Which is faster carb or Fuel injection?

[Rob Petrie E395]

Originally Posted by Chris Hill

Best thread in a long time!

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

[Lee Valentine]

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.

[Signman]

Originally Posted by Lee Valentine

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.

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.

[Lee Valentine]

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.

[Adger Smith]

14081005,004
10066015

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

[Signman]

Originally Posted by Lee Valentine

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.

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

[buzzinhalfdozen]

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.

[Ed Wright]

Originally Posted by buzzinhalfdozen

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.

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

[jmarkaudio]

Originally Posted by Lee Valentine

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.

What carb? Airflow makes a difference.

[pbp1]

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)