Hello to those new to Electronic Fuel Injection (EFI), as well as those who have been around it for a long time and have their own wealth of knowledge.

Here you will find snippets of information gathered over years of techinical diagnostics on EFI systems, both OEM and aftermarket. This page is written by the technical support team at Wolf Engine Management, the company that designed and manufactures the Wolf V500 engine management system.

The information that follows will cover general aspects of EFI, but will have some specific information on the Wolf brand of ECU.

While most people are familiar with tuning the fuel side of an engine management system, the ignition side can be a different matter.

Engine power is achieved not only with the correct air:fuel ratio, but also with the most appropriate ignition timing. Less timing generally results in less power. As you increase the ignition timing, the power generally increases ..... until..... you reach the point of engine knock.

Engine Knock occurs when the ignition timing is too far advanced for the current combination of fueling and air:fuel ratio (there are many other factors, but for now, lets keep it fairly simple).

If we start at a tuning point with the engine not knocking, lets say, 3,000RPM at full load with the air:fuel ratio (AFR) at 13.0:1. We start to increase the ignition timing, the power increases until we get to the point near the knock limit. At this stage, we put in a little more timing, but the power does not increase any more. If we continue to increase the ignition timing, the engine will start knocking. A little at first. But if we contunue further with the ignition timing, the engine begin to knock more and more. This will eventually lead to engine damage.

To move the engine away from the knock limit we can either retard the ignition timing from the knock limit, or increase the amount of fuel going to the engine from the initial 13.0:1 to say, 12.7:1. At this AFR we may get away with more ignition timing than we could at 13.0:1.

The problem is - How do you know if the engine is knocking?

On some engines you can hear engine knock with your ears without the aid of any headset or other equipment. The only problem with that is that enigne damage is already occuring at that point. You need to hear the engine knock before it is audible to the naked ear.

A device like the Knock Box is the best way to detect engine knock before it gets to the point of engine damage. You will be able to hear the engine knocking as soon as the slightest amount of knock occurs. You can then retard the ignition timing to eliminate the knock.

I just came back from checking a customers Throttle Position Sensor. He was complaining that the TPS value was fluttering just off-idle.

The problem was that I was put off the scent by an earlier problem the engine had. The TPS was originally mounted on a bracket that would vibrate under different engine conditions, and cause the TPS value to flutter a little as the TPS housing would move, ever so slightly, around the throttle shaft. This had apparently been fixed, but the same (or at least a similar) symptom was still occuring.

So, I went down to the customers workshop, and started looking at the vehicle. The new TPS bracket was extremely strong. There was no way this was going to move, so I thought the problem may be in the TPS itself.

So I could get a handle on what was happening, we started the engine. As small amounts of throttle were applied, the TPS value would jump up and down all over the place. From a value of 2 or 3 it would flash up to 80, then down again, then back up to 45 then down again. This would happen extremely quickly.

Before removing the TPS from the engine (I was going to see if the erractic TPS readings were due to engine vibration), I thought I'd have a quick look through the TPS setup. On a Wolf V500, you can either have TPS Closed and TPS Open voltages that set the endpoints for the TPS values, or you can use a table where you can plot the TPS values verses TPS voltage. The advantage of the Min/Max system is that it is very quick to setup. The advantage of the table is that you can setup a non-linear "curve" so you can have more tuneability just off idle, or wherever you need it most.

The problem was suddenly right in front of me. The table had 3 large spikes around just off-idle. The spikes went up to 45, 80 and 40. So as you slowly opened the throttle, the TPS value would read 1, 2, 3, 45, 5, 6, 7, 80, 9, 10, 11, 40, 13, 14.....

This made the engine impossible to tune just as you started to open the throttle.

Once these values had been rectified in the Throttle Position Calibration Table the throttle response returned and tuning the engine began to make sense.

I guess the thing to remember here is that the more programmable an EFI Fuel Injection Engine Management ECU is, the more you need to check and make sure that the things you can adjust, are adjusted correctly. Otherwise you can lead yourself on a bit of a goose-chase.

Until next time...

Having good quality clean Fuel Injectors is a must. The cost of using injectors from an unknown source with an unknown history can cause lost time and increased expense when it comes to getting your engine running or tuned.

If you have your injectors cleaned, use them straight away. If you are not going to use them in the near future, wait until a week before you are going to fit them and get them cleaned then. Injectors have been known to stick even weeks or months after being cleaned.

If you are interested in the flow rate of your injectors you can check out this Injector Flow Rate Table. There are a huge number of injectors here, with ratings in cc/min, lbs/hour and HP.

To get the best tune from your EFI Fuel Injected engine, you need the correct injector flow rates. If you don't, you will not be able to get the combination of the best idle quality, the lowest fuel consumption and the most power possible.

Sometimes when people are first trying to start an engine after a rebuild or when they have just installed an aftermarket EFI Fuel Injection ECU, is they do not check the ignition timing to make sure it is where it should be.

They usually do this because sometimes there is no easy to read ignition timing mark on the engine, which makes it quite difficult to check the timing. There problem here is, that if the ignition timing is a long way out, the engine will never start. They may continue to crank, and crank the engine, flattening batteries, and possibly damaging the startermotor.