A turbo question, does boost only occur at WOT?

[BigKriss]

Does an engine only produce boost at wide open throttle or does it occur at part open throttle also? Corky Bell (Maximum Boost), p9 thinks the former. (http://img382.imageshack.us/img382/4835/corky0ij.jpg)
I was thinking the latter but I'm unsure.

[wingman]

Excuse my ignorance but I thought it happened at a certain rev range not throttle position.

[e34nication]

Don't have to be WOT to produce boost... unless maybe you have an insanely enormous turbo. Case in point... listen to any SRT-4 owner when they're backing out of a parking space... tiny turbo=that car is boosting under light throttle at about 2krpm's. Boost will be created if there is enough exhaust being created by the engine (with enough force) going through the turbo to spool it up...

I'm no F/I expert by any means but that is my take on it... F/I guys can tear me apart and correct me please.

[winfred]

that about covers it


Don't have to be WOT to produce boost... unless maybe you have an insanely enormous turbo. Case in point... listen to any SRT-4 owner when they're backing out of a parking space... tiny turbo=that car is boosting under light throttle at about 2krpm's. Boost will be created if there is enough exhaust being created by the engine (with enough force) going through the turbo to spool it up...

I'm no F/I expert by any means but that is my take on it... F/I guys can tear me apart and correct me please.

[Bill R.]

throttle is open far enough and the rpm's are high enough to spin the turbo up to the point at which it will produce useable boost. Part throttle openings as he stated won't allow enough exhaust gas pressure and volume to spin the turbo up enough to produce useable boost. You gotta remember the engine is just a big air pump and if the throttle plate isn't open enough you can't pull enough air through.




Does an engine only produce boost at wide open throttle or does it occur at part open throttle also? Corky Bell (Maximum Boost), p9 thinks the former. (http://img382.imageshack.us/img382/4835/corky0ij.jpg)
I was thinking the latter but I'm unsure.

[kyleN20]

boost, will occur whenever your exhaust can push the turbo to suck air in, and force it into your intake. so the amount of rpm it takes to make boost is entirely dependant on the size of the turbo, and the size of the engine

big engine, small turbo, boost will occur at low rmp, NOT WOT

small engine, big turbo, you might get closer to WOT to get boost.

[Booster]

Very true.......although there is a baseline of different displacement in which the cars "IDLE" draw of cfm's is X and then there is the number of Y which begins the pressure increase above X.
All turbos must spin in order to not be a full restriction during start up and idle of course.....but a boost signal or climb is recognised at the gauge/meter long before its felt and the electronics and fuel do their part.
Pardon any redundant statements here.......:D
Vinny

[Guapo]

All depends on the size and efficiency of the turbo, the size of the motor, he efficiency of the intake tract, the exhaust, and gearing.

On my Z with stock T-25 turbos, I can be cruising along on the highway in 5th gear, and if I breathe on the throttle, I'm in boost.

[kyleN20]

sounds nice

[BobHarris]

Don't have to be WOT to produce boost... unless maybe you have an insanely enormous turbo. Case in point... listen to any SRT-4 owner when they're backing out of a parking space... tiny turbo=that car is boosting under light throttle at about 2krpm's. Boost will be created if there is enough exhaust being created by the engine (with enough force) going through the turbo to spool it up...

I'm no F/I expert by any means but that is my take on it... F/I guys can tear me apart and correct me please.


This is why the new 530 Diesel has two turbos. A little one and a big one.

All the best

Bob

[pyro]

throttle plate HAS to be open. you could be decelerating down a hill at 6000 rpm w/ throttle plate closed and the turbo probly won't be spooling at all

[Paul in NZ]

the throttle must be open,,not nec,full throttle.The Subaru Legacy(liberty?)turbo has twin turbos,one small one big.

[beetos]

very small throttle opening can make boost, any condition that loads the engine within the range that the turbo can make boost will do it. For example, my turbo will start to spool at about 3000rpm so any reasonable throttle opening at or above that engine speed will spool it. In higher gears the effect is more pronounced as the engine is loaded for longer at a particular rpm and the turbo has time to spool. Its not so much throttle opening as much as being above the spool rpm and creating some load on the motor.

Some turbo motors will make a lot of boost at small throttle openings and will have the boost controller mapped to throttle position to give some lineararity to boost response. Most stock management units do this by not allowing high boost until high throttle openings ,and you will hear people really praise simple mods like bypassing the stock boost control (cycling valve) for a mechanical check valve type controller that lets the boost pile on irrespective of throttle openings.

I love turbos.......:-)