Holley Terminator efi vs. FAST efi vs. MSD Atomic efi

[dieselgeek]

Eh, I'd go carburetor before a TBI.

Recently I helped a buddy of mine who runs a dyno shop in Lincoln, NE. He had a 3rd gen Trans am with a Butler-built crate Pontiac engine. Swapped the Holley 750 for an EZ-EFI. The engine started and ran better than the carb, but was down *20%* on horsepower at the wheels as measure on a Mustang chassis dynamometer. no dynojet tricks here. He fought with swapping ECUs and TBs but the thing was always way down on power. We switched him to a Megasquirt-3 controlling the same EZ-EFI throttle body, same exact problem. We then had his intake manifold set up for port injectors, ran that with the Megasquirt-3 and got our horsepower back - about the same as the carb, and a little more torque. If you run a TBI injection, I'd like to see pics of all 8 spark plugs after some run time. I see a lot of these systems, and one common observation is imbalanced fuel delivery to each cylinder. none of the plugs tend to look the same. It's possible with a lot of work to the intake that someone might be able to solve that problem but... I think there's a lot of non-factual information about how these TBI EFI systems work. I've never seen one do well when tested.

And after a lot of testing, I will disagree strongly with the suggestion above that Throttle Body is just as good as Port injection. Absolutely, unequivocally, NO. Port injection promotes better fuel distribution, and on some systems allows adjustment of quantity per cylinder and timing of the injection event - these two alone were worth 45hp on a 498" Gen 2 Hemi I tuned recently, and typically pick up 5-7% power every time I use them.

And if picking a system to use, if the Terminator software is anything like the new Holley Dominator and HP systems, that would be my preference. I really like the software used for tuning the new Holleys - they put a lot of thought into laying it out so it's easy for someone new to EFI to understand. That being said, a FAST XFI is also a really good system to use, and I have a lot of luck tuning cars that run it.

[Roadknee]

Dieselgeek - do you have any experience with Holley's 4bbl TB? I run a 900 cfm with 75 pph injectors controlled by a C950 ECU on about a 420 hp 383. It seems to run as strong as the 780 carb it replaced, but does use more fuel.

I've also tuned a friends C950 Stealthram on about a 450 HP 400. Gotta admit, this one was much less finicky to tune.

Finally, the Megasquirt guys tested a 900 cfm TB on a mild 350 in their nova. It made less power across the board compared to the GM style 2 bbl TB. Any idea why?

[My427stang]

Eh, I'd go carburetor before a TBI.

Recently I helped a buddy of mine who runs a dyno shop in Lincoln, NE. He had a 3rd gen Trans am with a Butler-built crate Pontiac engine. Swapped the Holley 750 for an EZ-EFI. The engine started and ran better than the carb, but was down *20%* on horsepower at the wheels as measure on a Mustang chassis dynamometer. no dynojet tricks here. He fought with swapping ECUs and TBs but the thing was always way down on power. We switched him to a Megasquirt-3 controlling the same EZ-EFI throttle body, same exact problem. We then had his intake manifold set up for port injectors, ran that with the Megasquirt-3 and got our horsepower back - about the same as the carb, and a little more torque. If you run a TBI injection, I'd like to see pics of all 8 spark plugs after some run time. I see a lot of these systems, and one common observation is imbalanced fuel delivery to each cylinder. none of the plugs tend to look the same. It's possible with a lot of work to the intake that someone might be able to solve that problem but... I think there's a lot of non-factual information about how these TBI EFI systems work. I've never seen one do well when tested.

And after a lot of testing, I will disagree strongly with the suggestion above that Throttle Body is just as good as Port injection. Absolutely, unequivocally, NO. Port injection promotes better fuel distribution, and on some systems allows adjustment of quantity per cylinder and timing of the injection event - these two alone were worth 45hp on a 498" Gen 2 Hemi I tuned recently, and typically pick up 5-7% power every time I use them.

And if picking a system to use, if the Terminator software is anything like the new Holley Dominator and HP systems, that would be my preference. I really like the software used for tuning the new Holleys - they put a lot of thought into laying it out so it's easy for someone new to EFI to understand. That being said, a FAST XFI is also a really good system to use, and I have a lot of luck tuning cars that run it.

Dieselgeek, where are you from? Papillion NE here. I assume you were at Dynosport? I hope he is doing well, we did some work on a drag car down there and he is a nice guy, at the time business was down due to the economy, hopefully he is keeping the rollers moving.

Your experience is interesting and has stumped me for a while. I certainly agree that a programmable SEFI would do great things, and the TBIs seem to gain drivability but lose power. However, what I haven't been able to wrap my arms around is the carb vs EFI issues, because they seem to act universally, but the systems are so different.

What I mean is, 4 TB injectors in a housing on an intake, "should" flow more air than an equivalent sized carb without a booster in the way, give it good fuel, it should make more power if the engine can take the additional air and fuel, but often they don't make more power, and as you have seen can even drop at the peaks. Common argument is that the fuel may not atomize as well as a carb's boosters. However the MSD theoretically should flow a little less air than the others, but they use an injector that feeds a booster, which in theory, should offset the atomization problem and essentially make it an electronic carburetor.

Thinking out loud, I wonder if the TB programmers sync up injector timing and with an injector duty cycle <100% creating a situation where the a/f mixture is cycling rich/lean faster than the sensors can report it? I can't think of any universal reason otherwise. Thoughts?

[dieselgeek]

It's good to see a local on here! I was working at Chad Fegley's shop on 33rd St. He has a Mustang dyno. I haven't been to Dynosport in a long time.

I am not sure why TBIs do not do well performance-wise, something to do with fuel not staying properly suspended in the incoming air charge obviously but I do not know the exact cause - others here can probably give better input on that.

I know it's relative to overlap on the cam, the problems get worse with more aggressive cam profiles.

[Carnut1]

Pricing on the Holley system with the fuel kit is about $2500. Not exactly cheap, I would pay a few $ more for a self learning port injection set up. I would run one of the tunnel ram injection systems but I am not sure how much low end torque that would give up over the TBI system on a modified dual plane. Has anyone used one of these tunnel ram injection systems on a high torque truck application?

[My427stang]

I haven't used a tunnel ram, but I expect it would work great with long runners and port injection. I went from a carb'd dual plane to a ported Victor SEFI and gained torque and drivability in every situation.

I agree with you that the more capable the system, assuming it fits in your budget, the happier you will be. However, keep in mind, the self learning stuff is decent, but its only a taste of what you can do with tuning.

Injector timing based on cam events, load, ignition timing, cycling between open/closed loop in certain situations, injector curves, MAF curves, you name it you can play with it. Unfortunately the new systems that self-learn really only just try to get A/F to a preset number, real good stuff for the average bear, but there is so much more you can do if you actually do some tuning and let the self-learning adjust for environmental conditions (when you want to let it do that)

[Carnut1]

[quote="My427stang"]I haven't used a tunnel ram, but I expect it would work great with long runners and port injection. I went from a carb'd dual plane to a ported Victor SEFI and gained torque and drivability in every situation.

I agree with you that the more capable the system, assuming it fits in your budget, the happier you will be. However, keep in mind, the self learning stuff is decent, but its only a taste of what you can do with tuning.

Injector timing based on cam events, load, ignition timing, cycling between open/closed loop in certain situations, injector curves, MAF curves, you name it you can play with it. Unfortunately the new systems that self-learn really only just try to get A/F to a preset number, real good stuff for the average bear, but there is so much more you can do if you actually do some tuning and let the self-learning adjust for environmental conditions (when you want to let it do that)[/quote



The projection 4di I can set the timing at any point the fuel curve at any point and the O2 trigger points for idle, cruise, wot, etc. The stock Holley curves were not close to what this engine wanted and I figured by now the processor power was up to the task of tuning better than my seat of the pants method by far. I have done the whole tuning nightmare and killed a few engines in the process. There has got to be a better way by now!

[Cutlassefi]

I agree with you that the more capable the system, assuming it fits in your budget, the happier you will be. However, keep in mind, the self learning stuff is decent, but its only a taste of what you can do with tuning.

Injector timing based on cam events, load, ignition timing, cycling between open/closed loop in certain situations, injector curves, MAF curves, you name it you can play with it. Unfortunately the new systems that self-learn really only just try to get A/F to a preset number, real good stuff for the average bear, but there is so much more you can do if you actually do some tuning and let the self-learning adjust for environmental conditions (when you want to let it do that)[/quote

I agree with most everything above but let me shed some further light on this if I may.

I've been a tuner for about ten years. I did the training video for Accel and have tuned other systems as well, both multiport and TBI. My car is a stock block Olds 350 Cutlass Supreme conv with an Accel Gen 7 multiport system.

Unfortunately there is a lot of bad info out there regarding the Self tuning stuff. For a mild build it's fine but even at that it doesn't maximize the applications' potential. A lot will say "it runs fine" but that doesn't mean it's performing as good as it could be with a better, more tunable system.
And for anyone to say there's no benefit in going to a multiport from a TBI probably has no real experience with either or both. Do you think the new Corvette could meet emissions standards and make the power and mileage it does with a TBI? Probably not. A fully sequential multiport system helps tremendously.

Any, Any TBI is at the mercy of any and all inherent flaws of the intake it's installed on. Its' nothing more than an electronic carb so puddling and other issues will still happen, although maybe not as magnified.

And imo any TBI without spark control is a waste, you can't discount the benefit it provides.

Thanks
Mark

[Carnut1]

Mark, thanks for your input. I have been thinking more about the multi port systems and would gladly pay more for a better running system. I agree on spark that is computer controlled, I would only run a system with a computer managed spark curve.

[My427stang]

I've been a tuner for about ten years. I did the training video for Accel and have tuned other systems as well, both multiport and TBI. My car is a stock block Olds 350 Cutlass Supreme conv with an Accel Gen 7 multiport system.

Unfortunately there is a lot of bad info out there regarding the Self tuning stuff. For a mild build it's fine but even at that it doesn't maximize the applications' potential. A lot will say "it runs fine" but that doesn't mean it's performing as good as it could be with a better, more tunable system.
And for anyone to say there's no benefit in going to a multiport from a TBI probably has no real experience with either or both. Do you think the new Corvette could meet emissions standards and make the power and mileage it does with a TBI? Probably not. A fully sequential multiport system helps tremendously.

Any, Any TBI is at the mercy of any and all inherent flaws of the intake it's installed on. Its' nothing more than an electronic carb so puddling and other issues will still happen, although maybe not as magnified.

And imo any TBI without spark control is a waste, you can't discount the benefit it provides.

Thanks
Mark

I think everyone is agreeing completely, multiport beats TBI for a multitude of reasons.

My point is why do carbs tend to peak higher than TBI? Even when TBI often has the capability of more air flow and we can tune easily to take advantage of it?

Seems to me something is going on here. If the intake is the same from a carb to TBI, and in Dieselgeek's case they used progressively more programmable controllers, AND we see the injector directly spraying into some and into boosters in others, the why would carbs tend to make more?

You'd think that at some point the electronic carb would equal a regular carb, but from most of the WOT dyno tests they seem to be down, despite part throttle feeling better

It has me thinking, that's why I brought up injector duty cycle, or even the injector slopes. Maybe the pulses of the injector are doing something per cylinder that we aren't seeing that a carb would keep constant.