External wastegate placement, need advice

[s13redmon]

Well, I'm rebuilding my CA but I'm putting it back together with an gt2560r. My only dilemma is where to put my wastegate. I'm thinking about flattening out the spot right above where the turbo bolts up and drilled it out to match the wastegate flange and then threading the holes for studs so I wouldn't have to worry about any welding (or cracking) of the cast manifold. What do you guys think?

Here's a pic of where i wanna put it.

[boost_boy]

If you must use this ridiculously difficult manifold, it would be wise to weld a steel goose neck and mount your wastegate to said goose neck.

[float_6969]

You're gonna have a REALLY hard time welding to that thing. If you decide to go down that path, make sure you get it centered over the internal divider.

[s13redmon]

So you guys think it would be better to weld it rather than bolting it there? If I went with the bolt route i would have a machinist mill it down for my gasket surface.

[sjbsuperman1425]

what I think they are saying is welding the flange onto the manifold that the wastegate will bolt to, which welding Cast Iron is quite difficult and will probably be very costly.

Why not just use the wastegate that comes on the turbo, or upgrade to an HKS internal wastegate?

[s13redmon]

Yea, if I do get it welded to the manifold I'm gonna let a pro do it, I can weld decently but I don't wanna eff this up lol But I'm using an external because the wastegate flap on my turbo was welded closed when I got it and I already have a brand new tial 38mm sitting in my room. Plus I've heard that externals work a lot better for higher boost, and I'm planning on running around 16-18 psi.

[BQ.05.TD]

cut hole at base of rear housing
weld desired pipe onto housing
weld gate flange onto pipe
bolt gate up to flange

have fun enoying the neighbours

[float_6969]

...Plus I've heard that externals work a lot better for higher boost, and I'm planning on running around 16-18 psi.

BLECH, not true! I have a friend that runs 20psi on an internal waste gate turbo. Works just fine. Here is when you need an external wastegate;

You have mis-matched turbo that has a small turbine side, and a big compressor side, as the turbo spools up, it settles at your wastegate pressure of 18psi. But as you continue to rev, the boost creeps UP to 25psi by redline. Your internal wastegate is too small to bypass the extra exhaust gasses, so the turbo spools faster once the internal wastegate opens all the way. So if you want to run 18psi on this setup, you need an external wastegate.

Now here is another scenario. You have the same, mis-matched turbo, only you want to run 27psi on it. The turbo will spool up, hit 27psi, but falls down to 23psi by redline. This can be caused by 2 different problems. The first is that you're over-revving the turbo, and it can't move enough air to make 27psi of boost pressure at redline. The second is that the spring in the wastegate is too weak to hold 27psi. If the turbo is big enough to make the boost, but your not keeping it, then you can still use an internal wastegate, you just need a stronger spring it in.

That friend I mentioned that was running 20psi on an internal wastegate was talking to me when he first installed it and complaining about the performance. I asked what the symptoms were, and he said that the turbo would spool up to the 15psi that the wastegate spring was set for, but by the time he got to redline, it was creeping to 20psi. I asked if he was leaning out or detonating at 20 psi, and he said he wasn't. I told him to buy a boost controller and run 20psi, then he wouldn't get boost creep anymore.

Same thing happened to me when I first had my T28 on my CA. I was trying to run low boost on it because I was waiting for E85 to be available in my area. But the combination of my high compression, ignition retard to fight detonation, and excess fuel to fight detonation, left so much energy in the exhaust that I'd hit my 5psi wastegate pressure, but at about 5K, it would start to creep, and by redline, I was up to 10psi. I had to take my redline down to 6K so that it wouldn't detonate until I could get to some E85.

[r34 gtr]

Being the genius that I am, I believe I have devised a perfect solution for your wastgate woes.

heres what you need to do:

First, go get your Tial wastegate. Now go get your camera and take some pictures of it.

Once you have done that, go to your computer and upload those pictures. Now create an eBay auction with the title "Tial 38mm WG for sale"

Wait for someone to buy it.

Now take your turbo and bolt it up like you normally would. Ignore the fact that there is no wastegate attached.

Now, and this is important, take the money you got from selling the Tial wastegate and use it to buy beer. Lots of beer.

Tune car for 25psi (you'll be fine, the gt28 is tiny) and congratulate yourself on a job well done by drinking the beer you just bought.

Huzzah!

If you need any more help, Ill be here all week.

[dash]

turbo fords
buick GNs
mkIII supras
1st gen 300zx
DSMs....
ALL upgraded their stock turbos and surpassed 450-500hp still using integral wastegate. Most with manual boost controllers too
Float outlined the reasons why int wastegates often get blamed. Set up wrong

[sldwys]

On my mrs. Ca18det, Were running a garrett gt3071 with an internal gate, Goes awesome, 18psi ( run in boost on new engine ) by 4,200. and IT hold 18 all the way. Weve also had it at 25psu on dyno and it held fine. Im running an external on mine, Beause My gt3540/t04z hybrid has no internal gate.

[float_6969]

Tim and I will actually be helping you to consume that beer. I'm sure with all of this great advice you've received, you'd be more than happy to share, right?

[s13redmon]

Thanks for all the help guys lol but Tim is joking about running it with no wastegate right? I mean will it just stay within its efficiency range?

[s13redmon]

Here you go lol

[float_6969]

Read that again, Tim is telling you to ditch the external wastegate and just run the internal wastegate, and if needed, buy the HKS actuator, but you won't need it, trust me.

[s13redmon]

Oh, I can't use the internal wastegate, the flap is welded shut, thats the only real reason I want to use the external. I didn't realize it was welded shut before I bought it and now I have this dilemma.

[sjbsuperman1425]

you could always buy this to revert back to the interal wastegate if you wanted. If you can get the flange welded to the manifold and have everything pan out to be cheaper than this housing below, do that. But in all honesty, this housing is the less painful way to take.

http://www.atpturbo.com/mm5/merchant.mv ... y_Code=GTH

[s13redmon]

Yea, I was thinking about doing that, I might but I'd have to buy an actuator too. For what its gonna cost to use this turbo I could have bought a new one lol. On a side note, have any of you used an e-mance tune? I'm thinking about it but I want a little more input. I was thinking about using it is a base tune and tweaking it with my safc. I know a standalone would be better but I don't really have the money for that and I already have the safc and an innovate wideband.

[sjbsuperman1425]

why not try and source a new turbo then? lol The big thing to me for your plans is the cast iron and having it welded.

[s13redmon]

yea i know lol but i payed 600 for it not realizing it was welded. what if I got the flange welded to the exhaust housing though?

[float_6969]

If ur dead set on getting a flange welded to the stock manifold, you just need to make sure the opening of the flange is centered EXACTLY over the divider so that you're exhausting equal amounts from both ports.

[s13redmon]

Oh yea I was definately gonna do that if I put it on the manifold, I guess I'm just gonna try that and if it cracks then I'll buy a manifold, I'm gonna let a better welder than me do it though lol. I'll let you guys know how it works out. What about e-mance though? Any of you guys have experience with his tunes?

[float_6969]

Ran one on a KA-T that I built. Worked great.

[s13redmon]

Alright, thanks man, i want nistune but if I don't do that then I'll get an e-mance tune.