external wastegate arrangement

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TURBOCITYCITY
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external wastegate arrangement

Postby TURBOCITYCITY » Tue Feb 12, 2008 12:02 pm

hi

my t2 engine is undergoing a full stripdown and performance rebuild and while it's in the shop I took the oppurtunity to remove the exhaust manifold and put thought into the placement of my tial 38mm external wastegate and 3 inch dumpy.. should I sit it right near the turbo at an angle to reduce turbulance? or is it more advisable to just jut it off a little way down the pipe..
I am planning on pairing it with a turbosmart single stage electronic boost controller for more precise control.. do I set the controller at the same psi as the spring in my wastegate? I know that an external wastegate is a more effective mechanical means of regulating boost but I'm not sure if improved performance or atleast more precise boost control can be achieved by installing it along side an electronic controller

what do you guys think?

Caleb

:?

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Postby TURBOCITYCITY » Wed Feb 13, 2008 9:25 am

replying to my own post.

what is the general consensus here on externally gating a t2?

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Postby TURBOCITYCITY » Wed Feb 13, 2008 4:54 pm

the disapproving weight of silence...

guys?

I searched through previous posts for any info on external wastegates
in city turbos but the results were minimal and nondescript.. just thought
someone might have more of an idea than me how to run an effective external gate with electronic boost control.. not too sure how the city engine would respond to such a setup. keep in mind I'll be running 18.5psi boost

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Postby James » Wed Feb 13, 2008 5:13 pm

OK, where do you intend to take the feed for the wastegate? Unless you are building a custom manifold you will need to weld to some cast iron somewhere, generally not a pleasant thing.

You will build boost slightly faster with an external wastegate, as you can use the boost to hold the gate shut, but with a boost controller a factory T2 turbo will build boost DAMN wuick anyway.

So you really dont need it, sure its cool but its really not necessary. A good boost controller should hold you at 18.5 easy, thats only like 6psi above factory boost. It only gets dodgy when you try and go like more than twice factory boost.

So my opinion is, hone out your factory wastegate, and sell the external to get more money to spend on getting a good tune, either a re-graphed dizzy for 96 or 98 octane gas or some form of fuel management you could do with both.

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Postby si » Thu Feb 14, 2008 5:08 pm

Unless you are running a bigger turbo and making a new manifold don't bother. If you are having boost control issues then grind out the internal wastegate a bit and use a decent controller and it should hold boost fine. As for the external gate with stock turbo, if you plan on using a screamer pipe then it's going to sound like arse because it will pretty much always be open.

Do as bigelboe says and spend the money elsewhere 8)

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Postby TURBOCITYCITY » Fri Feb 15, 2008 5:16 am

money isn't really a huge issue.. I'm getting $23 an hour at affco so I can save all I need in time...

as for the turbo I'm planning on using a ca18det and I won't be using a custom manifold I'm paying a shop to modify my existing cast iron manifold to accomodate the external.. bit of boring and welding is all it takes.. they're qualified welders I'm sure they can hack it. I just figure I should squeeze every bit of performance out of it as I can.. and I think external wastegates will always have a little over their internal counterparts in terms of spool time and...well... sheer coolness :D the fueling system is getting work done as well... I'm going to revert to the stock injectors and install some kind of pressure regulator that's adjustable and wire it to increase fueling with boost.. the heads also getting race ported as well as stainless steel valves and my cam is getting ground to the mugen specs... figure all this with a few other basic mods such as 3"dumpy with 2 1/2" exhaust and some others should bring me up around the 160hp mark... I eventually plan on incorporating some form of more advanced engine management...maybe an apexi unit but I'm not too knowledgeable in this field so would have to pay someone to get it all in.. :oops: damn expensive but worth it to build the a hothatch street rocket... can't wait to shit all over the damn near endless hordes of skylines and wrxs

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Postby James » Fri Feb 15, 2008 10:11 am

I would definately recommend you get a proper manifold made up, you are gonna want every little bit of help with spooling that turbo.

Otherwise it sounds good, who are you getting to do the engine and head work?

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Postby TURBOCITYCITY » Fri Feb 15, 2008 3:08 pm

I would like to get an equal length tubular manifold like you are doing with your 200hp build but I don't have access to a welder or the fabrication skills required to produce one...I would love to pay someone to make one but my mind boggles at what they might charge... getting the rebuild and engine work done at engine rebuilders in Wanganui and planning on getting it tuned up at mag n turbo warehouse in palmy

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Postby TURBOCITYCITY » Fri Feb 15, 2008 3:10 pm

you should make me one I could pay you a coupla hundie or whatever

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Postby James » Fri Feb 15, 2008 8:03 pm

You should be able to get a steam pipe one made for 3-400. I would love to make one but my welder got stolen 2 weeks ago :(

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Postby TURBOCITYCITY » Sat Feb 16, 2008 4:48 am

oh man... that sucks man. those thieving bastards never give up... :x
hmm.. where could I get one made though? would any engineering shop do it ya reckon? I guess I'd have to give them my old manifold to compare.. have you got any diagrams of the design for 'equal length tubular manifold'? I'm guessing it's just as the name says... all 4 pipes equal length and relatively free of bends, all tubes merging at the turbo end.. where would you put the wastegate on such a thing though.. just by the turbo connecting to a short pipe at right angle to the pipe?

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Postby TURBOCITYCITY » Sat Feb 16, 2008 10:29 am

si wrote:As for the external gate with stock turbo, if you plan on using a screamer pipe then it's going to sound like arse because it will pretty much always be open.


how do you mean always open?...
the gate shouldn't open until it's reached the boost rating of the spring inside... which is 18.5psi.. so it will only open when driving at full boost..

...right? :?

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Postby TURBOCITYCITY » Sat Feb 16, 2008 10:38 am

I mean... my understanding of an external wastegate is a mechanical pressure bleed valve so one would naturally assume that if the mechanism is rated to 18.5psi, it would only open when such pressure is attained...

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Postby TURBOCITYCITY » Sat Feb 16, 2008 10:53 am

oh also... bigelboe where did you buy your steam pipe? it'll no doubt cost me a large amount less if I can supply materials...

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Postby James » Sat Feb 16, 2008 11:15 am

TURBOCITYCITY wrote:oh man... that sucks man. those thieving bastards never give up... :x
hmm.. where could I get one made though? would any engineering shop do it ya reckon? I guess I'd have to give them my old manifold to compare.. have you got any diagrams of the design for 'equal length tubular manifold'? I'm guessing it's just as the name says... all 4 pipes equal length and relatively free of bends, all tubes merging at the turbo end.. where would you put the wastegate on such a thing though.. just by the turbo connecting to a short pipe at right angle to the pipe?


Any old engineering shop could do it but they will generally charge a lot more than somewhere more suited to doing the work, like a performance car workshop.

Do some googling and searching on Honda-Tech to find some turbo manifold designs, its not as easy as copying the factory manifold, you would need the whole car avaiable in order to make one that sits everything optmially.

External wastegate positioning is something that is quite critical to good boost control, its very easy to get wrong. I suggest you read Maximum Boost by Corky Bell, there are PDF copies available online.

Si means that with a factory turbo it is very easy to get to full boost when you have a decent boost controller on, so you would be screaming a lot. I recommend to not get a screamer either, they are gay and noisy and make it harder to get warrants.

Steam pipe and bends from Fletcher Easysteel, see phonebook for contact details.


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