Twin Carbs or EFI?

henry · rice boy Joined: 17 Oct 2001 Posts: 22

gday all .. just a quick question guyz . . on a wildy worked 1.8L
what has better dollar value versus HP gain?
EFI ?
or
Twin carbs ?

thanks guyz..

Woz · tinkerer Joined: 05 Oct 2001 Posts: 126

twin sidedrafts will reap the best hp for ur $$$.

efi using a rodeo manifold will never be as good as twin sides. efi with multiple throttle bodies will be better than twin side's, but cost shitloads.

henry · rice boy Joined: 17 Oct 2001 Posts: 22

thanks woz bro

MatMan · tinkerer Joined: 04 Oct 2001 Posts: 280

He's right you know,

Ben Wight · backyard mechanic Joined: 04 Oct 2001 Posts: 946

Have to agree with Woz,
since carbies and efi virtually do the same thing, the average twin carb manifold should flow alot more air than the average efi manifold (rodeo and piazza), whereas the price of a quad butterfly efi system is very high to buy off the shelf.

Therefore, the carbs will make more power and cost a lot less.

Ben Wight

henry · rice boy Joined: 17 Oct 2001 Posts: 22

thanx 4 tha replys boyz , i think ill go the twin webberz next..

Benjamin · backyard mechanic Joined: 05 Oct 2001 Posts: 525

Would I be better off with a Rodeo or similar EFI setup if I were to force feed the engine?
This is a long term goal, and my train of thought is EFI fuel management. Because I am force feeding, is flow rate not quite as important?
If it is (and I don't doubt it) what options to I have for EFI manifold? Or do I just port the existing manifold to buggery?

Ben Wight · backyard mechanic Joined: 04 Oct 2001 Posts: 946

Depends alot on what boost levels you desire. Carbs generally dont like being pushed into the 20+psi range, and fuel surge in the bowl can be an issue. Drag racing is generally not a problem.

However, a rodeo efi manifold will outflow a standard ported gemini manifold, plus the standard throttle bodies are about 60mm diameter. Most importantly though, the intake runners are near equal length, unlike the standard gemini manifold.

A rodeo setup with programmable management will be a supreme setup, as it is hard to get a carb to deliver a rich mixture under boost whilst still cruise fuel efficiently.

In the end, EFI is safer, (not really a consideration at low boost levels) but the biggest benefit is off boost economy. It is safer in than it is a more reliable method of fuel delivery at high boost levels. If 15psi or so was a maximum limit, I would have no hesitations using a carburettor however, I currently push mine around the 18psi mark.

More power can be had, not really from the fuel system but with a computer that controls ignition, more power is to be had by dialling in more advance where it is useful, but the standard dizzy cant be modified to deliver, such as more advance at full load but before boost conditions are present. Then the computer can retard timing dependant upon boost levels.

Flow of manifolding is still important when dealing with forced induction, a pressure drop will still exist from a poor flowing piece of hardware, regardless of whether atmosperic pressure is feeding the engine or double atmospheric pressure (15psi boost) is feeding the engine. It is more easy to counter though in a turbo car, because an extra pound of boost will makeup for the poor flowing head or intake manifold, etc.

Ben Wight

Benjamin · backyard mechanic Joined: 05 Oct 2001 Posts: 525

Wicked info, Ben, thanx Smile

I am still deciding between turbo and supercharge. Both have their merits, but the way I am thinking supercharging might suit my driving conditions a little better.

MatMan · tinkerer Joined: 04 Oct 2001 Posts: 280

I'm interested in supercharging mine too, I reckon the Toyota 1GG-ZE s/c would be the go. Just my 2c Smile

Benjamin · backyard mechanic Joined: 05 Oct 2001 Posts: 525

That's the plan Smile

Is this the higher boost model? I have read about the 4AG-ZE, which I am assuming is the lower boost version.

Ben Wight · backyard mechanic Joined: 04 Oct 2001 Posts: 946

Both blowers produce roughly the same boost on their respective engines, but the 4AGZE is a 1600, whereas the 1GUZE or something like that is a 2 litre, therefore, the 2 litre has a bigger supercharger, which means, it is more efficient at pumping greater volumes of air. All up, this means that the larger supercharger is better for running more boost, as it is more efficient, which means that outlet temps from the compressor will be lower, which means, etc. etc.

I have heard many stories of the 2 litre version being used to run 3 litre plus engines, at 10psi, but they do tend to wear out quickly becasue to generate that boost on that size engine required overrevving them, which wears out their teflon coated rotors. probably be good for 14 or so psi on a 1600 though.

I have only seen 2 installations of them onto gemini engines, and it seemed like a lot of work. You have to make up brakets, and pulleys, and then an induction system, blowing through a carburettor would be the easiest bet, that way you could intercool and run a pair of cheap bosch blow off valves in parallel to dump boost when backing off the throttle.

What looked loke a hassle was the extractors becasue they needed to hug the engine as the blower sits where the pipes usually run.

After all considerations, a smallish turbo might be the best option, due to minimal spoolup time (virtually instant dependant upon size, with a tronger midrange and equal top end to the supercharger alternative.

Ben Wight