How much more power can you get from FI than say side drafts?Are the forklifts the only place in the states that you can get the
FI?Is it tuneable?

I believe the conventional wisdom is not that the EFI makes MORE power, so much as it gives you a broader power band and better efficiency? The butt-dyno might not tell you much
difference, but I'd wager a real chassis dyno would. On L18/20's (my EFI converting experince) it really seems to bring the torque curve down lower, widens it a bit, and stops the
dreaded clutch-kill! ;^)

How much more power can you get from FI than say side drafts?

By: gt535
Date: 12/30/01 2:04 am

This "EFI makes more power theory" is pure BS, as is much conventional wisdom. Don't jump on me, but if you're interested read this through. EFI is better, but don't think it's a miracle
horsepower cure. Unfortunately this is very long and will take multiple postings.

If you don't want to know, please skip over them.
Andrew

There's no doubt fuel injection is heaps better, but not necessarily in outright power. The only limit to outright power is how much air and fuel can get in, and can they achieve the correct
mixture. Obviously with heavily modified carby V8's (or even turbo rotaries) running around getting sufficient air/fuel, there's not going to be a limit that a 1200 engine (or even a 1500
engine) is going to hit. Anyone think that an A series engine is capable (with ANY mods) of making more power than these types of engine is sadly mistaken.

Get the carby big enough to flow enough air, and get the jet sizes right, and it will get exactly the same PEAK horsepower as an EFI engine. (Assuming both can supply correct spark at the
correct time). Possibly, the carby engine could even make a slight power increase, due to the additional load that running heavier alternators makes on the EFI engine.

However, having said that - where fuel injection is better than carbies is basically EVERYWHERE else that the carby is not optimised for (in this case our carby engine was calibrated for max
hp).

A very simplistic view (*see carby addendum 1 - next posting ) is that a carby can be tuned for approximately 3 points - flat out, idle speed, and usually one more point in between.

A fuel injection system can be tuned for whatever the resolution of the fuel injection system allows. An extreme example of this is on some of your top end fuel injection systems, like MOTEC,
where you can set ignition timing, fuel delivery for every single mapping point on the power curve (by individual RPM, throttle opening, air density etc).

This is where fuel injection wins out. It can be tuned for so many more load points, effectively increasing at each of those points: Driveability, fuel economy, tuneability, throttle
response, reliability, power, torque. Wider power bands, more torque and often power are normal responses to EFI - but this is because factories don't usually set up their cars as undriveable
beasts with max horsepower the only goal. Because of the better tuning resolution of the EFI system, everything else can be setup for more peak horsepower (if that's what the factory wants),
without making the same sacrifices a carby engine tuned for peak power has to make.

The actual horespower figures are going to vary based on the state of engine tune, and how good the carb tune is versus how good the EFI system tune is.

Even retuning a stock EFI car (if the computer is retunable, or getting a rewritten chip if possible) can significantly improve horsepower, and replacing a FACTORY fuel injection computer
with a more powerful aftermarket computer can improve it further.

Hope you can use the info. In short, the only real way to find out how much "horsepower" it can improve your car's engine is to try. There were injected L series 4 cylinders and they're a
good example to use in this forum. You can usually guess at perhaps 20% and work up or down from there (CA20 vs. CA20E is very close to this mark). But also remember that it effectively
cannot improve the maximum horsepower to any more than the right carby and tuning could anyway, but where you'll see the benefits is EVERYWHERE else.

Carby addendum 1:
Also, different carby arrangements can enable closer resolution (tuneability) over the process. Single downdraft to dual throat, sidedraft to twin sidedraft, triple sidedraft, quad, etc....
Hence the reason why twin SU manifolds and GX heads (for 1200s), or why people put on twin dellortos, twin webers, etc.

Then we get into funny jet sizes and shapes, tapers of jets, more holes or different designs/shapes/angles of holes to allow better fuel atomization, accelerator pumps, narrowing passages in
the carby over jets to create additional vacuum directly above the jet, etc. this gets into gasflow dynamics and is very complicated science. The theories alone that some people have in this
field can be absolutely bizzare - to give an example of the detail, each individual jet in the carby's gas flow is going to have primary and secondary harmonic pressure waves (as does any
cylindrical shape used to flow gas) which could improve or reduce it's ability to flow fuel, on top of the size of the jet's bore, based on it's length, length versus diameter, the placement
of atomization holes, the shapes of the lip (tip) at each end. Remember, this is for a small piece the size of a pencil tip inside your carby. 100 years of development has gone into this from
every automobile engine manufacturer in the world.

In the bad old days of V8 drag racing, running twin 4 barrel downdrafts or quad twin barrel downdrafts with exactly tuned length velocity stacks was not uncommon. More air, more fuel, more
adjustability, and unfortunately more contstant retuning than anything a factory would ever sell to us.

Information overload anyone?