Re: Which is faster carb or Fuel injection?
 

That is more than I was told. Dave Layer knows. Maybe he will see this and let us know.

Re: Which is faster carb or Fuel injection?
 

Very good info right there that I had never heard before and it explains why an LT-1 can run
pretty fast as a SS'er or a Stocker...

Re: Which is faster carb or Fuel injection?
 

But, if carbs are flowed at 12", that makes the LT1 throttle body smaller. Quadrants are 750 & 800 at 12", right? That throttle body won't be that at 12".

Re: Which is faster carb or Fuel injection?
 

Holley four barrel carbs are flowed at 1 1/2" of mercury which is a little more than 20" of water. I don't know what others are tested at. The two barrel carbs from Holley are tested at 3" of mercury from what I have read.
Roland

Re: Which is faster carb or Fuel injection?
 

That would make it 660 cfm, which about what I was told. Dave Layer told me my LT2 SS engine would be done about 8200 due to the throttle body restriction. It falls off a cliff about 8300 on the dyno. The 305" TPI cars have the same size, if I remember correctly (been a couple of years now.) Dave said the 305"s run right up to 8800/9000. Hope I remember the numbers correctly.

Re: Which is faster carb or Fuel injection?
 

Joe ask the question: All things being equal in a stocker, lift, valve, piston, head, etc.. what would be faster a carb or fuel injection?

The question has not been answered, yet, and probably will never be because of those first 4 words in his question. I'll add 3 more words that will always keep them unequal... Wet & Dry flow.

Re: Which is faster carb or Fuel injection?
 

Finally, the magic words!

Re: Which is faster carb or Fuel injection?
 

Billy, I thought the magic words were "I love you or is it please and thank you"?

So the CFM of a FI and carb are currently not even if someone was to swap it out at the track? Also I presume the manifolds would not be an even swap????

When looking for an advantage in my original question how would you measure which would be faster or make more power theoretically? By CFM and or air volume?

By the by I have no idea what you FI guys are talking about with all that mojo but it sure is an education. Thank you!

Re: Which is faster carb or Fuel injection?
 

I got a pretty good example. We ran Top Stock with a 360 w/ported Edlebrocks, an 850 good carb and it performed well. When the DP's came along, we added FI bungs on the manifold, changed from an QAF 850 to a 1000 CFM throttle body and we were now fuel injected. Same motor, same cam, same everything. It made about 10 or 15 less peak hp, which surprised us. Spoke to Wilson Manifolds. They said quite normal because the fuel starts atomizing in the carb, and the injector is down in the runner. Also said the total management with the FI system makes it better overall, but more technical. Then when NASCAR got FI, the injectors are in the top of the runner, which I think would be legal in NHRA SS. We will get around to trying that someday. My 2 cents

Re: Which is faster carb or Fuel injection?
 

Joe,
I know this doesn't answer you question in a direct manner, but......
Take a look at The Engine Masters Challenge rules for last few years.
When Wesley and I were doing the rules we made some slight differences between FI and Carbs to try to keep them as equal as we could. The differences are not all in the sizing, it is in the total induction package. Study that and you might be able to get a handle on what/where the difference really is.
Billy,
Another magic word to add to the discussion: Atomization
That word adresses the wet flow and the quality of the A/F mixture in the chamber before the combustion process. (touched on earlier)

Jeff, wow! I see we were typing at about the same time, but your got there first. (RT) Great minds must ...well

Re: Which is faster carb or Fuel injection?
 

Absolutely! Holding fuel in suspension is critical in any engine be it carb or FI. I can't wait to see what direct injection will do to Stock and SS. It has to be in the racing programs somewhere.

Re: Which is faster carb or Fuel injection?
 

These are just my opinions, I'm not looking for any arguments here.
Joe, you are trying to find an answer that I don't think anyone can give you(I know I can't) because you are trying to compare carb and FI combos based on the restrictions of Stock Eliminator. Adger just brought up atomization, the biggest barriers to keeping fuel suspended are throttlebody(carb)size, manifold and port shape, how fast you can get velocity in both AND the intake valve. If you've got a carb 305 over here, it's got a really good intake and head, a big carb that has to mix fuel and air in itself and send this wet mixture through a runner at a speed that will keep all of those little droplets of fuel from falling out of suspension in the air while it travels through the carb, intake(lots of sharp turns, not good) and intake runner which takes velocity. So at low RPM you will have poor velocity but at high RPM you may be able to sustain a higher HP number(RPM potential). With a TPI 305, you have a dry throttlebody and intake that don't need to suspend those little droplets of fuel through all of those twists and turns BUT that nifty little intake is reasonably small and can't be easily "enhanced" like a regular Q-Jet manifold. It wasn't built to make HP at high RPM. Also, in a carb combo you don't gererally get any puddleing(sp?) at the intake valve like you would in a batch fire port injection combo. Sequential FI wouldn't have this problem.
I don't know where else to go with this Joe. I've tried to explain the differences in how these two combos work and why as simply as I can. That 305FI intake only gets worse on a 350. The LT-1s and LS motors don't have as much of a problem as they have better intakes. Remember, you were talking Stockers here.
And I won't even go into carb vs. FI headers.

Re: Which is faster carb or Fuel injection?
 

I think the magic 4 letters are the big factor here, AHFS. If the HP factors and all else is equal it should depend on if either the EFI or the carb can put more air/fuel in the cylinders. If the two engines are equal except for the rated HP you are not comparing apples to apples. Take a look at look at how many horse power hits the carbs have had over the past 30 years as compared to the EFI combo's in the last 10 years. 400 Chevy was 280hp now 324ish, 307 Olds was 180hp now 230ish. I think the carbs have took a worse beating just due to the EFI being relatively new. The EFI cars are becoming more abundant and are get equal attention from the AHFS crew. My brother has ran 4 carb and 2 EFI combos in SS and there are +'s & -'S to each. My simple mind prefers a fuel pump and a carb with no wires or sensors attached lol. Don Jackson

Re: Which is faster carb or Fuel injection?
 

Billy, a friend of mine is a calibrator (tuner) and engineer, retired from GM. He told me about those Tuned Port Injection ("TPI") set ups used on the '85 thru '92 cars. It was designed for the 305" Trans Am series cars. Back then it was (supposed to be <BG>) bone-stock 5.0L "pony cars" like the Camaro, Firebird and Mustang. The factories had their own teams. Those long intake tubes with small cross sections were designed to get those 305"s off the corners of the road courses they ran on. It looked cool and made for very clean smog tests, so it went on the Corvettes and 350" Camaro/Firebirds. Those long runners really come alive at 2800 to 3200 on a 350", so much we pull 2 degrees spark right there, then start putting it back at 3600. Only intake I have ever seen do that.

My friend tuned GM's team cars. They even had to have stock injectors. He has some very interesting story's about those days. But, us old guys have our stories, don't we? LOL

Re: Which is faster carb or Fuel injection?
 

Billy, maybe the header discussion needs a new post? Would love to hear some of your thoughts and experience there...

Adger and Jeff, your comments about wet and dry flow and atomization, are keys I think everyone would agree.

I was talking with Kyle Ratcliff and he reminded me of the cooling effect of the wet flow of the fuel through the intake on the carb setup. Does make a difference. That would really come into play with the peak HP number on a carb setup... goes with all of the atomization discussion from Billy and others... high rpm it can keep fuel suspended with good velocity.

We don't race dyno's. Not saying the peak numbers are not true, just that we all know the dyno numbers don't always prove perfect on the track. To me, it still looks like the FI combo, on a apples to apples deal, would be the better race track motor, due to the ability to tune the curve thru the entire RPM range... Apples to apples is key in MY thought here, as some motor combo's, intakes, runners, etc. have limitations that hurt them and take them out of play for normal comparison.

Joe, while not the direct answer to your original question, hope you are getting some good ideas to think about.

I enjoy listening and learning from all of you guys. I would love to have time, resources, etc to test a lot of ideas... but until I win the lottery, I will just keep listening and learning from you all. Thanks.

Ken

Re: Which is faster carb or Fuel injection?
 

Billy with your last post I finally (think) understand and I have it.

Thanks... great bunch of posts. I have my answer......(thanks DL for the 2 x 4 message)

Re: Which is faster carb or Fuel injection?
 

There a more things going on then have been touched on here. A carb will meter fuel and make changes almost instantly as the signal changes. A carb will also meter fuel in a continuous flow, constantly mixing fuel with the incoming air. Atomization is only part of the picture, how well the fuel is HOMOGENIZED or evenly mixed with incoming air plays a big part in a couple areas. A well homogenized mix early in the induction tract will more evenly distribute to the cylinders, when the mix is more equal you don't have to run the good cylinders rich to make up for the lean cylinders. Also a well homogenized mix will burn more consistently and evenly in the combustion chamber and without as much ignition lead. This make more power. A FI system send fuel in pulses, and unless you set it up with the injectors above the throttle blade like a formula one engine you will not mix it close as well into the chamber as a carb. And anyone that believes a FI will distribute more evenly even though the injector is placed right above the valve is dreaming. With a batch fire setup forget it, even with sequential you get fuel flying around in the plenum making distribution less than ideal. Sure you can tune each one, but what if it isn't consistent in where the fuel goes to all the time? And then there is the processing delay, it takes a very fast processing system to work best and still it will never respond as fast as a carb.

All considered, it is still a case by case deal as to what works best. If the carb is restricted by blade size and the FI is not as some of the Engine Masters have been, FI may win out. If cylinder to cylinder distribution is hampered by the intake design, like a dual plane, then FI may have an advantage. If g-forces change to extremes like a road race engine then FI may have and advantage. If fuel consumption is a key factor, number of pit stops, then FI usually will have the advantage. In a drag car with an optimized intake and no limit to throttle blade size, I'll take a carb.

Re: Which is faster carb or Fuel injection?
 

You are correct BUT, Joe is talking about Stock Eliminator type cars and their restrictions.

Re: Which is faster carb or Fuel injection?
 

Best thread in a long time!

Re: Which is faster carb or Fuel injection?
 

Hey, I didn't say FI or carb was the best. I didn't say FI or Carb won EMC because it was better. I said look at the rules and see what was done to make them as equal as possible in a dyno pull. That is all.... I also didn't say or imply we race dynos and one was better on the dyno than the other.
BTY: EMC it is not about top Hp. It is actually about Torque, HP and a set RPM range. The formula we came up with gives a score number. Highest score wins.
EMC is a competition just like running a Stocker, SS'er or Comp Car. Getting the max performance within the rules guidelines. Now, What works best??

Re: Which is faster carb or Fuel injection?
 

I guess the question is are there any Stock eliminator cars that have the option to go to one or the other? You are stuck with what came in the car in any given year, if there were any that came with both available it would have been rare.

Re: Which is faster carb or Fuel injection?
 

X2 I am hoping someone starts the thread about the difference between FI Headers and Carb Headers. Always learn alot here.

Re: Which is faster carb or Fuel injection?
 

1985 Camero came with both carb-263 hp or tuned port F.I.-258 hp. These are the NHRA factored ratings. Engine specs are the same excecpt for the induction.

Re: Which is faster carb or Fuel injection?
 

LEE, is the carb version what is called the big cam? If so don't think the TPI can run with it. Please correct me if I'm wrong.
Both can run at the same minimum weight, same cam, same piston and chamber, head castings are different.

Re: Which is faster carb or Fuel injection?
 

Check again Frank , 305-175 flattop-big cam carb and 305-215 TPI use all the same #'s and cc's . same cam ,416 head etc.

Re: Which is faster carb or Fuel injection?
 

14081005,004
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I could have Memory failure, but seems like one or all three of those '85 FI intakes are not so good.

Re: Which is faster carb or Fuel injection?
 

Lee, I stand corrected.
Both engines are the same but for the top.

Re: Which is faster carb or Fuel injection?
 

I've seen batch fire and sequential mentioned how bout timed injection? Having the ability to dictate when the injector pulses would seem to be of benefit. Not sure how many systems offer this or how much time has been spent testing it.Spraying fuel into an active air column would seem at least in theory to have some potential gains.

Re: Which is faster carb or Fuel injection?
 

Joe, you can time the injector pulse in the FAST XFI, and likely the other race systems as well.

Re: Which is faster carb or Fuel injection?
 

Yes Ed, wasn't sure about others, my ECU-882 has that ability however I've yet to do any serious testing using it. Would be interesting to hear from someone that has. At higher engine speeds I'm imagining a serious amount of feul vapor being flying around in my manifold....is it a detriment or a help...I'm not sure.I've even wondered if my manifold design since it was made for a carb is a hinderence guess time will tell. BTW my car has ran as fast if not slightly faster with the EFI versus the carb, though again it may be contributed to the manifold and head design more than the actual delivery system....sure can't beat the EFI throttle response though.

Re: Which is faster carb or Fuel injection?
 

Joe,
The V-6 engines you and I run might be the type engine that really benefits from EFI. As you know they are subject to some real weird pulses in the manifold. As you stated fuel in the intake a real problem. EFI could be a help. I have played with 5 different intake configurations to get the best. The best still has some crutches in to help the carb with mixture distribution. I think EFI would help because of the dry flow.

Re: Which is faster carb or Fuel injection?
 

What carb? Airflow makes a difference.

Re: Which is faster carb or Fuel injection?
 

After stumbling upon this thread, I couldn't help but to jump in. Even though I work in the EFI industry, I do not consider myself a guru, but rather a student of the game. Here are some observations I have made and theories I believe.
1. As originally stated, EFI offers much better control of fueling, individual cyll tuning, etc which should equal a "fuller" torque curve. That being said, it is rare to find a racer who is willing to invest the time and money required to get the last few potential horsepower out of their combo.
2. I believe that we are just at the beginning of manifold / head / header design dedicated to EFI engine packages. These three areas have been science'd out over the last 50 - 60 years for carbs, EFI technology in these areas has a lot of catching up to do!
3. There is a balance between atomization, airflow, and mass of the mixture that is required for not only optimum power, but accelleration. We have all seen or heard of Dyno heroes that made killer numbers but when put in the car, wouldn't accelerate. I have been told that a dry throttle body and intake runner can flow more air because there is no fuel occupying that space but the other side of that coin is that a mixture of air and fuel has more mass and velocity to help it enter the port. I am sure there are engineers smarter than me who can explain this better than me but what I have seen tells me that both are important. Injector type and placement is critical. I have seen some very "out of the box" ideas that looked ridiculous produce very good results, particularly in some Engine Masters projects I have had the privilege of being involved with.
4. As far as the throttle bodies being a limiting factor, I can affirm what Dave Layer has shared with Ed. My preference is to tune in Load Indexed Speed Density mode. In that mode, the values you put into your main fuel table are estimated Volumetric Efficiency numbers. You know that these are correct when the engine runs at your target air fuel ratio with minimal correction. When you get to this point with your tuneup, you have effectively built an accurate airflow model of your engine with the Base Fuel or VE table. My point in bring this up is that in an LT1 based SS engine, the VE numbers will dive at about 7800 and sometimes, the MAP sensor will even show slight vacuum in the manifold even at WOT. The throttle body is definitely a restriction.
The reason I love what I do is that there is still so much to learn and develop in the world of EFI.
To answer the original question, I believe most of the fastest Stock and SS combinations are EFI but more importantly, going forward, I believe there is more potential to find an advantage with hard work and ingenuity in an EFI application than there is with a carb application.
David Page
Fuel Air Spark Technology (FAST)

Re: Which is faster carb or Fuel injection?
 

Dave, It's great you jumping in here!

Agree the potential is there for EFI to out perform a carb BUT:

When we are talking about Stock we have what we have to work with. Super Stock is a different case with the only limitations nefore the intake port being the throttle body. If the stock throttle body originally rated at 600 CFM may fow up to 750 CFM, a carb originally rated at 750 CFM will outflow the throttle body.

Using sequential fueling and individual cylinder timing potentially can deliver flatter HP and TQ curves along with faster ETs. Reservations are with speed. The volume of commands the ECU must make at high RPMs processor speed along with sensor and injector speed / accuracy are limiting factors. Had a short conversation with a racer working with this and his comment was the injectors go static. Next step would be larger and/or faster injectors with more fuel pressure, probably double what we are using.

Re: Which is faster carb or Fuel injection?
 

Sorry, you are correct, my comments were focused on SS. As far as the speed at which commands are given from the ECU. I can only speak with authority about the system we make but we use dual 25mhz processors in our ECU so that gives us a potential of 50,000 commands per second. I seriously doubt any engine has a need for more than 50,000 different commands before you get past the 60' mark. LOL. Most modern ECUs have at least this much capacity. As for the injectors going static, that is a simple matter of running out of injector capacity. If your engine needs 288 pounds of fuel per hour and you are running eight 36 pound per hour injectors, the ECU cannot get any more fuel out of the injectors. Most injectors are not linear in their fuel delivery above 80% duty cycle. The ECU controls the injectors as to deliver the requested amount of fuel based on the injector flow rate you have defined in your tuneup. The ECU cannot know or account for inconsistencies in the injector flow characteristics (as you have above 80% duty cycle) so when you injectors are above 80%, the engine is not actually getting the fuel that you (or your ECU) thinks it is. He can turn the fuel pressure up effectively making his injectors "bigger" but there are limitations to that as well.

Re: Which is faster carb or Fuel injection?
 

It's not about stock. But I remember the old Rat Roaster manifolds for the hemis. The instructions from Chrysler to epoxy popsicle sticks in the manifold to stop fuel puddling.
Fuel injection solves problems like those. I had never had an ecu that was tuneable till my Neon. So it took a while till I could tune it myself (due to fear of new things)
I have just scratched the surface as far as tuning goes. When I get the car out again I'm going to switch from a MAP/RPM axis to a Throttle position/ RPM axis. To keep the plugs cleaner driving around the pits. I also will go in and smooth the boxes (go from 500 rpm increments to 100 rpm increments).
Any changes I make are done at the track, and I can go back to exactly what I was running before I made the change.

Re: Which is faster carb or Fuel injection?
 

Actually, big cam and cylinder head racing engines still have this problem, even with efi. ECR engines (sprint cup) went through a ton on development work when NASCAR switched to EFI - they lost a little power at first but with more work to cam/head/intake they eventually recovered the power. Of note though, they tested with a manifold incorporating a window in an intake runner and were amazed to see the fuel from the injector flowing BACKWARDS up the runner toward the plenum at certain speeds. The observation was backed up by readings from individual cylinder O2 sensors showing large amounts of fuel swapping from runner to runner necessitating a large amount of individual cylinder fuel corrections to make them run properly.

As for low speed tuning, I've tuned numerous racing engines with low vacuum and they CAN be tuned to run just fine (not loading up) in speed/density mode.