NewbVetteGuy

Anyone have any idea what this "Annular Discharge Ringe/Sleeve" feature is that some of the new gen TBI EFI systems are touting exactly is?


Holley is advertising it in the Terminator and Sniper EFIs and "Quick Fuel Technology" is advertising a VERY similar sounding tech in their new TBI EFI:

http://hotrodenginetech.com/quick-fu...ew-efi-system/

http://hotrodenginetech.com/holleys-...or-efi-system/

It certainly SOUNDS LIKE these EFIs are some how using injectors AND venturi tubes to get carburetor-like levels of fuel atomization....

Is this how anyone else interprets this?


If so, it sounds like some sort of TBI EFI holy grail.



"The patent pending 8-hole annular discharge sleeves inject fuel into a venturi where air speed is at its peak, and pressure is at its lowest, atomizing the fuel far better than any traditional injector nozzle can do. This results in a much more homogeneous fuel/air mixture that burns faster and more complete, producing more power and better response."

Marketing crap or actual improvement in an area that has been a huge weakness for TBI EFI?



Adam

Shark Racer

Anything that injects above the throttle blades is going to have problems at low throttle angles with the injectors spraying fuel into the blades and moving them out of suspension. At WOT, it may be better but at WOT a carburetor performs pretty much as well as any port fuel injection setup.

Anything that injects into the plenum, particularly with a dual plane setup, is going to have problems with fuel falling out of suspension while turning corners.

You can see on fuel puddling on the throttle blades at idle with my MSD Atomic EFI setup. It doesn't matter if it's coming in at direct injection pressures, it's out of suspension once it hits those throttle blades.

If you have the time and means, I'd skip TBI and go straight to port injection.

NewbVetteGuy

My understanding was actually that carburetors perform BETTER than fuel injection setup when it comes to fuel atomization; if this can some how both meter fuel accurately to provide dynamic, configurable and well managed- AFRs AND get the fuel atomization of a carburetor that would be ideal. (If the setup is essentially just using an injector as a valve to control the flow of fuel, you get the control over the AFR AND the atomization benefits of a carburetor's venturis -that sounds like WIN as far as TBI EFI goes.) -I've always thought that a carbeuretor retrofit with the ability to meter the flow of fuel through it precisely and all of the other EFI equipment would essentially be the best TBI EFI you could hope for; venturi's are better than injectors at atomizing fuel and nothing says that TBI EFI needs them; you just need the ability to accurately and rapidly meter fuel and control the AFR.


I thought that fuel falling out of solution was based upon runner length and particular twists and abrupt turns in the path; I don't understand why the problem would be worse with a dual plane vs. single plane intake. If you've got a pretty verticle- straight-shot intake design, but there's a dividing wall down the center opening of the plenum so that you have effectively two separate plenums, should it really make much difference?


Fuel puddles on top of carburetors- you can see it there too; that's how they're SUPPOSED to work; they still have GREAT atomization.


Of course, if I had infinite money a sequential port based EFI system would be better; I'm in no way convinced that when VALUE is factored in that port is the way to go. TBI EFI seems like a much, MUCH, MUCH better value right now.

The challenge is that at the low end of EFI the prices have dropped PRECIPITOUSLY in the past year or so and port-based EFI... not really much at all. $899 for a Holley Sniper TBI EFI; FiTech GoPort, if it ever releases will be the cheapest port-based EFI at $1,800 and that's without the fuel system including pump and injectors (which are NOT cheap), if I remember correctly. --I'm trying to figure out what the extra $1,100 to go to port EFI exactly will get me. For the teeny, tiny increase in fuel economy to pay the difference I'd probably have to put 200k miles on the system. --Technically it could allow me to switch to a LS-like intake that's REALLY good at getting lots of airflow and equal airflow to all cylinders, but I actually haven't seen any port EFI systems for early SBCs that even provide this as an option. (Sequential Port injection with a composite LS-like intake would be SOOO AWESOME even if it would have no hope of fitting under a stock C3 hood.)

-I like that a TBI EFI can hide under my 79 L82 dual snorkel air cleaner assembly and no one has to know it exists. If the price of sequential port aren't reasonable and there's no compelliing perf + fuel economy reasons to go that route, I'd personally rather have a "stealthy" EFI.

-In which case I'll just keep all the vacuum hoses and black paint all about the engine compartment; the EFI can be my secret.

Adam

Metalhead140

Hey mate,

I'm with you on preferring the hidden stock appearance of TBI and thinking it is better value at this point in time than port injection. However, if you want to fit your stock air filter then you probably should read this thread: https://www.corvetteforum.com/forums...ns-1979-a.html. My fitech doesn't go close to fitting under my stock '79 filter housing, though you could probably do it with a spacer between throttle body and filter housing, provided you have the bonnet clearance (which I won't due to running a Performer RPM intake manifold).

NewbVetteGuy

Thanks; I saw that thread, and I commented on it a while back.

I'm glad to hear from another 79 mid-rise hood owner on this, actually.

I really don't want to lose the cold air snorkel despite its archaic accordion vent connections (I'm actually shocked I haven't found an aftermarket smooth plastic replacement for those that limits air turbulence). -I'm HOPING that the Holley Sniper doesn't have the same fitment issues. When I look at it and the dimensions, I'm hopeful and I know that people are going to be getting the first units in November- I'm not ordering mine until the end of December so other people can be the guinnea pigs! lol!


I think I'd have to find a way to hack my dual snorkel and keep it.
Some day I'd like to get L88 hood, but NOT NOW. This thing is going to have to fit. I heard switching to solid motor mounts will buy you a tiny bit more hood clearance; if I'm only short a little bit, I'd probably go that route.


Adam

Shark Racer

I have the 78 with a mid-rise hood, same as yours, and am running the Atomic and my goal was a nice stealth look now.

Having said all that and LIVED IT I would rather have port fuel injection for the reasons I've already elaborated.

Take a look at where the air-fuel charge travels in a dual plane intake. With a single plane, the atomized mixture goes down and 90s straight to the runner. There are numerous curves the mixture has to travel in a dual-plane setup.


You don't even have to look at a cutaway to see that the path is much smoother for a single plane:


The amount of atomization that occurs in a carburetor depends on the speed of the air passing through the venturi. So at lower engine speeds/demands, there will be less atomization. With EFI, the amount of fuel atomization is constant.

GM TBI will have less, considering the nozzles are injecting at <20PSI. A modern TB-EFI system from the aftermarket is running 40PSI or greater (mine is in the low 60PSI IIRC).

Port EFI is not necessarily sequential EFI. I'm confident if I really wanted to I could have built a port system for the price of the Atomic EFI setup. I went down the Atomic EFI path for two reasons: CARB compliance (live in CA) and the stealth look.

As for the EFI and the "annular discharge rings", it's no different than a shower-head as far as what it does. Pressurized fuel comes through the rings at the rail pressure for your setup. Unlike a carb, there is little-to-no impact on the fuel delivery speed or atomization from pressure differential.

The benefits of TB EFI over other EFI setups are in packaging and ease of install. The fact that you can use any square-bore 4-bbl intake is a big win for cost and parts availability, not to mention the nostalgic look. I am at the point where I think a center-mount throttle body with a pair of port injector rails really wouldn't bother me too much.

If you'd like to see some pictures of how the 78 looks with the stock air cleaner on it, I can get them for you... but it looks pretty much like it did with the Q-Jet, I just have a different throttle cable bracket and two fuel lines coming off the passenger side.

NewbVetteGuy

Wow! This was one of the most educational posts ever truly appreciate all the time this probably took to put together.

I did not realize that at lower throttle positions that fuel injection had an advantage like this; I didn't understand that air speed determined how well a carb's venturi's would atomize fuel -I thought that was constant regardless of airflow.

Some folks on here have already been steering me towards a Weiand Team G single plane intake and after looking at the torque numbers vs. some dual plans I think it's not giving up much on the low to mid end and definitely gaining quite a bit on the high-end AND sounds like it'll be a great match for an EFI (plus they have a really short version that'll fit under my hood and hopefully let me keep my dual snorkel).

My hesitation with a single plane is that I remember reading that EFI systems like long-runners... Yet another reason for port injection as you can go with long runners and maximize air velocity for low-to-mid torque and you don't need to worry about what that's going to do to a fuel/air mixture... -I just wish the price points were a lot closer.


Adam

Adam

lionelhutz

Neither system uses a venturi like a carb. The "venturi" is just the throttle bore and they might have a slight reduction in bore diameter where the injection holes are.

Both throttle bodies basically use what appears to be standard port type injectors pushing fuel into a "ring" passageway around the throttle bores. Then, there are holes spaced around the ring where the fuel actually passes into the bore. The first advantage of these designs is likely the removal of the injector pod above the bore which makes the assembly taller and has the injector pod somewhat blocking the throttle bores. Another advantage of these designs is likely the fact that higher flow port injectors are readily available. Yet another advantage is that these designs can be build with multiple injectors feeding a single throttle bore. I'm not sure if Holley or Fitech do it, but I know FAST has a throttle body with 8 injectors.

The FiTech TBI dumps the fuel above the throttle plates. In a video I saw you can the fuel puddling on the throttle blades at low throttle opening. Their system simply avoids mounting injectors above the throttle bores because there are no other advantages compared to having an injector pointing down the bore.

The Holley dumps the fuel under the throttle plates. Otherwise, it's a similar design. This could have advantages in keeping the fuel suspended compared to injecting above the throttle plates.

Fuel injectors are rather good at atomizing the fuel. I'm not sure where you came up with a venturi being way better because injectors are rather damn good at it.

I'm not sure where you read that EFI likes long runners. Many port EFI engines seem to get away with shorter runners while still maintaining low end drivability and torque when compared to what is typically used with a carburetor to get the same drivability.

suprspooky

My understanding of runner length in a simplified sense is that longer runners (intake/exhaust) will have power peaking in the low to mid rpm range and shorter runners move the peak towards the upper end. There are some good papers written on this from the Mechanical FI days (think Can-AM racing). Carbs typically have some sort of emulsion system to pre-mix air and fuel before it's discharged into the throttle bore.

Ibanez540r

FiTech has both a 4 injector version and an 8 injector.

lionelhutz

One thing I did notice that I didn't comment on is that the FiTech system seemed to spray almost jets of fuel from the holes. To me, an injector does a better job then those holes.

Good to know. I suspected this was true with their higher power versions.