CARB or EFI and WHY??????????

[25thmustang]

What about gas mileage... I know carbs these days are much better than in years past, but will they get the mileage an EFI car gets. I recently went to SC (800 miles each way) with my car. At 15 degrees of timing and 38-40 psi of FP, I got 26-27 mpg cruising at 65-70, and 23-24 mpg cruising at 80-90. This was also with an easy 400-500 lbs of luggage (3 guys luggage for a week, 1 guys luggage for 4 months overseas) and 2 passengers (me at 190, friend at 230).

Would a carb car (not tuned for gas mileage, as mine isn't) see similar mpg as the EFI? Also would the swing in weather, from 100 degree and muggy to 55 degrees and dry, affect the carb a good amount?

 

[millhouse]

So you're right but only by the one chance that two guys would meet up on a hot humid day. LOL that's a lot of factors that have to fall into place just for the sake of being right. Practicality, yeah sure. Efficiency? Absolutely, why not. None of that equates to any reason that EFI makes more power than a carb setup. You're also thinking that the weather has some kind of astronomical effect on the carb's ability to make power, but that's just not so. If the weather is bad enough to make my carb run crappy then the EFI is going to be sluggish as well. That's just a plain simple fact of weather and air quality vs. the internal combustion engine, and a/f delivery isn't going to change that enough to make a win or lose difference.


This debate comes up like every other month, and no offense to anyone in particular but it just gets so tiring hearing the same thing over and over from people that i suspect have 0 carb tuning knowledge (again not directed to the quoted person, just an observation). People tend to be biased to what they know, and i'm just as guilty of that as anyone because i honestly know more about carbs than EFI, but i do know how EFI works in relation to a carb, and i do know that it all comes down to the tune on the carb...plain and simple. It'll take more work, sure, but the reward is the same...it's all horsepower and torque at the wheels, it just depends on how you want to get it and what you're willing to learn and do to make it.

It's not really a lot of factors…it can simply be a matter of running during the day and night. The point being made is the carb setup can react dramatically differently with large swings of weather.

Yes, EFI setups are effected as well…but to a much lesser degree. Because the fueling equation takes into account air temperature, barometric pressure, air density etc. the computer is able to compensate for the conditions. Not only does this effect drivability, but it can also have an effect at WOT.

Again, carb's are great for the dragstrip and scooting around town on the weekend…but I much prefer an EFI setup for all around performance. The pro's by far outweigh the cons IMHO.

 

[85_SS_302_Coupe]

What about gas mileage... I know carbs these days are much better than in years past, but will they get the mileage an EFI car gets. I recently went to SC (800 miles each way) with my car. At 15 degrees of timing and 38-40 psi of FP, I got 26-27 mpg cruising at 65-70, and 23-24 mpg cruising at 80-90. This was also with an easy 400-500 lbs of luggage (3 guys luggage for a week, 1 guys luggage for 4 months overseas) and 2 passengers (me at 190, friend at 230).

Would a carb car (not tuned for gas mileage, as mine isn't) see similar mpg as the EFI? Also would the swing in weather, from 100 degree and muggy to 55 degrees and dry, affect the carb a good amount?

If you modded your carb to have annular boosters at all 4 corners you'd come DAMN close.


Like said if it came down to mpg or all around efficiency, EFI wins hands down. Personally though, i'll drive a Prius if i want mpg and effiiciency. If i wanna go fast on a budget, EFI isn't part of the formula. Here in Cincinnati we see pretty much the full spectrum of weather. I've taken my car to the track on opening day when the temp was as low as the 30s, and i've ran it in the heat of summer in the '90s, and i can tell you with absolute certainty that track conditions come into play and become more important than how my carb is running when it comes to how my ET turns out.

So...excluding those people who might live in either Death Valley or Antarctica, if you wanna go fast for less, and you don't mind actually learning something along the way, carbs are superior. If you're concerned about mpg and you drive in crazy weather and you know you're not going to have the ambition to learn to tune a carb, then stay away from'em and go EFI.

Carbs aren't for everyone, but then again EFI isn't in everyone's budget either. I can also say i've seen a lot of equally modded EFI fox's at the strip running a half second slower than me, so it's not like EFI is a magical horsepower creater.

Like i said i'll take the horsepower challenge any day (lol if i had the cash to blow) and we'll both start from scratch and see who can build the most power with the same amount of money. I GUARANTEE you i'd end up with some kind of an edge for the same money spent....be it nitrous or something else i could afford while staying in the budget. When you're spending around a grand or more for your EFI top end, i'm spending $450 for mine....it's not rocket science.

 

[Busted07]

All of the people arguing gas mileage... you bought a performance car to start with, who cares about gas mileage.

The debate could go on for years, but this is what made me decide to go to carb:

Crank but no start checklist for carb:
------------------------------------------------

1. Look in carb, are you getting gas?
2. If not, get your screwdriver and make adjustment.




Cranks OK, but No Start Checklist for Fuel Injected Mustangs
-------------------------------------------------------------------------------

Revised 29-Jun-2007 to update TPS testing procedure for 94-95 Mustangs

All text applies to all models unless stated otherwise.

Note: 94-95 specific changes are in red

1.) Remove push on connector from starter solenoid and turn ignition switch on. Place car in neutral or Park and set the parking brake. Remove the coil wire from distributor & and hold it 3/8” away from the engine block. Jumper the screw to the big bolt on the starter solenoid that has the battery wire connected to it. You should get a nice fat blue spark.
Most of the items are electrical in nature, so a test light, or even better, a voltmeter, is helpful to be sure they have power to them.
No spark, possible failed items in order of their probability:
A.) MSD or Crane ignition box if so equipped
B.) Coil
C.) TFI module
D.) PIP sensor in distributor. The PIP sensor supplies the timing pulse to trigger the TFI and injectors. See paragraph 5A - a noid light will tell if the pip is working by flashing when the engine is cranking.
E.) No ECC or computer power - ECC or computer relay failure
86-93 models only: ECC relay next to computer - look for 12 volts at the fuel injector red wires
94-95 models only: EEC or PCM power relay in the constant control relay module. Look for 12 volts at the fuel injector red wires.
F.) No ECC or computer power - fuse or fuse link failure
86-93 models only: Fuse links in wiring harness - look for 12 volts at the fuel injector red wires. All the fuse links live in a bundle up near the starter solenoid.
94-95 models only: 20 amp EEC fuse in the engine compartment fuse box. Look for 12 volts at the fuel injector red wires.
G.) Ignition switch - look for 12 volts at the ignition coil red/lt green wire. No 12 volts, blown fuse link or faulty ignition switch. Remove the plastic from around the ignition switch and look for 12 volts on the red/green wire with the switch in the Run position. No 12 volts and the ignition switch is faulty. If 12 volts is present in the Run position, then the fuse link is blown.
94-95 models only: Check inside fuse panel for fuse #18 blown – 20 amp fuse
H.) Computer
J.) Engine fires briefly, but dies immediately when the key is released to the Run position. Crank the engine & when it fires off, pull the small push on connector (red wire) off the starter relay (Looks like it is stuck on a screw). Hold the switch in the crank position: if it continues to run there is a problem with either the ignition switch or TFI module. Check for 12 volts at the red/green wire on the coil with the switch in the Run position. Good 12 volts, then replace the TFI.

See the following links for wiring diagrams...

http://www.autozone.com/servlet/UiBr...3d8016713c.jsp for 79-88 model cars
Computer/fuel pump/ignition wiring diagram, 86 model http://www.autozone.com/images/cds/g...3d80167158.gif
Computer/fuel pump/ignition wiring diagram, 87 model http://www.autozone.com/images/cds/g...3d8016715e.gif
Computer/fuel pump/ignition wiring diagram, 88 model http://www.autozone.com/images/cds/g...3d80167162.gif

http://www.autozone.com/servlet/UiBr...3d8019595a.jsp for 89-93 model cars
Computer/fuel pump/ignition wiring diagram, 89-90 cars http://www.autozone.com/images/cds/g...3d8019595f.gif
Computer/fuel pump/ignition wiring diagram, 91-93 cars
http://www.autozone.com/images/cds/g...3d80195960.gif

http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model cars

2.) Spark at coil wire, pull #1 plug wire off at the spark plug and check to see spark. No spark, possible failed items in order of their probability:
A.) Moisture inside distributor – remove cap, dry off & spray with WD40
B.) Distributor cap
C.) Rotor
D.) Spark Plug wires
E.) Coil weak or intermittent - you should see 3/8" fat blue spark with a good coil

3.) Spark at spark plug, but no start.
Next, get a can of starting fluid (ether) from your local auto parts store: costs a $1.30 or so. Then pull the air duct off at the throttle body elbow, open the throttle, and spray the ether in it. Reconnect the air duct and try to start the car. Do not try to start the car without reconnecting the air duct.

Two reasons:
1.) If it backfires, the chance for a serious fire is increased.
2.) On Mass Air cars, the computer needs to measure the MAF flow once the engine starts.
If it starts then, you have a fuel management issue. Continue the checklist with emphasis of fuel related items that follow. If it doesn’t, then it is a computer or timing issue: see Step 4.

Clue – listen for the fuel pump to prime when you first turn the ignition switch on. It should run for 5-20 seconds and shut off. To trick the fuel pump into running, find the EEC test connector and jump the connector in the Upper RH corner to ground. The EEC connector is near the wiper motor and LH hood hinge.


If the relay & inertia switch are OK, you will have power to the pump. Check fuel pressure – remove the cap from the schrader valve behind the alternator and depress the core. Fuel should squirt out, catch it in a rag. Beware of fire hazard when you do this. In a pinch, you can use a tire pressure gauge to measure the fuel pressure. It may not be completely accurate, but you will have some clue as to how much pressure you have. If you have any doubts about having sufficient fuel flow/pressure, rent a fuel pressure test gauge from the auto parts store. That will tell you for sure if you have adequate fuel pressure.


4.) No fuel pressure, possible failed items in order of their probability:
A.) Tripped inertia switch – Coupe & hatch cars hide it under the plastic trim covering the driver's side taillight. Use the voltmeter or test light to make sure you have power to both sides of the switch
B.) Fuel pump power relay – located under the driver’s seat in most stangs built before 92. On 92 and later model cars it is located below the Mass Air Flow meter. Look for 12 volts at the Pink/Black wire on the fuel pump relay.
C.) Clogged fuel filter
D.) Failed fuel pump
E.) 86-90 models only: Blown fuse link in wiring harness. Look for 12 volts at the Orange/Lt Blue wire on the fuel pump relay.
91-93 models only Blown fuse link in wiring harness. Look for 12 volts at the Pink/Black wire on the fuel pump relay.
The fuse links for all model years 86-93 live in the wiring harness near the starter solenoid.
94-95 models only: 20 amp fuel pump fuse in the engine compartment fuse box. Look for 12 volts at the Dark green/yellow wire on the constant control relay module.
F.) Engine seem to load up on fuel and may have black smoke at the tailpipe. Fuel pressure regulator failed. Remove the vacuum line from the regulator and inspect for fuel escaping while the pump is running. If fuel is coming out the vacuum port, the regulator has failed. Check the regulator vacuum line for fuel too. Disconnect it from the engine and blow air though it. If you find gas, the regulator has failed.


5.) Fuel pressure OK, the injectors are not firing.
A.) A noid light available from any auto parts store, is one way to test the injector wiring.
The noid light plugs into the fuel injector harness in place of any easily accessible injector. Plug it in and it will flash if the injector is firing.
B.) I like to use an old injector with compressed air applied to the injector where the fuel rail would normally connect. I hook the whole thing up, apply compressed air to the injector and stick it in a paper cup of soapy water. When the engine cranks with the ignition switch on, if the injector fires, it makes bubbles. Cheap if you have the stuff laying around, and works good too.
D.) Pull an injector wire connector off and look for 12 volts on the red wire when the ignition switch is on.
E.) No power, then look for problems with the 10 pin connecter (salt & pepper shakers at the rear of the upper manifold).
F.) No power and the 10 pin connections are good: look for broken wiring between the orange/black wire on the ECC relay and the red wire for the 10 pin connectors.
G.) TPS voltage exceeds 3.7 volts with the throttle closed. This will shut off the injectors, since the computer uses this strategy to clear a flooded engine. Use a DVM, a pair of safety pins, and probe the black/white and green wires to measure the TPS voltage.
On a 94-95 Mustang, probe the black/white and grey/white wires to measure the TPS voltage
It should be .5-.99 volts with the key on, engine not running. Note that if the black/white wire (signal ground) has a bad connection, you will get some strange readings. Make a second measurement using the battery post as the ground to eliminate any ground problems. If the readings are different by more than 5%, you may have a high resistance condition in the black/white signal ground circuit.

6.) Spark & fuel pressure OK.
A.) Failed IAB (no airflow to start engine). Press the throttle ¼ way down and try to start the car.
B.) Failed computer (not very likely)
C.) Engine ignition or cam timing off: only likely if the engine has been worked on recently).
D.) Firing order off: HO & 351 use a different firing order from the non HO engines.
HO & 351W 1-3-7-2-6-5-4-8
Non HO 1-5-4-2-6-3-7-8
E.) No start when hot - Press the throttle to the floor & try starting it if you get this far. If it starts, replace the ECT.


Ill give up the troubleshooting headache for the ease of maintenance.

And sure, carb technology is old, but there is a reason ALOT of racers still choose carb over EFI

 

[Disturbed90gt]

ill stick with the carb setup for the go fast car and EFI for my daily driver. the mustang isnt driven daily. its a weekend warrior more than anything honestly. but the thunderbird is driven daily so i am worried about fuel useage on that one. but im an old school kinda guy and would rather have the carb over the EFI any day. ALOT less to go wrong and couse running issues and easier to tune

 

[85_SS_302_Coupe]

Hey let me throw this in and see what you guys think....


Lets say you have two guys who are running mostly stock 5.0s, but of course one is carbed and one is EFI. Both guys are about to buy superchargers and tune for MAX HP. Lets say both guys buy a Novi 1000 just so they've got the same SC for comparison reasons.


How much is the EFI guy going to spend from start to finish if he wants to make as much power as possible on his stock long block? Once he buys the intake, tb, injectors and all the other accompanying parts to support boost, and then has it tuned, how much has he spent? The options are pretty vast as far as parts, but seriously someone give me a realistic number and if you can, back it up with Summit website links to back up your prices. Regardless, considering a nice EFI intake is $500 plus, i've already got you beat with a carb setup....


The carb guy would buy his new intake and even to make it fair he's gonna buy a new carb as well. He's gonna spend around $400 for a decent blow through capable carb, and then no more than $240 for an intake (you can go with a Victor Jr for $235). And then all you need is a carb hat...maybe $50.

That brings our total to around $695. (just out of curiosity, how much is a Holley Systemax EFI intake? pretty close to that alone isn't it?) Now....you're gonna say something about tuning right? Well, jetting is simple enough....BUT lets say we order our carb custom from one of the reputable carb shops (duh, like The Carb Shop..lol). Let's get totally crazy and say for example purposes that you throw down a $1000 on a custom built blow through carb (which there's no way in hell you would even need). Now you've spent $1295.....but the catch is you're not going to have to tune anything because when you ordered it, you told the guy on the phone what your setup was and the carb was built to suit that setup...you just bolt it together and hit the street.

Now...wouldn't it be safe to say you're going to spend more than $1300 on EFI parts alone? Coming from a stock EFI engine, you might be able to spend less than that if you buy lower end parts, but then you're gonna lose in the HP war. If you wanna buy top notch parts to make the most power, you're gonna spend a bundle. THEN you're going to have to get it tuned...


Then lets say down the road we both wanna up the power and pully up to add more boost. My combo is as simple as changing the jets and maybe adjusting the timing. Lets say you went cheap and didn't buy the best intake you could have....you're going to eventually have to buy another intake and blow a bunch more money. My intake on the other hand (assuming we bought the Vic Jr) is capable of breathing up to 7000rpm. Even then, if that intake wasn't enough, i simply buy the Super Victor for $385 which can run clear up to 9k. That probably wouldn't be necessary though as we'd both be out of head/cam flow by then.


It's simple math guys. When it comes to tinkering around on the street, yes EFI wins hands down if you wanna nit pick the details about mpg and heat and cold and all those variables which i can tell you are NOT a big deal because i deal with them just about every time i drive my car. BUT if you wanna go racing, and you wanna be fast and stay competitive on a much smaller budget, you can't beat a carb setup. It's cheap, it's flexible, and the biggest factor in making it work is the USER and his initiative to learn and work to make the most out of it.

 

[Boss 351]

I admit the carb checklist is shorter, but the EFI can run for 20 some years without any problems. CFI is even better, my dad's 84 Lincoln 5.0L NEVER has needed the air filter cover removed besides to change the filter. He has so few problems with his engine that the hood is almost rusted shut

This is my second EFI Mustang and it's VERY reliable. My carb'd one needed adjustments every once in a while. My 650 double pumper (first carb) gave me headaches (it was used). I eventually bought a new vacuum carb for the street.

Case and point: My cousin's 454 powered pontiac had some dirt fly past the fuel filter, he had huge problems with his carb, the car would stall and he needed a tow truck to get it back home. I had a simular problem with my coupe. The fuel filter hasn't been changed, in what seemed like, 10 years. I had brown dirty fuel leak out of the filter (with filter particles to boot). You know what? My car brought me home, it had a weird problem when I floored it, but it drove back home without too many problems. I changed the cheap fuel filter, put some injector cleaner in the tank and I was off. I didn't need to rebuild a carb.

After having both carb'd and EFI, I'm sticking to EFI. Now that I understand our EFI systems, it's a piece of cake. Yeah it's more expensive to mod. But we are in 2007! Laws are only going to get more strict, what if we suddenly have to convert our cars to Hydrogen ....

 

[85_SS_302_Coupe]

I admit the carb checklist is shorter, but the EFI can run for 20 some years without any problems. CFI is even better, my dad's 84 Lincoln 5.0L NEVER has needed the air filter cover removed besides to change the filter. He has so few problems with his engine that the hood is almost rusted shut

This is my second EFI Mustang and it's VERY reliable. My carb'd one needed adjustments every once in a while. My 650 double pumper (first carb) gave me headaches (it was used). I eventually bought a new vacuum carb for the street.

Case and point: My cousin's 454 powered pontiac had some dirt fly past the fuel filter, he had huge problems with his carb, the car would stall and he needed a tow truck to get it back home. I had a simular problem with my coupe. The fuel filter hasn't been changed, in what seemed like, 10 years. I had brown dirty fuel leak out of the filter (with filter particles to boot). You know what? My car brought me home, it had a weird problem when I floored it, but it drove back home without too many problems. I changed the cheap fuel filter, put some injector cleaner in the tank and I was off. I didn't need to rebuild a carb.

After having both carb'd and EFI, I'm sticking to EFI. Now that I understand our EFI systems, it's a piece of cake.

So....rebuild the carb maybe? In reality you wouldn't even need that...just clean the dang thing out. Let's say you get something REALLY nasty through your filter and you ruin an injector....what's that going to cost you?


BTW FBD that's hilarious...lol

 

[Boss 351]

So....rebuild the carb maybe? In reality you wouldn't even need that...just clean the dang thing out. Let's say you get something REALLY nasty through your filter and you ruin an injector....what's that going to cost you?

an injector, maybe 40 bucks... it takes about 2 minutes to remove the upper intake to reach all the injectors... It's not that bad really... I've fixed a car with a strange EFI problem (would jump to 3000rpm on start up and stall if the car went below 2000rpm). Turns out a diode shorted out and caused the idle control part of the computer to die. I changed the guy's computer and fixed his harness. It took me maybe 2 hours to fix and cost him a little over 100 bucks total.

Carb IS cheaper, I won't argue. But for the cost of doing a PROPER EFI to carb swap with the fuel pump, distributor, modding the engine bay harness for the duraspark (or going MSD)... It would make more sense to stick to EFI and mod that. It's not an evil system, they aren't complicated for our fox mustangs. Now maybe the new shtuff is scary with all the extra pollution controls they have. It's like the Borg taking over an engine Carb well... if it has spark, it's time to check the carb, pretty easy to manage

 

[85_SS_302_Coupe]

Ya know to be completely honest, if i had money coming out my arse i'd probably run EFI for boost....but that's probably the only reason.

Don't get me wrong guys, i'm not knocking EFI. My only point here is that EFI isn't so superior as to make a carb a hands down loser by any stretch, and it's about half the price to boot. Money is a huge factor for me because i DON'T have it coming out my arse...lol. I learned early in the game that if i wanted to be fast with pretty much any car, EFI wasn't going to do it because EFI=money if you want power.

My first 'stang was an '88 GT and i think knew the first time i flipped through my first Mustang mag looking at the prices of everything it was going to take to get my car past 300hp that EFI wasn't for me. I knew that with a carb i can use my head and my hands to make power, and those are free.

As for swapping to a carb setup....i actually don't even like the idea. I say if you don't like EFI, sell the car and get an '85 or older car, and i know that's not an option for most guys, but that's exactly what i did.

 

[millhouse]

Seeing as I'm currently at work , I don't have the time to devote in a complete response. Yes…if your building from complete scratch it's tough to beat a carb setup dollar for dollar. Most of us however luckily are not…and even more are quite frugal. There are a vast array of OEM parts that swap quite easily on a fuel injected 5.0 (intake, throttle body, injectors etc.) that can be had for cheap. There is simply no need to buy a $500 intake or $200 throttle body to compete with a carb (unless were talking big money budgets).

The same goes with tuning. I built my megasquirt for ~ $150. Add the cost of the wideband (~$200) and you now have the ability to tune wherever you go. Again, no need for dyno time and really not that expensive. It also gives you by far more adjustability than a carb setup.

I'd just like to touch on the subject one more time of the impact of weather on carb setups. The perfect example of this is guys bracket racing. It is an absolute must to know your sh^t with tuning a carb for temperature/pressure/humidity differences. Running the heat's during the day and mains at night (which typically is how it works) wreaks havoc on the carb's ability to be consistent. Seeing as constancy is the name of the game in bracket…you better be on your game if your trying to compete with a carb.

 

[jrichker]

From an old post of mine on the same subject...

One of the important things is consistency: that’s why automatic transmission cars are so good at bracket racing. With a little effort on the driver’s part, they get off the line the same every time. Transport that idea to EFI and carbs: the EFI system is like the auto trans, and the carb is like the 5 speed. It can be much more difficult to get consistent 60 foot times with a 5 speed than an auto trans.

Large changes in temperature or barometric pressure can affect power output due to the change in air/fuel ratio in carb systems. EFI takes care of that problem by getting input from the sensors and adjusting the injector pulse duration .

Sample examples:

Carb: You take your new hotwheels 351 with a carb, fancy heads, hot cam, built C4, etc., etc. to the local tuner whiz. He’s a little peculiar, one of those hair on fire, can’t stand still kind of guys, but he gets results. He also gets $100 an hour plus $300 for dyno usage, so wasting his time isn’t healthy for your wallet. It’s 60 degrees and dry as dust as you pull into the dyno shop. The first pull is terrible, and he shakes his head and makes some insulting remarks about your hat size. Out come the tools and 15 minutes later he’s ready for another run. This one is better but flattens out near the top. He’s thinking a different power valve is the fix. More tool turning, another 15 minutes and he’s ready to go at it again. Next run looks really good on top end power, but the mid range torque is down and isn’t what he wants. Time to change more parts… Out comes the jet kit and he finds the proper size, along with another 15 minute slice of your wallet. Fire up the engine, re-adjust the idle and accelerator pump linkage and run it up. This one makes him smile – a little. He tells you that this isn’t the ultimate, but it is good. Pleasantries are exchanged, along with $400 of your money. Weeks pass and spring turns to summer, along with several trips to the track. The track results have been good, but the times seem to increase as the temperature rises. Today it’s 95 and so humid that everything has a layer of sweat. First run, power is down, the car seems to bog, the trap speed is down and the ET is up. You check the timing, tire pressure, fuel pressure, all OK. Second and third runs produce similar results. Another run and you do a clean cut at the last light. Coasting into the return lane, your pit crew buddy meets you with a plug wrench and some extra bodies to push the car out of the way. Plugs come out, inspection is done and you conclude that the engine is running rich. A call to the tuner guy results in him digging out the dyno sheet and looking at his notes. More insulting remarks follow, and he asks you if you expected the same tune that ran good at a dry 60 degrees to run the same at a sweaty 95 degrees. You say yes and then he tells you to get a life and some more education on how temperature and humidity affect engine performance. He offers a retune for the current weather at a discounted $300 flat rate. A sudden pain in your wallet springs to life as your credit card starts to throb like a stubbed big toe…

EFI: Your new EFI 351 is all ready to go, hot HCI combo,70 MM TB, 30 pound injectors, 80 MM MAF, built C4, stock computer and a lot of time and effort. A trip to the dyno is scheduled and it’s a fine day, 60 degrees outside and bone dry. You pull up to the dyno shop and are greeted by a little guy with frizzy red hair that looks like an explosion in a mattress factory and is wearing a T shirt that says “DynoGuys” on it. He seems a little weird, but he is supposed to be the best. Five minutes later, he has a laptop connected to the computer port and is ready to roll onto the dyno and prep for a run. Tires, timing, fuel pressure & idle are checked and pronounced acceptable. First run is a baseline and shows there is more on the table. “DynoGuy” shakes his head, mumbles something and does a tap dance with his fingers on the laptop keyboard. Two more up and down runs, and he smiles, showing the braces on his teeth. The engine returns to idle and it seems a little rough. “DynoGuy” dances on the keyboard some more and things smooth out. Another run up and down and he hands you the dyno sheet and asks if that was what you had in mind. You say yes, he shuts everything down, disconnects the laptop and heads for his office. Five minutes later he is back with a little black box that the plugs onto the car’s computer where his laptop was plugged in. He plugs in the black box, secures the loose pieces and kick panel. So far so good – then he hands you a bill for $475. You look and see $300 for the dyno, $50 worth of his time and $125 for the custom chip he just installed. Ouch! Well, at least your air miles on your credit card just went up.
Weeks pass and the miles go by. The car even passes the gas stations, something it never did before. Several trips to the track prove fruitful, the car just keeps getting better. You decide to make a July 4th bonus race, even though it is 95 degrees and so humid that even your cat is sweating. Off to the track: first run good, second, third and forth runs are good too. You look in the glove compartment at your previous time slips. All are tightly grouped with about a 1/10 of a second between the highs and lows. Bonus time comes up & you win $75 for the most consistent times for the season.

The point is EFI is a consistent performer, hot or cold, rain or shine. Differences in temperature and humidity are accommodated by the computer’s programming. No jets to change, no linkages to adjust, no power valves to tinker with. No getting stinky smelly from gasoline while playing with tiny parts that seem to want to run away and hide from you.

Consistent all weather performance, good gas mileage, and no failing the smog check because of non standard equipment are the pluses of an EFI car. Cars that were EFI and have been converted to carb will not pass smog testing. That may not be a problem now, but if you move or sell the car to someone in an emissions regulated are, it will be.

 

[GTOreturns]

Excellent explanation! Thanks!!

 

[25thmustang]

I wasn't "arguing" anything with fuel economy, and did NOT buy or build my car to get good gas mileage, but to be honest, getting mid to upper 20s on the highway is a great thing. Last year I drove a car to SC that got 16-18 on the highway. After 2000 miles of driving 18 mpg vs 27 mpg...

2000/18 = 111.11 Gallons of gas

111.11 x $3.00 = $333.33

So last year I spent roughly $333 on gas.

2000/27 = 74.1

74.1 x $3.00 = 222.3

And this year, roughly $222 on gas.

This left me with $111 to spend on, booze, food, and tons of other stuff.

Now I would NEVER go out of my way to build a performance car for gas mileage, but I do like the fact that mine gets decent mileage. I like being able to go 300 miles on a tank as well. I know this is straying from the carb vs efi debate, but its part of the equation. Not to mention I barely passed CT emissions with my Long Tubes and EFI, toss a carb on there and I can't even drive the car, they would fail me before ever putting it on the rollers.

 

[Modular2v]

Carbs are cheaper and more simplistic. Anyone who says EFI makes more power, i'll match you dollar for dollar and we'll build an engine from scratch and lets see who makes more power.

fully agree! Performance wise a carb wipes the floor witha efi car! I have owned both! If you want effeciency and control use the efi

 

[Modular2v]

hands down carb would win.

I went the carb route because I had to upgrade so much to stay EFI. Since my car was a 86 and it was speed density. The carb route was cheaper. It isn't all that friendly before it warms up but after it has it's a beast.

Another pro to having a carb is the sound of the 4 barrels. Nothing quite like it.

This is the exact reason i went carb.... i have less than 7k dollars invested in my whole car (including the price of the car) and i run 10s.... efi takers?

by the way dan...have your distributor re-curved and that warm up problem wont be an issue!

 

[Modular2v]

All of the people arguing gas mileage... you bought a performance car to start with, who cares about gas mileage.

The debate could go on for years, but this is what made me decide to go to carb:

Crank but no start checklist for carb:
------------------------------------------------

1. Look in carb, are you getting gas?
2. If not, get your screwdriver and make adjustment.




Cranks OK, but No Start Checklist for Fuel Injected Mustangs
-------------------------------------------------------------------------------

Revised 29-Jun-2007 to update TPS testing procedure for 94-95 Mustangs

All text applies to all models unless stated otherwise.

Note: 94-95 specific changes are in red

1.) Remove push on connector from starter solenoid and turn ignition switch on. Place car in neutral or Park and set the parking brake. Remove the coil wire from distributor & and hold it 3/8” away from the engine block. Jumper the screw to the big bolt on the starter solenoid that has the battery wire connected to it. You should get a nice fat blue spark.
Most of the items are electrical in nature, so a test light, or even better, a voltmeter, is helpful to be sure they have power to them.
No spark, possible failed items in order of their probability:
A.) MSD or Crane ignition box if so equipped
B.) Coil
C.) TFI module
D.) PIP sensor in distributor. The PIP sensor supplies the timing pulse to trigger the TFI and injectors. See paragraph 5A - a noid light will tell if the pip is working by flashing when the engine is cranking.
E.) No ECC or computer power - ECC or computer relay failure
86-93 models only: ECC relay next to computer - look for 12 volts at the fuel injector red wires
94-95 models only: EEC or PCM power relay in the constant control relay module. Look for 12 volts at the fuel injector red wires.
F.) No ECC or computer power - fuse or fuse link failure
86-93 models only: Fuse links in wiring harness - look for 12 volts at the fuel injector red wires. All the fuse links live in a bundle up near the starter solenoid.
94-95 models only: 20 amp EEC fuse in the engine compartment fuse box. Look for 12 volts at the fuel injector red wires.
G.) Ignition switch - look for 12 volts at the ignition coil red/lt green wire. No 12 volts, blown fuse link or faulty ignition switch. Remove the plastic from around the ignition switch and look for 12 volts on the red/green wire with the switch in the Run position. No 12 volts and the ignition switch is faulty. If 12 volts is present in the Run position, then the fuse link is blown.
94-95 models only: Check inside fuse panel for fuse #18 blown – 20 amp fuse
H.) Computer
J.) Engine fires briefly, but dies immediately when the key is released to the Run position. Crank the engine & when it fires off, pull the small push on connector (red wire) off the starter relay (Looks like it is stuck on a screw). Hold the switch in the crank position: if it continues to run there is a problem with either the ignition switch or TFI module. Check for 12 volts at the red/green wire on the coil with the switch in the Run position. Good 12 volts, then replace the TFI.

See the following links for wiring diagrams...

http://www.autozone.com/servlet/UiBr...3d8016713c.jsp for 79-88 model cars
Computer/fuel pump/ignition wiring diagram, 86 model http://www.autozone.com/images/cds/g...3d80167158.gif
Computer/fuel pump/ignition wiring diagram, 87 model http://www.autozone.com/images/cds/g...3d8016715e.gif
Computer/fuel pump/ignition wiring diagram, 88 model http://www.autozone.com/images/cds/g...3d80167162.gif

http://www.autozone.com/servlet/UiBr...3d8019595a.jsp for 89-93 model cars
Computer/fuel pump/ignition wiring diagram, 89-90 cars http://www.autozone.com/images/cds/g...3d8019595f.gif
Computer/fuel pump/ignition wiring diagram, 91-93 cars
http://www.autozone.com/images/cds/g...3d80195960.gif

http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model cars

2.) Spark at coil wire, pull #1 plug wire off at the spark plug and check to see spark. No spark, possible failed items in order of their probability:
A.) Moisture inside distributor – remove cap, dry off & spray with WD40
B.) Distributor cap
C.) Rotor
D.) Spark Plug wires
E.) Coil weak or intermittent - you should see 3/8" fat blue spark with a good coil

3.) Spark at spark plug, but no start.
Next, get a can of starting fluid (ether) from your local auto parts store: costs a $1.30 or so. Then pull the air duct off at the throttle body elbow, open the throttle, and spray the ether in it. Reconnect the air duct and try to start the car. Do not try to start the car without reconnecting the air duct.

Two reasons:
1.) If it backfires, the chance for a serious fire is increased.
2.) On Mass Air cars, the computer needs to measure the MAF flow once the engine starts.
If it starts then, you have a fuel management issue. Continue the checklist with emphasis of fuel related items that follow. If it doesn’t, then it is a computer or timing issue: see Step 4.

Clue – listen for the fuel pump to prime when you first turn the ignition switch on. It should run for 5-20 seconds and shut off. To trick the fuel pump into running, find the EEC test connector and jump the connector in the Upper RH corner to ground. The EEC connector is near the wiper motor and LH hood hinge.


If the relay & inertia switch are OK, you will have power to the pump. Check fuel pressure – remove the cap from the schrader valve behind the alternator and depress the core. Fuel should squirt out, catch it in a rag. Beware of fire hazard when you do this. In a pinch, you can use a tire pressure gauge to measure the fuel pressure. It may not be completely accurate, but you will have some clue as to how much pressure you have. If you have any doubts about having sufficient fuel flow/pressure, rent a fuel pressure test gauge from the auto parts store. That will tell you for sure if you have adequate fuel pressure.


4.) No fuel pressure, possible failed items in order of their probability:
A.) Tripped inertia switch – Coupe & hatch cars hide it under the plastic trim covering the driver's side taillight. Use the voltmeter or test light to make sure you have power to both sides of the switch
B.) Fuel pump power relay – located under the driver’s seat in most stangs built before 92. On 92 and later model cars it is located below the Mass Air Flow meter. Look for 12 volts at the Pink/Black wire on the fuel pump relay.
C.) Clogged fuel filter
D.) Failed fuel pump
E.) 86-90 models only: Blown fuse link in wiring harness. Look for 12 volts at the Orange/Lt Blue wire on the fuel pump relay.
91-93 models only Blown fuse link in wiring harness. Look for 12 volts at the Pink/Black wire on the fuel pump relay.
The fuse links for all model years 86-93 live in the wiring harness near the starter solenoid.
94-95 models only: 20 amp fuel pump fuse in the engine compartment fuse box. Look for 12 volts at the Dark green/yellow wire on the constant control relay module.
F.) Engine seem to load up on fuel and may have black smoke at the tailpipe. Fuel pressure regulator failed. Remove the vacuum line from the regulator and inspect for fuel escaping while the pump is running. If fuel is coming out the vacuum port, the regulator has failed. Check the regulator vacuum line for fuel too. Disconnect it from the engine and blow air though it. If you find gas, the regulator has failed.


5.) Fuel pressure OK, the injectors are not firing.
A.) A noid light available from any auto parts store, is one way to test the injector wiring.
The noid light plugs into the fuel injector harness in place of any easily accessible injector. Plug it in and it will flash if the injector is firing.
B.) I like to use an old injector with compressed air applied to the injector where the fuel rail would normally connect. I hook the whole thing up, apply compressed air to the injector and stick it in a paper cup of soapy water. When the engine cranks with the ignition switch on, if the injector fires, it makes bubbles. Cheap if you have the stuff laying around, and works good too.
D.) Pull an injector wire connector off and look for 12 volts on the red wire when the ignition switch is on.
E.) No power, then look for problems with the 10 pin connecter (salt & pepper shakers at the rear of the upper manifold).
F.) No power and the 10 pin connections are good: look for broken wiring between the orange/black wire on the ECC relay and the red wire for the 10 pin connectors.
G.) TPS voltage exceeds 3.7 volts with the throttle closed. This will shut off the injectors, since the computer uses this strategy to clear a flooded engine. Use a DVM, a pair of safety pins, and probe the black/white and green wires to measure the TPS voltage.
On a 94-95 Mustang, probe the black/white and grey/white wires to measure the TPS voltage
It should be .5-.99 volts with the key on, engine not running. Note that if the black/white wire (signal ground) has a bad connection, you will get some strange readings. Make a second measurement using the battery post as the ground to eliminate any ground problems. If the readings are different by more than 5%, you may have a high resistance condition in the black/white signal ground circuit.

6.) Spark & fuel pressure OK.
A.) Failed IAB (no airflow to start engine). Press the throttle ¼ way down and try to start the car.
B.) Failed computer (not very likely)
C.) Engine ignition or cam timing off: only likely if the engine has been worked on recently).
D.) Firing order off: HO & 351 use a different firing order from the non HO engines.
HO & 351W 1-3-7-2-6-5-4-8
Non HO 1-5-4-2-6-3-7-8
E.) No start when hot - Press the throttle to the floor & try starting it if you get this far. If it starts, replace the ECT.


Ill give up the troubleshooting headache for the ease of maintenance.

And sure, carb technology is old, but there is a reason ALOT of racers still choose carb over EFI

another check mark in the "bad ass" column for fbd!

 

[millhouse]

This is the exact reason i went carb.... i have less than 7k dollars invested in my whole car (including the price of the car) and i run 10s.... efi takers?

by the way dan...have your distributor re-curved and that warm up problem wont be an issue!

Head on over to the TM forums and you'll find guys that could smack you around with less invested on EFI setups. I'm not sure I see your point…once you start getting into forced induction the carb vs. EFI argument becomes much more blurred. The EFI setups typically will still have better drivability though…get better fuel economy and many will still pass emissions.

 

[Modular2v]

Head on over to the TM forums and you'll find guys that could smack you around with less invested on EFI setups. I'm not sure I see your point…once you start getting into forced induction the carb vs. EFI argument becomes much more blurred. The EFI setups typically will still have better drivability though…get better fuel economy and many will still pass emissions.

my point is FOR DOLLAR TO DOLLAR PERFORMANCE YOU CANT BEAT CARB
And ...i thought this had already been covered but ill say it again....Who cares about fuel economy in a performance car???????????? buy a honda hell

on a side note...im a member over at the tm forums. Some of those guys have 2k invested in just tuning software!!!!!!!!!!

 

[millhouse]

my point is FOR DOLLAR TO DOLLAR PERFORMANCE YOU CANT BEAT CARB
And ...i thought this had already been covered but ill say it again....Who cares about fuel economy in a performance car???????????? buy a honda hell

It greatly depends on what your starting with and how frugal you are. Just because you achieved your times with a $7k carbed setup does not mean you can't do the same with fuel injection.

Yes, building from scratch with a carb is going to be cheaper…I have no qualms with that.

As far as fuel economy goes…there are plenty of us who like to have our cake and eat it too. I myself am capable of 24mpg on the freeway. When all is said and done I should be looking at a 10 second @ 125-130mph capable car that runs on premium, drives, idles and cruises excellent…and again…gets decent fuel economy. FYI, my setup didn't exactly break the bank either.