Twin 70’s, no boost?
Launching!
Joined: Aug 2015
Posts: 206
Likes: 11
From: Duvall, WA
They are not talking about the ports. They are talking about how you've got the wastegate itself mounted. The wastegate piston normally seals against the header/manifold/up-pipe, so that exhaust backpressure tries to push the piston. This is not how you've got them oriented, and you are likely to have boost control issues if those things ever spool.
What is this setup meant to be? Drag car, street car, show car? If I were sizing twins for a street setup, I'd be using something much, much smaller than that. Short of that, after checking for leaks and ruling out silly stuff like incorrect cam installation, I'd be using smaller exhaust housings. Just to put things in perspective, I am using a single .96 AR T4 (PTE 76mm CEA) on a H/C/I 6.0L (which is, admittedly, an aggressively small turbo for that setup, because I wanted a very torquey setup for street use). I realize you are using a slightly smaller compressor, but I can't imagine having enough exhaust energy to spool two of those.
What is this setup meant to be? Drag car, street car, show car? If I were sizing twins for a street setup, I'd be using something much, much smaller than that. Short of that, after checking for leaks and ruling out silly stuff like incorrect cam installation, I'd be using smaller exhaust housings. Just to put things in perspective, I am using a single .96 AR T4 (PTE 76mm CEA) on a H/C/I 6.0L (which is, admittedly, an aggressively small turbo for that setup, because I wanted a very torquey setup for street use). I realize you are using a slightly smaller compressor, but I can't imagine having enough exhaust energy to spool two of those.
I truly appreciate the input guys.
I am am looking for recommendations for the best and least destructive/painful recovery.
Is is the best course of action the replace the exhaust housings at this point?
My size/choice was based in large part on another members phenomenon results on a twin LS1.
I am am looking for recommendations for the best and least destructive/painful recovery.
Is is the best course of action the replace the exhaust housings at this point?
My size/choice was based in large part on another members phenomenon results on a twin LS1.
Andrew
I setup a regulator hooked up to air compressor for bench testing gate springs. Gives an idea how much back pressure will open them. I've ran twin s366's on a
5.3 & they were full boost around 4500rpm, these should spool fine after you get the gates right.
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Thread Starter
Launching!
Joined: May 2013
Posts: 270
Likes: 30
From: Detroit
Ok duh, so obvious now. The way I have them, the exhaust pressure is pushing the valve/piston against the seat.
This totally screws up my OCD for symmetry and how they are presented.
Clearly this is an issue, but not why I'm not seeing any appreciable boost. This way in fact, they are not even functional.
The answer to my intent for the car is a potent street, a little show, occasional strip.
This totally screws up my OCD for symmetry and how they are presented.
Clearly this is an issue, but not why I'm not seeing any appreciable boost. This way in fact, they are not even functional.
The answer to my intent for the car is a potent street, a little show, occasional strip.
Ok duh, so obvious now. The way I have them, the exhaust pressure is pushing the valve/piston against the seat.
This totally screws up my OCD for symmetry and how they are presented.
Clearly this is an issue, but not why I'm not seeing any appreciable boost. This way in fact, they are not even functional.
The answer to my intent for the car is a potent street, a little show, occasional strip.
This totally screws up my OCD for symmetry and how they are presented.
Clearly this is an issue, but not why I'm not seeing any appreciable boost. This way in fact, they are not even functional.
The answer to my intent for the car is a potent street, a little show, occasional strip.
Have you done leak down testing of the hot and cold side? Is the blow off valve plumbed properly?
Andrew
Thread Starter
Launching!
Joined: May 2013
Posts: 270
Likes: 30
From: Detroit
Haven't thought much about hot side. Not much to it, headers->WG->turbo->3.5" exhaust. I was planning to pressurize the WG reference line to see where they open. If I had done so, I would have realized they were reversed. How do you typically test hot side?
Not sure how I could screw up the BOV plumbing. It only has one port.
TECH Fanatic
Joined: Jun 2013
Posts: 1,163
Likes: 16
From: Avon, Ohio
Sorry just saw this.
Yes, #1 gates re on backwards. It wont work like that- ever.
Other advice, although he CX racing headers are cheap and effective, the primaries and collector are WAY to large unless you want 1500 HP+. Exhaust velocity is key for making turbo systems responsive. Cam, runners size and length all have a factor in this. Stock manifold and 2 inch up pipes make 1200hp and spool good for a reason!
But, I think fixing #1 will fix your issue. Also make sure the fire ring is in there or again, it wont work.
And to those that thing this wont "work"- here is bigger twins on a smaller motor in my 6 speed 900whp RX7
Yes, #1 gates re on backwards. It wont work like that- ever.
Other advice, although he CX racing headers are cheap and effective, the primaries and collector are WAY to large unless you want 1500 HP+. Exhaust velocity is key for making turbo systems responsive. Cam, runners size and length all have a factor in this. Stock manifold and 2 inch up pipes make 1200hp and spool good for a reason!
But, I think fixing #1 will fix your issue. Also make sure the fire ring is in there or again, it wont work.
And to those that thing this wont "work"- here is bigger twins on a smaller motor in my 6 speed 900whp RX7
Thread Starter
Launching!
Joined: May 2013
Posts: 270
Likes: 30
From: Detroit
I drove the car a little more. When I get into it, the car is a handful to say the least. It’s all over the road.
So so I took my son with me and he was watching the boost gage.
We we were able to observe boost probably~15 at peak times at high RPM. It’s hard keep an eye on even for a passenger.
I am am still considering downsizing the exhaust housing. Based on the feedback I’m getting, the boost will come on at a lower RPM and perhaps not as violently
So so I took my son with me and he was watching the boost gage.
We we were able to observe boost probably~15 at peak times at high RPM. It’s hard keep an eye on even for a passenger.
I am am still considering downsizing the exhaust housing. Based on the feedback I’m getting, the boost will come on at a lower RPM and perhaps not as violently
Thread Starter
Launching!
Joined: May 2013
Posts: 270
Likes: 30
From: Detroit
TECH Enthusiast
Joined: Dec 2017
Posts: 676
Likes: 72
Dont drive it anymor till you fix the wastegates. You said your on the base tune hitting 15 pounds. Your basically driving a lit firecracker. Get the .68 housings. Get it tuned and imho get a progressive boost controller. I honestly feel a probrammable boost controller is a must. But thats my opinion and like butts everyone has one.
Thread Starter
Launching!
Joined: May 2013
Posts: 270
Likes: 30
From: Detroit
Yes I agree, I was not expecting to see any boost at all.
I was planning to just use a manual air bleed type controller.
I cant say I"ve researched it a lot, but my perception is the Electric is more of a nice to have., to optimize performance.
I may have more than I can use on the street with street tires.
I have a couple calls into On3 and my tuner to discuss the 0.62 housings as well.
I was planning to just use a manual air bleed type controller.
I cant say I"ve researched it a lot, but my perception is the Electric is more of a nice to have., to optimize performance.
I may have more than I can use on the street with street tires.
I have a couple calls into On3 and my tuner to discuss the 0.62 housings as well.
Thread Starter
Launching!
Joined: May 2013
Posts: 270
Likes: 30
From: Detroit
So bought the 0.62 housings. Remarkably smaller. Have to cerakote them and install soon.
I also went to flip the waist gates. Unfortunately the flanges are different sizes. The mating flanges are welded on the elbow and dump pipe. That is going to be a real pain.
Any thoughts? Adaptors?
I also went to flip the waist gates. Unfortunately the flanges are different sizes. The mating flanges are welded on the elbow and dump pipe. That is going to be a real pain.
Any thoughts? Adaptors?
So bought the 0.62 housings. Remarkably smaller. Have to cerakote them and install soon.
I also went to flip the waist gates. Unfortunately the flanges are different sizes. The mating flanges are welded on the elbow and dump pipe. That is going to be a real pain.
Any thoughts? Adaptors?
I also went to flip the waist gates. Unfortunately the flanges are different sizes. The mating flanges are welded on the elbow and dump pipe. That is going to be a real pain.
Any thoughts? Adaptors?
Andrew