The term 'Sports' exhaust is about as misused as the term 'of course I won't forget ' It sometimes seems as though every bolt on bit of metal to a car somehow improves the performance regardless of whether any testing has been taken. Now obvioulsy we (TMS) are biased, we're the UK distributor for Milltek, we designed and developed the VXR Astra exhaust with Milltek and we were responsible for all the testing and development so we 'know' that it improves performance, as does Vauxhall with whom we shared all the data. However, sometimes in the tuning World vested interests get in the way of accurate data collection and some people (some of whom should know better frankly) have been commenting that the VXR Sports exhaust does not add any performance to the Astra VXR (to have the balls to call Vauxhall a liar is actually pretty impressive but there you go ) Well, everyone is entitled to their opinion but we figured the easiest thing to do was actually conduct some open testing to prove it does what we already know.
The process was simple. We took 4 completely standard cars on the same day and dyno ran each one to get a standard power figure. We then fit full VXR sports exhausts onto all 4 then ran them on the same dyno, same time to see how they performed. Three of the cars provided almost identical power figures as standard (189bhp at the wheels) and the 4th a much higher figure of 198bhp at the wheels, so we excluded that car from the reuslts. In other words we took the 'worst' performing cars as a measure not cherry pick the best one we had, these cars all vary off the production line so we know to take a measurement we can replicate.
The results are pretty clear:
Power at the wheels
Looking at the chart the VXR exhaust adds both power and torque throughout the rev range but importantly significantly adds higher power for longer at the top end. The standard car power drops off significantly from 5600rpm whereas the VXR exhaust allows the car to continue to run higher power right to the red line. This is typical of motorsport cat equipped sports exhaust systems - the extra breathing the system allows the car to run full power for longer, the standard system 'strangles' this output. The VXR sports system uses larger diameter pipework, deletes the standard cars precat and replaces it with a straight through pipe and importantly replaces the standard cars 400cell cat with a 200cell motorsport cat. The important word here is 'motorsport', as not all catalytic converters are made equal, whilst the simple measure is the number of cells they have (determines the density of the internals) a full motorsport cat has a different make up in terms of the quality of coatings used inside, the overall design and internal flow rate. Comparing 200cell to 200cell is only part of the story.
The VXR Sports exhaust uses an HJS Motorsport cat, basically if its not a branded cat then its not a motorsport specification.
The chart for power at the flywheel (calculated, so not as reliable a measurement) shows the same story:
Power at the flywheel
We're not in the least surprised at all this, we know from previous testing that the system on its own gives a measurable increase in performance and we know anectdotally from owners they ALL feel the increase in performance but sometimes people need to be shown this performance in tangible testing before they are convinced - which is great, as we specialise in delivering real World gains and not pub talk. Its also especially important when some people with a vested interest seek to criticise a product without even testing it (mad, but it happens) so testing like this does have the effect of shutting them up
To re-iterate, we took 4 separate cars, all owned by customers (not our own development cars) and very clearly showed them what we were doing (they were already convinced on the product, they were already there of course ) and showed them the results as they happened. All the owners paid for their tuning (all were there for stage 2 ECU remaps as well) and all left very impressed. I've no doubt if some/any of them wish to post their thoughts (good or bad) then they will but we have influence over that decision. This was proper testing to show that proper performance gains can be achieved with proper upgrades - don't trust your money to anything else.
