Compressor Surge

[Hiro Protagonist]

ET pulsar/exa for a start and there are several more.

 

Don't recall the 7AFTE Sportivos having one either, but could be wrong. They were running such piddling boost anyway.

[tas_ae71]

diesels don't run a BOV lol

 

i love the sound of spool, hate the sound of PSSHT.

 

ill re-co my standard BOV thank you very much lol

Edited September 23, 2009 by tas_ae71

[Evan G]

diesels don't run a BOV lol

 

i love the sound of spool, hate the sound of PSSHT.

 

ill re-co my standard BOV thank you very much lol

 

 

Thats cause diesel control the amount of fuel not the amount of air like petrol cars do

 

 

:P :cool: :) ;)

[camerondownunder88]

Yes if you google this issue of SURGE a LOT of people get it totally f@$ked up and don't know what there on about.

 

I build commercial gas turbines for a living and I see a lot of surge. If you want to know about surge look up surge in aircraft way more in depth info and it is the same and the person who wrote on it prob explained it better.

 

Turbine in essence can't swallow air so comes back out compressor is VERY short but violent. I have seen 2000HP gas turbines main shafts fail and twis backwards due to it. Same can happen to a turbo. But RARE in a car to happen as you have pistons in between your turbine and compressor so they help.

 

Many new GT range on garret etc have surge grooves cut into the front of the compressor scroll. i wont go into how they work on here I think ill max out my word limit in a post..LOL

 

Cheers

Cameron

[Evan G]

Yes if you google this issue of SURGE a LOT of people get it totally f@$ked up and don't know what there on about.

 

I build commercial gas turbines for a living and I see a lot of surge. If you want to know about surge look up surge in aircraft way more in depth info and it is the same and the person who wrote on it prob explained it better.

 

Turbine in essence can't swallow air so comes back out compressor is VERY short but violent. I have seen 2000HP gas turbines main shafts fail and twis backwards due to it. Same can happen to a turbo. But RARE in a car to happen as you have pistons in between your turbine and compressor so they help.

 

Many new GT range on garret etc have surge grooves cut into the front of the compressor scroll. i wont go into how they work on here I think ill max out my word limit in a post..LOL

 

Cheers

Cameron

 

whats the money like in building gas turbines? :P

[philbey]

Diesels run at a much more constant and narrow power range. They also don't need spool up as rapidly. Damn, diesel turbo trucks I've driven were power on 1000-1200rpm and redline at 2000rpm.

 

CA18DET's run no BOV.

 

Z18s. I dunno but do SR's even run them?

 

Sigma Turbo's don't.

[camerondownunder88]

I have never owned a factory turbo car but I though lots ran waste gates over a blow off valve?

[Evan G]

Diesels run at a much more constant and narrow power range. They also don't need spool up as rapidly. Damn, diesel turbo trucks I've driven were power on 1000-1200rpm and redline at 2000rpm.

 

CA18DET's run no BOV.

 

Z18s. I dunno but do SR's even run them?

 

Sigma Turbo's don't.

 

 

most of the trucks at work have a power band of 500 rpm. ive seen a public transport bus with a redline of 1100rpm? and they idle at 500ish rpm

[philbey]

I have never owned a factory turbo car but I though lots ran waste gates over a blow off valve?

 

Yes they run wastegates, although that's not doing the same thing as the blowoff valve.

[GTS-T_Sedan]

yeh every turbo has a wastegate wether internal or externally run

and yeh sr20s run bovs but the return is to small so it flutters

 

compressor surge is bad, normally when the front compressor cover not matched correctly with the exhaust housing

a lot of hi-flows (even gcg were having problems on there skylines hi-flowed turbos)

when coming/on boost they would get jolty and hesitate

 

compared to mad flutterz where you either run no bov from factory or block it off

where the compressed air can't escape from the system (bov will release) they will get pushed back into the compressor blades of the turbo

that then makes the loud chopping noise - aka tssuuu tsuu tsuu

 

not benifical on a street car, besides the look at me ima sick kent noise factor

on a track car it actually helps keep the turbos pressure up so in fact lessens the lag

however it still limits the life of the turbo to what it could be

 

my car running a garrett hiflow, and through a gtr bov on 19psi still flutters when ive got a pod on

but I'm not a fan and try to keep car legal so i keep my airbox on

Edited September 23, 2009 by GTS-T_Sedan

[flat out]

not evering turbo has a waist gate aswell, we have a truck thas no bov, intercooler or waist gate, its diesel but belive me there is no waist gate

 

if you want to make noise why not run no bov? unless there plum back there ilegal,

[Evan G]

explains all

[styler]

iv heard the argument both ways...

 

its bad:

its bad because the turbo is spooled up and feeding air into the intake and the intake shuts off

with the air still feeding in from the turbo, the air builds up pressure in the intake and causes a

surge of back pressure to flow back into the turbo, against the flow of the impeller causing it to

have a higher load on it, and it slows down as it is no longer under power from the exhaust to

counteract this back pressure, although if it was under power from the exhaust it would be worse.

 

its not bad:

its not bad because impellers are designed for load, what are they doing before this surge? sitting around?

no they are taking load pushing air into the intake, so what if they get a pressure against the blades, thats

how they work in the first place to push air forwards into the intake. once the intake shuts the exhaust no longer

powers the turbo and it doesnt have load on the impeller trying to push air at full boost, the air builds up pressure

in the intake and causes a surge of back pressure to flow back into the turbo, against the flow of the impeller

causing it to have a higher load on it, and it slows down as it is no longer under power from the exhaust to

counteract this back pressure, although if it was under power from the exhaust it would be worse.

 

i think it depends on a few things...

 

levels of pressure on feed and surge

rates of pressure buildup and surge buildup

periods of pressure and surge

turbo impeller materials, design and strength

turbo impeller rotational inertia

gas volume and speed

characteristics of gas flow and turbo operation

 

my theory is that if the two levels / rates / periods of the exhaust unloading the turbo and the surge loading

it back up are similar or within range of the impeller strength then its not a problem, i think this makes sense

pending gas flow and turbo operation but i may have missed something...

 

...yeah like in the end if you believe its a problem then run a bov, if you don't then don't run a bov, end of story... :P

 

edit - hmmm was relating to bov surge but seems like its another discussion entirely... interesting though

Edited November 29, 2009 by styler

[curly]

not evering turbo has a waist gate aswell, we have a truck thas no bov, intercooler or waist gate, its diesel but belive me there is no waist gate

 

if you want to make noise why not run no bov? unless there plum back there ilegal,

Diesels don.t have a butterfly so they don't need a bov and they limit the boost by the size of the exhaust, intercooler is just being lazy

[philbey]

Again, the definition of surge vs. turbo flutter is confused.

 

And the theory of turbo blades being designed to take stress is sound, but remember they are only designed to take a certain amount of stress. The point of both cases (Surge and Flutter) is that you are likely to stress them beyond their design capacity.