TB EFI and Carburetor Questions

[XH29N0G]

I have followed the prior EFI vs Carburetor discussions and would like to avoid starting a big argument, but I have a question and am looking for an answer to it.

I do not have EFI and have had very good experiences with carburetors.  My carbureted car starts within a second of starting to crank.  It idles smoothly, is responsive and looks to do everything that I want it to do. I am presently using a mechanical secondary with annular boosters and 1.45 " venturies (QF 950 AN) and couldn't be happier.  The A/F is very stable, and after a lot of tinkering I think I have it dialed in pretty well.  My most recent revelation was had after writing a small program for an arduino to log AF, RPM at high enough precision (I think I am +/- a few RPM) to see changes in acceleration, and a vacuum sensor.  My local track closed last year so I have not been able to go there, but I have been able to do repeatable pulls in 3rd gear and adjust jets, spacers, pump shots to optimize and I was able to pick up more time than I expected.  It also jets richer (about 12.6) than what was set by the engine builder on the dyno (about 13.1 when in the car), but it is quicker with the richer mixture.

So my question.  People often say that Throttle body EFI will solve a lot of the issues that I have solved with air bleeds, IFRs, jets, etc....  This I can accept. I have also read that throttle body EFI will not necessarily be as fast at the track as a well set up optimal carburetor.  This puzzled me.  Is there a real difference.  It seems with EFI that one could change AF on the fly and optimize for each RPM interval, maybe even better than one can do with a carburetor.  It suggests to me that either the EFI can compete, or something is different in how the air gets in or how the gas is atomized.  

I know that the type of EFI like CDR has is much better.  So why can't the TB EFI do similarly well to a carburetor.  Or can it and it is really just how good one is at setting it up to dial it in.  Just like a carb.

Again.  I hope I haven't opened up a can of worms, but I would appreciate hearing some thoughts.  (I am not considering EFI yet.  I think the next things for my car with either be brakes, something with suspension, or maybe a solid flat tappet cam and work on the heads).  

[John_Kunkel]

I wonder how many people who claim the TB EFI isn't as fast at the track have actually done comparisons on the same car or are just parroting what they've heard.

[Kern Dog]

When dyno tests show that the peak numbers of EFI are not higher than a well tuned carburetor, it seems reasonable to expect zero change for the better on the strip.

[XH29N0G]

That makes sense and would suggest that the top end of a well-designed and appropriately sized TB EFI should be similar to that of a well-designed and appropriately matched carburetor. Different carburetors yield different results, so too, I suppose, do different TB EFI designs.  Thanks.  I'm interested in any additional informatio.

[c00nhunterjoe]

The gains and losses are fairly negligible given both systems are tuned. The biggest gains will be on boosted applications. Throttle body injection is 1980s tech. Its basicly an electric carb. If you want real advantages from an efi swap, multiport is the way to go but despite popular beleif, it is not plug and play. Any gains you may get over a carb will be negated by the weight of the fuel injection setup. Yes, its that close.
    Bottom line- in your case you have a properly setup carb system. You know what you are doing. A tb swap will disapoint you.

[XH29N0G]

Thanks.  I was mostly curious. 

I am very happy with the carburetor I enjoy working with it.  It is a fairly easy and simple system to adjust.  With an AF gauge, I get an idea what the mixture is doing when I make changes. 

This discussion helps me understand and sort through the various things I read and hear.

[c00nhunterjoe]

How oftern do you need to make changes? From a race car standpoint i dont adjust mine- ever. Set it and forget it essentially. From fellow stock and superstock racers, i watch them make adjustments to find that "perfection " when the weather changes and we are talking about 1 to 2 hundreths in the 1/4 mile. I also ask if when carbs were oe equipment, did we constantly run them to the shop for jet changes and timing adjustments when it went from winter to summer?
  Not trying to bust your chops, more of a generic question to the masses that argue tb injection makes adjustments for weather changes automaticly  that you cant do automatically with a carb. On a 9 second drag car, those adjustments are worth .01, so is tbi really worth it on a 13 second street car? To me, converting is more about want then need. And that is perfectly fine. If someone wants fuel injection, hey, its your car. But to think its going to make your car "better", thats where comes down to what we are comparing it to.

[John_Kunkel]

When dyno tests show that the peak numbers of EFI are not higher than a well tuned carburetor, it seems reasonable to expect zero change for the better on the strip.

One of the most common misconceptions is that the car with the higher horsepower will be the faster car. Way too many variables.

My comment was about at-the-track comparisons of EFI vs carb on the same car at the same time.

[c00nhunterjoe]

When dyno tests show that the peak numbers of EFI are not higher than a well tuned carburetor, it seems reasonable to expect zero change for the better on the strip.

One of the most common misconceptions is that the car with the higher horsepower will be the faster car. Way too many variables.

My comment was about at-the-track comparisons of EFI vs carb on the same car at the same time.

In one of my cases, 92 lx 5.0 mustang. Factory style multiport fuel injected. Stock bottom end, f cam, 1.7 rockers. Mild ported E7te heads. Gt40 intake, 24 lb injectors, no egr ports, big throttle body. Long tubes, 2.5 exhaust, 4.30s, 5 speed. 28 inch Slicks. Best i ever got was consistant 12.50s at 106. Car was tuned and dialed correctly at the track and on a dyno. Converted to carb. Performer rpm intake, 750 holley, holley blue fuel pump, no other changes. Car went 12.10s at 109 from that point on after a day retuning at the track. No other changes made to the car.

[XH29N0G]

Thanks.  This is the type of story I am interested in hearing.  It would be interesting to see a comparison of one of the TB EFI vs a carb on the same intake at the track.

[Kern Dog]

The advantages that I have read about usually revolve around driveability. Cold weather operation, travelling through high elevations, etc.
EFI has a place, no denying that but for a car that is a "toy" in a fair weather environment? It is a big investment for what seems like a small gain, if any.

[c00nhunterjoe]

The advantages that I have read about usually revolve around driveability. Cold weather operation, travelling through high elevations, etc.
EFI has a place, no denying that but for a car that is a "toy" in a fair weather environment? It is a big investment for what seems like a small gain, if any.

There it is- traveling through high elevations.... i dont recall my parents or grandparents telling me stories about having to stop for rejets during family road trips in the 50s and 60s....

[XH29N0G]

For some reason that makes me think that maybe, just maybe, they stopped along the way at the local drag strips to see if things were optimal.

It also brings back a dinner table conversation between my dad and my mom's dad when they both realized they both went to the same local WWII airstrip to test and race their cars.  But at different times.

[Kern Dog]

The advantages that I have read about usually revolve around driveability. Cold weather operation, travelling through high elevations, etc.
EFI has a place, no denying that but for a car that is a "toy" in a fair weather environment? It is a big investment for what seems like a small gain, if any.

There it is- traveling through high elevations.... i dont recall my parents or grandparents telling me stories about having to stop for rejets during family road trips in the 50s and 60s....

I didn't have problems with my carbureted vehicles going from 200 ft above sea level to 8000 ft in East California snow country. Some might, I didn't.

[cdr]

With e10 fuel, winter, summer fuels, todays pump gas is a bitch in a carburetor, Down here in the heat its REALLY bad to get & keep a consistent Carb tune.  For me EFI is the best way to go for my street drivin Charger, I have over 10k miles on it with the 512 cid, about 7k were a very well tuned carb & the rest EFI, that said I am always messing with the tune with the EFI, fine tuning the low RPM cruise areas of the Fuel map, but I am VERY picky about drivability , most people would never notice the little things that drive me nuts . for me & my car EFI is the way to go, I am not going to argue what is best Carb or EFI, been Installing aftermarket EFI's since the late 80's, I have been around for awhile, will be 58 this month, I am STILL learning & hope I never get to where I think I know everything, My car is faster with the EFI, the reason it is ,IS because of the intake design not because its EFI. In my opinion the throttle body EFI is great in low performance applications.

[c00nhunterjoe]

With e10 fuel, winter, summer fuels, todays pump gas is a bitch in a carburetor, Down here in the heat its REALLY bad to get & keep a consistent Carb tune.  For me EFI is the best way to go for my street drivin Charger, I have over 10k miles on it with the 512 cid, about 7k were a very well tuned carb & the rest EFI, that said I am always messing with the tune with the EFI, fine tuning the low RPM cruise areas of the Fuel map, but I am VERY picky about drivability , most people would never notice the little things that drive me nuts . for me & my car EFI is the way to go, I am not going to argue what is best Carb or EFI, been Installing aftermarket EFI's since the late 80's, I have been around for awhile, will be 58 this month, I am STILL learning & hope I never get to where I think I know everything, My car is faster with the EFI, the reason it is ,IS because of the intake design not because its EFI. In my opinion the throttle body EFI is great in low performance applications.

I hope everyone that swears by efi reads this. Charlie is GOOD, he knows what he is doing. Efi is not plug and play. You still have to work for it. It comes down to what you want to do. Either setup will work depending on the end user.

[John_Kunkel]

Haven't driven my FI Tech equipped Plymouth in several months. Went out the other day, never touched the throttle, turned the key to start, fired right up and settled into the programmed idle of 800 rpm.

[c00nhunterjoe]

Haven't driven my FI Tech equipped Plymouth in several months. Went out the other day, never touched the throttle, turned the key to start, fired right up and settled into the programmed idle of 800 rpm.

The fact that you haven't driven it in several months is a bigger concern the carb vs injection...

[Kern Dog]

On House Arrest again?   

[John_Kunkel]

The fact that you haven't driven it in several months is a bigger concern the carb vs injection...

With 4 cars and limited car activities around here, what am I supposed to do?

[c00nhunterjoe]

The fact that you haven't driven it in several months is a bigger concern the carb vs injection...

With 4 cars and limited car activities around here, what am I supposed to do?

I would suggest driving 1 of those 4 cars each day. There are 7 days in a week. I dont always go to sanctioned events. Sometimes i like to just drive

[XH29N0G]

John and others.  Thank you very much for your replies.  This has been very informative.  I appreciate it.

My activities have also been limited.  I have been out on a few Sundays early.  I really enjoy it and I also enjoy the conversations with people along the way.  I find it relaxing, so my two cents is to get out and drive around a little, tinker some, and enjoy.

[Mike DC]

      

There it is- traveling through high elevations.... i dont recall my parents or grandparents telling me stories about having to stop for rejets during family road trips in the 50s and 60s....

I've read that Indian/Nepalese truck drivers used to actually do that in the Himalayas.  They had customary stopping points for it partway up the mountain passes where everybody re-tuned the vehicles.


At North American elevations you could leave the carb alone and just advance the ignition timing a few degrees.

[INTMD8]

The advantages that I have read about usually revolve around driveability. Cold weather operation, travelling through high elevations, etc.
EFI has a place, no denying that but for a car that is a "toy" in a fair weather environment? It is a big investment for what seems like a small gain, if any.

I'm going efi only for fuel composition sensor as I'm going to be running E85.

For the amount of money it's costing I've thought a few times maybe I should have tried the carbs first 

[John_Kunkel]

I would suggest driving 1 of those 4 cars each day. There are 7 days in a week. I dont always go to sanctioned events. Sometimes i like to just drive

I spent a few years driving for a living so the thrill is gone. Only way I really get a blast out of driving is in a new (to me) car, once I have a few miles in a car I don't drive them that much.

It took me many years to realize I like working on cars more than driving them, that's why my cars are never "finished".