Following on from the big reveal in evo issue 180 that Stealthzilla is now running 717hp, courtesy of a brace of Litchfield “Stage 4.5” turbos and matching Milltek downpipes, the question arises: How usable is that level of power and is it too much?

Of course the weather has been generally pretty atrocious since the conversion to LM700 spec was done (Litchfield reserve LMxxx nomenclature for cars that have the appropriate brake and suspension mods to match the level of power), but I have taken the GT-R out for the occasional run when the roads haven’t been overly coated in salt.

Iain has been cautious in tuning his Stage 4.5 cars to keep torque and boost lower in the lower reaches of the rev range in order to preserve the standard con rods. My car is running about the same torque as it was before, 620lb.ft, but it is produced further up the rev range and sustained higher too.

Now I’ve had a chance to get acclimatised to it, there is less of an instant kick in the back, but there is a wonderfully linear increase as the tacho winds round to the redline. On the standard turbos, the engine has done its best work by 6500rpm, now there is more to come right up to 7200.

Despite the more linear power delivery, traction is –rather predictably- a bit more of an issue than before, particularly on cold, damp tarmac. When the current set of Michelin Pilot Super Sports wear out, I am going to investigate slightly wider options for the rear pair.

However, “traction issues” is a relative term in a GT-R. Even flashing TC lights (in Race mode) do not mean the car is not accelerating, and accelerating hard. Accompanied by the slightly deranged howl from the Milltek downpipes feeding the Akrapovic titanium system, Stealthzilla simply catapults itself down any given straight piece of road. The linear torque delivery means it is easier to mete out that acceleration on corners too.

So the answer is, 700+ hp is eminently usable and is in no way too much. In fact, it would be nice to have more low down grunt, which means changing the rods. Which means I might as well change the pistons… uh oh.

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