efi or carb

[sandking]

I have noticed that most (if not all) TT are running carbs. Why not use a more accurate fuel system such as the FI? I am looking into building a 500+hp LS1 motor, and have noticed that someone makes a "kit" to switch to a carb, why? Is just the fact that a carb is just simply easier to tune? Just looking for input.

[FABRICATOR]

This has been covered before. To bad there isn't a way to catagorize things. Using the search does'nt always provide desired results. A good part of information on RDC is burried in semi-related titles or threads.

There has not been that much development of balls out EFI for small block V-8s. The highest output FI's are either exotic as hell or non-electronic. Most EFI's disregard many inputs and go to specific ploted parameters at high RPM and throttle opening. Accuracy at an engine's highest possible output is touchy and questionable at best. The only things you are likely to gain are some improvement to mileage and throttle response. You would need a near perfect system to deliver more horsepower than a well tuned carburetor. Reliability is another factor. Carbs rarely stop the show.

[WoodyW]

"exotic as hell"-----(read Expensive as hell)

[ntsqd]

About a month ago one of the guys at work, who is Extremely knowlegable about EFI, showed me a pic of one of the Herbst machines. Can not recall the name of the maker of the EFI and Data Acquistion hardware, but they had redundant boxes for both. He told me those 4 boxes were worth about 50k. That's just the boxes. No wiring, no support bits, no intake, no programming software, etc.

[therail]

those boxes are worth more than my truck, and then some.

[ntsqd]

Obviously those boxes are at the high end of the high end. The polar opposite is MegaSquirt (http://www.megasquirt.info/)

[BAPerf]

It seems to me that there are quite a few TT's that are running EFI. There are a few systems capable of doing quite well in our offroad environment. Motec (Renezeder TT, LeDuc, etc), EFI Technologies (Herbst), Pectel (3 CORR Pro-4 Championships w/ Walker Evans, Carl Renezeder, and Johnny Greaves), Magneti Marelli, etc... There are some systems that are less expensive, but generally you get what you pay for!

Most guys that are familiar with decent EFI set-ups would never run a carb again. Carbs don't sense altitude, they have to be burped on long dry lake runs, heat soak, etc...

[phorensic]

Supras are making in excess of 1,000hp to the wheels with EFI setups, among other types of engines (RB26DETT comes to mind). I can see that a v8 would need to flow more air, but that shouldn't change the game much. To my understanding, the only limitation of a standalone EFI system horsepower wise would be how big of injectors you could use/control. The EFI system in our 5 car didn't run right at all with noobs trying to tune it, but in the hands of a dyno tuner we got it running perfect.

To make an engine run right you need air and fuel, and a way to measure and control both. Well, the basics of the system would be an AFM and injector pulse width control. Of course this skips over things such as an 02 sensor reading, timing, RPM monitoring, TPS monitoring, etc. However, the basics are still there. As long as you can measure an intake of +/-1000cfm of air and control an output of +/-800cc/min of fuel, the other sensors just tune that stuff based on what the motor is doing. Am I missing out on why it would cost $50K to get a v8 to do 800hp N/A with EFI???

Note: airflow and fuel numbers were totally just pulled off the top of my head, that's not necessarily what a TT sees.

[DuffcoDan]

I was once told by a guy that runs a motor dyno that there is no difference in power output from a properly tuned carburator vs. EFI. the difference is once the motor is run in real world condition the EFI motor power remains the same. the EFI motors are generally more efficient and gain torque and driveability.

[phorensic]

No difference in power, yet they gain torque? Can you re-read your post and confirm whether or not an EFI system gains torque (horsepower is a calculation based on torque and rpm, therefore more torque would equal more [horse]power).

[BAPerf]

Most "Good" EFI tuners can taylor the fuel and timing maps to outperform a carb. How many carbs can perfectly tune the mixture curve per cylinder at various load points?

I think that there are definitely more people that can get a carb to run acceptable than there are EFI turners that can make the engine run great all the time. True, Hp. is a derivative of torque and rpm, but keep in mind that most engines (carbed) that are tuned for max hp. in a given range, aren't correctly fueled in other areas.

[DuffcoDan]

in real world conditions (outside of the dyno room) the EFI motor can adjust to changing atmospheric conditions. Once the engine is installed in an off-road vehicle my understanding is the EFI motor retains the same power as the carbed motor did on the dyno. the carbed engine might be subject to fluctuations in power by the beating of an off-road vehicle and changing atmosperic conditions.

torque measures ability to get work done at a given rPM

more torque translates to more hP?

[phorensic]

If I understand what you guys are saying correctly, then you are trying to say that if you took two motors set up with similar horsepower, one EFI and one carb, the EFI would be all around better. For the simple reason that the carb is tuned to put out max power from 4500-6000,7000RPM, at one altitude, under a constant load, for short periods of time (burping was mentioned). Whereas an EFI setup will account for proper tuning below 4500RPM, all altitudes, under varying loads (whoops), and infinitely long periods of time. I can understand this by standing next to a desert track and listening to the carbed v8's that stutter below 4500RPM and sound funny under weird loads.

BTW, yes, more torqe=more horsepower. Did you know that nobody has EVER *measured* horspower? A dyno cannot measure horsepower, all it can do is measure torque and compare it against the RPM to calculate the horsepower. Don't believe me? Go read some books or something :p

[jcorsico]

My impression was that most, if not all, of the better TT's run fuel injection. I know the Herbst's have been running it for years. A picture that I have from 1999 shows a Kinsler injection system on the engine for truggy. They are at http://www.kinsler.com. I'm not sure what they are running today, but I think the engine managment system they are running is from Motec (but it may be controlling an EFI from a different company). http://www.motec.com. Herbst used to run (or maybe still runs) a logger/computer from PI Research, which is at http://www.piresearch.com. I'm not sure if PI makes engine management stuff.

Lots of the midget race car applications run EFI. Those guys all run like 800hp small blocks, which is what most TT's run, so there is defintely pre-existing systems out there that can handle an american V8.

[jeff]

Off-topic...
James Watt (the same Watt that came up with Watts used to measure light bulbs, etc.) coined the term horsepower. He said that a pony could do 22,000 lbs of work in a minute. Figuring a horse could do 50% more work than a pony, Watt said that one horse (horsepower) could do 33,000 lbs of work in one minute. A horse could raise 330lbs of something 100 feet in one minute. Or raise 33lbs of something 1000 feet in one minute. Hence the ft / lbs rating. So technically speaking, Watt was the first person to measure a horsepower and he did so without using torque in his equation. So technically speaking, measuring horsepower on a dyno is indeed possible and was done back in the early 1800's.

Farther off-topic...
The Japanese built a diesel that produces 108,920 hp at 102 rpm and 5,608,312 lb/ft at 102rpm. Look at a typical 5.9L Cummins diesel found in a Dodge truck... 625 lb/ft and 325 hp. And to make any sense of those numbers you must know the RPM the engine is turning at. Without knowing the RPM the numbers mean nothing. Horsepower = Torque x RPM / 5252

Aloha

[ntsqd]

Torque is the AMOUNT of work that can be done.

HP is the RATE at which you can do the work. Rate means time valued, how much over how long a time span. Jeff's post illustrates this.

BTW, the 5252 divisor only applied to internal combustion (IC) engines. Electric motors, Gas Turbines, and Steam Engines use a different divisor. Consequently 1HP electric motor does NOT exactly equal a 1 HP IC.

back to your regularly scheduled dezert bench racing.....

[BAPerf]

As posted above, I do believe the Hebst vehicles use EFI Technologies for both the engine and trans. The engine would require it's own box, while the trans would use some of the same sensor signals , but fed into the second ECU to control the trans.

As for Pi Research, they do not have any engine control units. They do however own Pectel, a leading manufacturer in the WRC, BTCC, Indy Lites, Toyota Atlantic, etc... The guys that own "CART" (brain fade on the new name) have recently purchased Pi Research, and all it's holdings. Pectel manufactures 4 stand alone ECU's, ranging from the T2 used in Formula Ford, CORR Pro-Lites, Class 10 buggies..., to the T10 used in WRC. The T10 has the capabilities to control the entire drivetrain, not just the engine, all in one box.

"Sprint Cars", do indeed have either 360cu.in. or 410cu.in. small blocks, but the must be mechanical injection. EFI is not legal. Ed Pink Racing Engines does however use EFI Technologies boxes to control the ignition. The midgets are 4-cylinder, and also limited to mechanical injection. The Kinsler brand of mechanical injection components are very popular in both the midgets and sprint cars.

[therail]

As posted above, I do believe the Hebst vehicles use EFI Technologies for both the engine and trans. The engine would require it's own box, while the trans would use some of the same sensor signals , but fed into the second ECU to control the trans.

I dont understand, why do the trucks need EFI for a transmission?

[phorensic]

To tell the tranny how to shift based on what the motor is doing: RPM, load, etc. I would imagine with that trick of a setup, you could tell the tranny to shift harder or softer based on conditions.

[BAPerf]

As stated above, the Transmission doesn't use EFI, but it does have an ECU that probably controls the shift points, along with the possibility of locking and unlocking the differentials based on throttle, steering, brakes, load, RPM, wheel speed sensor, etc... Many modern cars and trucks have a chassis ECU to control the converter lock-up, shift points, shift feel, cooler fans, etc...

[ntsqd]

BAPerf,
Out of curiousity, is my co-worker's $ estimate of the EFI Tech. boxes close?

[BAPerf]

$50K for just the boxes? That's probably a tad high. Add in all the sensors, wiring, and actuators, and $50k would be cheep for what the Herbst Bros. are running. I know of a few TT's that have at least $5k in just the main wiring harness'. Having redundant ECU's is un-necesary for most folks, but if money was less important that finishing position, go for it!

I would guestimate that 2 EFI Technologies engine ECU's, 2 Drivetrain ECU's, Mil-Spec wiring, quality sensors, plus the actuators on each vehicle.... probably ~$65k. <-- that's my guess.