turbos.....

[CJ_Derv]

Dave what does efficient mean?

[Ruan]

Boost does equal flow... It's efficiency that affects things...

When you're spinning a baby little t2 to make 30psi with 28lb/min, you might have a chance of moving that air, but then you consider that the shaft speed would be something like 350,000 you've maybe got 30% efficiency... It's predicted compressor outlet temperature is probably close to 300*c... So in actuality because the air is so thin on the output, you'd only receive quarter of that due to the heat... Then after intercooling you might regain a little, if you're lucky up to a half...

You need to understand the relationship between boost, flow and shaft speed... The higher the shaft speed, the higher the heat, the more work the turbo does, the less efficient... However drop the shaft speed too low, you'll run into surge... Push the other way, you're into choke... It's all a fine balance... But it all boils down to efficiency. If you're in the turbos peak efficiency island, you don't have to do much intercooling, its an easy life, and gt2052s and 2056s are slap in the middle at about !60-180hp

[declantg]

get da biggest 1 yo

[Dave]

Boost does equal flow... It's efficiency that affects things...

When you're spinning a baby little t2 to make 30psi with 28lb/min, you might have a chance of moving that air, but then you consider that the shaft speed would be something like 350,000 you've maybe got 30% efficiency... It's predicted compressor outlet temperature is probably close to 300*c... So in actuality because the air is so thin on the output, you'd only receive quarter of that due to the heat... Then after intercooling you might regain a little, if you're lucky up to a half...

You need to understand the relationship between boost, flow and shaft speed... The higher the shaft speed, the higher the heat, the more work the turbo does, the less efficient... However drop the shaft speed too low, you'll run into surge... Push the other way, you're into choke... It's all a fine balance... But it all boils down to efficiency. If you're in the turbos peak efficiency island, you don't have to do much intercooling, its an easy life, and gt2052s and 2056s are slap in the middle at about !60-180hp

<

get da biggest 1 yo

Well said...

[Ryan@306]

so what does a VNT do differently to a normal turbo?

[Chris]

Its very naughty





Na seriously though wiki it.

[CJ_Derv]

VNT is the answer to all your problems hooking it up and getting it to work as well as Ruan has is another story lol

[Ryan@306]

yeah doesn't seem a case of a bolt on application tbh

edited** when is anything a bolt on applicaion lol

[Ruan]

Imagine a hosepipe, if you stick your finger over the end, you get a lot of backpressure, but the speed at which the water exits the nozzle is very high - resulting in it goes miles, release your finger and the backpressure drops but the flow increases... This is often known as the turbos aspect ratio - A/R... Being variable, it gives all the advantages of a large turbo, with none of the drawbacks of a large unit...

That's essentially how a VNT works, the Variable Nozzles sit infront of the exhaust gas flow and accelerate the gasses into the turbine wheel, obviously this increases backpressure - not good, however at low rpms it doesn't matter, as soon as the turbo spins up to speed and the inlet manifold pressure increases, the vanes open up, dropping the backpressure, but allowing a greater flow in the process... Controlling this is a nightmare as on the motorway, the backpressure is too high, a normal boost controller isn't intelligent enough to open them a little bit whilst cruising, but be closed when you stomp on it and it doesn't allow for the fact that at low rpms it doesnt stop the turbo producing too much backpressure and therefore too much boost, causing surge...

[Ryan@306]

ok quick question do dturbos have a throttle plate?

and how do you get around the back pressure on the motorway then?

[puglove]

and how do you get around the back pressure on the motorway then?

Dont drive it on the motorway, simples

[Ryan@306]

so basically if your driving a a constant steady speed (say 60-70) and a boost controller won't open because it isn't clever enough to open then surely the backpressure is going to push the heat back and engine will overheat and or overload the cooling system?
because if that's the case even driving long distance at steady speeds would provoke problems with the vnt?

[Kwik]

The trick is working out a way to control mechanically what a vnt ecu does and it's not that easy. The waste gate will act normal but then you would need an actuator to control the vanes. Chevy did a mechanical vnt but details are scarce online

[Ryan@306]

yeah the gt20v which is what is on ruan's dt , i will have a look but not sure if i would want the hassle of a vnt to be honest if they're a nightmare to set up and to get running well

[Ruan]

so basically if your driving a a constant steady speed (say 60-70) and a boost controller won't open because it isn't clever enough to open then surely the backpressure is going to push the heat back and engine will overheat and or overload the cooling system?
because if that's the case even driving long distance at steady speeds would provoke problems with the vnt?

Well, the biggest problem isn't so much the heat, it's the pumping losses that the engine endures, it'll be pumping all that gas at high pressure when it's not needed, high inlet temperatures due to the boost and yes, it can overheat the head as the gas can't get out fast enough...

Any steady speed will cause the problem, but it's very noticable on the motorway - or just cruising...

[Ryan@306]

are there no ways around it then?

[Ruan]

Do what I did with the electronic controller that reads RPM and throttle position..

There's a post about it somewhere...

[Ryan@306]

ah is there? I'll have a search , cheers bud

[craig-dodd]

i have a GT2052S would this be a good upgrade for my 1.9?

[strictly_perv]

i have a GT2052S would this be a good upgrade for my 1.9?

NO, they are totally crap, would be lagggy as fuuuuuck with crap flow rates. I'll buy it off you as it will be no good for you

[4WayDiablo]

Iirc a 2056 is more suited but yeah it should do well :-)

[craig-dodd]

cheers, il have a go with it then

[n0v0s]

right i want to put a bigger blower on the dt but dont know what to use, i don't fancy beating the bulkhead to fit a td04 but want to know other turbos that would fit down behind block that are worth changing the turbo for ?

Bashing the bulkhead is a rite of passage if fitting a larger turbo. If it fouls the servo, then you have a problem. Either re-angle the flange or adapt the servo... If you're brave (stupid perhaps?)

My turbo clears the steering knuckle JUST, and that's after taking a grinder to the compressor cover