Pressure Bleed valve instead of Wastegate?

[Deezul1]

I am thinking of going to a 16cm housing without wastegate. Is there any way to bleed of boost pressure with an adjustable valve? It seems to me I have seen something like this a long time ago.

 

[SEmerson]

My thoughts on this is that it would only give a delay. So the boost would slowly drop off becouse of a opening gate. I disabled my all together.

 

[Beast2B]

peak boost?

SEmerson,

With your wastegate totally disabled, what kind of boost numbers are you seeing? Do you get a spike or surge before it "settles" to a maximum pressure without fluctuations? Just curious, cause with my boost elbow I'm seeing 32-34 on the boost gauge.

 

[Jim Fulmer]

John

I put one on a while back and love it, helps in the EGT department but I'm not the best example as the transmission is still stock(DTT next weekend) I do think it will help yours unless you plan on going to a HX-40 later on. My boost number went up a bit but I hadn't played with the wastegate arm, now it goes instantly to 32lbs and tops out at 34 in upper RPM but I'm not chasing boost numbers, what I want is good numbers while the turbo is still in the map area so as not to heat the air too much, example a 35 verses a 40 at the same boost level. If everyone keeps having good luck with Piers's HX-40's then I will get one later on then add more fuel to match it.



Jim

 

[SEmerson]

stock with a ez -27-28

injectors, ez- 31-32

injectors, ez, blue box it buries my 35# guage.



No spike just rolles up to max

 

[Deezul1]

What I am thinking of is not a way to control the waste gate because the 16cm housing doesnt have one. I am interested in bleeding off pressure from the charge air side via some sort of pressure sensitive valve sort of like a safety valve on an air compressor.

 

[SEmerson]

Why??????????????????? the object of the waste gate is just to take the stress off the turbo. It would be a waste to stress the turbo to make the pressure then just vent it.

 

[Deezul1]

SEmerson

THERE IS NOOO WASTE GATE on a 16 housing. Object is to control boost by other means.

 

[SEmerson]

I see the point. But if it is a waste gate you want why not trade someone for a gated version. It just seems like alot of work to make a waste gate work around. And many of use dont even use one.



But point taken I now see what your looking for.

 

[Deezul1]

Its not the wastegate I want, its the 16 housing for EGT control and right now with a 12cm with a functioning waste gate I am making 40lbs boost and would like to reduce that some

 

[SEmerson]

but by lowering your boost you egt will climb. You would have some gain with the larger housing but some lose with the lower boost.

 

[Deezul1]

Thats an interesting thought, havnt seen anything about that relationship and will check it out. I may be beating a dead horse.

Thanks

 

[JR2]

There is such a thing as too much boost, as some point the turbo is out of its efficiency map and actually heats up the air. I had my punny little HY35 putting out 40 psi, but my egt was 1500 degs. So yes a waste gate or some other way of bleeding off pressure is a good thing if it is all set up correctly.

 

[SEmerson]

But ... ... ... . and correct me if I am wrong. In his case the bigger houseing will put him back in the efficancy range of his turbo. So he would get cooler air at the same psi. After changing to the bigger houseing he will drop his egt's by giving him a cooler blast. Now if after that he drops his boost then that will raise his egt's. Which will but him back where he started. Just poorer.

 

[Beast2B]

Help me ObiWan!!

So where is the definitive chart/graph showing the max boost or max efficient boost for any given turbo in any given configuration? From what I've seen, it's been a fairly subjective issue. Lag versus boost versus EGT versus every other factor...

:-{}

 

[SEmerson]

Holset has the graphs on there web site.

 

[Deezul1]

Air compressed to 40 psi develops the same heat no matter the the size of the exhaust housing. The heat in the charge air side is directly related to being compressed. The 16cm exhaust housing reduces EGTs because it is less resrictive on the hot side of the turbo. There are 2 different heat areas in the turbo, exhaust which is measured with the EGT gauge, and intake which is not measured at all. The heating of the charge air by being rapidly compressed will effect EGT but a larger housing will help reduce the overall retention of heat by allowing exhaust gasses to exit sooner.