Which is faster carb or Fuel injection? - Page 6

Billy Nees · 07-28-2013, 09:51 AM

Quote:

Originally Posted by Adger Smith

Another magic word to add to the discussion: Atomization

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.

Billy Nees · 07-28-2013, 10:55 AM

Quote:

Originally Posted by Joe DeMarzo

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?

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.

Bench Racer · 07-28-2013, 11:05 AM

Quote:

Originally Posted by Joe DeMarzo

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

Don't worry Dennis I am having a cigar, backing off. lol

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

Ed Wright · 07-28-2013, 11:27 AM

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

Kegracing · 07-28-2013, 11:48 AM

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

Joe DeMarzo · 07-28-2013, 01:00 PM

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)

jmarkaudio · 07-29-2013, 05:28 PM

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.

Billy Nees · 07-29-2013, 06:43 PM

Quote:

Originally Posted by jmarkaudio

There a more things going on then have been touched on here. In a drag car with an optimized intake and no limit to throttle blade size, I'll take a carb.

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

Chris Hill · 07-29-2013, 11:11 PM

Best thread in a long time!

Adger Smith · 07-30-2013, 12:42 AM

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??

07-28-2013, 11:27 AM	#54
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 389 Times in 168 Posts	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 __________________ Ed Wright 4156 SS/JA

07-28-2013, 11:48 AM	#55
Kegracing Member Join Date: Jun 2002 Location: Red Oak, TX Posts: 441 Likes: 0 Liked 0 Times in 0 Posts	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

07-28-2013, 01:00 PM	#56
Joe DeMarzo Senior Member Join Date: Oct 2002 Location: Mahopac, NY Posts: 666 Likes: 48 Liked 114 Times in 9 Posts	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) __________________ Joe DeMarzo 1317 STK

07-29-2013, 05:28 PM	#57
jmarkaudio Junior Member Join Date: Apr 2008 Posts: 83 Likes: 0 Liked 0 Times in 0 Posts	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.

07-29-2013, 11:11 PM	#59
Chris Hill Senior Member Join Date: Jan 2002 Posts: 653 Likes: 8 Liked 238 Times in 25 Posts	Re: Which is faster carb or Fuel injection? Best thread in a long time! __________________ Chris Hill https://ihmusedparts.com

07-30-2013, 12:42 AM	#60
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,348 Likes: 434 Liked 677 Times in 261 Posts	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?? __________________ Adger Smith (Former SS)