tristan your explinations are spot on every time

and people are debating different things, tristan is saying you cant really brake boost from a standstill in a manual (automatics can, my brother has done it), and everyone is saying you can, but they are saying while moving anyways.

so technically i think almost everyone is right; the amount of realism in using the technique in the example situation is questionable, but in theory would work.


off topic: today my friend on demo asked me what the numbers in the dash were...i said gears and he wondered what i was talking about. this world is going to sad places

There is one more thing that I don't understand about this turbo thingy generating less psi under no or little load.
The way I understand it, the engine produces exhaust which in turn drives the windmill on the "exhaust part" of the turbocharger, and the windmill of the "exhaust part" is connected to the windmill located in the "intake part" of the turbochargers and turns it as more exhaust fumes are moving through the exhaust headers, and "intake part" sucks in more air with the help of its windmill.
But then, why would it be more difficult to spin the windmills if there is no load on the wheels? Is the car using up less fuel and thus generating less exhaust if there is no load? Or what's the trick that I'm missing here?
I'm sorry for so many questions that might seem obvious to you, but I'm really confused about this whole turbo part. I know my way around the car to the length that I can change my own oil/brake pads/disks/etc, but this turbo thingy is just Chinese to me.

Okay, maybe load is the wrong term. Think of throttle opening. The greater the throttle opening the more gas flow through the engine, and the greater the exhaust heat. Turbos are driven more by the heat energy in the exhaust that the rate of flow (although that does come into it slightly).

At a standstill, in neutral, it doesn't take much throttle before the engine redlines. With a heavy flywheel you could open the throttle 100% and within a second or two be bouncing off the rev limiter. To hold, say, 5000rpm for a launch only requires say 10% throttle - and not much boost is generated at 10% throttle.

If you have a small enough turbo, and time it right so that you're at full throttle, with the revs climbing and the boost building, then you can be at high boost (if not max) as the lights go out for a quick start. You don't need to hold the car on the brakes for this!

But if your timing is out you'll either be too late (in which case your revs will be low and the boost will be low) or too early (in which case the engine bounces off the rev limiter, the boost drops and you have a boost-less start).

A bigger flywheel (so the engine revs slower) might help. A racing car, with the lightest flywheel that can be used, will rev very quickly, so there is little chance of building boost at a standstill without slipping the clutch against the brakes (effectively to slow down the engine revving up at full throttle, allowing boost to build).

Of course, some ECUs will have been mapped so that full throttle at very low speeds (standstill) will retard the ignition and lean the fuelling so that more heat is generated in the exhaust, which will also reduce power causing the engine to rev up slower.

In short, the best way is to use the right size of turbo, time your launches, and accept that high-boost as the lights go out isn't very likely, but will occur a second or so later. I don't think any car modified after manufacture has used a correctly sized turbo - everyone bolts on the biggest one they can find thinking it'll be better.

DUHAST, sadly if you ask for help on this forum, people will look for a reason to flame you. Anyway, I always understood 'brake boosting' as reducing the required pressure needed on the brake pedal by using a vaccume source from the engine on one side of the diaphram.

But it would seem from the posts, your asking about the turbo? and about it being ready for your exit of the corner? If you want to keep the turbo spinning up.... left foot braking!

Anyway, to the point, this is JUST a simulation and is far from the real thing, keep that in mind when considering your expectations!