Forum Chat #1 – Bamford Rose

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Welcome to BamfordRose. This is a segment that we’re going to call “forum chat”. We’re going to take clips of questions, pictures, comments, subjects, in the forum and just bring them to life. In a bit of a light-hearted way, sometimes we’re going to be talking about technical matters, and someone might make a comment about a particular aspect, that isn’t quite technically right. I don’t expect people in the wider world to be engineers and know the ins and outs. We don’t mean to cause anyone an offense. But we’re just going to pick some subjects and just have a bit of chat around them.

Okay, so this forum chat is copied from a Facebook group where V8 Vantage was put on the dyno, and in non-sport mode, it recorded 380 horsepower which it should have done. But when the magic sport button was pressed, it was 446 horsepower. So, with an electronic press of a button, there’s 60 odd horsepower sprung into life, that simply doesn’t work. The sport button on those cars changes where the engine peak revs might allow you to hit the red liner. If it’s a sport shift, it’s going to change the shift maps.

But whether it’s in non-sport or sport mode, when you give it a hundred percent pedal demand from your foot, that’s going to get you wide open throttle blade that the overall engine performance achieved is going to be no different. I’m not disputing that on one test this particular car might have had a horsepower figure, and then on a subsequent test to have a different horsepower figure.

Now you’re getting into the repeatability of dinos and just how accurate that testing is, and it’s very inaccurate unless all the reference ambient and temperature conditions are respected.

A 4.3 v8 is going to be 380 horsepower at the flywheel. On the dyno, that’s measuring wheel horsepower and there’s a transmission in the middle of the flywheel and wheel. You need to account for that loss. The flywheel power is the manufacturer declares performance at. The transmission loss on that six-speed graziano box is going to be something like 65 bhp at 7000 rpm. So, a wheel figure of about 320 is going to be correct for 4.3. If you add your 60 odd bhp loss on to that, we’ll figure that gets you up to a rough flywheel figure of 380. But then coming on to get 446, as it says in this piece, out of a 4.3 v8 at the flywheel unless it’s at a serious amount of engine tuning exhaust manifolds catalysts ecu remapped, it’s not going to get that and especially just by pressing a magic sport button.

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