10k in pocket. New block or EFI ?

[Cobrabill]

Originally Posted by FUNFER2

I agree. With EFI supporting the cfm and other parameters, with the computer adjusting on the fly, how can a carb. do the same ?

Keven,does that computer change how much air will fit thru the throttle blades,intake runner or past the valve?

[Cobrabill]

[quote=Great Asp1) Do you know what a T-bone looks like?

2)When someone says that let me know.

3)Gee thanks. I guess a Volkswagon would have been more practical. I'll have to re-think this whole Cobra thing E[/QUOTE]

1)Sure.Another non-sequitur would be nice
2)You did.But not in so many words.
3)Don't get all worked up fer christ sakes.If WE were the pratical type,this board would be a ghost town.And the last time i looked,the FI/carb debate wasn't Cobra specific.


My whole point is that for people chasing the almighty HP,FI isn't the answer.

[Great Asp]

Bill,

1) Do you know what a T-bone looks like? "Sure.Another non-sequitur would be nice" Do I have to tell you how to look?

2)When someone says that let me know. "You did.But not in so many words." Thanks clearing that up, you are right, I'm sure

3)Gee thanks. I guess a Volkswagon would have been more practical. I'll have to re-think this whole Cobra thing E "Don't get all worked up fer christ sakes.If WE were the pratical type,this board would be a ghost town.And the last time i looked,the FI/carb debate wasn't Cobra specific." I didn't think it was a big leap to the statement I made based on your comments.

E

[olddog]

Originally Posted by Cobrabill

Injection is injection.I don't care who's it is.Peak HP is determined by how efficient a air pump the engine is.Fuel delivery system is ALMOST irrelevant.

You can flow a bunch more air down a pipe, at a given delta pressure, than you can air with 8% gasoline mixed with it. Fuel laden air does not flow well in a manifold. So at least in theory, an engine can pump much more air if you don't mix the fuel into the air right at the begining, like a carb or throttle body injection does. Ideally the fuel would go in via direct injection into the cylinder after the intake valve was closed.

By its very nature a carb has to create a low pressure zone to suck the fuel through the jets, creating a flow restriction. EFI does not have this problem.

Now the factory EFI stuff was designed for good emissions and low end torque. On Hp it does not compete with a carb. Most of the aftermarket stuff is patterned off the factory systems and still trying to meet emissions. It would not surprise me at all if an aftermarket EFI system, that was design from the ground up to make power and not care about emissions, made more power than a carb.

[stuartb]

For me it was an easy choice, EFI was the way to go with a change in altitude of about 5000 ft. on my normal drives.

[Cobrabill]

Originally Posted by stuartb

For me it was an easy choice, EFI was the way to go with a change in altitude of about 5000 ft. on my normal drives.

I was going to mention "your" situation but i thought it would be a digression of sorts.But that is one advantage of the "correct" FI system.

[Cobrabill]

Originally Posted by olddog

1)You can flow a bunch more air down a pipe, at a given delta pressure, than you can air with 8% gasoline mixed with it. Fuel laden air does not flow well in a manifold. So at least in theory, an engine can pump much more air if you don't mix the fuel into the air right at the begining, like a carb or throttle body injection does. Ideally the fuel would go in via direct injection into the cylinder after the intake valve was closed.

2)By its very nature a carb has to create a low pressure zone to suck the fuel through the jets, creating a flow restriction. EFI does not have this problem.

3)Now the factory EFI stuff was designed for good emissions and low end torque. 4)On Hp it does not compete with a carb. 5)Most of the aftermarket stuff is patterned off the factory systems and still trying to meet emissions. 6)It would not surprise me at all if an aftermarket EFI system, that was design from the ground up to make power and not care about emissions, made more power than a carb.

1)That's why manifold designs(wet vs dry) are different.The amount of air an engine can pump IRRELEVANT to the fuel system.
2)And yet,it(the carb) still makes as much(or more) HP as FI.Go figure
3)Factory EFI was designed for emissions-PERIOD.
4)Yes-it does.Look at all the Viper,Vettes & such.But we aren't talking about factory-are we?
5)False
6)Too ridiculous to respond to.

[RodKnock]

For better Webers versus Dynatek numbers, as they relate to Dean Lampe's RCR40, I started this thread some time ago.

Dynatek & Dean Lampe's RCR 40 in Kit Car Mag...again

I'm willing to bet that Dean had both his Weber and Dynatek setup operating at or near peak efficiency. The winner was Dynatek. The only negative is cost from what I can see.

[cobrarkc]

I no expert but the Dynatek system will flow 3000cfm and with EFI and a wideband O2 sensor you can infinately adjust the A/F for optimum efficiency the whole rpm range. How could you possible do that with a carb?

[Cobrabill]

[quote=cobrarkc;. How could you possible do that with a carb?[/QUOTE]

Easy-get a big enough carb.For example:Two Dominators would fill that bill.And what good does a 3K flow capacity do for you if you don't have the intake,cam,heads or exhaust system to utilize it?

Rich-please read what i typed.I said there ARE other benifits to FI.Such as more precise A/F metering.That does not increase peak numbers.

[Fordzilla]

A Hampton Blower was the choice for me. Plenty of flow!!

[olddog]

Bill I likely agree with you on more things than I would disagree.

I take it that your point of view is that if the air fuel ratio is 12.5:1, it makes absolutely no differance how it got there. The fuel system is irrelevant. All that matters is how good an air pump is the engine. Not trying to put words in your mouth, but that is my interpretation of what you said.

If you could conveniently totally seperate AFR and flow, I would absolutely agree. However the fuel delivery can affect the air flow into the pump (engine). Look at a dual plane verses a signle plane intake or what a carb spacer can do to flow. Now is it so hard to fathem that where the fuel is introduced could impact how much air can flow into the engine?

Last I was on Edelbrocks web site they were advertising several of their engines with both carb and EFI, and they claimed the EFI version would make more Hp. Ridiculous I guess.

Edit: I just checked Edelbrocks site and it no longer lists different Hp for carb verses EFI. Don't know what to make of that.

Edit 2: Well it depends on how you get there. If you look at the chevy 555 cid Pat Musi engine 650 hp is the carb version and 675 hp is the EFI version. Same cam and heads. Different induction systems. EFI torque looks to be higher both low and high rpms. Both engines peak 650 lb-ft @4500 rpm.

[mr. oz]

From Pro Systems website:

Carburetors and Electronic Fuel injection are two completely different systems. They share no concepts and each has a different theory.

EFI's claim is this: I will supply sprayed droplets of fuel at the proper air to fuel ratio all the time.

Carburetors claim: I will supply a pre-emulsed froth of fuel and air into the engine at a preset ratio.

The results proved the analysis of the concepts to be correct. In this case, the carburetor was supplying the engine in question with the proper air to fuel ratio, so the EFI's advantage was gone. Remember, EFI has a computer to tune the engine. You have you. If you know how to tune you'll have the advantage. Carburetors (at the risk of sounding chauvinistic) are a man's game. Guessing rarely works. You have to know how to actually tune an engine.

Remember a carburetor is an atomization/emulsion machine. An injection system is a proper air to fuel delivery ratio machine. Two different concepts. If a carburetor can be designed to supply the perfect air to fuel ratio all the time it should consistently outperform EFI. Its design lends itself to have an unfair advantage in atomization.

Obviously adiabatic expansion is the next question on the list. So if we take a good look at the carburetor we see its not only a perfect machine for atomizing fuel, it also has another advantage. The Joule-Thomson effect.

Tests performed using quartz plates and infra red sensors located in the plenum area beneath an NHRA Pro-Stock engine revealed an intake manifold temperature drop on a 85 degree day of almost 20 degrees as a result of the the carburetor creating this effect.

So when your neighbor with EFI is ingesting 85 degree air, your power-plant could be ingesting 65 degree air.

That's a nice advantage.

But let's not skip over the atomization advantage. In a high end designed carburetor the fuel is emulsed to lift it. Its a controlled froth. I won't kid you, it's very difficult to control. Its much easier to build a carburetor that operates on a vacuum to ratio concept. But the fogging advantage is gone. So when a customer asks, why is this carburetor more expensive than that builders carburetor as they look basically the same. Most of it is all in the emulsion package and the time spent flowing it and tweaking it to do its job. Remember in a high emulsion design .001 of an inch is a big deal. They're difficult to balance and require sophisticated equipment that many shops have never seen. Also, don't go poking things into the metering block passages to inspect them or look around. You might just lose 10 lbs of torque.

The disadvantage of carburetors used to be restriction. I remember back 20 years ago before booster technology really took off you had to size carburetors to operate on 1-2 inches of vacuum in the plenum at the starting line. The restriction alone was probably costing these engines a 2-3 percent power loss.

Tests we performed at Sonny's racing 5 years ago showed us numbers of about .6 in the plenum and spikes of about 1.1 to 1.3 in the runner at the finish-line. That's a pretty huge decrease and just for dynos sake when we built carburetors large enough to reduce this number by on average 40 percent we saw an increase of only about 3-5 horsepower on an IHRA Pro-Stocker. SO that advantage for EFI is now also gone.

Now that these same engines can operate on as little as .5 hg of vacuum at the starting line and only 1-1.2 at the finish-line, the restriction is nil. Really it all comes down to getting the air to fuel ratio correct. If a carburetor can do that, it should win the race every time. After all, by design, it's a superior emulsion machine.

Originally Posted by olddog

Bill I likely agree with you on more things than I would disagree.

I take it that your point of view is that if the air fuel ratio is 12.5:1, it makes absolutely no differance how it got there. The fuel system is irrelevant. All that matters is how good an air pump is the engine. Not trying to put words in your mouth, but that is my interpretation of what you said.

If you could conveniently totally seperate AFR and flow, I would absolutely agree. However the fuel delivery can affect the air flow into the pump (engine). Look at a dual plane verses a signle plane intake or what a carb spacer can do to flow. Now is it so hard to fathem that where the fuel is introduced could impact how much air can flow into the engine?

Last I was on Edelbrocks web site they were advertising several of their engines with both carb and EFI, and they claimed the EFI version would make more Hp. Ridiculous I guess.

Edit: I just checked Edelbrocks site and it no longer lists different Hp for carb verses EFI. Don't know what to make of that.

Edit 2: Well it depends on how you get there. If you look at the chevy 555 cid Pat Musi engine 650 hp is the carb version and 675 hp is the EFI version. Same cam and heads. Different induction systems. EFI torque looks to be higher both low and high rpms. Both engines peak 650 lb-ft @4500 rpm.

[fkemmerer]

Originally Posted by mr. oz

From Pro Systems website:

Carburetors and Electronic Fuel injection are two completely different systems. They share no concepts and each has a different theory.

EFI's claim is this: I will supply sprayed droplets of fuel at the proper air to fuel ratio all the time.

Carburetors claim: I will supply a pre-emulsed froth of fuel and air into the engine at a preset ratio.

The results proved the analysis of the concepts to be correct. In this case, the carburetor was supplying the engine in question with the proper air to fuel ratio, so the EFI's advantage was gone. Remember, EFI has a computer to tune the engine. You have you. If you know how to tune you'll have the advantage. Carburetors (at the risk of sounding chauvinistic) are a man's game. Guessing rarely works. You have to know how to actually tune an engine.

Remember a carburetor is an atomization/emulsion machine. An injection system is a proper air to fuel delivery ratio machine. Two different concepts. If a carburetor can be designed to supply the perfect air to fuel ratio all the time it should consistently outperform EFI. Its design lends itself to have an unfair advantage in atomization.

Obviously adiabatic expansion is the next question on the list. So if we take a good look at the carburetor we see its not only a perfect machine for atomizing fuel, it also has another advantage. The Joule-Thomson effect.

Tests performed using quartz plates and infra red sensors located in the plenum area beneath an NHRA Pro-Stock engine revealed an intake manifold temperature drop on a 85 degree day of almost 20 degrees as a result of the the carburetor creating this effect.

So when your neighbor with EFI is ingesting 85 degree air, your power-plant could be ingesting 65 degree air.

That's a nice advantage.

But let's not skip over the atomization advantage. In a high end designed carburetor the fuel is emulsed to lift it. Its a controlled froth. I won't kid you, it's very difficult to control. Its much easier to build a carburetor that operates on a vacuum to ratio concept. But the fogging advantage is gone. So when a customer asks, why is this carburetor more expensive than that builders carburetor as they look basically the same. Most of it is all in the emulsion package and the time spent flowing it and tweaking it to do its job. Remember in a high emulsion design .001 of an inch is a big deal. They're difficult to balance and require sophisticated equipment that many shops have never seen. Also, don't go poking things into the metering block passages to inspect them or look around. You might just lose 10 lbs of torque.

The disadvantage of carburetors used to be restriction. I remember back 20 years ago before booster technology really took off you had to size carburetors to operate on 1-2 inches of vacuum in the plenum at the starting line. The restriction alone was probably costing these engines a 2-3 percent power loss.

Tests we performed at Sonny's racing 5 years ago showed us numbers of about .6 in the plenum and spikes of about 1.1 to 1.3 in the runner at the finish-line. That's a pretty huge decrease and just for dynos sake when we built carburetors large enough to reduce this number by on average 40 percent we saw an increase of only about 3-5 horsepower on an IHRA Pro-Stocker. SO that advantage for EFI is now also gone.

Now that these same engines can operate on as little as .5 hg of vacuum at the starting line and only 1-1.2 at the finish-line, the restriction is nil. Really it all comes down to getting the air to fuel ratio correct. If a carburetor can do that, it should win the race every time. After all, by design, it's a superior emulsion machine.

Here's some additional things to consider on the questions of EFI vs. carbs. First, in a race motor (ex drag racing), the engine spends almost all of its time operating in the sweet spot of the cam/induction/exhaust and at wide open throttlle. Its not really hard to get a carb to work well in such a narrow range of operation.

In a street situation, things get alot more complicated especially as the engine combination gets more radical. Consider this: suppose you are running a a typical "mid-range" CAM shaft with a power band from say 3000 - 6500 RPM. Most of the time that you drive on the street, you are operating below the 3000 RPM level. Lets also say that you are using a big carb (say 900 cfm on a 427 ci motor) to get the package to really haul from 4000-6000 RPM. When this combination idles or you drive it at part throttle below 2000 RPM, the overlap in the cam will cause serious intake reversion problems which will play hell with the carb's metering circuits. You'll probably have to jet/adjust the idle side so rich to compensate for this that you can hardly breath in your garage when the thing is warming up. How does EFI help? First off injectors (stacks or a throttle body) don't rely on a venturi effect to draw the fuel into the motor. This makes the EFI setup is much less prone to reversion problems and the associated need to get the car rich. Secondly, you have a much greater level of control over fuel (and timing) delivery than you can every get with a carb and no computer. I've had engines that will have a flat spot or hesitation at a certain throttle position and engine speed in both the TWM injected 482 ci FE and my 383 ci blown and injected SBC. In the FI case, I change maybe 4 specific cells in the fuel and timing tables to correct these probelms without effect the rest of the the tune at all. If I had to correct these problems with carbs I would have needed to make changes effecting a much larger area of the fuel and timing curves which would have created performance compromises elsewhere. Also, the large throttle blade area of the big carb choosed for high end performance along with the low vacumn of the cam make it very difficult for the carb to metter the fuel properly at low speed. The EFI system can much more accurate determine the amount of air acutally going into the motor and meter the fuel much more accurately. This is why you can get setups like the one shown below to run well on the street.



Lastly, the EFI controlled motor can make much better corrections for conditions than a carb can. Those with carbs ever notice that their cars perform much better at certain temperature/humidy conditions than others? Ever have you performance car run poorly when you took a drive to a higher altitude? Some of this is about air density and oxygen content but it is also about the carbs limited conditions to compensate for air temperature, humidy, and pressure. EFI systems have sensors that detect and will correct for all of these problems and many will used closed loop operation to deal with other issues and wear. Issues like these (as well as emmisions and fuel economy) are the reason that almost every production performance car made today uses EFI including cars like the Viper, GT500 mustangs, and Z06 vettes.

So why isn't everyone using EFI? Well for one thing, it costs more than a carb (althought the gap is getting more reasonable if you use quad throttle body systems). Its also more difficult to tune. All of the control and flexibility means that there are alot more "knobs" that you can turn. I would say that its not that much more difficult to put a near perfect tune on and EFI system than it is to do the same on a carb based motor (although the carb motor may still be subject to the comprimises listed above). The problem is that you can put a so-so tune on a carb much easier than on an EFI system. There is also the work to retrofit a vehicle that is not set up for EFI (especially an existing older car) to use EFI. Biggest areas of work here are 1) upgrading the fuel system to use a high pressure pump and a return line, 2) beefing up the electrical system to reliabily run the electronics, and 3) finding a spot to hide the computer and running the wiring. None of these things are particularly difficult but they do take some work.

I've built or messed with a lot of performance engines in my time (both race and street motors). The last two projects that I've done with EFI are probably two of the most radical that I've run on the street yet they are the two highest performance and most streetable engines I have worked with.

Net is that in practical terms for high performance motor used on the street, its hard to beat EFI. The biggest downsides are the cost, extra work to install, and the technical knowledge required to tune. If you bite the bullet and deal with these issues up front, you get rewarded with a car that usually performs much better/is more streetable and is therefore more fun to drive. BTRW, these days, the tuning part can be handled by many chassis dyno shops at pretty reasonable cost.

All of this said, a carb really is the best choice for many projects. This approach is certainly much simpler and usually more authentic for 60's-80's based muscle cars. The budget factor is also very important for most of us. I would have to say that one could almost always improve the OVERALL performance (not just peak HP/Torque at WOT) with an EFI system on the street over a carb though.

I hope this helps those of you having the EFI vs carb debate.


- Fred

[olddog]

Originally Posted by mr. oz

From Pro Systems website:

Carburetors and Electronic Fuel injection are two completely different systems. They share no concepts and each has a different theory.

EFI's claim is this: I will supply sprayed droplets of fuel at the proper air to fuel ratio all the time.

Carburetors claim: I will supply a pre-emulsed froth of fuel and air into the engine at a preset ratio.

Interesting mr. oz.

A 20 degree drop on an 80 deg day would increase the air density about 4%. That would be aroung 16 hp on a 450 hp engine.

If the fuel does go through a phase change from liquid to a gas it would cool the air. The phase change would have to happen in the plenum to be a benefit. It sounded like not just any carb would do this well.

Since gasoline at atmouspheric pressure needs to be up near 500F to phase change to a gass, it does not want to do this. I really do not understand the physics behind emulsed froth. I don't understand why the fine spray of an injector is totally different from this. Maybe someone can enlighten me. I'm always willing to learn.

[Great Asp]

Is there existing, or start a new "EFI compared to Carb" thread?

I have more to post but this is taking away from the OP's original topic, IMO.

E

[FUNFER2]

It don't matter to me E, it's all very interesting.

[ZOERA-SC7XX]

I don't wanna highjack the thread, but how would the Dynatek EFI improve a medium HP engine like mine (428 10:1 CR, iron heads, maybe 400/425 HP). I like the idea of improved torque and HP, but at 5G's, it ain't cheap. Any thoughts?

[Great Asp]

Originally Posted by ZOERA-SC7XX

I don't wanna highjack the thread, but how would the Dynatek EFI improve a medium HP engine like mine (428 10:1 CR, iron heads, maybe 400/425 HP). I like the idea of improved torque and HP, but at 5G's, it ain't cheap. Any thoughts?

Rather than us telling you how, call the guys at DynaTek and ask them. They gave me hard dyno numbers to back up their claims. I think the big incease would be in torque.

Your right, it's not cheap.

I have not taken delivery of my car (yet), so I can not speak of how well it drives. But I will be posting late Friday night on my build thread as I am going to Plano to see the chassis dyno, and drive the car.

E

[Barry_R]

I have run the same 505 inch, 676 horsepower FE engine on a dyno with both multiport EFI and a carb. Documented in Hot Rod magazine in 2004.

Same intake - a converted Dove single four barrel. We never touched a thing on the package - unbolted the throttle body and bolted on a 950HP, unplugged the injector wiring from the harness and hooked up fuel to the carb.

Based purely on airflow the EFI throttle body should have won. It didn't. A statistical dead heat - but the carb had single digit higher peaks on both torque and horsepower.

Testing done at Wheel to Wheel Powertrain - at the time one of the foremost EFI tuning facilities in the country. The EFI is better at almost every non-WOT and transient driving parameter - but peak power is not one of them.