QUOTE(Brando @ Apr 26 2007, 02:22 PM)
With the right FI setup, you can meet and/or exceed carbureted power. Both systems tuned properly will net reliability.
A properly configured PEFI system will run excellent.
A properly configured carb system will run excellent.
Only differences would be... How many possible failure points in each? How tuneable are they? How expensive are they?
Carbs you get three settings usually. 1) Idle 2) Midrange 3) WOT.
PEFI you get... Wow, the whole RPM range can be configured.
But I like FI, and would love to switch to a PEFI system.
I hear you - I'd like to go to PEFI on my 914, too.
There are a lot of different operating conditions that a fuel system needs to accomodate, and many of these conditions are interactive:
1. Cold start (sitting overnight)
2. Cold-cold start (engine temperature under 32 deg. F)
3. Warm start (engine not fully warmed up)
4. Hot start (engine fully warmed up)
5. Warm-up (affects all load and engine speed mixtures)
6. Part-load (low throttle angle)
7. Moderate load (transition region)
8. Full-load (WOT)
9. Overrun (closed throttle, coasting)
10. Acceleration (rapid throttle closing)
11. Altitude compensation
12. Ambient air temperature
Oh, and you've got to do all of this while optimizing performance, maintaining good fuel economy, and producing low HC, CO, and NOx emissions.
Doing all that with carbs proved impossible for auto manufacturers as emissions regulations tightened, hence the move to EFI through the 70's and 80's. I was always impressed by Honda, how long they held out against going to EFI. Some of the carbs they put on the Accord in the '80s were freakin' insane, with about a billion vacuum hoses and all kinds of little gizmos attached.
I had a 2.2L with 40IDF Webers before I converted back to D-Jet FI. I really liked that motor, it had gobs of power and sounded great. Wasn't that bad to tune and maintain, but you did have to stay on it. But it didn't have a warm-up system, drank fuel like booze, and put out gobs of pollution. Carbs also are intrinsicallly unable to be as efficient as FI due to poor fuel atomization.
I think carbs are great for modder's, but as people have become more familiar with FI, PEFI systems are now the tool of choice. Even better are systems that permit full engine management, with active control (e.g. idle speed control, and active mixture control w/oxygen sensors).