Matt Gruber

12-09 issue page 93. No news here, but a few may think that the reverse is true.
Their test used a 750 Holley VS, which can't perform like a double pumper (and past dyno tests in their mag is where i learned that. ) Kudos to them for saying "in fact, a carb will usually make a few more peak hp than EFI" in trying to explain how a low cost efi beat a VS carb.
Using a street 4165 double pumper would be a helpful comparison test IMO.

63mako

Do a back to back dyno run on both. Average HP and torque will be much better with a properly tuned, properly sized EFI as will MPG, low speed driveability, idle quality and plug life. A few peak HP may or may not be a trade off others are willing to make for the other advantages. Different strokes for different folks.

gerry72

This is not now or has it ever been news. Context is important, though. A carburetor perfectly matched to the engine will produce more peak (not average) horsepower than a production efi due to the carbs ability to atomize the fuel better than efi. This produces a more homogineous mixture, which burns better. This will not happen in an off-the-shelf carb, like a 4165, since it is not tuned for any partuclar engine. For you to realize the performance difference -and it's very slight- you'd have to go to a custom carb. Oh, and efi will match or exceed a carb when you move the injectors substantially further upstream. Putting them in the port that close to the valve is good for emissions, but compromises performance. EFI is beyond a doubt a much better method for fuel delivery than a carb for any engine that will operate at less than full-throttle all the time.

billla

Hot Rod Magazine back-to back comparison with carbs and FAST EZ EFI:

http://www.hotrod.com/techarticles/e...ion/index.html

A key quote, in context:

"We honestly didn't expect to see any power gain by switching to the EZ-EFI (in fact, a carb will usually make a few more peak horsepower than EFI), but within a couple of pulls, it had picked up slightly to 414 hp and 426 lb-ft."

"On both engines, the system fired right up and settled into an idle, and its self-learning function caused each engine to pick up a little more power after a few pulls on the dyno. Surprisingly, it actually made a tad more horsepower on the small-block when compared with a Holley 750 carburetor."

"we tuned the carb as well as we could, then took the car on a 100-mile mileage loop. The carb delivered 13.2 mpg. With EZ-EFI, the exact same mileage loop brought home 18.5 mpg."

"So there you go-FAST's EZ-EFI is a bolt-on that works, goes on easily, returns better fuel mileage, and in some cases might squeak out a few more horsepower. When it comes to electronic fuel injection, it just doesn't get any easier."

MotorHead

I agree with gerry72, you can't take a carb out of the box and slap it on your motor and expect good results. You have to tune it to the motor and that means usiing a wideband O2 sensor. The trouble is not many bother to do this for different reasons, one being the expense of the wideband and another being the knowledge needed to tune the carb after you get the wideband.

There are not many left that actually know how to tune a carb other than changing jets, squirters and few other simple things. The carburetor is a very complex and not very well understood piece. It took a long time to tune my Demon carb properly even with the wideband so along comes and EFI kit and there is little wonder why everyone is excited. It practically tunes itself or it does tune itself, I don't know I don't have one....yet

But once you start tuning your carb with an wideband 02 senser you can minimize the advantages of EFI and you can probably still make more peak HP.

I do like that dual throttle body F.A.S.T. EZ-EFI setup though

billla

A well-tuned, correctly sized and operating carb is the best option short of the expense of EFI. The best carb accessory I ever bought was my Innovate LM2

The problem is people don't tune 'em, they buy ones that are too big and they don't make sure they're working right.

Golden

If you say a carb will pull more peak BHP than injection then the injection isn't set up properly.

Retro fit carbs probably will out perform factory injection as it's mapped for economy and emissions.

A properly fitted and tuned EFI system will always out perform a carb.

7t2vette

You quoted that article out of context; the EZ EFI went on to make MORE HP and TQ than the carb in their test on the small block. Let's also not forget how they recorded a more than 5 mpg increase with the EFI.

EFI > Carb

Get over it.

LFZ

Carbs will make more HP at the peak. Part of the undisclosed reasons why NASCAR uses them. Although, with today's technology, you can get EFI to outperform a carb all around the board and not fall far behind or even surpass peak hp in some carbed comparisons. Too many variables.

Bullshark

A paper written by Russ Collins - RC Engineering

ATOMIZATION
High atomizing injectors are usually used in Throttle Body applications only, and have a rather wide spray pattern. A wide, finely atomized pattern is wonderful for emissions and economy but can cause problems in higher performance engines. At low RPMs, with a low air flow rate, the slow moving finely atomized fuel has enough time to get past the valve and create a close to stoichiometric mixture. (Air/Fuel mixture of 14.70 - Chemically ideal) As RPMs increase this mass can't keep up, with valve open time, and many of the fuel droplets impinge the port wall and condense. Atomized fuel can only travel at "port air speed" and in large quantities it can actually displace air in the port. With a highly atomized mix in the port, at intake valve opening, the lighter droplets of fuel will be partly blown back up the port [intake port reversion]. This is caused by the residual exhaust pressure [overlap period] still residing in the combustion chamber. Some of this reverted mixture will adhere to port walls and condense. This puddling fuel may find its way home, on the next intake cycle, but it will cause cycle-to-cycle air/fuel ratio variances. The higher inertia of the more condensed fuel will carry it to its target. "The liquid film that wets the walls represents a capacitance that greatly reduces the transient response of the engine." (SAE 950506) This problem is compounded in Gang fire and Semi-gang fire systems, but is not as troublesome in sequential fire systems. Gang fire systems fire all injectors, every rotation, at the same time, discharging half of the required fuel at each event. Semi-gang fire systems fire groups of injectors in the same fashion, half-and-half, each rotation. Sequential systems fire each injector at a pre-determined time and discharge all required fuel in one event, prior to intake valve opening. In either of the Gang fire systems there is no timing-of-event technology in operation, and as you can see it's a rather simple system.

At 8000 RPM the intake valve is opening and closing at 66 times a sec. and is only open for an average of 9 Mil/Sec. At this cyclic rate the transient time to complete the delivery of fuel from injector to valve, is critical. This is why Indy car injectors are very precisely targeted and timed to provide a solid stream of fuel with non-existent atomization, LBDS - Laser Beam Delivery System. In these engines the injectors can discharge fuel, at a "just prior to valve open position" and get it all down the hole. As the fuel impinges the hot intake valve it virtually vaporizes and mixes quite well with the incoming air forming a very homogeneous charge. This is one of the most extreme situations but it's a real interesting one. As an added benefit, the latent heat of fuel vaporized in the chamber also provides charge cooling that makes the mixture denser. A denser, heavier mixture (cold and thick) will produce more power then a thin (hot and light) charge. This is why Turbo intercoolers are so effective. Injector timing, phase angle, is altered by the ECU according to RPM in these systems and can control the delivery impact time precisely. In a Steady State Pressure Fuel System, the injector pulse is always moving at the same speed, regardless of engine speed changes. The velocity of discharged fuel is relevant to the area of the discharge port and the net operating pressure. Pressure changes activated by boost, at a 1:1 ratio, only compensate for port pressure and don't change the static pressure, flow rate or velocity. RPM adjusted fuel timing is utilized for this reason, it advances the injector timing based on engine speed, and maintains perfect impingement timing at all speeds.

It's a known fact that you can't burn fuel until it's atomized. It's also known that you can't burn fuel without air. The most important, of all known facts is that you can't burn anything, if it's not in the combustion chamber. The secret is to provide 'adequately atomized' fuel with as much air as possible. 'Adequately atomized' is the secret phrase of the day. Fuel does not have to be completely atomized at the injector tip (SMD of 10um - 20um) but it does have to get past the valve to do us any good. The more condensed the fuel delivery is the faster it will travel, (regulated by discharge area and pressure) and the more accurately it can be targeted. Recent (S.A.E.) "Injector Atomizing and Targeting" studies have provided us with one of the most prominent advances in High Performance Engine Management. These test programs have concluded that "accurate impingement onto the center of the valve head is vital for good vaporization" and "the targeting orientation of the injected fuel spray is a critical parameter in fuel evaporation" also that "fuel injected directly onto the intake valve yields a significantly better engine response" (SAE950506) What all this means is, different engine designs require a different type of injector to operate efficiently and that 100% atomization is not always required or desired. In racing situations we usually have to do the best we can with what we have or what's available. The goal, of course, is to do the best in all cases and in all situations. The best injector for your engine is the one that will yield an optimal fuel-air mixture and provide the required power output consistent with smooth and reliable operation.

Bullshark

BTW, The new Holley EFI systems and probably others soon to be released, have the capability to drive multiple sets of injectors (up to 3 sets of 8), which can be strategically placed to optimize fuel delivery
They can also tune fuel delivery individually to each cylinder to further optimize HP peak or otherwise.

Matt, givie it up and come into the 21 century

Golden

Mmmm yes I had exactly the same discussion with Ron Dennis the other day.

LFZ

??????

Golden

That was sarcasm.

NASCAR use carbs because they're cheap, easy to regulate and appeal to the man in the street, it's got nothing to do with peak power.

There is no way on gods green earth that a carb will always generate more peak power than EFI. If this happens it means the human that programmed the EFI screwed up, not the EFI.

LFZ

Notice how I said, "undisclosed" reasons....

Golden

I still don't get what you're saying.

Are you saying NASCAR fit carbs because they make more peak power, then refuse to admit the fact?

LFZ

No, I agree that NASCAR uses carbs because it's cheap, simple, easier to build, and maybe market to the hot rod builders...but these are all reasons that have always been speculation...maybe a word mentioned here or there. Peak HP was brought up about carbs while I was at a private gathering at a local well known NASCAR team here in Mooresville, NC. Nothing factual or written in stone.

EFI will out perform a carb, but peak HP might be squeezed out by the old carb when comparing apples and apples.

With technology today, and the possibility that GM will have direct injection in the Corvettes...there is no doubt, EFI is the way to go.

billla

I think NASCAR to some extent tries to stay true to the 'old skool' technology...although a current NASCAR engine is anything but low tech. But if you offered a chance to go EFI, I don't think any of the NASCAR guys would hesitate for a second!

Racing specs take a looooonnnnggg time to change - heck, a number of companies still make "stock replacement" copies of 60's SBC heads (castings '041, '186, '291, '462 and '492) for the circle track guys!

mrvette

BUT DPFI will make more instant TORQUE and pedal response then any carb....open up a couple 58mm bores, 1000 cfm, drop mani vac to nearly zero, and VE goes up, **** the gas down after the airflow, and you got a LOTTA torque.....

even little ol' me, working hin his garage in '92, put a DPFI system on a olde tyme Pontiac 455 .....so instead of 550 ft lbs at 3000 rpm it was more like the car would flip over backwards at idle.... AND it picked up some 40% on fuel economy....

but from ten mpg to 14 mpg is not a LOT, bue the % looks impressive, course if I took my toes outta the t-body, maybe it would have gotten better economy....ya THINK??



edit....I guess another way to look at it, there is a much broader area under the curve....the curve is flatter then possible with most any carb....and the results much more repeatable, due to the computer.....I just wish LM1 sensors and recalibrating computers at 17-1 a/fuel ratio would be much better for power and economy....hell with the EPA stuff....

gerry72

If NASCAR crew chiefs had a choice in the matter, they'd go with EFI. They've even said so. But it wouldn't be a system that has any similarity to the designs used in a street system. They don't use carbs because they're cheap. What's a $10,000 EFI system to a race team with a $10M budget? How much do you think the carb guy gets to keep them on top? The cost component is an absurd arguement. Carbs used on the race teams are also not easy to tune. They are much harder to set up than EFI since the carb guy has to shoot for what he believes will be racing conditions throughout. There's nothing adaptive about them.

And the laborous Collins copy and paste is very superficial, really. These things (and one, better vaporization not mentioned in a carb) are very well known quantities and are well accounted for with people who make their living making horsepower -particularly with carb, intake, and cylinder head design. One reason why EFI used on race engines put the injector well upstream of the valve is to allow the atomized fuel to reach a vapor state. Fuel plating is less of a problem than the presentation allows. It may not have been intended to be more than a once over lightly, but if you don't know the issues and the physics then it leaves you with a false impression of the merits. In short, there's way, way more depth to the discussion than this forum would allow.

tt 383

Well they let efi into Engine Masters this year and it did perform good for the first year. The funny thing is the air wasnt very good and the efi guys should have been able to use it to their advantage. The main thing I see is that you can rarely get an apples to apples comparison. Runner length for runner length, or the fact that a carb/efi would need a different cam. Seems that when on a dyno @ WOT a carb will always pull more power. EFI clearly has its advantages in road course, packaging of intake and better mpg. The magazine article proves that if you have money they will print what ever you want them too no matter how incomplete or shallow the testing.