thats true, but with fuel injection you dont have to worry about jetting, or anything of the sort. just plug it into your computer and type in what mods you have or make a custom map and its "exactly" the way it should be.
I've never "worried" about jetting, I have been much more aggravated with my computer than I ever have been with a carb.
Fuel Injection: Better than Carburation?
It's easy to think of Fuel Injection as "an electronic carburetor replacement". Because it truly is no more or less than that. It is a device that mixes fuel with the incoming air so that the mixture is ignitable in the combustion chamber. Fuel Injection can be a wonderful thing, but it isn't as simple, or reliable, as carbureting. Fact: there is a lot more things that can go wrong with FI than with a Carb. There is the same power potential with both, too. Neither one forces air into your engine. They are both just ways of mixing fuel with what airflow the engine is pulling in.
1. Decades before there was Electronic Fuel Injection, there was Mechanical Fuel Injection, even on some of the first Corvettes, although they weren't the first of their kind. Both types still fall under the parent category of Fuel Injection.
2. Unless you have a dyno that is A/FR meter equipped, a person isn't going to have clue one about how far out they are from correct jetting, or any idea of how much adjusting it will take to get to correct either. You could adjust all you want, but without before and after runs on an AFR equipped dyno, you are just throwing darts in the dark. Venom does have an in-house Dynojet Dyno, along with the $3000 A/FR wideband meter, and the Power Commander tuning setup on the Dynojet's PC. And it still takes time and experience to dial in a correct A\FR map for a modded machine.
You can make a jetting adjustment for every change of 250 RPM, plus those changes need to be mapped at those RPM increments over discreet throttle settings from near closed throttle to wide open throttle. This is all because the mapping for 5000 RPM at half throttle is WAY different from 5000 RPM under full throttle, as well as snapped open full throttle from 3000 RPM. You get the picture. There are literally hundreds of adjustment points that cover the injector setting mapping from all rpms and all throttle positions. So, as I said, change ANY component that changes airflow and you need different map settings.
The ATV manufacturers could certainly supply fuel injection units that are self calibrating, changing the maps themselves based on factors like:
Air Density (which takes into account altitude)
Air Flow
Temperature
Oxygen content measured in the exhaust
But they don't. Their systems are just about as basic as EFI can get, and their self adjusting is VERY limited. So much so that pulling an airbox lid and pulling the spark arrester out of the exhaust REALLY stretches their capability to the end of safe A/FR ranges. In that regard, the FCR carbs currently on machines have a wider range of self adjustment than the current crop of A/FR systems on ATVs. The carb's metering can and does adjust based on mass airflow through the carb's venturi. More airflow means a stronger vacuum signal, which means more fuel will be drawn into that airflow. Not a wide range for sure, but you get the jets in a decent range for the current mods of the machine and actual airflow will change what gets metered through it to some degree.
Put more air through the current crop of EFI on the ATVs, and since there is no vacuum sensitive part to the injector's metering, the EFI just basically knows RPM and throttle opening, NOT actual airflow, so it just sprays the same amount that the map tells it to for that RPM and throttle opening until someone dyno AFR's the setup and re-writes the mapping.
Another thing: whatever "MAP" is loaded into the Power Commander module contains several hundred points of jetting to cover the grid of throttle opening VS RPM. All of those points have a huge range of adjustment when using the PC3 program on a computer, but the controls on
the PC3 module itself only allow for a bulk 10% change of the downloaded base map's curve, and each control "button" makes for bulk changes to approximately 1/3 of all the RPM\Throttle control points in the base map.
So if you get the base map tuned dead on for the center point of all the AVERAGE conditions you ride in, like temp and altitude, and don't change any engine mods, you will have 10% bulk mapping curve adjustability on the controls of the PC3 unit itself.
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Once again, with the current crop of basically NON-self-adjusting EFIs on ATVs, all of this is predicated on a correct base mapping as tested and tuned on an A/FR equipped dyno over all throttle settings and RPM's. Anyway, the primary focus of this thread was to address all the question "How much HP does fuel injection add to the new machines" that I have been getting.
For all the potential benefits of a high end FI system, which the ATV's do not have. The HP answer is still the same -- no difference at all.
Properly tuned CARB and properly tuned A\FR are equals for power output.
I will say that A/FR, with all its dependence on computer control, injector action, fuel pumps, and filters to save the pumps and injectors, is a far more fragile system than a simple/mechanical pressure differential metering device like a carb.
If my life depended on a particular off road engine's 100% reliability, I’d still take the carb.
The fact is that when an FCR carb is open, only the thin needle remains in the airflow path, but when the throttle body of EFI is open, you still have the whole butterfly and shaft assembly in the flow path.
If someone were to buy a Fuel Injected ATV with the systems they currently outfit them with, and never plan to do any modiifications to the engine, they would be just fine. Although they would still have more weak points of potential failure liability -- CPUs that can burn out, fuel pumps that fail, electronic injectors that can stick, filters that clog, and TPI's that give the CPU bad readings. And all of those components are NOT cheap, and NOT cheap to troubleshoot either. BUT, given the fact that most people buy sport quads with the intent of making them faster, you would need to dyno a\fr re-map for EVERY single mod you do the engine, not to mention immediately needing to buy a PC3 CPU that is programmable in the first place, so it would be best to break the bank and buy everything you ever wanted to put into your engine mods and then custom dyno tune it all in on only one occasion.
So, even if the manufacturers offered better/self adjusting FI systems, they still have all the potential failure areas that were mentioned above. But the least the manufacturer's could do for sport off-road machines is offer the best of what's available in EFI from the beginning.
