at what point should i consider an external wastegate?
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Woody - based on how I understand things, that is what I would expect to see. I would think that an external gate located up there at the turbine and dumping right back into the elbow would offer no hp advantage over an internal gate. An external gate on the crossover can offer a hp gain due to lower backpressure. It may not be enough to be noticeable, kinda depends on the setup that is already in place and how good it is.
Also, there might be other advantages to an external gate besides a reduction in backpressure, ie controllability for example. But, like I said (or tried to say), the better the dp the less extra hp an external gate will have to offer.
Oh yeah, forgot my usual disclaimer: I have no practical experience here, just going on what I know about compressors and turbines and such (being the design engineer that I am). So, if you think I'm lying, you may be right. I acknowledge that I may be wrong. I just don't think I am
John
Also, there might be other advantages to an external gate besides a reduction in backpressure, ie controllability for example. But, like I said (or tried to say), the better the dp the less extra hp an external gate will have to offer.
Oh yeah, forgot my usual disclaimer: I have no practical experience here, just going on what I know about compressors and turbines and such (being the design engineer that I am). So, if you think I'm lying, you may be right. I acknowledge that I may be wrong. I just don't think I am
John
Thanks for the excellent clarification John. I often re-read my posts and wish I had used better tone. I apologize to Woody if I came across tersely or as a know it all.
The ATR header which takes the gas out just prior to the turbine inlet is better than the turbine area but the gases are really coming together and creating a high velocity column, you sort of disrupt that when you suck some out there with a pressure rise and disruption in the laminar flow.
You can take a little heat out of the engine compartment and it actually does make the car easier to work on.
There should be a flow improvement at the turbine outlet as well. When the gases are coming out they are in a vortex and as that area opens up you would create a "cloud" of gases that has to reorganize to get down the pipe. The faster you turn that helical flow into a straight column the faster it gets the heck out of there.
If it makes it more palatable, I'm a recovering design engineer (as well as manufacturing engineer) for Cat & Deere but work in HR now.
The ATR header which takes the gas out just prior to the turbine inlet is better than the turbine area but the gases are really coming together and creating a high velocity column, you sort of disrupt that when you suck some out there with a pressure rise and disruption in the laminar flow.
You can take a little heat out of the engine compartment and it actually does make the car easier to work on.
There should be a flow improvement at the turbine outlet as well. When the gases are coming out they are in a vortex and as that area opens up you would create a "cloud" of gases that has to reorganize to get down the pipe. The faster you turn that helical flow into a straight column the faster it gets the heck out of there.
If it makes it more palatable, I'm a recovering design engineer (as well as manufacturing engineer) for Cat & Deere but work in HR now.
i was leaning toward the external now
now if you put the gate on the x over, are you worried about damage from road debris? i saw a set up that jack cotton did, he welded a small pipe and flange to the stock passenger header and then vented the gate to atmoshere. i am concerned about the noise with that. are these loud? i like the atr dp and gate set up. it looks nice but will it work with stock headers or atr headers?
now if you put the gate on the x over, are you worried about damage from road debris? i saw a set up that jack cotton did, he welded a small pipe and flange to the stock passenger header and then vented the gate to atmoshere. i am concerned about the noise with that. are these loud? i like the atr dp and gate set up. it looks nice but will it work with stock headers or atr headers?
when I ran a THDP and stock wastegate and I would experience boost creep at high boost levels. My car required an external gate to control boost creep since I couldn't bore out my wastegate hole any larger. Every car is different. Some run fine with a stock style wastegate, they seem to have ported heads though. Now that boost creep is eliminated, I do not have to worry about leaning out at the top end due to the boost increasing.
My W/G tucks up tight on the PS corner where it bends to go up to the PS header. I GTAW'd a 1-5/8 stainless pipe to a WG flange so it stuck out proud then oriented the flange to point the WG exit towards the cutout. I haven't connected it to the exhaust though.
You can definetly tell when it's opening. Not the sexiest sound either. If you like queefs, you'll love the WG moan. Rushing air and a mad 3 cylinder is the best way for me to describe it. Wakes up anyone nearby! I'm used to it now so I like it. It would be easy to plumb into the exhaust.
You can definetly tell when it's opening. Not the sexiest sound either. If you like queefs, you'll love the WG moan. Rushing air and a mad 3 cylinder is the best way for me to describe it. Wakes up anyone nearby! I'm used to it now so I like it. It would be easy to plumb into the exhaust.
On the ATR set up the gasses are bled before the turbine coming off the up pipe to the turbine housing. This IMO is a better place because its using all 6 cyls to scavange, and not just 3 form the cross over. This also gives better boost control. Anytime you can bleed the boost before it enters the turbine housing, youll see a decrease in BP and a gain in HP.
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