here is a real life example from years back (as best as I can remember the numbers) - 3s-gte (2l 16v turbo) later design engine on pump gas:
1) standard output 240hp/320 or so nm at 0.8bar;
2) replace ecu - map it, 280hp/380ish nm at the same 0.8bar;
3) 1.2bar 320ish hp/450nm;
4) stock turbo and pistons are replaced with something better 1.8 bar 480hp/610nm;
if you will plot those numbers with regard to air pressure - they will tell you only half of the story, what you didn't see here (and I purposly didn't add rpm to hp and nm) is that although from 1. to 2. there is no difference in pressure and not a huge difference it max power and torque numbers, in reality the total amount of power output went up by like 30%, how? because those 320nm in the first example were at lets say 4500rpm, then after the remap (2.) that torque of not much more - 380nm starts to become available 1k rpm earlier - from 3500, but because of the limitations imposed by the poorly performing stock turbocharger - the max power output hasn't changed much, but performance wise - the change was like day and night
I could go on and explain that the change in the performance from 2) to 3) wasn't nearly as significant as was from 1) to 2), although the numbers on the paper are similar, the thing is - you cannot dumb down these things to "rule of thumb" type of calculations that include 4th grade math and expect any useful result, it simply doesn't work like that
Last edited by jz11 on 21 Jul 2015, 20:27, edited 1 time in total.
here is a real life example from years back (as best as I can remember the numbers) - 3s-gte (2l 16v turbo) later design engine on pump gas:
1) standard output 240hp/320 or so nm at 0.8bar;
2) replace ecu - map it, 280hp/380ish nm at the same 0.8bar;
3) 1.2bar 320ish hp/450nm;
4) stock turbo and pistons are replaced with something better 1.8 bar 480hp/610nm;
if you will plot those numbers with regard to air pressure - they will tell you only half of the story, what you didn't see here (and I purposly didn't add rpm to hp and nm) is that although from 1. to 2. there is no difference in pressure and not a huge difference it max power and torque numbers, in reality the total amount of power output went up by like 30%, how? because those 320nm in the first example were at lets say 4500rpm, then after the remap (2.) that torque of not much more - 380nm starts to become available 1k rpm earlier - from 350, but because of the limitations imposed by the poorly performing stock turbocharger - the max power output hasn't changed much, but performance wise - the change was like day and night
"I could go on and explain that the change in the performance from 2) to 3) wasn't nearly as significant as was from 1) to 2), although the numbers on the paper are similar, the thing is - you cannot dumb down these things to "rule of thumb" type of calculations that include 4th grade math and expect any useful result, it simply doesn't work like that"
PlatinumZealot wrote:
This is a real world rule of thumb. For newer engines it is even higher.
that's not possible.... If you don't double the mass airflow you can't double the HP
I didn't even touch on mass flow yet. The question was about boost pressure and I have taken my liberties within that criteria. Notice there are a whole bunch of things you can do to optimize a turbo system to keep the same boost pressure and make more power. The proper selected turbine, compressor, exhaust headers, down-pipe, inter-cooler etc There is so much you can do.
Read a few car magazines and see. This is nothing new, really.
jz11 wrote:I could go on and explain that the change in the performance from 2) to 3) wasn't nearly as significant as was from 1) to 2), although the numbers on the paper are similar, the thing is - you cannot dumb down these things to "rule of thumb" type of calculations that include 4th grade math and expect any useful result, it simply doesn't work like that
No kidding...But let's not get too carried away
Besides it will place you within + or - 10% of actual power. Also engine mapping isn't related to turbocharging.... apples and oranges really
Assuming rpm and displaced volume are the same, the increase in engine power is mostly a function of how much additional oxygen (or mass airflow) the turbocharging system delivers to the cylinders. Making more power essentially requires burning more fuel. And burning more fuel requires proportionally more oxygen.
"Q: How do you make a small fortune in racing?
A: Start with a large one!"
