Had to explain the finer points of carby turbos to the owner.

 

Can anybody see why he has no boost!? :y: Engine is an A12.

 

Had to explain the finer points of carby turbos to the owner.

 

Can anybody see why he has no boost!? :y: Engine is an A12.

 

Thats a ZD30 VNT turbo Si, if there's no vacuum to the actuator can then all exhaust will go to waste.

 

Thats my guess by the picture.

 

Matt

It should work, he's used zip ties...

Yeah 3 litre patrol turbo......1.2 litre engine! :y:

 

Theres actually a vacumm line from the manifold to the gate, its post butterfly.

 

Do those actuators work in reverse or something Matt? Ie vacumm pulls gate shut? If so then how does boost control work!? :P

Yeah 3 litre patrol turbo......1.2 litre engine! :y:

 

Theres actually a vacumm line from the manifold to the gate, its post butterfly.

 

Do those actuators work in reverse or something Matt? Ie vacumm pulls gate shut? If so then how does boost control work!? :P

 

To create boost it needs the actuator lifted upwards when its on the right way up, so it would need the actuator to be pulled towards the engine.

 

They work by redirecting the exhaust gases onto the turbine wheel,depending on how the vanes are positioned to how much gas actually drives the turbine wheel,hence how much boost they make.

 

They need a vacuum source ALL the time to control the actuator,so even if it has vacuum at idle once it trys to make boost it will relax the actuator making no boost.

 

Tell him to try holding the actuator SAY half way open and try it.

 

Matt

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Edited May 24, 200818 yr by Sbox

Ok I'm sorta with it now, but theres still one think I can't quite understand.

 

Trying to think of a way of explaining this...

 

Vacuum at manifold = Gate closing (or wheel exposed) = Makes boost

 

No boost or vac at manifold = gate opened (or wheel covered) = boost control (sorta)

 

But,

 

Boost at manifold = more of the above effect creating a loss of boost! :y:

 

OR, do these diesel waste gates also do something (in the other direction) when they have boost on them?

 

Do you get what I'm asking? Casue I've half confused myself!! :P

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Edited May 24, 200818 yr by Sbox

Yeah I know how a normal waste gate works man. I'm sick I trying to explain it to my mates! :y:

 

But I think these deisel turbo work different, read Matt's post above^

Every turbo I have seen has the wastegate controlled by the boost. Boost from the impeller (or somewhere close by on the manifold) side travels via the tubing to the actuator and it in turn opens the waste gate. More boost pushes it open more, maintaining a slightly variable but set amount of boost in the manifold. Otherwise it would keep adding boost until the engine went biga badda boom.

 

Diesel's work on a different basis as petrol engines for example they make no vacuum thats why they have auxillary air pumps for brake boosters and so on.

Ok I'm sorta with it now, but theres still one think I can't quite understand.

 

Trying to think of a way of explaining this...

 

Vacuum at manifold = Gate closing (or wheel exposed) = Makes boost

 

No boost or vac at manifold = gate opened (or wheel covered) = boost control (sorta)

 

But,

 

Boost at manifold = more of the above effect creating a loss of boost! :y:

 

OR, do these diesel waste gates also do something (in the other direction) when they have boost on them?

 

Do you get what I'm asking? Casue I've half confused myself!! :P

 

Ok there is NO!!! wastegate.

 

How it works is by directing the gases onto the turbine wheel at different angle hence causing greater or lesser turbine wheel speed inturn making more boost right!.

 

So what the vacuum does is moves the actuator up or down depending on how much boost the computer tells it to make depending on load /rpm/etc,etc.The vacuum signal is NOT dependant or directly variable by any engine condition it is only a means to move an actuator.

 

So even if it has vacuum at idle there is not enough engine speed or load(fuel) to make boost,And by the time the engine has made enough rpm/fuel load to make boost there is no vacuum in this engine to hold the actuator at an angle that will result in turbine drive.

 

BTW, if you are using a diesel turbo on a petrol, normally double the engine size is acceptable due to the extra RPM that petrols do and airflow requirements.

 

MAtt

:P Got it, cheers.

 

So if you do use a deisel turbo on a petrol car, whats an easy way to control boost? :y:

:P Got it, cheers.

 

So if you do use a deisel turbo on a petrol car, whats an easy way to control boost? :y:

 

 

Its not the diesel turbo thats the problem Si,its that some of these new turbo diesels use a VNT to get them into boost earlier.

 

Otherwise they normally just use a wastegate like anything else mate.

 

MAtt

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Edited May 24, 200818 yr by Sbox

yeah I've seen deisel generators like that before sbox with no gate, sounds cool when you load them up hard you can hear them spool! :y: I'm an audio visual tech, no it not hard to pull a coupla thousand watts in an instant! :dance:

 

So how's this for an idea...If you replaced that solinoid with a normal petrol waste gate, and set it up so that when the gate was static it has the rod pulled back towards the engine. Then when you put boost on the waste gate it will cover the exhaust wheel controlling boost.

 

D'reckon it'd work? :P

 

I know it'd just be a hell of a lot easier to just change the turbo, but I'm just trying to think of a way to work with what he's already got. :)