The Benefits of a Good Exhaust System – Astra VXR

On more than one occasion we have extolled the virtues of a good, free flowing 76mm sports exhaust system for Astra VXR to get the best performance results out of remapping correctly.

Well here is another classic example……..

The car in question is an Astra VXR 2.0 Turbo which was fitted with a Stage 1.5 Hybrid K04 turbo (with exhaust wheel cut back), a large full height front mounted intercooler and a ‘one-off’ made to the car exhaust system which in places reduced to 50-57mm.

Once mapped the results were as follows:

Astra VXR Stage 3 : Poor Exhaust System : Before

Astra VXR Stage 3 : Poor Exhaust System : Before

Results: 278 bhp and 318 lb ft torque.

Upon examining all the evidence from the rolling road and datalogging, we concluded that the exhaust system was the limiting factor. Some might say it was easy for us to blame the exhaust (which we didn’t supply)….. why could it not be the installed software??

Well, we could comfortably rule out software based on the fact that all our maps are optimised on the rolling road and datalogged. so we knew we couldn’t get any more ignition timing into the software or take any more fuel out (without risking safety).

So we had the car back a couple of months later and fitted our full 76mm sports exhaust system, changed nothing else and ran the car back on the same rolling road, resulting in the following:

Astra VXR Stage 3 : 76mm Exhaust System : After

Astra VXR Stage 3 : 76mm Exhaust System : After

Yes, no word of a lie results of 305bhp and 348 lb ft torque, aided by the Stage 1.5 hybrid turbo, the full 76mm system and the cold February dyno cell temperatures.

Here is the before and after graph. The gains speak for themselves. Lots more power and torque right across the rev range:

Astra VXR Stage 3 - Good Exhaust vs Poor Exhaust : Before and After Results

Astra VXR Stage 3 – Good Exhaust vs Poor Exhaust : Before and After Results

So if you are trying to decide on which exhaust system to fit to your Astra VXR, we think we’ve just made the decision much easier for you. A good exhaust system may cost a little more, but you will get the benefits from fitting it.

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