When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
One pull with the gates open and he'll be cutting a hole in his downpipe and recircing them. Mark my words!!!
I know you mentioned your last manifold cracked...any idea what cause it to crack? Think it was expansion related without enough flex or just a case of a failed weld due to contamination and not full pen?
I am by no means a welding expert or even remotely close to that status so please don't take this the wrong way but I see what appears to be porosity in your o2 housing before your downpipe. Is that the case? Have you thought about getting a dual flow regulator so you can back purge the inside with some argon? Can understand now wanting another cylinder but a simple reg swap and hose with aluminum foil might make all the difference there. Alternatively I know some folks have had success using flux so might be interesting to try that out and see how it works for you.
After all these years of always running recirc gates, I'm surprised to see you go external.
I'm just curious to see how much power it makes with open gates before I decide what to do longer term. I ran open gates on my 240Z 19 years ago
Originally Posted by heel2toe
I know you mentioned your last manifold cracked...any idea what cause it to crack? Think it was expansion related without enough flex or just a case of a failed weld due to contamination and not full pen?
I am by no means a welding expert or even remotely close to that status so please don't take this the wrong way but I see what appears to be porosity in your o2 housing before your downpipe. Is that the case? Have you thought about getting a dual flow regulator so you can back purge the inside with some argon? Can understand now wanting another cylinder but a simple reg swap and hose with aluminum foil might make all the difference there. Alternatively I know some folks have had success using flux so might be interesting to try that out and see how it works for you.
There is definitely not porosity in the welds that is for certain. It just looks way because the garage is very dark so if I take it in the sun it is colorful. I clean the inside of the pipe to bare metal and then apply SolarFlux B, which creates a inert barrier on the inside similar to purging. The SolarFlux can pull into the weld and combined with the fact I didn't wire wheel the outside it can cause a dulling due to slight contamination. If I wiped off the ends and really cleaned the outside it looks like a rainbow, but I just don't care enough on downpipes because they almost never have an issue. With that said, I clean the pipes thoroughly inside and out when doing the header and wipe it down with acetone to keep contaminants from entering the weld.
I also think some of it has to do with the fact I went with 321ss bends vs the 304 I used on my short runner. That manifold cracked once on a runner after a few years of use, but I welded it with a high nickel rod and it never had an issue again even after several years. It was likely something I did wrong that caused it to crack, but who knows.
Last edited by 240Z TwinTurbo; May 14, 2020 at 03:45 PM.
This is what I was referring to but I can also totally understand lighting playing tricks on what Im seeing
Please understand that I wasn't trying to be negative whatsoever. Personally I've only been welding for 10 years, started with stick then bought a MIG and now have my TIG welder going on a couple years. I am always curious of other people's process in terms of prep, filler metal used, shielding gas techniques etc so I can learn and better my welding.
You clearly have some sort of engineering background so I was really interested to hear your thoughts on what you think could have caused the cracks so thank you for the additional color. This is an open forum and I learn by asking questions and getting feedback from those who know more than me on the subject matter in hopes that I can apply the knowledge down the road. And glad to hear you too have positive experiences with solarflux. The majority of my welding has been basic A36 mild steel so little bit more forgiving. Im starting to play around with some stainless and thought I would grab a dual flow regulator but also wanted to give the flux a try and see how that works for now.
Anyway, keep up the good work and good luck getting her back together! Miss my evo...one of these days I'll finally have pistons again and then I too can party!
It's all good and because it is my car I can do whatever I want. That blackish looking stuff is just the solar flux and dirty used pipe surface rising to the surface, which comes right off with a wire wheel. When I used to fabricate for people 17 years ago I made sure to prep everything really well before welding. I was welding several times a week for a few years back in the day, but do it only a few times per year these days and only for my personal stuff. I can't imagine the cost to have this stuff done by a professional!
The pic below is two virgin pipes that were not cleaned on the outside prior to welding.
I know I have some explaining to do, but all in good time. The vaccum pump, block vent (-10 from valve cover) and intake manifold PCV will all connect to this one can. I put an extra -10 AN male fitting on the top in case I want to tie in the -10 AN breather from the oil filler cap, which I have sitting on my bench. Made progress, but not finished.
PCV tank is complete and I started the car today a few times just to check for leaks and start burping the coolant. I hooked the PCV can to my boost gauge so I could read the vacuum in the can and here are the results from idle.
With the pump off and car at idle, the can registers atmospheric pressure
With the pump on and engine off, the can pulls -3in.
With the pump on and engine on, the can pulls -6in at idle.
When I pulled the PCV valve off the can during idle, the vacuum was not consistent and very weak so I suspect the PCV valve is sticking because the can vacuum should be close to the intake manifold vacuum. I will clean it out tomorrow with carb cleaner and try again.
Waiting on a silicone outlet hose and a dang rubber isolator for the pump so should be wrapped up Saturday by noon.
I think I figured out the PCV valve issue. I cleaned it thoroughly with carb cleaner and then started playing around with it trying to figure out why it flows well sometimes and not others. Essentially, it has a metal stopper that slide back and forth within the tube and a spring on the end towards the hose barb side. Essentially, the valve has to be angled down in order to work properly or the stopper blocks the flow. I had an extra 90deg so I added it to the PCV can to angle the valve down about 60deg. Unfortunately, the lift is right below the master bedroom so I dare not start the car with my wife asleep!
When the car is off boost the intake manifold draws a vacuum on the can, which is connected to the valve cover vent via a -10 AN line. Although the can is also connected to the vacuum pump, the vacuum pump outlet is connected to a catch can that has a one way valve so you can only blow through it.
When the car hits boost a hobbs switch kicks on the vacuum pump at +4psi. The intake manifold pressurizes the one way PCV valve and closes it so the vacuum pump is hooked directly to the -10 AN valve cover line. The pump then pushes the air to the catch can and past the one way valve going out only.
There is a point between 1psi and 4psi where the intake manifold PCV is closed and the pump is off. However, at this point the system acts like a VTA setup as any positive pressure can push past the one way valve on the catch can.
So the car is officially running again and I took it through the initial heat cycle to burp the coolant. I will take it through one more heat cycle before I start tuning.
I figured out why the can was not registering any vacuum at idle, which is due to the catch can one way valve leaking. If I cap off the line at the PCV can or at the catch can it reads -2", but with it hooked to the can it pretty much reads 0. When I go cruising and the car is off boost it will hover between 0 and -1" so I need to replace the valve on the catch can with something more sensitive (for several reasons). You can find attached a video of the vacuum gauge when the car is cruising and the vacuum pump is off.
So I then proceeded to go into boost, but remember the pump does not cut on until 4psi based on the Hobbs switch. While there is a one way valve to relieve pressure on the catch can when the car is between 1-3psi of boost, the PCV can was registering 1psi of positive pressure prior to the pump kicking on when I slowly went into boost. I need to change the Hobbs Switch to kick on at 1psi of boost. The good thing is that once the pump kicked on the PCV can registered -4" of vacuum. You can find attached a video of the vacuum gauge as I went from off boost and slowly increased boost until it kicked on the vacuum pump.
Not quite there, but I think I have it figured out.
So I pretty much got it dialed in after about 10 passes. The new turbo lags about 400rpm with the 66mm compressor vs the 62mm compressor. VD results are not showing any significant change in power despite running more boost, 1 deg more timing, open wastegate dumps and no CAT. Going to do a boost leak check later to make sure I don't have a leak issue. Otherwise, going to stick it on the dyno and see what it does! Might just swap back to the 62mm if the change is not significant along with recirculating the gates. BTW, the gate noise is not that bad, but I prefer the sound of turbo!
May 14, 2020, 12:47 PM
