how do you control the amount of boost?

[LSOfreak]

Without using a manual boost controller, and say i wanted 4-6psi with a t25/gt17/k03 turbo, how would i set that amount of boost? Is it down to the mapping to set how much boost? sorry im a bit of a newb when it comes to turbos, thanks

[LeeM]

I still don't know the full workings of turbos, but it's to do with the actuator. Once the boost reaches a point, the actuator opens a flap and reduces the pressure inside the turbo

[blackie_2k5]

yeah, manual or electronic boost controller, or adjustbable actuator...... or a set actuator, can usually get diff springs for most set actuators to get the boost pressure you need

[AXracing]

Normally turbo setups use a wastegate to let the exhaust bypass the turbo when it is producing the required boost.

http://forums.audiworld.com/picture.php?albumid=12010&pictureid=40215
The wastegate is operated by a pressure actuator that works off the boost pressure.

http://www.autosportracetech.com/RX-7/TurboActuator.jpg

[LSOfreak]

cheers axracing that helps. so to answer the question, without electronically adjusting the boost, you set it with the actuator. So will i have to buy another 'low boost' actuator if i wanted to run low boost?

[axsaxoman]

I think you will have confused them more with the lower picture of an actuator,which is not correct anway
you cannot control boost with vacum as you have no vacum -- the diagram is wrong .both of those connections are fed with boost pressure --one way it will increase spring tension --the other it will reduce it

you would need a 4 way pwm device to control that ,

for the newbies - look at top picture and connect the actuator ,where the arrow points ,with pipe where it says charge pressure. that is how std turbo,s are connected
when that pressure equals/overcomes the strength of the spring in the actuator then waste gate opens and keeps boost at that level.
you can raise the pressure simply by allowing an air leak in this connecting pipe (bleed valve)
but you cannot reduce the level that way
simples

.you cannot get the turbo to work at a pressure lower than the actuator presssure on a simple one hose connection actuator .

you need to look at lower picture--the pipe marked vacum is labelled wrong
this type of actuator allows you to apply preesure to either side to either raise the static spring pressure value or lower it by means of a pmw valve .depending which side you apply the boost to
you cannot get the turbo to work at lower pressure than the spring rating on a simple actuator -that only allows you to apply pressure to one side of the diaphram.
so minimum boost pressure when turbo is spooled up is the spring pressure exerted by the actuator

the other option you can try is just ot loosen off the connecting rod between actuator +turbo on some types this will reduce boost pressure ,by allowing the wastegate to push open slightly before the spring pressure takes over

[blackie_2k5]

you options in order of chepest-expensive

by a manual boost controller, this goes on the vac/boost pipe inbetween the actuator and the wastegate, set it to what you want and it will do the job £20<
^^^^^ worth noting as john pointed out you cant go below he stock pressure of the std actuator

diff actuator springs but i dont know if youll find a correct one for 5-6psi £40<

by and adjustable actuator and set to what you want £100<

3 is most expensive and essentially does the same thing as the first option but theres no standard, just set parameters between x and y :y:

[LSOfreak]

ok thanks. So by doing option one, how would you know what to set it to to get what psi?

[blackie_2k5]

ususally youll get instructions with the controller which will tell your for exampple each 1/4 turn will be equal to say 1psi(just an example), start it from screwed shut and work up to what you want,this should get you somewhere near, then you fine tune it by your boost gauge

but as mentioned, if using option one itll will depend on what the std actuator is set to in the first place, you cant go lower then this...... why 5-6psi btw? could easily run alot more then that on std internals so long as the mapping is good

[axsaxoman]

ok thanks. So by doing option one, how would you know what to set it to to get what psi?
I wonder why i bother sometimes

[LSOfreak]

axsaxoman dont get me wrong, you've explained it well, im sorry if i seem ungrateful for you writing a fair wack to help explain it. i was just still a bit unsure of how you know what psi its running at without it being electrical/having a guage

[LSOfreak]

ive also run out of 'thanks' :S

[J222JRA]

Isnt the amount of boost displayed normally on a guage??

[LSOfreak]

ususally youll get instructions with the controller which will tell your for exampple each 1/4 turn will be equal to say 1psi(just an example), start it from screwed shut and work up to what you want,this should get you somewhere near, then you fine tune it by your boost gauge

but as mentioned, if using option one itll will depend on what the std actuator is set to in the first place, you cant go lower then this...... why 5-6psi btw? could easily run alot more then that on std internals so long as the mapping is good

cheers mate, i just thought that would be a safe figure to run with standard internals/gearbox. what psi would you suggest (on a vtr if that makes a difference?)

[blackie_2k5]

plenty ppl have run 1 bar and its lasted a long time with good mapping and intercooling, also depends on how you drive the car, i personally wouldnt want to go more then 10psi, but john and axracing should b able to ive good input on this, as they have wintessed alot built first hand.......

[Gary-VTR]

Fuck running 1bar on a Saxo engine with stock internals tbf. ^

[blackie_2k5]

Fuck running 1bar on a Saxo engine with stock internals tbf. ^

it can and has been done many times, pretty sure thats what danny is going to run on his when its sorted??

[LeeM]

i want one of these, run 7psi on one setting and 20 on the other haha

[atspeedracing]

electronically controlled all the way... i dont have to burn my fingers to adjust your damn actuators then! in fact, i can do it sat in the comfort of the car, whilst drinking tea :)

http://atspeedracing.co.uk/products/index.php?main_page=index&cPath=20

oh, and also added benifit of on the fly adjustable selectable boost memories with independant gain and duty control. as well as features like overboost protection, spike stop, open/closed loop boost control etc. even RPM selectable on some controllers.

- colin.

[AXracing]

The second photo is correct but I agree is is quite confusing John. The vacuum is in relation to the boost. In most situations the vacuum is actually normal air pressure. So most people would not even call it a vacuum. The first picture is also correct. It is just a different style of actuator. The top one will push open and the bottom one pulls open.

[blackie_2k5]

when my cars is up and running it will be with a manual boost controller, but the first thing on the list after a diff is a gizzmo elec controller..... guessing thats what colin has linked too?

[LeeM]

i guess boost is set when the cars mapped? if you turn it up after the map is put on does it mess up the map or what? boost still confuses me slightly

[LSOfreak]

confuses the hell out of me too. reading the comment on your thread saying to almost double any price figure in your head is real put off :(

[LeeM]

haha, fuck it it'll be worth it in the end. think i might just start collecting bits untill ive got everything then fit it all next year

[blackie_2k5]

yes lee, boost is set to its highest when mapping is done, can be turned down and back up after mapping and the ecu will adjust the fuel to suit, it cannot be turned up above what it was initially mapped to or it will under fuel and your engine components will turn to liquids :y:

[axsaxoman]

yes lee, boost is set to its highest when mapping is done, can be turned down and back up after mapping and the ecu will adjust the fuel to suit, it cannot be turned up above what it was initially mapped to or it will under fuel and your engine components will turn to liquids :y:
only if it has been mapped with boost correction --which is only possible on some types of after market ecu --certainly not possible on std ecu .
the man asking the questions knows nothing of turbo,s --so please don,t give him false hope about getting a safe conversion without spending on correct control systems.
fi you asked me could you run 1bar of boost on std internals i would say no

[blackie_2k5]

only if it has been mapped with boost correction --which is only possible on some types of after market ecu --certainly not possible on std ecu .
the man asking the questions knows nothing of turbo,s --so please don,t give him false hope about getting a safe conversion without spending on correct control systems.
fi you asked me could you run 1bar of boost on std internals i would say no

haha :p yeah, i never meant a stock ecu.... maybe should have made that a bit clearer.... i was going to but decided against using anything less then a standalone management system, im not trying to give anyone false hope lol, IMO if your gonna run boost you should stick with the pressure your aiming for, although many do like dropping the boost on daily driver's etc.. jst depends how you use the car really

surely youve seen/set up many cars running up to and around 1bar on stock internals?, after all there is plenty about, even a few on this site.... or is that a personal preferance you wouldnt run 1 bar on stock internals?

[atspeedracing]

generally the tuner will tell you your maximum safe mapped boost level.

most forced induction cars are mapped with manifold pressure vs rpm. so the load columns/rows correspond to boost pressure (or vacuum) so raising the boost simply puts you into the next load row/column.

you can use boost corrections fuel % e.g @ 1bar is + 100%, 2 bar + 200% fuel etc. so yes the fueling is there (if injectors etc support it) this is very handy with supercharged cars. as you can have the fuel mapped as TPS main load with background pressure corrections, and ignition map on MAP.

turbo cars however i still prefer to have fuel and igntion both with MAP as main load,

generally a mapper will safeguard the engine against user fiddling, if the user decides to run the engine to boost that exceed the components or where the car was mapped to, by either boost cuts, or removing ignition / adding fuel at unsafe boost sites. bit like you would with a rev limiter. its important to remember, generally the tuner knows more than you do, so you should trust with what they believe is a safe level.

(MAP = manifold absolute pressure)
(TPS = throttle position sensor)

- colin.

[axsaxoman]

surely youve seen/set up many cars running up to and around 1bar on stock internals?, after all there is plenty about, even a few on this site.... or is that a personal preferance you wouldnt run 1 bar on stock internals?
Ive seen everything you can imagine and also alot of bullshit about how much boost people are running ,and dodgy boost gauges or taking boost reading from the wrong place .
1Bar + stock internals will not last --so as a professional i would never tell anybody that is safe on a tu engine .that was never meant for boost to start

[blackie_2k5]

ai there is alot of bull shitters about.... and its defo safe to say it would never last lol, out of curiosity from someone with experience...... even though you probs wouldnt reccomend it, what would you say was the most sensible boost to run on stock internals provided the car has good intercooling and will have good mapping, will not be totally abused and the owner is in full knowledge the engine could give up at any time... but would still prefer it to last over 1 year.....

i know its a how long is a piece of string question.... but given all is "good" and the engine to begin with isnt in bad shape... what would you say?

[AXracing]

All depend how reliable you would want it to be. There are plenty of people who have run 1 bar with just lowering compression and some have done a fair few miles. But so many factors are involved. Unsurprisingly a nice low mile engines with plenty of cooling, good servicing, quality oil, well mapped, always warmed up, cooled down and driven with sympathy will last much longer then a botch job driven by loon on a old abused engine.

Edit: The more efficient your intercooler the harder a given amount of boost will be on the engine. The air expands when it is heated so for a given boost the warmer the charge the less weight of air the engine is actually taking in.

[axsaxoman]

Yes you could fit loads of head gaskets ro get the comp right down ,but then its going to eat half the boost you are putting in to lift the comp back up ,so its far more sensible to run less boost --have it so its not totally dead off boost .
back to you --what bhp are you wanting ,as all these issues are a function of power developed + is it going to be a stand alone ecu --not just add on injectors with no ign adjustability and relying on std kncok sensor to retard the thing .


fitment of a w/b to check fuelling under all load conditions is the best money a DIY man will spend ,then you can see exactly whats happening as the boost comes on ,or if you lift it a bit over what it was originally set at
inivate w/b+ gauge £165+vat

[LSOfreak]

whats a w/b :oops:

[luthor1]

I map turbo's with TPS as the main load, I 'multiply' the MAP value (kPA) into the equation, and I use an AFR correction table.

This means that 110kpa the multiply map bit will give you 10% more fuel, but if the 100kpa AFR table say's 13.1, and the 110kpa AFR section says 12.9 then the fuelling is altered.

It allows change of AFR while keeping the multiply map correction as a straight line.

It's a little tricky to explain/conceptualise, I hope you see what I mean!

Andy

[AXracing]

whats a w/b :oops:

He is talking about wide band oxygen sensor and display to analyse exhaust gasses.

[blackie_2k5]

i was just curious tbh, will be watching a few threads on here to see what they can push to, im already forged so i can go high boost :D i was going to do low boost but tbh with all the money it costs to do it at least half right you may aswell go all out ad so i have