Adaptronic Newsletter - September 2009

In This Issue

1. New Product Feature - MAP Prediction on the e420c for awesome throttle response!

2. EDN Innovation and Engineering Excellence Awards

3. Andy's Corner - Tuning!

4. Team Member Profile - Nick Ray

5. Drift Australia & Pulse Racing Track Day!

1. New Product Feature - MAP Prediction for the e420c!

Throttle response is one of those areas which has traditionally been hard to get right. It's been hard because it is the sort of condition that affects different engines very differently, depending on throttle size, plenum volume and engine capacity, as well as dynamic variables such as load and engine speed.

Most ECUs (including the e420c until recently) had options for additional enrichments based on the throttle opening, or a rate at which the throttle was opened, as well as options for additional fuel pulses out of the normal injection sequence. The enrichments often prove hard to get quite right, because a certain enrichment at one condition (such as opening the throttle to 10% off idle) doesn't give the correct amount at another condition (eg, full open throttle off idle).

The reason for this is actually fairly straightforward when you think about why an ECU actually should need throttle pump settings. It's because of two things:

Firstly, the MAP sensor doesn't respond immediately to a change in manifold pressure. It is possible to make the MAP sensor more responsive, but that can lead to unstable MAP readings, depending on plenum design and the pick-up point for the MAP sensor. So if you suddenly fully open the throttle off idle, the MAP sensor will still indicate 33 kPa absolute, where the plenum actually has a full atmosphere of air in it (100 kPa absolute). To provide enough enrichment to cover this problem, you would need 200% extra fuel! Clearly this is the wrong tool for the job. Instead of an enrichment, we should have a MAP signal the ECU can use which changes immediately the throttle is opened.

Secondly, unless the injection sequence is set up perfectly, there will be a lean spot as the injector pulse width changes within the ECU. This is because if the ECU delivers a pulse to the injector before the inlet valve opens, and the throttle is then opened before (or while) the inlet valve is open, the ECU can calculate the next fuel pulse as fast as it likes but it's already delivered the pulse for that stroke! So we need a way to give another injection squirt out of the normal injection sequence. Previously on the e420c (and other ECUs), this was done with a separate table of the milliseconds to deliver to the injector as a function of engine speed and/or load. Rather than doing that, we can now look at the change in the injection duration and give an extra squirt of the difference. For example, if the engine is idling with 2.2ms, and the throttle is suddenly opened, requiring 7ms of injection, the ECU can deliver an additional injection squirt of 4.8ms.

Setting this up is quite straightforward; all you need to do is tell the ECU the MAP value at different RPM/load combinations. This will be made adaptive (automatic) in future software/firmware versions.

Of course you can update your existing e420c with this new feature. Please visit our downloads page to download the latest software / firmware and start experimenting!

2. EDN Innovation and Engineering Excellence Awards!

The Engineering Excellence Awards are run by Engineers Australia, the professional body of engineers in Australia. Adaptronic were finalists in the Control Systems and Communications category, and received a highly commended award for the brand new e1280s Super ECU. You can see some pictures on the night on our Facebook page.

The EDN Innovation awards are put on by the Electronic Design News (EDN) magazine, and Adaptronic were finalists in the Best Application of Field Programmable Logic. The judges said that all three finalists were world class and it was extremely difficult for them to pick a winner.

3. Andy's Corner

Hi everyone! Thanks for reading this newsletter and what we have to say. This issue I have decided to talk about tuning. No doubt all of you experienced tuners out there will know this already, but many individuals out there don't, so this should serve as a good introduction.

What are we trying to do?

Firstly, we should make it clear that there are several objectives that people aim to meet when tuning an engine. These can be roughly categorised as follows:

1. Performance (torque / power)
2. Low emissions
3. Engine life / reliability
4. Fuel economy

What can we control?

By adjusting the ECU's parameters, the tuner can control the following variables:

1. Air-fuel ratio (fuel quantity)
2. Ignition timing
3. Valve timing / Intake controls

These all have an effect on the above objectives.

Air-Fuel Ratio

The air-fuel ratio is the most basic quantity that the tuner can control. The following table shows the basic effects on the above objectives, based on the actual air-fuel ratio:

You may be curious as to why factory ECUs on turbocharged vehicles run very rich under high boost conditions. It would appear the main reason for this is that it's the most conservative; richer mixtures mean lower combustion temperatures, which means greater tolerance to low quality fuel and less risk of engine damage. In terms of the effects on emissions, while this does mean very high HC and CO emissions, the standard emissions test doesn't test this high boost condition in the fuel map.

Therefore, it is often possible to increase engine performance, and reduce emissions, under high boost conditions, of  a factory tuned car, through better fuel tuning.

Ignition Timing

Ignition timing refers to the angle within the engine's rotation at which the spark plug is fired (on spark ignition engines such as petrol engines). This has to happen before the piston reaches the top of its travel (TDC, top dead centre), because the combustion takes a finite amount of time to complete. If ignition is fired too early or late, the peak pressure in the chamber will not be as high as it could be, which reduces the amount of torque that can be produced.

There are two potential problems with ignition timing being too advanced. The first, and best known, is knock. Knocking is also known as detonation, pinking and pinging, and caused by uncontrolled combustion in the cylinder. The explanation of how ignition timing being too advanced can cause knock is beyond the scope of this article, but knock is sensitive to:

1. Fuel quality (octane rating): higher octane fuel is less likely to knock
2. Ignition timing: more ignition advance (further before TDC) is more likely to knock
3. Combustion temperature: higher internal temperatures make knock more likely (this could be due to a hotter engine, i.e. engines are more likely to knock once warmed up than when cold, and in addition leaner mixtures (which lead to higher combustion temperatures) are also likely to exacerbate knock)

It makes sense that the best ignition timing tuning would be performed by finding the ignition timing that makes the most torque, and if that causes knocking, to retard the timing until the knock is eliminated.

Because the torque is maximised at a particular ignition timing, there is a range of ignition timing angles that give almost the same torque. The graph below shows the torque produced at constant RPM (2000), constant AFR (14.7) and variable ignition timing.

As you can see, the ignition timing can be varied by about 5 degrees from the peak at 25 degrees with only minimal changes to the torque. From seeing this graph though, it makes sense that retarding the timing by about 2 degrees from the optimum will hardly affect torque but could make a significant difference to knock sensitivity.

Another variable not shown on this graph is the generation of NOx as an exhaust emission. NOx is caused by high combustion temperatures, in the same way that knock is made more likely by high combustion temperatures. Therefore retarding the ignition timing from the optimum point also reduces NOx emissions.

Valve Timing / Intake Controls

The induction system of an engine is complicated. It is much more complex than a simple flow of air through a pipe because the flow varies as each cylinder (or rotor) undergoes its induction stroke. The pressure pulses that occur travel through the intake air at the speed of sound, which itself varies with respect to air pressure and other variables. Because the pressure pulses take finite time to travel, whereas the starting and stopping of flow occurs at a fixed engine angle, the effects of these dynamic intake effects vary with engine RPM.

For this reason, engine builders can select different camshaft profiles; for example a larger valve overlap may increase the torque at high RPM but reduce the torque at low RPM. The camshaft profile is a compromise, optimised based on how the engine will be used.

For some time, manufacturers have been including variable induction components, such as variable valve timing (VVT, VTEC, SVT etc) as well as additional intake runners allowing lengths to be selected at different RPM. The Mazda RX8 has four different intake control valves that open and shut under different engine conditions to optimise torque.

When tuning, the objective is to select the setting to obtain the best volumetric efficiency at any given engine speed, because the highest VE will give the greatest torque. This can be tested on a dyno by performing a power measurement with different settings and seeing what gives the greatest torque at each RPM. This should be done by optimising one variable at a time; for example on the H22A engine (Prelude VTiR), there is a VTEC solenoid and a separate variable intake control. We did the tuning on this by optimising the VTEC solenoid first, and the variable intake control afterwards. With continuously variable valve timing (eg i-VTEC, VVT-i and so on), you can either optimise the valve timing at each RPM point as you tune the map, or you can perform power runs at fixed valve timing angles and determine what timing is optimum at each RPM from the resulting graphs.

Conclusion

There are many variables to consider when tuning to optimise the engine performance. Manufacturers are often forced to compromise between low emissions, high torque, high fuel economy and low risk to engine components, leading to a less than optimal solution for any one of these parameters. For this reason, it's often possible to improve any one of these through tuning. For more information, contact us on our forum, or contact one of our dealers.

4. Team Member Profile - Nick Ray

How long have you been with Adaptronic?

Close to 18 months. Previously I worked as a Telecommunications Engineer!

How did you get involved in Adaptronic? What study did you do and what qualifications do you have?

Andy and I both completed a Bachelor of Mechatronic Engineering at the University of Sydney, which led us to become acquainted when I started back in 2001. When I left my job as a Telecommunications Engineer, Andy gave me a call!

What do you do (within the company)?

I do development, installations, support, and even some manufacturing! With regards to product development, I'm mainly focussed on hardware design and implementation rather than writing code. I enjoy the 'hands-on' and problem-solving aspects of the job.

What kind of car do you drive? What's your dream car (or cars)?

Outside work I'm more of a Dieselhead than a Petrolhead and drive a 1985 medium wheelbase, turbo Diesel Landcruiser. I've almost completed a full mechanical restoration, doing most of the work myself. I've fitted a range of aftermarket accessories and it's well on the way to being a reliable tourer and very capable off-road.

Aside from this I am a fan of the V8 Supercars, but I'd probably rather own a turbocharged 6. They go just as hard plus I love turbo engines!

What are your favourite hobbies?

Working on the 'Cruiser. What started out as just making repairs has become almost a full restoration. It also allows me to get out there and enjoy touring, camping, and four-wheel driving.

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5. Drift Australia & Pulse Racing Track Day!

As we all know, Oran Park is closing down. However, one of the most recent events at Oran Park was Drift Australia, where we sponsored the Boost Bitz S15 which qualified first and finished fifth in SuperDrift! Well done James and Chad!

In addition, Adaptronic will be attending the Pulse Racing Track Day at Oran Park on the 19th of October. Should be a blast - as well as the obvious track time there will be professional driving instructors to help out. For more information visit the Pulse Racing website.

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