Turbocharge your knowledge (Learn how Turbochargers work)

raihan · 18th April 2005, 11:41

Guys,
Can someone explain to me what is the purpose of a blow off valve & waste gate in a turbo system ??
thanks,
Rai

iceman91 · 18th April 2005, 12:01

they are control units for the turbo.
waste gate
.A trap door-like device on the exhaust side of a turbocharger that limits the amount of boost a turbo can produce. The waste gate consists of a spring-loaded diaphragm. A vacuum hose connects the diaphragm to the intake manifold. When boost pressure starts to exceed the rating of the waste gate, the diaphragm pulls open a bypass flap in the turbo housing. This allows some of the exhaust to go around the turbo impeller which slows it down.

Domnic · 18th April 2005, 12:05

HI,
simple... first some basics, the turbo forces air into the engine. The pressures increase on some cars till 2.5 bar which is a great amount. When you leave the throttle, the turbo is still spinning and forcing air, but when the throttle plate (butterfly) shuts the pressure builds up and can destroy the impeller (compressor). So a blow off valve is used to vent the air.

a wastegate ... same principle as above but when you close the plate there is a valve on the exhaust which bypasses the exhaust gasses through the turbo, so the turbo drops speed and the intake pressure too drops... simple isnt it

Cheers
Dom

iceman91 · 18th April 2005, 12:05

blow off valve
A blow-off valve is mounted in the intake plumbing between the
turbocharger compressor and the throttle plate. The blow-off valve is a
second safety measure against the turbocharger over-boosting and damaging
the engine

raihan · 18th April 2005, 12:28

Thanks guys, so as I understand its something like a safety valve found on a pressure cooker, which allows the food to be cooked without the cooker blowing off due to pressure build up.

cheers,
Rai

P.S Another thing the blow off valve & waste gate come into play only when u get off the throttle right??

iceman91 · 18th April 2005, 13:24

yeah you got it right just like a pressure cooker's safety valve.

they come off when the throtle is cloed hence you here the famous phsssssssssss when you shift gears or hit the rev limit

ZenGT · 18th April 2005, 14:37

when u shut the throttle on boost, the turbine is still doin its job.. so the forced air bounces back to the impeller which causes it to rotate the opposite direction... which is a very bad thing for the turbo... that air is released through the bov... and hence phssssss

z klasse · 18th April 2005, 14:54

I think its more like phussssssssss!

shravan316 · 18th April 2005, 16:10

Guys guys.... dumb question, but, i still gotta ask. Does Turbocharging a car increase the backpressure??

Mpower · 18th April 2005, 20:29

Quote:

Turbochargers for diesel and petrol engines have the same design. It is much easier to install a turbocharger on a diesel engine compared to a petrol engine due to some factors.

Petrol and diesel turbos are conceptually the same, but differ in terms of materials used. Petrol turbos run extremely high EGTs (exhuast gas temps) and this forces the use of exoctic alloys for both the turbohousing, exhuast manifold and the impeller. High boost turbos like the Evo and the Skyline use titanium and ceramics for the impeller. (BTW, my housing and ex-man have started showing hairline cracks due to the thermal stress)
Diesel turbos and much simpler and cheaper because diesel exhuast is cooler (because the combustion is more efficient). Also diesel turbos dont need BOV since they dont have a throttle body. Diesel are controlled by fuelling. They may not have wastegates either but I'm not sure of that.

Quote:

Guys guys.... dumb question, but, i still gotta ask. Does Turbocharging a car increase the backpressure??

Big time. The Dodge Neon SRT4 turbo does not even use a muffler. The turbo and the cat generate so much backpressure that they are able to absorb the noise.

shravan316 · 18th April 2005, 21:35

Quote:

Originally Posted by Mpower

Big time. The Dodge Neon SRT4 turbo does not even use a muffler. The turbo and the cat generate so much backpressure that they are able to absorb the noise.

Didn't quite get you there.... what does the turbo and the catcon got to do with noise absorption??

Mpower · 18th April 2005, 23:00

Quote:

Didn't quite get you there.... what does the turbo and the catcon got to do with noise absorption??

Energy in the exhuast which is in the form of sound/pressure and heat is absorbed by the turbo and is used to spin the compressor. A muffler also absorbs the sound energy but it simply dissipates it instead of using it for any purpose. Cat's primary job is to clean up the exhuast but the honeycomb structure causes backpressure and works as a silencer. U have to generate backpressure to silence the noise. (Unless its one of those straight thru jobs which use a glass-wool absorption mat)

Notice that an Indigo engine is more silent compared to a Indica because of the turbo.

raihan · 19th April 2005, 11:10

Quote:

Originally Posted by Mpower

(BTW, my housing and ex-man have started showing hairline cracks due to the thermal stress)

If I'm right that would be ur eclipse right? would u recommned the eclipse to someone looking for a quick car?
cheers,
Rai

turbs · 1st May 2005, 10:56

turbocharging a car will increase ur backpressure

Gordon · 9th March 2006, 08:58

Thread revived! Didn't know whats turbocharginig exactly?! Go on and read this topic.

And if you also didn't know what NOS is, then check out this topic:

n2o - all we "Need 2 knOw"
http://www.team-bhp.com/forum/techni...ed-2-know.html

18th April 2005, 11:41	#16
raihan BHPian Join Date: Nov 2004 Location: CA/bangalore Posts: 271 Thanked: 112 Times	Guys, Can someone explain to me what is the purpose of a blow off valve & waste gate in a turbo system ?? thanks, Rai
	() Thanks

18th April 2005, 12:01	#17
iceman91 Senior - BHPian Join Date: Nov 2004 Location: melbourne/banga Posts: 1,961 Thanked: 34 Times View My Garage	they are control units for the turbo. waste gate .A trap door-like device on the exhaust side of a turbocharger that limits the amount of boost a turbo can produce. The waste gate consists of a spring-loaded diaphragm. A vacuum hose connects the diaphragm to the intake manifold. When boost pressure starts to exceed the rating of the waste gate, the diaphragm pulls open a bypass flap in the turbo housing. This allows some of the exhaust to go around the turbo impeller which slows it down.
	() Thanks

18th April 2005, 12:05	#18
Domnic Senior - BHPian Join Date: Mar 2004 Location: bangalore Posts: 428 Thanked: 6 Times	HI, simple... first some basics, the turbo forces air into the engine. The pressures increase on some cars till 2.5 bar which is a great amount. When you leave the throttle, the turbo is still spinning and forcing air, but when the throttle plate (butterfly) shuts the pressure builds up and can destroy the impeller (compressor). So a blow off valve is used to vent the air. a wastegate ... same principle as above but when you close the plate there is a valve on the exhaust which bypasses the exhaust gasses through the turbo, so the turbo drops speed and the intake pressure too drops... simple isnt it Cheers Dom
	() Thanks

18th April 2005, 12:05	#19
iceman91 Senior - BHPian Join Date: Nov 2004 Location: melbourne/banga Posts: 1,961 Thanked: 34 Times View My Garage	blow off valve A blow-off valve is mounted in the intake plumbing between the turbocharger compressor and the throttle plate. The blow-off valve is a second safety measure against the turbocharger over-boosting and damaging the engine
	() Thanks

18th April 2005, 12:28	#20
raihan BHPian Join Date: Nov 2004 Location: CA/bangalore Posts: 271 Thanked: 112 Times	Thanks guys, so as I understand its something like a safety valve found on a pressure cooker, which allows the food to be cooked without the cooker blowing off due to pressure build up. cheers, Rai P.S Another thing the blow off valve & waste gate come into play only when u get off the throttle right?? Last edited by raihan : 18th April 2005 at 12:29.
	() Thanks

18th April 2005, 13:24	#21
iceman91 Senior - BHPian Join Date: Nov 2004 Location: melbourne/banga Posts: 1,961 Thanked: 34 Times View My Garage	yeah you got it right just like a pressure cooker's safety valve. they come off when the throtle is cloed hence you here the famous phsssssssssss when you shift gears or hit the rev limit
	() Thanks

18th April 2005, 14:37	#22
ZenGT BHPian Join Date: Jan 2005 Location: mumbai Posts: 90 Thanked: 2 Times	when u shut the throttle on boost, the turbine is still doin its job.. so the forced air bounces back to the impeller which causes it to rotate the opposite direction... which is a very bad thing for the turbo... that air is released through the bov... and hence phssssss Last edited by ZenGT : 18th April 2005 at 14:39.
	() Thanks

18th April 2005, 14:54	#23
z klasse BHPian Join Date: Jun 2004 Location: Mumbai Posts: 351 Thanked: 28 Times View My Garage	I think its more like phussssssssss!
	() Thanks

18th April 2005, 16:10	#24
shravan316 Senior - BHPian Join Date: Apr 2004 Location: Bangalore Posts: 1,029 Thanked: 9 Times	Guys guys.... dumb question, but, i still gotta ask. Does Turbocharging a car increase the backpressure??
	() Thanks

1st May 2005, 10:56	#29
turbs Newbie Join Date: Feb 2005 Location: bangalore Posts: 8 Thanked: 0 Times	turbocharging a car will increase ur backpressure
	() Thanks

9th March 2006, 08:58	#30
Gordon Senior - BHPian Join Date: Feb 2004 Location: Mumbai Posts: 2,546 Thanked: 483 Times View My Garage	Thread revived! Didn't know whats turbocharginig exactly?! Go on and read this topic. And if you also didn't know what NOS is, then check out this topic: n2o - all we "Need 2 knOw" http://www.team-bhp.com/forum/techni...ed-2-know.html
	() Thanks