Is multiport injection worth the extra cost??

[eschaider]

There is a (very) limited capability to accommodate altitude changes in some (but not all) speed density EFI systems. There is a reason the auto manufacturers worldwide use MAF based systems to meet emission targets — speed density systems can not and the fines for non-compliance are impressive.

We don't care about emissions non-compliance. For the most part our cars have been exempted. We do care about performance and drivability. That along with proper fueling under all conditions is the calling card of the MAF based systems. That doesn't mean the speed density systems can not, in controlled scenarios, perform similarly — they can.

The challenge is when you start to change ambient air conditions and / or engine components. A retune will be necessary to bring the engine back to where it was. Small changes are sort of like a carb. So what, when I return home it will work fine. Large changes are a different story.

If speed density systems were capable of that sort of performance, automobile manufacturers worldwide would embrace them in a New York minute! An auto manufacturer would sell their mother to save a few pennies on each vehicle. The difference in cost between the two different fueling models is significantly more than a few pennies — even at the OEM level.

With respect to racing, unless you are rules limited to using old fashioned mechanical fuel injection, the top classes today rely on MAF based systems for the same precision in fuel metering that the commercial auto manufacturers use it for in emissions compliance. The difference is not an emissions compliance issue, it is a fuel management issue, power production issue and engine responsiveness to driver inputs issue, among a slew of other considerations that causes F-1 cars to use it.

We are no different, unless we choose to be and that is all right — as long as it is a conscious election. The self learning or auto calibration logic in the various ECU's will get enough of the tuning job done to allow you to drive to a shop to get the car properly tuned. The self learning tuning result is not the same as a knowledgeable and skilled fuel system calibrator (tuner).

Tuning for max power is only a snippet of what a properly skilled tuner does for you at the dyno. The meat and potatoes will be all the drivability work, MBT calibration, fuel cut at higher manifold vacuums, tip in fuel enrichment and ignition timing management throughout the engine's operating range, at part throttle cruising, WOT max power and deceleration fuel cutting.

This stuff is absolutely doable by anyone wiling to take the time to learn — but learning it is a much steeper hill climb than you might at first anticipate it to be. In the end everyone's car is his own toy and the choices he makes do not need to be the same as someone else's.

Think for a minute about all the posts on CC asking how to do simple things, like which wire goes where, why does my engine stumble or perhaps why doesn't my car start when it is hot? This is kid's stuff compared to proper engine calibration with EFI. Do things that make your hobby easy and fun. Your 'simple' carb is already misbehaving and frustrating you. Why expand and complicate the problem?

Here is an interesting conundrum to ponder. How do you describe the color blue to someone who has been blind from birth? It is impossible! Without ever having the ability to see any color, the blind person has no known reference for comparison — and you have no ability to describe the color blue to him.

Watch how the auto manufacturers have evolved their fueling technology and strategies. Take advantage of their research and copy what they did — as luck would have it, it turns out to work pretty well!

We have enough hard things to do in the real world. These cars are supposed to provide escape and attitude adjustments for us after we have been abused all week long in real life.


Ed