The Best Engine Tune

How to you define what the best engine tune is?

Firstly, lets understand that this article is written about EFI (Electronic Fuel Injection) and Engine Management. And more accurately, it's about programmable or performance fuel injection. This is not so relevant to factory fuel injection, where the word "tuneup" may mean to check the sparkplugs and airfilter.

This article is about programmable fuel injection and engine management systems that allow the engine to be tuned for both maximum power, but also great drivability and fuel economy.

There are some obvious things like, how much power does the engine make, how much torque does the engine make. They are the easy ones. But often, there are less important than many people realize.

We are involved in tuning cars almost every day. And although engine power and torque are obviously important, there is one thing that almost all customers want from their engine and vehicle.

Drivability.

That's it.

While power and torque are very important, in the end most people are most impressed when a car drives well.

For most customers there is nothing more disappointing, or frustrating than a car that doesn't start well, doesn't idle and doesn't drive well for the 90% of the time that the car is driven. Since, for around 90% of the time, many cars are driven in traffic, or at least driven below 90% throttle.

That is why, when we are doing a tune on a car, we generally ask to have the car for 5 days.

On the first day, the car arrives and the engine bay is checked over to ensure there is nothing that looks like a potential hazard later on, both in terms of incorrectly fitted hoses, lines, throttles, etc. But also in terms of safety. Since, if anything falls off an engine while it is running flat out on the dyno, there is always the potential for disaster.

We also make sure the person doing the tuning has a good understanding of what the customer wants to achieve in this tuning session. If the car is a daily driver, fuel economy may be of high importance. But if the car is a 1/4 mile stomer, then there are other factors to consider. This is discussed at some length with the owner of the car before the engine is tuned.

Once the pre-dyno checks are completed on day 1, day 2 is dyno day. Depending on the original state of tune, what modifications have been done to the vehicle, and how highly modified the engine is, the amount of time required on the dyno can vary greatly from 1-2 hours, up to several hours. Your dyno operator will probably be able to give you some indication of the number of hours your tune should take, so long as everything on your engine is working together properly.

If, for example, you have modified your turbo, but not increased the amount of fuel your fuel system can deliver. In this case there may be a point at which the fuel delivery is maxed out, and no matter what the tuner does, he/she can not get any more fuel delivered into the engine.

At this point, the tuner should stop the dyno tune, and report the situation to you, with one or two suggestions on the course of action required to get past this problem. The solution may be larger injectors, or an adjustable fuel pressure regulator. Experience will allow the tuner make the most appropriate suggestions.

Day 3, is cold start day. Once the engine is tuned for maximum power and torque, it is time to start tuning the starting fuel and transient fuelling. We want to start the engine cold and see how it reacts to throttle movement. This can be a tricky time, as the fuel and ignition maps work in conjunction with the temperature compensations, and the acceleration enrichment adjustable values.

Day 4, cold start and hot start day. Once again, cold starts in the morning followed by warm and hot starts, as well as some cold and hot driving. EFI systems should be checked for correct tune at all operating conditions.

Since everyone drives differently, it is a good idea (if possible) for someone beside the tuner to take the car for a drive with the tuner in the passenger seat. Everyone drives differently to everyone else, so try to have the car driven by at least 1 person other than the tuner before delivering it to the customer.

If the tuner is happy with the car at this point, he usually calls the customer to let the customer know that his car should be ready to be picked up the following afternoon.

Day 5, is final cold start day. One more cold start and immediate cold driving to make sure everything is optimized for the first couple of minutes of driving.

If all is OK, the customer gets the final phone call and can come and pick up their car.

Just a couple of notes:

1: You would have seen that there is a ratio of 3:1 for the amount of time the tuner spends making maximum power, verses making the car drive great under all operating conditions. I know this sounds like a lot of time, but as a customer, we want you to go away raving about how well your car drives as well as how much power it produced on the dyno.

2: If the car is tuned in summer, and even though all care is taken to ensure the engine will start and run smoothly when the customer goes to start the car in the middle of winter, it sometimes does not work out perfectly. Your tuner should remember to tell you this when you pick up your car, but if he doesn't, you will remember that during the colder months of the year, you should feel like you can drop your car in for a cold start or two during the colder months.

3: An engine management system may do so much more than just run your enigne. It may turn on your intercooler water spray above a certain road speed, but only if the intake air temperature has reached a certain level. If can also control your electronically controlled automatic transmission, changing shift points and shift hardness.

So, although there is a lot of specific detail I've left out of this article, that about covers it for a basic overview of what is considered to be a fairly comprehensive tuning session.

In the end it may turn out that the best tune is a comprehensive tune.

www.wolfems.com

Steven Taylor has been involved in the performance aftermarket and engine tuning industry. www.wolfems.com