1 PSI boost to 3.5 PSI back pressure???

[JLE58]

If you reduce back pressure you reduce boost only way to lower it is to lower boost with out changing parts. If you have 14psi of back pressure at 7psi of boost you will still have 14 psi of backpressure at 7psi with 1,2,3 30, waste gates. They use two waste gates for better control of pressure. I'm sure they have a larger housing than this turbo that's why they have a little lower backpressure.

[Unreal]

Originally Posted by jordoza

Waste gates control turbo boost pressure by bypassing exhaust around the turbine and into the down pipe which reduces exhaust flow and pressure thru the turbine which slows the turbo and hold or reduces boost pressure. So when a wastegate opens it reduces pressure. So if you had two waste gates of 35 mm when fully opened you would bypass exhaust thru a 70mm pipe into the low pressure gases in the down pipe so how do they not relieve pressure. If I'm wrong please explain how. I've been around turbos all my life and actually work with them on a daily basis professionally. I'm also a professional tech so I'm pretty confident in my statements but I'm always open to correction. Are multiple or larger waste gates a good way to relieve back pressure. No does it work. Kind of but not well but it worked for the tnetics crowd so they could use a turbine that is to small on an ls3.

You are correct, except then it would make no boost. Bypassing more air before the turbine will lower pressure, but then it will lower boost. At 10psi with 1,2,10,20 wastegates the pressure pre turbine will be the same. Just means each wastegate opens less to maintain the 10psi.

[jordoza]

I would agree with that but as an engine increases rpm it increases exhaust flow due to the amount of air being drawn in. A waste gate doesn't open solely on boost pressure alone it also works off exhaust pressure also. Example would be a car with high back pressure requires a 14 pound boost spring in the waste gate but the gate controls the boost to 8 psi or even lower. I have seen that multiple times. So in this case the engine makes 8 pounds of boost at say 2500 rpm well it doesn't have 30 pounds of back pressure then I'm sure but as the rpm increases the engine takes in nmore air and puts out more exhaust and the waste gate can flow enough exhaust to control boost but due to its small area the exhaust begins to build pressure until at high rpm 30+ pounds of back pressure. If the waste gate where large enough it could bypass the restriction (the turbine) but still keep enough exhaust going thru the turbine to maintain boost pressure. It does work. I have seen it. Caterpillar uses a system much like this on there c15 acert compound turbo set up. The compressors are compound but the turbines are more of a series set up but that's another explanation. I've seen this on a two. Turbo 400 SBC that had t3 housings. They where way to small but due to twin 60mm waste gates the back pressure never went higher then 2 to 1 which is acceptable. Not good by today's standards but acceptable. Anyway one way or the other its not a great idea but it is the wat tnetics set there's up. Other wise there hot side would be showing very high back pressure with a 68mm turbine like the ops car does. No bullshit I swear this works. Its a crutch but it does work.

[jordoza]

I believe the reason nobody is buying this is because why would anyone try to make a turbo that is to small work when you could just move to a larger turbine. I've seen this in action due to being around very large engines. 14 ltr and up. The compromises get larger when you are trying to make an engine have awesome off idle torque but still decent top end for a diesel. I honestly should have probably just kept my mouth shut and not got into it but I thought the tnetics kit was a good example and I could explain it well enough. I do know this works but I think my examples and explanations would just muddle things more then they already are because it would be like comparing apples to oranges and things wouldn't translate well. I bow out.

[grocerygetter]

Sign of needing a second or larger waste gate would be a boost spike or not being able to keep boost down...OP mentioned neither.

[JLE58]

A wastegate does not lower back pressure without lowering boost... They are relative to each other. When the wastegate is open it is just dumping the air not used to keep desired boost if you use two you just cut the cfm across the two instead of one. You cant use a compound turbo set up as an example because the wastegate size between the two could change things.

[JLE58]

Originally Posted by jordoza

I believe the reason nobody is buying this is because why would anyone try to make a turbo that is to small work when you could just move to a larger turbine. I've seen this in action due to being around very large engines. 14 ltr and up. The compromises get larger when you are trying to make an engine have awesome off idle torque but still decent top end for a diesel. I honestly should have probably just kept my mouth shut and not got into it but I thought the tnetics kit was a good example and I could explain it well enough. I do know this works but I think my examples and explanations would just muddle things more then they already are because it would be like comparing apples to oranges and things wouldn't translate well. I bow out.

I'm sorry but it doesn't work thats why we arent buying it.I've had this same debate more than a few times....