Boost in Neutral??

[MaXiMuS007]

Just a technical question guys,

Why is it that you get no boost when you rev the car in neutral or with the clutch in? :headspin:

[GTRman1992]

There is no load on the engine. Therefore not much air flow.

[JimX]

What do you want boost in neutral for anyway?

[Jay95R33]

No load = not enough exhaust gas flow to spin the turbo fast enough to generate boost.

Boost at idle (neutral) is great for hard launches, ie. launch control :headspin:

[JimX]

I can get plenty sideways without boost and fat 255 tyres Of course boost picking up soon after launch helps it stay sideways, but I've never needed it off the mark.

[GunMetalR33]

Having about 5 psi for launchs is a real advantage when draging. But I must admit that I am also running 275 rubber...

[MaXiMuS007]

I had heard it was load related but I don't understand what that means... don't a certain amount of revs mean a certain amount of air is flowing in and out of the engine (hence spooling up the turbo), loaded up or not?

I was asking b/c I was talking to a mate about why auto's are better than manuals and he said that the stall converter in an auto allows boost from launch (true)

[JimX]

Air doesn't match revs. The more load on the engine the more air is in the cylinders because it takes more pressure to move the piston.

[GunMetalR33]

I think this is how it works:

The computer will dump in more full under different load point on the fuel map. Therefore when you are in neutral there is no load on the engine so not as much fuel therefore not as much exaust to spool up the turbo...

Launch control on the other hand retards the ignition so the fuel gathers and explodes in the exaust manifold with creates the flow to spool up the turbo...

Correct me if iam wrong...

[Kinks]

Retarded ignition means that the combustion has less chance of doing useful work, so it will either burn at the bottom part of the compression stroke or once the exhaust valve opens. I've heard that retarded timing can burn your valves, but probably only on older engines.. But yes, retarded timing means a given fuel/air mixture is doing less useful work on the engine and therefore you can use more air/fuel to run at the same point (which is fine if you are in neutral and want your turbo spinning, but useless if you want to accelerate).

[cameron]

we get boost in neutral,

just stick the gear in neutral and leave clutch out ?

cause the bov is freakin loud!!!

[Gizmo73]

Sorry to half-hijack, but somewhat related...

If this is the case, does the boost level come on later when you are in high revs in 5th gear if its related to manifold pressure ??

[Gson]

JIMX

"I can get plenty sideways without boost and fat 255 tyres Of course boost picking up soon after launch helps it stay sideways, but I've never needed it off the mark."

well as soon as the clutch is droped there is Load...... Thus boost!

thats if the clutched is droped when the rpms are at a good level!

[JimX]

But while it's in neutral, no boost. What do I want to do with boost, get from 0-5000rpm quicker before releasing the clutch?

[Cecam]

Well if you give it a quick rev you will generate boost as the engines temporary loaded accelerating its own rotating mass, but thats very short, so thats why you hear the bov when you give it a quick stab... which can make you launch abit harder if you time it right... autos have boost because of the resistance/load from the torque converter...

I know of a few conversions where a rb20det turbo and manifold has been fitted to a rb25de (changed ecu and injectors obviously) and that made boost at idle.... looks weird when you go to take it for a test drive and the gauge is sitting at 5psi while its just idling away...

[MaXiMuS007]

Thanks guys for the answers

[Guest RedLineGTR]

thanks for the info too

[Gson]

But while it's in neutral, no boost. What do I want to do with boost, get from 0-5000rpm quicker before releasing the clutch?

you just said that you can get plenty sideways without boost!!

just commenting that most likley it is With boost!

cheers:)

[JimX]

you just said that you can get plenty sideways without boost!!

just commenting that most likley it is With boost!

 

cheers:)

Oh Well, the initial wheel spin happens without boost, and I daresay it wouldn't really need boost to continue (although boost makes it easier). So although I am getting boost by a certain stage, I doubt it's absolutely required.

Any NA SKyline owners want to confirm or deny that?