What is Turbo Surge?????
05-02-2004, 12:18 AM
#42
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I've had a few chats with peolple in the know and have been given conflicting explanation of surge - 
in the end i decided to speak to a turbo manufacturer to get the story
basically as a car comes on boost it is possible for the turbo to struggle to provide enough air that the engine is capable of consuming, the engine will kind of cough - this is evidence of surge
generally speaking - It happens on engines with a good Volumetric efficiency as they come on boost
it can also be an effect of a mismatched turbo with incorrect ex and compressor wheels
in the end i decided to speak to a turbo manufacturer to get the story
basically as a car comes on boost it is possible for the turbo to struggle to provide enough air that the engine is capable of consuming, the engine will kind of cough - this is evidence of surge
generally speaking - It happens on engines with a good Volumetric efficiency as they come on boost
it can also be an effect of a mismatched turbo with incorrect ex and compressor wheels
05-02-2004, 12:21 AM
#43
Mike Gurney,
basically as a car comes on boost it is possible for the turbo to struggle to provide enough air that the engine is capable of consuming, the engine will kind of cough - this is evidence of surge
basically as a car comes on boost it is possible for the turbo to struggle to provide enough air that the engine is capable of consuming, the engine will kind of cough - this is evidence of surge
05-02-2004, 12:26 AM
#44
In fact, whoever told you that was MILES out Mike!! 
What your saying there:
The engine this turbo is fitted to is making peak VE at a point where its gasflow is only just enough to spin a turbo up
Yet at the same time, this turbo is overspeeding to supply this engine?
You sure you didnt missunderstand Mike?
What your saying there:
The engine this turbo is fitted to is making peak VE at a point where its gasflow is only just enough to spin a turbo up
Yet at the same time, this turbo is overspeeding to supply this engine?
You sure you didnt missunderstand Mike?
05-02-2004, 12:39 AM
#46
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Stu will correct me if I'm wrong I hope, but "chatter" is the air coming back against the impellor when you lift off. The louder the chat, the more the force = not so good for the impellor or shaft.
05-02-2004, 01:40 AM
#50
I took my Bayleys Atmospheric Dump Valve off my cossie because i was worried that it was open and sucking on idle, so therefore i am now getting wastegate chatter. 
Do you think that i should put it back on even though it's open on idle sucking in unfiltered air? (a little bit)
Cheers
Do you think that i should put it back on even though it's open on idle sucking in unfiltered air? (a little bit)
Cheers
05-02-2004, 08:50 AM
#52
Norris Motorsport
Quote:
Mike Gurney,
"basically as a car comes on boost it is possible for the turbo to struggle to provide enough air that the engine is capable of consuming, the engine will kind of cough - this is evidence of surge"
Quote by Stu:
"Sorry Mike, that's bollox, and if youve ever mapped a surging turbo you will know thats bollox as well mate, to stop it surging we have to slow it down 9 times out of 10 "
As Stu has rightly said you've got it totally wrong Mike.
In very simple terms surge is caused by the compressor wheel trying to process more air than the engine can consume. This is a result of using a compressor wheel that is too big for the shaft speed.
This is usual on any turbo that tries to use a large compressor wheel/housing with a small turbine housing/wheel.........e.g. T38, MD240 etc.
The correct way to overcome surge is to match the turbo specificcally to the engines VE. I achieved this on my engine by using the correct head porting and cams and have now totally eliminiated surge at all boost levels and rpms.!!
Mike Gurney,
"basically as a car comes on boost it is possible for the turbo to struggle to provide enough air that the engine is capable of consuming, the engine will kind of cough - this is evidence of surge"
Quote by Stu:
"Sorry Mike, that's bollox, and if youve ever mapped a surging turbo you will know thats bollox as well mate, to stop it surging we have to slow it down 9 times out of 10 "
As Stu has rightly said you've got it totally wrong Mike.
In very simple terms surge is caused by the compressor wheel trying to process more air than the engine can consume. This is a result of using a compressor wheel that is too big for the shaft speed.
This is usual on any turbo that tries to use a large compressor wheel/housing with a small turbine housing/wheel.........e.g. T38, MD240 etc.
The correct way to overcome surge is to match the turbo specificcally to the engines VE. I achieved this on my engine by using the correct head porting and cams and have now totally eliminiated surge at all boost levels and rpms.!!
05-02-2004, 08:52 AM
#53
Originally Posted by Stu @ M Developments
Morning Dave,
I hear your missus was very popular tonight mate, well done
I hear your missus was very popular tonight mate, well done
I do of course mean Daves missus's business was catering for the PF southend meet last night and her food was very popular!!
05-02-2004, 09:03 AM
#58
Norris Motorsport
As said surge is caused by the compressor wheel trying to process more air than the engine can consume.
This is the same phenomenam whether changing gear (i.e. throttle shut) or when using a compressor wheel with excessive shaft speed relative to engine V.E.
(This is usually caused by using a turbine wheel/housing too small for the compressor stage.)
This is the same phenomenam whether changing gear (i.e. throttle shut) or when using a compressor wheel with excessive shaft speed relative to engine V.E.
(This is usually caused by using a turbine wheel/housing too small for the compressor stage.)
05-02-2004, 09:41 AM
#59
PassionFord Post Whore!!
so if a small exhaust housing and large compressor housing cause this why are they sold ?
are there engines these would be good on ?
if im right it seems that the compressor pushes more air into the engine than the exhaust housing can deal with or have i got it wrong :blonde:
are there engines these would be good on ?
if im right it seems that the compressor pushes more air into the engine than the exhaust housing can deal with or have i got it wrong :blonde:
05-02-2004, 11:36 AM
#60
Karl,
This is the same phenomenam whether changing gear (i.e. throttle shut) or when using a compressor wheel with excessive shaft speed relative to engine V.E.
This is the same phenomenam whether changing gear (i.e. throttle shut) or when using a compressor wheel with excessive shaft speed relative to engine V.E.
On gear change we are far more likely to get compressor stall than surge.
Dont you agree Karl?
05-02-2004, 01:34 PM
#62
Norris Motorsport
Well Stu yes and no to your question.
Either way it is the same issue. The compressor wheel is trying to process more air than the engine can consume. When we lift off the throttle the engine still consumes some air BUT a lot less than the compressor wheel is trying to process. As such the air effectively goes back through the compressor wheel giving rise to a noise similar (i.e same but more severe) to normal on boost surge. Both cause turbo stall its just more dramatic when you lift off the throttle but the same phenomena is occuring.
Either way it is the same issue. The compressor wheel is trying to process more air than the engine can consume. When we lift off the throttle the engine still consumes some air BUT a lot less than the compressor wheel is trying to process. As such the air effectively goes back through the compressor wheel giving rise to a noise similar (i.e same but more severe) to normal on boost surge. Both cause turbo stall its just more dramatic when you lift off the throttle but the same phenomena is occuring.
05-02-2004, 02:58 PM
#64
DaveEsCos,
Yep, her baps went down a treat
Yep, her baps went down a treat
Karl,
Either way it is the same issue. The compressor wheel is trying to process more air than the engine can consume. When we lift off the throttle the engine still consumes some air BUT a lot less than the compressor wheel is trying to process. As such the air effectively goes back through the compressor wheel giving rise to a noise similar (i.e same but more severe) to normal on boost surge. Both cause turbo stall its just more dramatic when you lift off the throttle but the same phenomena is occuring.
Either way it is the same issue. The compressor wheel is trying to process more air than the engine can consume. When we lift off the throttle the engine still consumes some air BUT a lot less than the compressor wheel is trying to process. As such the air effectively goes back through the compressor wheel giving rise to a noise similar (i.e same but more severe) to normal on boost surge. Both cause turbo stall its just more dramatic when you lift off the throttle but the same phenomena is occuring.
IJust wanted to clarify it for all these folks that will quote us in 9 mths time when weve clean forgotten what was said and why we said it!!
Anyway..
On with that other thing we spoke about now.. will have result for you in 5mins
05-02-2004, 03:03 PM
#65
Norris Motorsport
Yeah I know exactly what you mean stu, and totally agree with the closed throttle that you do not get surge in the same form as on boost. I simply meant the issue of excessive air passing back through the compressor wheel causes the similar noise! Cheers will speak to you soon.
05-02-2004, 11:05 PM
#69
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Originally Posted by Stu @ M Developments
Mike,
I always had you down as someone who could use logic to define both what is and conversely, what is not, feasible.
Do you not see any flaws in the version your "Turbo manufacturing expert" told you?
Does mine not make far more sense?
I always had you down as someone who could use logic to define both what is and conversely, what is not, feasible.
Do you not see any flaws in the version your "Turbo manufacturing expert" told you?
Does mine not make far more sense?
and ditto cossieEdd
07-02-2004, 08:38 PM
#70
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this one is getting good.
It looks like one of the best know tuners in the country has got it wrong (not someone who uses this BB ) at first look that doesn't seem feasable at all
quick question guys - if an turbo was surging at the top end of the rev range where there is more air being consumed - shouldn't the surge line on a turbo be on the right of the compressor map and not on the left
It looks like one of the best know tuners in the country has got it wrong (not someone who uses this BB
) at first look that doesn't seem feasable at allquick question guys - if an turbo was surging at the top end of the rev range where there is more air being consumed - shouldn't the surge line on a turbo be on the right of the compressor map and not on the left
07-02-2004, 09:29 PM
#73
When i play with my car, a sapphire 4x4 cossie, it only chatters when i lift of throttle or when i change gear, revs have to be above 2000 with a decent amount of throttle used.
From the above, this is not turbo surge. Correct or not.
Another thing, should i fit a dump valve as there isn't one on mine, the previous owner removed it feeling the car performed better without it?
By the way great topic, before reading this i knew nothing about turbo surge, never even thought about it. Good thread Tiff
From the above, this is not turbo surge. Correct or not.
Another thing, should i fit a dump valve as there isn't one on mine, the previous owner removed it feeling the car performed better without it?
By the way great topic, before reading this i knew nothing about turbo surge, never even thought about it. Good thread Tiff
07-02-2004, 10:03 PM
#74
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Fookin ell, straight over my ed!!! Is chatter a bad thing or not cus I've spent a good hour today timeing it right to scare coffin dodgers walkin there poodles with me lovely loud chatter!!! Proper Bo. 
08-02-2004, 04:07 PM
#75
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here is a compressor map of a 4x4 cossie compressor wheel
if you were to look at 1 bar boost (2.0 pressure ratio) the turbo will go into the surge area as the car is processing approx 100 bhp
(has anyone got a dyno plot of a stg1 4x4 cos ?)
if you were to look at 1 bar boost (2.0 pressure ratio) the turbo will go into the surge area as the car is processing approx 100 bhp
(has anyone got a dyno plot of a stg1 4x4 cos ?)
08-02-2004, 04:25 PM
#78
Mike Gurney,
if you were to look at 1 bar boost (2.0 pressure ratio) the turbo will go into the surge area as the car is processing approx 100 bhp
(has anyone got a dyno plot of a stg1 4x4 cos ?)
if you were to look at 1 bar boost (2.0 pressure ratio) the turbo will go into the surge area as the car is processing approx 100 bhp
(has anyone got a dyno plot of a stg1 4x4 cos ?)
SO how do you figure we are in surge at 100bhp mate?
08-02-2004, 04:34 PM
#79
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Doh - I posted it first to make sure the picture would show ok
anyway - if you were to run a 4x4 cossie on 1 bar boost the only place it will get near surge is around the 100 bhp mark which would have to be as it comes on boost
anyway - if you were to run a 4x4 cossie on 1 bar boost the only place it will get near surge is around the 100 bhp mark which would have to be as it comes on boost
08-02-2004, 04:38 PM
#80
Mike Gurney,
Last edited by Mike Gurney on Sun Feb 08, 2004 5:11 pm; edited 1 time in total
Last edited by Mike Gurney on Sun Feb 08, 2004 5:11 pm; edited 1 time in total
Mike Gurney,
if you were to look at 1 bar boost (2.0 pressure ratio) the turbo will go into the surge area as the car is processing approx 100 bhp
(has anyone got a dyno plot of a stg1 4x4 cos ?)
if you were to look at 1 bar boost (2.0 pressure ratio) the turbo will go into the surge area as the car is processing approx 100 bhp
(has anyone got a dyno plot of a stg1 4x4 cos ?)
Mike Gurney,
Thats strange Stu, i havent edited my post at all, maybe theres something wrong with your forum times and dates?
anyway - if you were to run a 4x4 cossie on 1 bar boost the only place it will get near surge is around the 100 bhp mark which would have to be as it comes on boost
Thats strange Stu, i havent edited my post at all, maybe theres something wrong with your forum times and dates?
anyway - if you were to run a 4x4 cossie on 1 bar boost the only place it will get near surge is around the 100 bhp mark which would have to be as it comes on boost