07-02-2012, 03:18 PM
You're looking at ONE component of the torque/power curve...
Darren's engine was exactly the same, just turn down the power a bit to 200 or so, the peak torque would have come at around 4200 and peak power at around 4800rpm... But that's because of the big turbo...
You have to look at the whole graph to get the entire picture...
You could make your PD what you'd call "petrolly" if you wanted... I.e. no torque low down, rising to a big peak in horsepower but giving a low torque figure... All you'd need to do is make the torque limiters pull back all fuel low down, so your torque curve would just go up and up and up until the peak, it'd be a shit engine because you'd have to rev the TITS off it to make it go anywhere, which is kinda pointless, when a Diesel can produce the full 250lb.ft torque from just off idle... That's like saying I want a petrol engine like a Diesel, so I'm going to make the cams so that it can get NO air in up high, but loads of torque down low...
It's just that you're thinking when you see a high torque figure, you assume that's an un revvy, no HP up high... But of course, that's because you had a SPIKE down low... You need to look at the entire graph... Get my drift?
It's all to do with the fact that when torque dies off it feels like it's going slower, even though the HP figure might still be rising, or even staying constant... It's just that Diesels FEEL as if they die, even though often they're increasing in HP.
Darren's engine was exactly the same, just turn down the power a bit to 200 or so, the peak torque would have come at around 4200 and peak power at around 4800rpm... But that's because of the big turbo...
You have to look at the whole graph to get the entire picture...
You could make your PD what you'd call "petrolly" if you wanted... I.e. no torque low down, rising to a big peak in horsepower but giving a low torque figure... All you'd need to do is make the torque limiters pull back all fuel low down, so your torque curve would just go up and up and up until the peak, it'd be a shit engine because you'd have to rev the TITS off it to make it go anywhere, which is kinda pointless, when a Diesel can produce the full 250lb.ft torque from just off idle... That's like saying I want a petrol engine like a Diesel, so I'm going to make the cams so that it can get NO air in up high, but loads of torque down low...
It's just that you're thinking when you see a high torque figure, you assume that's an un revvy, no HP up high... But of course, that's because you had a SPIKE down low... You need to look at the entire graph... Get my drift?
It's all to do with the fact that when torque dies off it feels like it's going slower, even though the HP figure might still be rising, or even staying constant... It's just that Diesels FEEL as if they die, even though often they're increasing in HP.
