tbi questions

[bigboi328]

HI I WAS WONDERING IF ANY ONE HAS EVER TRIED TO USE A JEEP 4.0 L TBI ON A CHEVY INLINE 6. THE REASON I ASK IS THE 4.OL JEEP HAS A FIRING ORDER OF 1-5-3-6-2-4 AND THE 230 CHEVY HAS THE SAME FIRING ORDER.

[sean1969c10]

If I remember right the 4.0L Jeeps were all Multi Port Injected not Throttle Body Injected.

[gofastnut]

I don't know if it'll work, I agree with sean above. I DO know that http://www.cliffordperformance.net has several TBI/FI setups. Hope this helps.

[joedoh]

unless they say "sequential fuel injection" on them somewhere, most EFI systems are batch fired, which means half the injectors are fired every revolution. this also means that sometimes they fire when the intake valve is open, and sometimes when the intake valve is closed. Sequential systems fire the injector only when the intake valve is open which on the surface sounds like a good thing except 1) the injector has to be larger to meet the largest fuel demands of the single cylinder and 2) eventually at higher rpm under load the injector is open longer than the duty cycle and either requires a very fast and accurate processor or more likely switches over to batch, allowing the injector to divide the fuel demands over two revolutions of the motor instead of only when the intake valve is open.

batch is not all bad, people like to think of fuel pooling or dripping past the valve when actually intake air bounces back and forth in the intake in pulses. Ever wonder why a longer, thinner, intake makes more low end torque? this is why, because the resonant frequency (most work, least effort) of the tube happens at a lower rpm. The proof of this bouncing can be seen by spinning a 2 inch hose in one hand creating a tone, the air is bouncing back and forth between the ends of the hose at that frequency. If you cut the hose in half and spin it, the frequency goes up. This bouncing lets fuel stay atomized and not pool, making it really independent of when the fuel is injected as long as the right amount is there when the valve opens. I digress.

TBI is almost always batch, or really it is more a of a continuous injection system, similar to a carb except instead of the cylinder vacuum pulling fuel through the carb the TBI precisely measures the airflow and pushes the fuel through the throttle body. TBI systems use one or two HUGE injectors at the throttle body to meter fuel and supply all the cylinders at once and are not ever tied to ignition events or intake events

So a TBI system could be from a V8 or a 4 cylinder and still work on a straight 6 as long as the injectors were capable of supplying the fuel required by the engine. If you were looking for a system that managed spark in addition to fuel, then you would need the ignition system too, but firing order wouldn't matter at all, just the number of cylinders, because you would use number one as number one cylinder and then just follow the distributor around hooking up the next cylinder for the engine, the distributor wouldn't care.


This sounds like a neat project, I love the efficiency of EFI especially on older trucks so definitely keep us in the loop if you get to doing it.

[Alan's Classic]

Moved to engine and drivetrain.

[Corts60]

Originally Posted by joedoh

unless they say "sequential fuel injection" on them somewhere, most EFI systems are batch fired, which means half the injectors are fired every revolution. this also means that sometimes they fire when the intake valve is open, and sometimes when the intake valve is closed. Sequential systems fire the injector only when the intake valve is open which on the surface sounds like a good thing except 1) the injector has to be larger to meet the largest fuel demands of the single cylinder and 2) eventually at higher rpm under load the injector is open longer than the duty cycle and either requires a very fast and accurate processor or more likely switches over to batch, allowing the injector to divide the fuel demands over two revolutions of the motor instead of only when the intake valve is open.

batch is not all bad, people like to think of fuel pooling or dripping past the valve when actually intake air bounces back and forth in the intake in pulses. Ever wonder why a longer, thinner, intake makes more low end torque? this is why, because the resonant frequency (most work, least effort) of the tube happens at a lower rpm. The proof of this bouncing can be seen by spinning a 2 inch hose in one hand creating a tone, the air is bouncing back and forth between the ends of the hose at that frequency. If you cut the hose in half and spin it, the frequency goes up. This bouncing lets fuel stay atomized and not pool, making it really independent of when the fuel is injected as long as the right amount is there when the valve opens. I digress.

TBI is almost always batch, or really it is more a of a continuous injection system, similar to a carb except instead of the cylinder vacuum pulling fuel through the carb the TBI precisely measures the airflow and pushes the fuel through the throttle body. TBI systems use one or two HUGE injectors at the throttle body to meter fuel and supply all the cylinders at once and are not ever tied to ignition events or intake events

So a TBI system could be from a V8 or a 4 cylinder and still work on a straight 6 as long as the injectors were capable of supplying the fuel required by the engine. If you were looking for a system that managed spark in addition to fuel, then you would need the ignition system too, but firing order wouldn't matter at all, just the number of cylinders, because you would use number one as number one cylinder and then just follow the distributor around hooking up the next cylinder for the engine, the distributor wouldn't care.


This sounds like a neat project, I love the efficiency of EFI especially on older trucks so definitely keep us in the loop if you get to doing it.

Well explained. Nice job.

[D13]

Why not run a GM V6 TBI? Parts are cheap and either way you'll need an intake adaptor and a new fuel system. Ignition is pretty easy.

[bigboi328]

thanks for all of the info. i thought i could go inline 6 to inline 6, but oh well ill keep looking