boost: 101

[kingcorolla]

hey guys. just got a couple of turbo q's, but 1st i got a story. If u wanna jump to the questions, skip 1st 2 paragraphs

Being 17, me and most of my mates are still hangin around the oldskool toyota "phase", and ive hardly expeirience the pleasure of boosting, much
my whole outlook on engine modification changed recently when i got the chance to ride in a JZA-80 2jz supra... with 20,000 invested in the engine.
cant really list half mods, but i noticed a 2 stage boost controller, headers, front mount etc. this thing was crazzy. pushin 22-24psi. Just THRILLING man! any way, got me thinkin bout turbo setups, im illiterate with the way it all functions, just a couple of q's..

(these are sorta my turbo n00b questions )

1)- wastegates, they bypass exhaust gas, passed the turbine wheel, but it seems the bigger they get, the bore effective they are, how? And what are the benefits of having and external over and internal?

2)- Boost contoller, i under stand these are made to somehow bypass boost charge.. and make the turbo work harder...?... and some how "control boost"? (:roll: no shitt), and "boost taps" work the same too?

3)- define the term "free boosting"? the term to me sounds, as if theres a front mount, post t/b and is still boosting off-throttle..? Yes?/No?

anyway, cheers in advance guys.

Mike

[ELOK]

i can answer the 3rd one seeing as that was a problem i had when i first got my car.

freeboosting in my words is basicly your boost isnt controlled, so you can floor it and ur boost will keep going up and up untill it cant go no higher and blow up kinda thing,
my car has a cut at 16psi so when i was free boosting it would boost up to 15 and then once it hit 16 the car would jump hardout. freeboosting is not good! feels kool tho when u boost more than ur supposed to.

hope that helps im not good on how all the shit works aye

[kingcorolla]

ok, so free boosting is all of your compressed charge from compresser turbine, is ALL going to the throttle body, with out being controlled via wastegate/contoller..?

..its sorts coming together now..

[slonlo]

http://auto.howstuffworks.com/turbo.htm

have a read covers most of what your after

[Lloyd]

1) A wastewage is basically a bypass valve so that you dont have too much boost going to the throttle body. There is an actualor which is having compressed air from the intake side if your engine being stuffed into it. At a certain pressure it will start to open and therefore let exhaust gases go past the turbine on the turbo and straight into the exhaust. This way your turbo cant really spin any faster because its only getting a limited amount of exhaust gases spinning the turbine. And thats your way of controlling boost.

2) Boost controller is a little bleed valve that goes in the hose from the compressor side of your turbo to your wastegate actuator. In the actuator as above you'll have a point where the actuator starts to open (lets say 10psi). If you put a bleed valve in then some of that pressure is allowed to escape so when you are actually getting 10psi in your intake the wastegate is only seeing this as 7psi (or whatever) so you'll need to make 14psi in the inntake before the wastegate sees it at 10 and starts to open. And there is your extra boost.

3) Free boosting is basically when you have no wastegate/actuator. Or weld the wastegate shut. You will have uncontrolled boost and as your revs go up you'll be making whatever boost your turbo is capable of which (as I'm sure you can work out) is not really a good thing.

[CozmoNz]

1) A wastewage is basically a bypass valve so that you dont have too much boost going to the throttle body. There is an actualor which is having compressed air from the intake side if your engine being stuffed into it. At a certain pressure it will start to open and therefore let exhaust gases go past the turbine on the turbo and straight into the exhaust. This way your turbo cant really spin any faster because its only getting a limited amount of exhaust gases spinning the turbine. And thats your way of controlling boost.

2) Boost controller is a little bleed valve that goes in the hose from the compressor side of your turbo to your wastegate actuator. In the actuator as above you'll have a point where the actuator starts to open (lets say 10psi). If you put a bleed valve in then some of that pressure is allowed to escape so when you are actually getting 10psi in your intake the wastegate is only seeing this as 7psi (or whatever) so you'll need to make 14psi in the inntake before the wastegate sees it at 10 and starts to open. And there is your extra boost.

3) Free boosting is basically when you have no wastegate/actuator. Or weld the wastegate shut. You will have uncontrolled boost and as your revs go up you'll be making whatever boost your turbo is capable of which (as I'm sure you can work out) is not really a good thing.

damn u!, bet me to it .

um, adding a boost tap can help quite a bit, even if set on *normel* boost.

instead of the wastegate opening slowly (which can cause overboost on oldercars (180sx!)), installing a tap can instead, cause, sudden snap of wastegate open. so instead of... 7..8..9...10...9...10...9 psi. it would be 8..9...9..9..9 etc. cant hurt anyway.

freebosting is fun... just remove the vacume hose from the wastegate and plug up the compressor side hose outlet (dont wanna lose all that boost!). this happened to my old leone

[ELOK]

hell yea freeboosting is fun! but as said above its not good for the engine/turbo and very distracting having to watch the boost guage all the time to make sure u dont overboost, i almost hit a few cars doing that

[kingcorolla]

yea, cheerz for the info guys. anothher question,

do you have to have a wastegate for a boost contoller to function effectivly? i meen, if no wastgate, the theres no point in bypassing it passed nothink?

[rage]

without a wastegate you can not control boost.

the wastegate is a physical port with a flap which allows exhaust gas to be directed straight into the exhaust.

[Al]

um, adding a boost tap can help quite a bit, even if set on *normel* boost.

A boost tap will still let the wastegate open before the preset level is reached resulting the similar to stock spool. Boost taps or bleed valves are nasty nasty wastes of money.

A proper ball/spring manual boost controller or electronic boost controller will keep the wastegate shut until the desired pressure is reached.