A disparity of 34 wheel wheel horsepower before the tune? Vivid Racing then claims 407 wheel horsepower after adding their VR ECU tune. That means a difference of 62 wheel horsepower between what Active Autowerke is showing and Vivid Racing is showing on a Mustang dyno. So what is going on here?
Vivid Racing definitely has their dyno reading high. Why is this? Because it exaggerates the gains and the peak figures making them look more impressive to generate sales. BimmerBoost hates when people exaggerate the numbers for sales figures. Active Autowerke could do the same but they choose not to. Vivid should at least tell us they set it higher.
Now, there is no doubt that Vivid Engineering and their VR Tune program is getting nice gains out of the S65 V8 with a tune. It is 2014 now and people have been getting large gains out of the S65 V8 for 5 years now. They are trying to enter the market and it seems they are doing so by throwing out some huge dyno figures to get attention.
One should not expect 407 wheel horsepower, certainly not a Mustang dyno on 91 octane, from just a tune and exhaust. It is not a realistic representation of the horsepower. Even on a Dynojet this car would not be making over 400 wheel. Cracking 400 wheel on the S65 V8 naturally aspirated is possible but it will take some aggressive tuning and additional mods such as an underdrive pulley.
Just another lesson in all dynos not being equal and why you should put a premium on third party results (even though sometimes those are thinly veiled marketing as well):
Vivid Racing Graph:
Active Autowerke Graph: