I'm sure this gets asked & answered about once a month, but unfortunately I don't know enough about the Garrett part numbering system to make much sense from what I'm getting out of search results.

A friend currently has an older FMII system on a 1.6. So I'm assuming that this is a GT25xx series turbo. The motor is just about gone and he's thinking about doing a 1.8 upgrade, retaining as much as practical of the present turbo setup. So at the very least we're looking a new manifold and probably a custom downpipe. Additionally, he'd like to explore doing an external wastegate setup.

Problem is that as soon as we start talking something other than the Mitsu TD04H I get a little lost. I don't know a T03 from a GT35R.

Are there any good manifolds out there to fit this turbo which either have a wastegate port already installed, or are of tubular design such that one could be easily added by someone more competant with a TIG welder than myself?

Or under the premise of "teaching a man to fish" perhaps someone could instead point me towards a primer on the various manifold flange styles and their cross-compatability? Ie: are the terms "GT25" and "T25" referring to the same design?

 

As he already has the downpipe just order the 1.8 mani from fm.

 

GT25 is basically a T25 sized turbine. It uses the same inlet and ALMOST the same outlet. There's a different downpipe hole pattern.

ATP has a flange that illustrates the point but their website is sucking *** at the moment.

 

Ok, so a manifold built with a "T25" flange will mate to a GT25 Turbo. Thanks.

I didn't even think about ATP- but they too had some helpful info on the subject.

FM and Bell manifolds are all cast as far as I know. Cast manifold = very hard to mate an external WG to.

 

Look at Bell's Stage 4 and stage 5 manifolds. It's exactly what you're looking for. The S5 is designed for external wastegate.

<edit> I think it'd be tough to put an external gate on the S4

 

And the Series 5 is for T3's, plus I'm not sure the FM downpipe would mate up to those.

 

HKS but as you mentioned.. external wastegate= no no

 

JGS might make you one if you ask.

 

I was thinking about that. They have a pre-built "generic" 1.8 BP manifold in the kit section, and they sell a T25 flange in the DIY section. Probably be best to buy them seperately and take them to a weldor so that perhaps the turbo can be mounted in such a way as to re-use some of the old downpipe.

Thanks for the good ideas, guys. I'll pass it along.