Boost In 4th Gear

[Stel]

Hey Guys,

Me and my mates have a little bit of trouble understanding this.

If you are in 4th Gear doing about 50km....your revs are at about 2k right?

Why is it, that when you plant your foot on the accelerator...boost comes on straight away....

I mean the car doesnt move..but there is a boost reading of 7 psi with a stock R33.

Just wanting to know the EXACT reason why this happens....

Thanks

Stel

[Sydneykid]

There is more load (resistance) on an engine in 4th gear than in the lower gears. The more load an engine has, the more exhaust it produces. The more exhaust it produces, the faster it spins the turbine. The faster the turbine spins, the more airflow the compressor produces. The more airflow the compressor produces the higher the boost potential

Remember that boost is simply a measure of resistance to airflow, not a measure of the airflow itself.

cheers

[Links]

in an R33 full boost comes on by about 2,500/3,000rpm..

this is to do with the volume of air and the load that is going through the engine.. the higher the volume the quicker it will spool the engine up..

for a turbo to get going the engine has to have a fair bit of load on it so that the air will spin the turbo up to a high enough RPM to create boost which isn't till about 20,000rpm..

this is why in 1st gear you won't tend to make much boost as the volume + load isn't for a long enough duration to really spool it up till higher in the rev range..

by putting a higher load on the engine the car will dump more air + more fuel to get it going.. this air is what spins the turbo as it comes out - higher flow of air will spool it up quicker..

hope that helps.. probably not the best description..

[Links]

well sydney kid said it in about half the amount of words of me and probably about 10 times better.. so read his response

[Stel]

Geez,

That was quick....

Thanks for the response guys....

Thats was what we thought it was...just wanted to make sure....

Thanks

Stel