Need advice on what to do

[Gary Lewis]

Is the Holley Sniper with throttle-body fuel injection really that much better? I would have thought the multi-port fuel injection Ford was using on their F-Series trucks even at that time would still be better than any throttle-body fuel injection system.

When your fuel economy dropped on your Motorcraft 2150 because of the change to ethanol fuels, did you try to re-tune the carburetor to compensate? Some of the "four-eyed" Mustang guys who run the stock Motorcraft 4180 have had the same complaints as you, and they have regained their lost power and economy by increasing the jet size and squirters by two.

I am running an Autolite 4100 on Lucille, and I can get about 18 mpg on the highway if I drive it right. When I tuned it, I got better power and economy by going from the stock size 49 jets to 50 on the primaries and from the stock size 58 to 60 on the secondaries.

Let's face it, the engine doesn't know if it has a carb or EFI on it. And if whatever it is gives optimum AFR then you'll get the same MPG regardless.

But a carb, by itself, gives a static AFR at its point of tune. So if the air temp, air pressure, fuel level in the carb, or anything else changes the AFR will not be the same. And, a carb is giving you an air/fuel mix at a central point, but that won't be the same at each cylinder due to the intake manifold.

That's where the feedback carb system came in. The ECU tried to adjust the carb to keep the AFR at the best setting. But the ECU's didn't have the bandwidth nor the inputs to allow it to do so at all times. Still, it was better. However, it is still limited by the intake manifold.

Then there's EFI. Throttle body systems can give "best AFR" at all times since it adjusts for all of the variables. But it is still limited by the intake manifold, so each cylinder is going to see a different AFR.

Enter multi-port EFI. These systems read not only all the parameters but also can vary the amount of fuel going to each cylinder. So now we are approaching "optimum AFR" at each cylinder. And this combo will give the best MPG.

[1986F150Six]

Let's face it, the engine doesn't know if it has a carb or EFI on it. And if whatever it is gives optimum AFR then you'll get the same MPG regardless.

But a carb, by itself, gives a static AFR at its point of tune. So if the air temp, air pressure, fuel level in the carb, or anything else changes the AFR will not be the same. And, a carb is giving you an air/fuel mix at a central point, but that won't be the same at each cylinder due to the intake manifold.

That's where the feedback carb system came in. The ECU tried to adjust the carb to keep the AFR at the best setting. But the ECU's didn't have the bandwidth nor the inputs to allow it to do so at all times. Still, it was better. However, it is still limited by the intake manifold.

Then there's EFI. Throttle body systems can give "best AFR" at all times since it adjusts for all of the variables. But it is still limited by the intake manifold, so each cylinder is going to see a different AFR.

Enter multi-port EFI. These systems read not only all the parameters but also can vary the amount of fuel going to each cylinder. So now we are approaching "optimum AFR" at each cylinder. And this combo will give the best MPG.

Just for the discussion regarding optimum air/fuel ratios... Gary monitored the ratios of a certain 4.9L equipped F150 [modified fuel/ignition system] while being driven under varying conditions. At one point in the drive, AF ratio was recorded @ ~17:1.

Remember, Gary?

[Gary Lewis]

Just for the discussion regarding optimum air/fuel ratios... Gary monitored the ratios of a certain 4.9L equipped F150 [modified fuel/ignition system] while being driven under varying conditions. At one point in the drive, AF ratio was recorded @ ~17:1.

Remember, Gary?

I remember it well, David. I used the term "optimum AFR" on purpose. That isn't exactly 14:1. It varies by what you are wanting to do. If you are wanting power it needs to be closer to 12:1. If you want economy it needs to be more like your 17:1. And along with the varying AFR comes varying ignition timing.

Carbs and "dumb" ignition systems just cannot be "right" at all points like today's multi-port EFI systems that control not only the AFR but also the ignition timing and transmission gear and, therefore, RPM.

[1986F150Six]

Carbs and "dumb" ignition systems just cannot be "right" at all points like today's multi-port EFI systems that control not only the AFR but also the ignition timing and transmission gear and, therefore, RPM.

Life is a compromise!

 

[Gary Lewis]

Carbs and "dumb" ignition systems just cannot be "right" at all points like today's multi-port EFI systems that control not only the AFR but also the ignition timing and transmission gear and, therefore, RPM.

Life is a compromise!

Yup. So true.

[LARIAT 85]

I remember it well, David. I used the term "optimum AFR" on purpose. That isn't exactly 14:1. It varies by what you are wanting to do. If you are wanting power it needs to be closer to 12:1. If you want economy it needs to be more like your 17:1. And along with the varying AFR comes varying ignition timing.

Carbs and "dumb" ignition systems just cannot be "right" at all points like today's multi-port EFI systems that control not only the AFR but also the ignition timing and transmission gear and, therefore, RPM.

But wouldn't that be an advantage to having a carburetor?

These "dumb" systems cannot prevent you from tuning *your* vehicle the way *you* want to. If your goal is maximum power, your carburetor and ignition timing can be tuned to achieve a 12:1 AFR. Likewise, if your goal is maximum fuel economy, your carburetor and ignition timing can be tuned to achieve a 17:1 AFR.

Wouldn't that also mean that - with all other things being equal - a carburetor can be adjusted to have more power than an EFI system, OR it can be adjusted to get better fuel economy than an EFI system?

An advantage to EFI is the ability to self-tune - but isn't is programmed to always revert to the "optimum" AFR of 14:1?

 

[Rusty_S85]

With a sniper youll see easily out of the box a 3 to 5 mpg increase in economy over a carb. If you take and have it tuned professionally Ive seen people get as much as 8 to 10 mpg increase in economy over a carb.

I would say that getting an 8-10 MPG increase over a carb means that the carbed system was working very poorly in the first place. I'll drive to Texas tomorrow if somebody guarantees that I'll see an 8-10 MPG increase in swapping my 600CFM Holley for a Sniper EFI.

I'm not saying that EFI isn't superior...clearly it is, but lets not get carried away with the claims here. You're talking 30% to 50+% improvements in efficiency in switching to a throttle body EFI system.

Thing is how many people are actually going to the trouble some of us have to tuning a carb to its limits.

Majority of people out there are either running a bone stock OE carb or they are running a aftermarket carb out of the box.

I do know that when it comes to the sniper itself in typical holley fashion they have it set to run on the rich side for safety. This results in lower fuel economy than if you were to have it tuned to what your engine actually needs.

Same with my 2150 OE 2V, that carb is getting me around 12 mpg city during summer months and 11mpg city during winter months. Highway is around 14 to 15 mpg. In my case over my OE carb, I will see a good increase in economy as there is no reason for me not to see 14 to 15 mpg city. With tuning I dont believe there is a reason why I couldnt see 16 to 17 or possibly even 18 mpg city.

In the end those that actually change the AF ratio by playing with jets, and secondaries and accelerator pumps are actually in the minority when it comes to people that are building vehicles. Majority that I see come through where I work just bolt parts on and dont really touch them. Those are the same people that are making the switch to EFI as they say carbs are junk. I dont believe carbs are junk, I just dont care to invest the time to mess with a carb to get it where it needs to be when I can just spend a little more money and go EFI.

[ArdWrknTrk]

Thing is how many people are actually going to the trouble some of us have to tuning a carb to its limits.

Majority of people out there are either running a bone stock OE carb or they are running a aftermarket carb out of the box.

I do know that when it comes to the sniper itself in typical holley fashion they have it set to run on the rich side for safety. This results in lower fuel economy than if you were to have it tuned to what your engine actually needs.

Same with my 2150 OE 2V, that carb is getting me around 12 mpg city during summer months and 11mpg city during winter months. Highway is around 14 to 15 mpg. In my case over my OE carb, I will see a good increase in economy as there is no reason for me not to see 14 to 15 mpg city. With tuning I dont believe there is a reason why I couldnt see 16 to 17 or possibly even 18 mpg city.

In the end those that actually change the AF ratio by playing with jets, and secondaries and accelerator pumps are actually in the minority when it comes to people that are building vehicles. Majority that I see come through where I work just bolt parts on and dont really touch them. Those are the same people that are making the switch to EFI as they say carbs are junk. I dont believe carbs are junk, I just dont care to invest the time to mess with a carb to get it where it needs to be when I can just spend a little more money and go EFI.

I have a quick change spring kit on my Holley 750, and two pit boxes full of floats, jets, boosters, etc...

I do not however have an AFR installed, sooooo ?

[Rusty_S85]

Is the Holley Sniper with throttle-body fuel injection really that much better? I would have thought the multi-port fuel injection Ford was using on their F-Series trucks even at that time would still be better than any throttle-body fuel injection system.

When your fuel economy dropped on your Motorcraft 2150 because of the change to ethanol fuels, did you try to re-tune the carburetor to compensate? Some of the "four-eyed" Mustang guys who run the stock Motorcraft 4180 have had the same complaints as you, and they have regained their lost power and economy by increasing the jet size and squirters by two.

I am running an Autolite 4100 on Lucille, and I can get about 18 mpg on the highway if I drive it right. When I tuned it, I got better power and economy by going from the stock size 49 jets to 50 on the primaries and from the stock size 58 to 60 on the secondaries.

I did not, I didnt mess with the carb I just left it like it was and lived with it cause the truck was like a clock till the balancer broke and took out the crank. I just kept going cause the truck kept going.

Now that I need to pull the engine to at least put a crank in it I said I am not going to pull the engine throw a $200 cast crank in on a engine that used oil from day one since it was rebuilt.

That is where my 306 built comes in and eventually the EFI that I am running now.

Now true EFI multi-port is better than TBI EFI, but the thing is I dont know about the MPI EFI that ford was using in 84/85 if it was sequential fire or group fire. Many manufacturers I know started off with group fire with EFI where all injectors fired even if the valve for that cylinder was closed. If the 84/85 trucks were a group fire just like the TBI`s were then the economy wouldnt be that much better than a TBI cause you are still wasting fuel spraying it against a closed valve.

Dont get me wrong I am not saying TBI is the best, TBI is a stout design that just works. Sure its not as percise as true sequential fire MPI EFI and Holley does offer the MPI setup but we have one at work the guy wants taken off and a sniper put on cause it has been nothing but trouble and has been to 6 different tuners and it still doesnt work right. If I were to go MPI, I would probably grab a late model MPI factory system and convert to that. But as a bolt on upgrade in place of a carb I would go with a TBI. It is better than a carb but not as good as true MPI EFI.

Basically its Carb < Computer Carb < TBI = Group fire EFI < Sequential fire MPI EFI.

For me, my truck is a daily driver or was and will be again once I get the engine done. I dont want to have to do trial and error with tuning the carb and then possibly have to deal with the possibility that the summit carb I have will be like most aftermarket carbs out there and be picky and need periodic adjustment. My 2150, it was never touched after the carb was rebuilt and was used at the same settings with no problem for 10 years when it was rebuilt again. That is where the Sniper for me came in, I wont have to disassemble it to make changes if changes are needed. I also wont have to rejet after I move due to a change in elevation as the sniper will compensate for the altitude change.

Now is the sniper much better than the OE systems, honestly if you have it properly tuned by someone that knows what they are doing I believe the TBI sniper system is on par with OE systems. Compared to feedback carburetors I think they are superior as a TBI is the next step in evolution from carb to fuel injection.

[Rusty_S85]

Let's face it, the engine doesn't know if it has a carb or EFI on it. And if whatever it is gives optimum AFR then you'll get the same MPG regardless.

But a carb, by itself, gives a static AFR at its point of tune. So if the air temp, air pressure, fuel level in the carb, or anything else changes the AFR will not be the same. And, a carb is giving you an air/fuel mix at a central point, but that won't be the same at each cylinder due to the intake manifold.

That's where the feedback carb system came in. The ECU tried to adjust the carb to keep the AFR at the best setting. But the ECU's didn't have the bandwidth nor the inputs to allow it to do so at all times. Still, it was better. However, it is still limited by the intake manifold.

Then there's EFI. Throttle body systems can give "best AFR" at all times since it adjusts for all of the variables. But it is still limited by the intake manifold, so each cylinder is going to see a different AFR.

Enter multi-port EFI. These systems read not only all the parameters but also can vary the amount of fuel going to each cylinder. So now we are approaching "optimum AFR" at each cylinder. And this combo will give the best MPG.

And that is where the TBI and true MPI EFI are different.

The TBI is the next evolutionary step after the feedback carb. Its more precise than the feedback carb and has the ability to make more adjustments.

But the engine doesnt know what it has on it for feeding it with fuel and air. But the nice thing about the sniper is you can vary the AFR quite a bit to the point where you can lean it out to the point of burning holes in pistons and you can set the target AFR for idle, cruise, and wot settings or if you have a laptop you can put in a custom fuel map and be even more precise which is why people are seeing a increase in fuel economy with a custom tuned sniper over an out of the box sniper as in typical fashion Holley has the AFR set on the rich side as on the rich side wont kill an engine unlike on the lean side.