EFI - Electronic Fuel Injection » Turbocharging

Superchargers | Fuel Injection Systems Melbourne | Dyno Tuning Melbourne

wolfems — Thu, 18 Nov 2010 10:35:27 +0000

Dyno Tuning Tips with Robbie McQueen http://www.wolfems.com Rob talks about the difference between centrifugal and positive displacement superchargers for engine management and fuel injection systems.

Dyno Tuning Melbourne – Superchargers

The difference between centrifugal and positive displacement blowers, is that basically a centrifugal is similar to a turbo charger. It doesn’t rely on exhaust to push it around, but it relies on the engine RPM to spin it up.

The more you spin it up, the more boost you get.

Generally you find a centrifugal supercharger mounted off the side of an engine. They’re generally made to be mounted on the side of engines, away from the top of the manifold. One of the advantages to a centrifugal blower (over a positive displacement blower), is that you can mount an intercooler fairly easily, so you can get more performance out of it.

The other advantage is that generally they are a lot quieter than a positive displacement blower. And, placement of them is fairly easy. You can place them above, below, in front, behind. So, there are many places they can go, so long as they line up with whatever is driving them.

Positive displacement superchargers generally have to go on top of the motor, or at least on top of the intake manifold. So, fitting an intercooler can still be done, but it is often more difficult than when fitting an intercooler to a centrifugal supercharger. There is a lot more engineering and pipework needed to fit up an intercooler to this type of supercharger.

The main positive for a positive displacement supercharger is that the minute you crack the throttle you have boost, where with a centrifugal one, often you have to build up the revs before you start seeing boost, and you often won’t see boost straight away.

There are two main types of positive displacement superchargers. There is the roots type, and the screw type. Generally you find the roots superchargers to be more noisy, and less efficient unless you put some type of intercooler on it.

The screw type, positive displacement, they are very good, but they are generally a long unit, so room has to be allocated for it.

If you see a boost curve when doing a chassis dyno tune, you will quickly see the difference between a centrifugal and a positive displacement supercharger.

For more information, you can contact Robbie McQueen at:

Advanced Engine Management / Wolf Motorsport
22 Melrich RoadBayswater, Melbourne
3153, Victoria, Australia
Ph: (03) 9761 3161

EFI Tuning and Overspeeding Turbos

wolfems — Wed, 09 Sep 2009 13:30:01 +0000

Hi There.

This is going to be a quick one today.

I’m not going to go into real detail here, but I want to give you a quick overview on one area of turbo charging.

Now, we know that turbos spin fast. Really fast. But there is a limit to the speed (RPM) that a turbo will work efficiently. And this RPM is different for every type and combination of turbo.

Needless to say, that when a turbo goes towards the upper end of its working RPM, it doesn’t keep pumping out more and more boost as you keep trying to increase the boost pressure.

This post is not about the specifics of that, but it is about being able to use your ECU to ensure you don’t work the turbo too hard above its efficiency curve.

Let’s say for example, you have a 4L 6 cylinder engine with a turbo on it and you keep increasing the boost pressure, and you keep making more boost and more power at 4,000 RPM, but at 5,500RPM the power is not increasing. This may mean that the turbo is no longer efficient at that engine and turbine RPM. This only has the effect of heating up the intake air more than it should, and possibly damaging the turbo.

What to do?

As the RPM increases past that maximum power point, start decreasing the turbo valve position until you just start to lose a little power in that RPM region. Now you are putting the turbo under less stress than it would have otherwise been. This is not necessarily the only piece of information you need when it comes to setting up your turbo boost curve, but as there are many variables, this will at least give you an insight into one aspect of tuning your boost control system.

PS: We may be able to put you in touch with a turbo expert/supplier. If you’d like to talk further, you can contact us as wolfemail@wolfems.com.au.

Change Your Turbo Boost Pressure At Different Road Speeds

wolfems — Tue, 08 Sep 2009 10:54:13 +0000

Now, I know a lot of people reading this don’t have a turbo-charged engine.

But that does not mean that they wont in the future. So even if you don’t currently run a turbo engine, you still may find this email of interest.

A lot of high powered turbo cars have too much power in the lower gears. This can actually make the car slower than if it had less power, as the driver needs to spend more time reducing engine power (with his right foot), than getting on with the job of driving.

Using Road Speed as a reference to map boost with allows you to optimize engine power at different speeds.

To do this, you will need an ECU with a wheel speed input, and the ECU will need the ability to map the boost valve position vs road speed or wheel speed.

Most EFI cars have an electronic speedo, so you can pick up on that for your wheel speed.

That is a pretty quick and easy way to get wheel speed into your ECU, but it does not address one thing. That the “driven wheels” may be spinning at 100 kph, but the vehicle is actually standing still.

So, to get the best (and most accurate) result, you would be best to have a wheel speed sensor on an “undriven” wheel.

That will show the real road speed, and allow you to maximize your vehicle’s acceleration so you can concentrate on winning the race, beating the time, or just having more fun.

As a side note, you can also map boost against throttle position to have the engine power delivered in a more linear manner as you open the throttle.

PS: If you have any specific questions about turbo boost over road speed, you can contact us at wolfemail@wolfems.com.au