should take an afternoon and a few hundred bucks on top of the pump cost). The only way you could make the injected option as hard for yourself as the carbs option is if you wanted to have ITBs. Then your manifold problem comes back and some of your ECU problems start to come back. This would almost certainly be the most expensive option (sound the best though, see that video, above!).

[KiwiRS4T]

9 hours ago, CowboyZbop said:

I don't quite understand this post. The bits I need to make it work are readily available? Keeping it fuel injected, yes. It's mostly wiring and changing fuel delivery which has been documented. Going carb'd, no. As the info? Also none that I can find. 

 

Sorry if I wasn't clear - I meant the bits needed to make it work as per OEM (with fuel injection) are readily available... so the easiest route. I don't see any haters on this thread - if you want multiple carbs in your Z fire away... I just see people trying to save you from a world of headaches!. My first sports car was an Austin 7 hill climb special with twin Amal carbs and I later had an Austin Healey 3000 with twin SUs (they gave up on the triple carbs) but when my work mates blew me away with their (fuel injected) V6 Capris I saw the light. Tuning with EFI is so much more precise.

[tridentt150v]

Just send a marriage proposal to the dori hina that made/milled her own.  Now that would be a girl worth marrying.

[CowboyZbop]

13 hours ago, GTSBoy said:

Easier often comes with cheaper. It's not really true in either case with this decision though. Going carbs will cost more in time, effort and money than keeping the injection. If you put carbs on it you're going to have to come up with an inlet manifold and solve all the other issued I've raised. If you keep injection, the inlet manifold comes for free, the management problems go away. You only need to add the fuel system (which should take an afternoon and a few hundred bucks on top of the pump cost). The only way you could make the injected option as hard for yourself as the carbs option is if you wanted to have ITBs. Then your manifold problem comes back and some of your ECU problems start to come back. This would almost certainly be the most expensive option (sound the best though, see that video, above!).

Get out of here with that LOGIC man! I can already see myself going the EFI route but I will always have that nagging in the back of my head. If getting an ECU was on par with the cost of converting a fuel pump and whatnot then I would still be really determined to go carbed. I spoke with some ECU companies that were really helpful as well. But the prices, yeesh. I thought there would be cheaper options for these things available.

Thanks for twisting my wrists. You win. For now!