If one is good, then would two be better?

[jj big shoe]

Okay...it seems that one of the most restrictive areas of the intake would be the throttle body opening and since porting and polishing can only get you minimally better flow, would dual TBIs work? Nevermind the mechanics and clearances of a dual setup, I'll figure that out later. Also disregard what a strange looking thing it might end up being.

What I'd like to know is if you could run duals from the stock ECU somehow or would you need a piggyback ECU to manage it, would you run a progressive linkage like the old "six pack" carbs, and would a second TBI really benefit the VG30 or would it just be too much air/fuel for the 2960cc engine.

Bear in mind this would be fitted on a motor that's already had P&P heads, hotter cams, headers and larger exhaust.

Just an idea since my mind works like that, haters need not reply.

 

*and to think they called me mad at the institute, muwaahahahaa!*

[unccpathfinder]

Theoretically, yes you could do that. I don't have much experience in A/F mixtures but I would think that if you could maintain that stability you could use dual TBs

 

The way to go about the dual TBs I would think is to monitor the signal to the fuel injector and then create a module that would take the signal from the ECU and then send an equivalent signal to both injectors...my thought process is if you split the signal it will decrease and not preform properly so if you had a control unit that could make sure the right signals got to the injectors you should be in fat city with the exception of maintaining your AF mixtures.

 

I suspect if the AF mixture is proportional to the original then the O2 wont have a problem with it

 

 

just a thought to get the ball rolling...may be completely off base but it makes sense to me in theory...

[GhostPath]

No. GM tried this and it was a miserable failure. There were multiple problems with it - not least of which being that it actually produces *less* power than a properly tuned port injection system. In addition, it costs more, has more parts to break, and it *still* has the uneven fuel distribution issue that only port or individual-cylinder fuelling can solve.

 

Far, far cheaper and easier for you to convert your truck to the later port fuel injection system. Carbs suck, TBI sucks only slightly less.

 

FYI, GM's take on this was called the "Cross-Fire Injection System" and it was foisted off on buyers of Camaros and Corvettes in the 1980s.

 

 

Worst. Injection. System. Idea. Ever.

Edited October 11, 2007 by GhostPath

[5523Pathfinder]

Well, the 90-95 300zx had dual throttle bodies. A common air flow meter watched the air pass by, and the intake runners crossed and were completely seperate. So, yes, the VG30 "could" do it. As for your application, who knows. If it was possible, and it may be, you could take the intake plenum and runners from a VG30DE and try and fit them. I would also imagine a custom ecu would be necessary to properly control air and fuel mixtures. Ideas are fun!

Edited October 11, 2007 by 5523Pathfinder

[SnakeS]

it would probably benefit more with a power adder because you are still relying on the engine's vacuum to suck the air in and might have less velocity if it's vacuum is split between two inlets. A shaker or ram air setup might help get more cool dense air into the engine.

[88pathoffroad]

Lee (formerly of L&P) had the same idea. He never got around to doing it, though. The stock single TBI flowed enough air to feed 15 psi on top of a blower! That says "good enough" to me!

[GhostPath]

Well, the 90-95 300zx had dual throttle bodies. A common air flow meter watched the air pass by, and the intake runners crossed and were completely seperate. So, yes, the VG30 "could" do it. As for your application, who knows. If it was possible, and it may be, you could take the intake plenum and runners from a VG30DE and try and fit them. I would also imagine a custom ecu would be necessary to properly control air and fuel mixtures. Ideas are fun!

 

 

It had dual TBs, but was not TBI. It had six injectors, one per cylinder, mounted facing each intake port.

 

The reason it had dual TBs was because it was a V6 engine with twin turbos and trying to route the intake otherwise would have been a nightmare in that engine bay..

[zonianbrat]

No. GM tried this and it was a miserable failure. There were multiple problems with it - not least of which being that it actually produces *less* power than a properly tuned port injection system. In addition, it costs more, has more parts to break, and it *still* has the uneven fuel distribution issue that only port or individual-cylinder fuelling can solve.

 

Far, far cheaper and easier for you to convert your truck to the later port fuel injection system. Carbs suck, TBI sucks only slightly less.

 

FYI, GM's take on this was called the "Cross-Fire Injection System" and it was foisted off on buyers of Camaros and Corvettes in the 1980s.

 

 

Worst. Injection. System. Idea. Ever.

 

Yeah but that was "GM" back in the 80's Alot of what they did were miserable failures. I believe with the right research and some $ you can do it better.

[GhostPath]

Yeah but that was "GM" back in the 80's Alot of what they did were miserable failures. I believe with the right research and some $ you can do it better.

 

 

Unfortunately, the guys with the Vettes and Camaros that got stuck with these have been modifying and completely rebuilding the system. I say unfortunately, because people have thrown thousands of dollars at it to get it to work better, and then discovered that just changing to a port fuel injection system would yield still more power. One guy went to the trouble of fitting two Edelbrock BBC-intended TBI units to his and ran it with a MegaSquirt. Eventually he decided to go to a port setup so he could do a blower, but did some dyno runs after converting and before installing the blower. 35 horsepower difference in favor of port injection.

 

Put it to you this way - GM couldn't make it work properly, so they tried to get Bosch (who designed the Nissan port fuel injection system) to fix it for them as part of the deal under which GM would license L/LH-Jetronic from Bosch. *Bosch* couldn't make it work, and they invented modern fuel injection and engine management.

 

I think just just needs to be tossed in the "failed ideas" hole.

Edited October 12, 2007 by GhostPath

[5523Pathfinder]

It had dual TBs, but was not TBI. It had six injectors, one per cylinder, mounted facing each intake port.

 

The reason it had dual TBs was because it was a V6 engine with twin turbos and trying to route the intake otherwise would have been a nightmare in that engine bay..

 

Correct! The idea was to add more power and tuneablity. The TBI will be challenged to help put out more power than what it is doing already. A modified connversion of the MPI with the intake is what im getting at. Thats why I said custom ECU and getting it all to fit. The air would have to be measured seperatly if two TBI's were used, or you could convert to a MAP sensor setup. That, of course, would be similar to the GM setup. Obviously this would be all custom.

 

Oh, and the intake was designed to fit the design of the car, not the engine. Not all z cars were turbos. Well, my 91 wasnt anyway.

[GhostPath]

Correct! The idea was to add more power and tuneablity. The TBI will be challenged to help put out more power than what it is doing already. A modified connversion of the MPI with the intake is what im getting at. Thats why I said custom ECU and getting it all to fit. The air would have to be measured seperatly if two TBI's were used, or you could convert to a MAP sensor setup. That, of course, would be similar to the GM setup. Obviously this would be all custom.

 

Oh, and the intake was designed to fit the design of the car, not the engine. Not all z cars were turbos. Well, my 91 wasnt anyway.

 

 

The original poster was saying that he wanted to put dual TBIs on, not just dual throttlebodies on an MPI system.

 

Thing is, the Z31 guys have already been over this. Without a turbo, even with the PF intake, the VG30E (note - NOT the twin-cam DE that you had in your Z32) is limited by the air it can take in, which in turn is limited by the small cylinders, ports, and valve areas. Dual TBIs or just dual TBs is not going to help. One of the NA guys over there at Z31.com put on the PF intake, giant throttlebody, and bored everything that he thought was restrictive out - and he only got 10hp for his troubles.

 

Unless you have a blower or turbo, the VG30E just doesn't flow air that well. And that's the true restriction. Going to two, three, four, five or even six TBI units isn't going to help. The VG30DE is another matter entirely, but we didn't get those engines in our trucks.

 

Finally, even if you do stick them on there, you are NOT going to have the precise per-cylinder fuelling control you need to get the most power out of the engine. You're going to have some cylinders running lean, some running rich, etc., etc. That's not good for emissions OR power.

 

Just convert to MPFI already.

Edited October 12, 2007 by GhostPath