lemming104

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.

mshadow

I have twin 71/73s .88 AR on 5.3 no issues making boost on the street, on 2step or anywhere else for people saying twin 70s is excessive.

lemming104

At what RPM does it start making positive pressure, and at what RPM do you make full boost?

Project GatTagO

iTrader: (7)

I would address the waste gate plumbing issue first. Again, we are not talking about how the dome ports are plumbed, but how the exhaust is routed. From the collector the exhaust should go to the bottom port (opposite the dome) and exit out the side.

Andrew

spray280

iTrader: (5)

Like Lemming said, they are mounted wrong. The way they are mounted if it would make boost there would be 0 control.
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.

47ford

Turbos are fine buddy, get the little bugs worked out and enjoy. I have a friend who has twin 78/75 on a 6.0 and sees positive pressure around 3800.

panda240ss

now that you say it, im totally confused how he put the wastegate?

3 window

iTrader: (1)

Curious as to how they’re installed since the gates are plumbed backwards?

panda240ss

guessing he switched it up. but thats just weird. its a clean build though!

Jwooky

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.

Project GatTagO

iTrader: (7)

You are right in the fact that the waste gates are not functional right now.

Have you done leak down testing of the hot and cold side? Is the blow off valve plumbed properly?

Andrew

Jwooky

No I think that is my next step. I have an idea how to do the cold side. Going to get a 4" PVC cap, drill a hole and put an air compressor fitting in it. Silicone couple that to the compressor wheel inlet.

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.

coltboostin

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

Jwooky

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

3 window

iTrader: (1)

Sorry if I missed it, but what type of boost control are you using?

Jwooky

none. Just wastegate spring, but since they currently backward I essentially have nothing

jordoza

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.

Jwooky

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.

Jwooky

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?

Project GatTagO

iTrader: (7)

You may not want to hear this, but my thoughts are that you need to take it all apart, get the grinder and welder out and redo it.

Andrew