Waste gates: pros and cons?

[Blakers]

What purpose do waste gates serve? What are the avantages of having them on your turbo? Advantages of no waste gate? How will an engine perform differently with or without a waste gate? My truck originally had one, but now has a 16 cm housing without.



Thanks guys,



Blake

 

[illflem]

The purpose of the wastegate is to provide adiquite boost at low rpms without over-boosting at high rpms. At high rpms when the wastegate opens exhaust is routed around the turbine fan thus lowering the boost. Seems to me that without a wastegate you will either be overboosting at high rpms or under-boosting at low, the wastegate makes the engine much more efficient. Remember the higher the boost the poorer the fuel economy.

 

[Dieselnerd]

Like illflem said, with a wastegate you can use a small 12 cm turbo that spins up fast with less turbo lag. That same small turbo will develop too much boost as you get up to full power so you need a wastegate to dump the excess pressure. Overboost without extra fuel just increases cylinder pressure to higher levels and reduces power.

 

[illflem]

Here's some good info

 

[SLang]

I'm not trying to step on any toes and these guys are mostly correct.



Now as far as waste gates go... they were introduce to help the diesel engine performance memic the gasser. A gas engine has very quik throttle responce with the power available as soon as the drive rolls into the throttle. The diesel with out a turbo are weak as can be seen by the GM 6. 2L. So a turbo was added to increase power to a usable point and at the same time increase MPG and decrease pollutants. Now everyone thought the gasser acceleration was better so the diesel had to be changed to keep up. Thus the small turbo housing to have more power quicker and the waste gate to control cylinder pressure and RPM of the turbo impeller.



If you want to know the *best* (remember this is a relative term) way to produce usable power and maintain long engine life look to the large NTC and N14 performance guys. They have engines out there that are 700+HP/2000+T and still drive them 100K++ per year.

 

[Blakers]

Thanks guys for all your replies. I now know more than I did before. Mine runs great without a waste gate so I guess that is ok. I know we had a 1979 Mercedes 300SD without a waste gate and a 1981 300SD with a waste gate. I don't know if there is much difference in power.



Blake

 

[JohnE]

More variables than just a waste gate for turbo charging an engine once you move beyond the Cummins envelope.

Detroit Series 50 diesel and CNG engines are available with a Garrett waste gated and <b>variable</b> turbo.



If you run a narrow or fixed RPM engine than a waste gate isn't <em>usually</em> required. As SLang pointed out, once you introduce the gasser parameters of expecting throttle response the rules change. Why do you thing GM & Ford went with a V-8 diesel? I don't think it was for the shorter length versus a I-6.



I'm still looking for the <em>throttle</em> on my truck



John