How A Turbo System Works For Newbies - Beginers Read up, Compressor Surge etc.  

rprznt

the compressor flutter or surge is about the worst thing that you can do to a turbo, it can bend the shaft,
damaging the bearings, leading to metal to metal contact between housing and wheel, destroying the turbo.
ALWAYS run a BOV, on both maf and map systems, but not diesels or suck-through turbos, there's no need

rprznt

anti-lag: some rally drivers get on brakes and accelerator at some time to build boost, works because engine is under load, load + rpm = boost
another way is that in some *special* DOHC turbo engines, ecu can retard the exhaust cam timing, or manually holding the exhaust valves open, building boost.

thats_hott_11

yea good 4 u guys there is still stuff i dont get ARGH
i read it and it makes sense but the next day ill come bac and i will have forgotten most of it

DED-SXC

that was incredibly informative, i had a basic idea but that told me everything i needed 2 know in-depth

raven_lunatic

so the fact that i've got a BOV and i still get the "flutter" sound which seems to come from the air filter would mean???
I'm guessing the BOV is either siezed or not connected properly

LANCER_PEPS

So if you run a turbo less than 6psi there is no point for a bov?

TwinCam16

No that is not the case.

The bov is there to protect the bearings in the turbo.

If your bov doesnt work at low boost then you have a too hard spring in it.

vl_turbo_man

I'm only running 6psi without a BOV and I'm still getting the flutter at 2500-3000rpm. I don't even need to take the revs high. (And yes I know I should have a BOV on but I lost it when I got my new piping and no workshops are open to put my new one on yet)

GTRwilson

where abouts can a BOV be placed? for example, does it HAVE to go be4 the turbo or HAVE to go after turbo and does it make any difference? hope that makes sence

vl_turbo_man

It has to go after the turbo or there would be no build up of air pressure, but it makes no difference going before or after the intercooler.

TwinCam16

Actually you are wrong.

The bov is best placed as close to the turbo as practical.

Its job is to take the pressure away from the inlet wheel, hence saving the bearings.

Aiko

Sort of like saying the sky is not red. True, but doesn't quite give the full picture.

The BOV also keeps up the rpm of the turbo (while changing gear) so you'll have less lag as you accelerate after sliding in the next gear.

From this, if you take a while to change gears, (ie. typical street driving) then BOV closer to the turbo is a good thing, however all the air in the plumbing and intercooler must reverse direction to head back to the BOV and change direction again when you accelerate, each time you accelerate the air it is using up HP.
If you change gears quickly (but not flat shifting where you don't take your foot off the throttle to change gear) then you don't want this direction changing.
If the BOV is closer to the throttle body, this direction change of the air doesn't have to happen and you conserve the momentum of the air, however the turbo is now working against the pressure drop of the intercooler before it gets to the BOV, which will slow down the compressor a little more, but now you don't have to reaccelerate the air in the plumbing/intercooler when you stamp on the throttle again.

Then, just to make things ugly, you can't have it right at the throttle plate either, as doing this can miss the intial pressure wave sent back from the throttle plate as it closes both delaying the BOV opening and sending an unwanted pressure wave to the turbo. Bareing in mind at this point this is all to find that 0.1% gain and the fluidic modelling to find the ideal point is just goind to send most people

GTRwilson

it was actually ure pic that got me confused TwinCam16. thanks for the info anyway guys. https://www.boostcruising.com/forums/index....showtopic=45275

(3rd pic)

TwinCam16

Ahhh ok.

the valve was there to hide it.

It should have gone on the other side of the cooler, but since that was before i could weld, i had to get someone else to make the pipework up for me, hence, not being where it was meant to be.

Faircall!

(mr2)

is ther any reason why you couldent have 2?
one close to the turbo and one close to the trottla body?
or would that not have a big enough effect to worry about doing it?

TwinCam16

The effort and expense wouldnt be worth it.

philsTH

Thats a great explination, if anyone wants to build on this here is a sites with a great explination of turbo workings.
turbos explained

A turbo is type supercharger, but it is always called a turbo.

sussba

wtf u need a waistgate anyway unless u hava elec bov that control boost

Benny R,

thnks heaps mate learnt alot from that

BkD

Completely understand now, had an alright idea before hand.
Thanks man.

Now to find out exactly how a Supercharger works.

demonik699

great work mate i lernt heaps of stuff from this that i didnt know thanks!

Alpin3

Very well put

Hater

Nice work -

ridin

well done man that was a great help and really easy to understand .....thanks heaps

1ggte

if i set up a plum back system would i have to go before the air flow meter and does this mean i have to tune the comp or does the air flow meter send the signal for mor fuel ? why i ask is my twin turbo supra is runing a bov veting to atmosphere and im trying to get roady

Turbo_Mirage

I was wondering if any one could give me a list of pros and cons between turbos and superchargers??

YoungGun

Very easy to understand, concepts are easy to grasp!

A quick Q, is there such thing as a Twin BOV? Im a newbie to this sorta thing but I wasnt sure if there was or not. If there is such thing, imma give it a go n say it will go with a Twin Turbo?

Cheers

walker2008au

Awesome read, however your not 100% correct. Below is according to GCG Turbo's:

You may be getting a little confused with compressor surge and air reversion. Compressor surge is usually experienced under load in a high gear (say 1500rpm in 4th gear), whereas a compressor wheel/turbine wheel combination may be too large or a mismatch to the engine, so air will be pushed back the opposite way through the turbocharger. This is under LIGHT ACCELERATION, and will usually make the car feel like it has a boost cut/fuel cut, with violent hesitation and what can be described as a "choofing" sound.

What you are experiencing (not running a BOV or the valve not fully opening) is Air Reversion, which is the excess air travelling back thorugh the intercooler piping, and through the turbocharger making a flutter sound, when you BACK OFF the throttle. Although it is highy recommeded to run a BOV, there has been no extensive testing or conclusion to turbocharger wear due to not running a blow off valve. Again, I will stress that a BOV does what it is supposed to do, which is to prevent air reversion, and also keeping air in the intake piping to allow for quicker spooling during gear changes.

jnrb89

na. try www.howstuffworks.com and read how a turbo works, sounds like your still a bit confused.

Rid_S13

Thanks heaps mate

NOS440

an easy read done in layman terms for the simple.

autech gtr 4 door

so is (bov flutter/compressor surge/air reversion) at low boost ok or bad for turbos? because i just got new bovs for my gtr and can make them flutter or not at low boost by adjusting the springs. but i noticed my standard bypassvalve's use to flutter at around 3-4 psi anyway. so this cant be that bad eh?.... I just dont like that loud woosh noise when your just cruising love that rattlesnake flutter tho at low revs..

holidayalpine

very helpful thanks