Announcement

Collapse
No announcement yet.

EFI vs. a Carb: Which makes more Horsepower?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • EFI vs. a Carb: Which makes more Horsepower?

    I have heard the controversy for years. I saw a 2 x 4 carb set-up on a tiny motor (260 inches) at Bonneville last summer that made obscene HP. Can anyone quantify why a carb is supposed to make more HP! Have there been truly fair dyno runs to compare? If a carb always has unequal port length how can cylinder AFR ever be equal? Are density and physics the key? Is injector PWM limitations hamstringing EFI? Oh so many questions . . . ;)

  • #2
    Re: EFI vs. a Carb: Which makes more Horsepower?

    Depends on where your trying to make the power....
    There are very few people in this world who's opinion I value, you are not one of them.

    300 in 1999

    Comment


    • #3
      Re: EFI vs. a Carb: Which makes more Horsepower?

      Originally posted by Dynoroom
      Depends on where your trying to make the power....
      What is the max rpm limit for EFI?

      Comment


      • #4
        Re: EFI vs. a Carb: Which makes more Horsepower?

        Originally posted by Saltfever
        Originally posted by Dynoroom
        Depends on where your trying to make the power....
        What is the max rpm limit for EFI?
        Same as a carburetor...
        There are very few people in this world who's opinion I value, you are not one of them.

        300 in 1999

        Comment


        • #5
          Re: EFI vs. a Carb: Which makes more Horsepower?

          Originally posted by Dynoroom
          Depends on where your trying to make the power....
          What is it about either one that creates that choice? I know you are busy Michael but geeze, your experience is costly valuable! ;D

          Comment


          • #6
            Re: EFI vs. a Carb: Which makes more Horsepower?

            Speaking from an outsider of the world of high end engine build prospective so I will feel no ill will at being corrected.

            Carbs tend to do 1 or 2 things very very well, meaning if you want an all out race motor or a constant rpm boat motor, its very easy to get it to do that very very very well. The fuel spray out of the venturis generally also gives a slight aftercooling effect due to the phase transform energy needed to get it into a gas in the air. They have also be around longer and more people are familure with them in the world of "most" racing applications.
            EFI is more adaptable to most circumstances and since the fueling is independent (from a mechanical standpoint) of the engine vacuum it can be minutely adjusted for a much wider range of parameters. EFI also generally includes the ability to adjust the ignition aswell allowing for a simular capability on the timing. Some really fancy EFI systems can adjust for airflow distrobution to individual cylinders to alter fueling and timing per cylinder under the same range of conditions.
            In summary, EFI works very well for which the situation is not well defined and/or varried. Carbs work very well for singular purposes such as racing. Carbs you have to physically adjust, EFI once its well tuned does it automatically.

            When it comes to power on an engine, the two generally employ different intake styles too since EFI is dry, carbs are wet. EFI intakes are usually either factory intakes designed for a useful powerband for a street vehicle while off the shelf high performance carbed intakes are much more race oriented. On a comparison between a custom sheetmetal tunnel ram specifically designed for the fueling method.... ask the proffessionals.
            Central TEXAS Sleeper
            USAF Physicist

            ROA# 9790

            Comment


            • #7
              Re: EFI vs. a Carb: Which makes more Horsepower?

              Fever you changed your question, that's alright but the answer depends on a lot of different issues. Your right I don't have time to go in to detail now (I'll try later) and most of my answers on a forum like this need to be short and to the point depending on what the person is really trying to achieve. In your case you have never stated what it is you want to do so I (and others) can't really help other than generalities.

              Robbie's 260" engine is a very good at what it doing, running at WOT on the salt for 5 miles. A tunnel ram manifold with a plenum can be tuned to match almost any FI system at one or 2 data points but the efi will/should always be able to do better over a broader rpm range. That being said Robbie's engine doesn't need that range, do you?
              There are very few people in this world who's opinion I value, you are not one of them.

              300 in 1999

              Comment


              • #8
                Re: EFI vs. a Carb: Which makes more Horsepower?

                Thanks, CTX. I get the feeling you won't be a "Jr" member for much longer ;D Looking forward to many more of your future posts.

                As you say the carb can be optimized for a known combination. However, the EFI with its inherent flexibility should be even easier to optimize. Granted its usefulness is in its wide range adjustability. However, that ability could be focused in the same limited area of a carb as well. I don't think CPU electronics is at play here at all. I think it is about the physics of wet-flow inertia that I don't understand. It is all about VE. One technology is better than the other and I would like to know why.

                Comment


                • #9
                  Re: EFI vs. a Carb: Which makes more Horsepower?

                  I think that comes down to resolution, the ECM data resolution is determined by the bit processor of the ECM, the Buick Grand National LC2 has an 8-bit processor, thats 256 data points on a table that is a 16x16 table of parameters, the L67 PCM is a 16 bit processor, thats 65536 data points on a 256x256 table, the Gen III/IV and the Series III 3800 (and I think all new GM engines) use a 32 bit processor. With the same range to cover, the more cells you have, the more specific each one can be and the tighter the tune.

                  The intake.... I'm not an aerodynamicist or thermodynamicist so I can't comment as much on that subject. The fuel is denser than the air, even when vaporized, and doesn't want to change directions as easily. So in an EFI system you can direct just the air to where you want it then add the fuel close enough to not have to force it to turn more but far enough away for it to truely become emulsified in the air stream. Ford even tried to assist thing on the 200-2002 3.9L AJ V8 by putting air pressure to the sorround of the injector to try to get it to mix better for better cold start. It went away in 2003 when they added the VVT on the intake cam and redesigned the intake with TBW but it obviously had enough merrit to attempt on a production level.
                  Central TEXAS Sleeper
                  USAF Physicist

                  ROA# 9790

                  Comment


                  • #10
                    Re: EFI vs. a Carb: Which makes more Horsepower?

                    Originally posted by Dynoroom
                    Robbie's 260" engine is a very good at what it doing, running at WOT on the salt for 5 miles. A tunnel ram manifold with a plenum can be tuned to match almost any FI system at one or 2 data points but the efi will/should always be able to do better over a broader rpm range. That being said Robbie's engine doesn't need that range, do you?
                    You "hit the nail square on the head", Mike. How did you do that! ;D That is precisely the essence of my question. I about fell over when I saw that little "E" motor go 201 mph. They are great guys and that is an incredible motor. So my question is; could it go even faster by adding EFI? If it can't, then why? If it can then why? There is so much controversy about carb vs. EFI technologies but no one says they are the same! I can't filter the bs. Which one is better for LSR?

                    Comment


                    • #11
                      Re: EFI vs. a Carb: Which makes more Horsepower?

                      Originally posted by Saltfever
                      Which one is better for LSR?
                      dude, what's best is what works for you!!! that's the answer to your question. There's no wrong or right!


                      On combos I've converted from carbs, I generally pick up quite a bit more HP but more often, a ton of torque. In my opinion, the *real* challenge is taking a bone stock OEM motor that was already fuel injected, map out the factory tune, and see if we can pick up power and torque from there. But as DF pointed out to me once, all the EFI systems I converted from carbs, ALL had improved intake manifolds installed as part of the "conversion"

                      Here's one downer with EFI. A car I support, had electrical noise problems that caused our MSD and EMS to behave weirdly for the first three days of Speedweek last year. Meanwhile, Keith and David's car with it's very simple ignition and carb setup, ran flawlessly the entire time. I spent three days on my back on a tarp, regrounding and powering the management systems in the car because the salt was killing all the electrical connections...


                      CTX, your point about the bit resolution in modern computers is actually quite a bit more complicated. I have a friend who writes code for one of the big EMS companies, he says when they went to 16 and 32 bit computers, software got HARDER to write. Higher sampling rates meant smaller deltas in things like Throttle Position Travel. Also, I've used 12x12 maps and find 16x16 maps are a total waste of time. Any properly built engine will run great with as few as 144 edit points on the map. I've never found myself at the dyno wishing I had "more resolution" even on the most basic 8-bit computers. So, in theory you are right, more resolution and faster sampling SHOULD make it "easier" to dial in a good tune - but the reality is, all that performance is giong towards emissions performance (which is the real PITA to tune!! crazy difficult!) - not power production.

                      -scott
                      www.realtuners.com - catch the RealTuners Radio Podcast on Youtube, Facebook, iTunes, and anywhere else podcasts are distributed!

                      Comment


                      • #12
                        Re: EFI vs. a Carb: Which makes more Horsepower?

                        (Off-topic re: LSR, but within the same parameters)


                        A terrific example of the power of electronics

                        & EFI & ECM is the Z-06 (& soon the Z-R1).


                        Look at their horsepower & ETs...then look at their incredible mpg! :o


                        As some have said, at some "tipping"-point for a gallon of gas,

                        hot-rodders will look at their carbs differently. And if you do

                        cruise very much, & you're not wealthy, you're gonna do what

                        you may not want to do in order to keep on crusin'...EFI/ECM.


                        You will not let the price of gas force your ride to

                        stay in the garage, so the carb's future isn't very bright.


                        -------------(O/T off, back to LSR)--------------

                        Comment


                        • #13
                          Re: EFI vs. a Carb: Which makes more Horsepower?

                          Here is another take from my point of view -

                          On v8's - These motors have had some of the best R&D and real world development on the intake side FOR CARBS.
                          EFI is still fairly new on the high performance side. The OEM's have put a lot of money to get usable power and fuel economy with EFI. But EFI designed manifolds are still lagging behind. Also I believe that injector placement in conjunction with the manifold has not really been worked hard enough.

                          Comment


                          • #14
                            Re: EFI vs. a Carb: Which makes more Horsepower?

                            Originally posted by Dynoroom
                            A tunnel ram manifold with a plenum can be tuned to match almost any FI system at one or 2 data points but the efi will/should always be able to do better over a broader rpm range.
                            Thank you!

                            FYI, I have done the EFI versus carb thing five or six times, all using the same manifolds with both setups. In every case, the carb made more PEAK power at the same fuel curve. They say it has to do with droplet separation versus port injection. But for driveability, tuneability, average power, mileage, etc, it's EFI every time. But EFI is also the best choice for complexity and high cost. Per Scott's example, and lots of Turk examples, I'd never have a carb at Bonneville AT THE POWER LEVELS I HAVE RUN (not the important caveat).

                            FWIW, I've driven and ridden in a LOT of cars with aftermarket EFI swaps, and can say that the vast majority are not as seamless as OE setups. Most have some hiccups somewhere...along the line of what carbs give you. I'm sure that ace tuners can solve that, but...

                            (Scott: start the EFI version of the Tommy Lee rant in 3, 2, 1...)

                            (and I'm willing to be wrong again)

                            Comment


                            • #15
                              Re: EFI vs. a Carb: Which makes more Horsepower?

                              Originally posted by Saltfever
                              Originally posted by Dynoroom
                              Robbie's 260" engine is a very good at what it doing, running at WOT on the salt for 5 miles. A tunnel ram manifold with a plenum can be tuned to match almost any FI system at one or 2 data points but the efi will/should always be able to do better over a broader rpm range. That being said Robbie's engine doesn't need that range, do you?
                              You "hit the nail square on the head", Mike. How did you do that! ;D That is precisely the essence of my question. I about fell over when I saw that little "E" motor go 201 mph. They are great guys and that is an incredible motor. So my question is; could it go even faster by adding EFI? If it can't, then why? If it can then why? There is so much controversy about carb vs. EFI technologies but no one says they are the same! I can't filter the bs. Which one is better for LSR?
                              Scott's answer is right... what works best for you.

                              Now let me tell you what REALLY makes efi better at the salt, or any other race venue. If you do your home work before you leave for the "Great White Dyno" you're done! Altitude compensation is a wonderful tuning tool ;). If you want to try other things like more or less timing, add fuel, or ??? go ahead, but the basic package should be dialed in at home (on the dyno) and anything else you do is because you want to. You'll find out soon enough that your not going to "find" 10 mph in the tune up unless you forgot to do your homework.

                              And Dave, you're welcome..... ;D
                              There are very few people in this world who's opinion I value, you are not one of them.

                              300 in 1999

                              Comment

                              Working...
                              X