Cast manifold and dump fit WRX turbo to 1.8L MX5

[omx500]

Hi everyone. I have been thinking about going turbo on my NA8 for some time (years). I was browsing on eBay the other day and found this manifold and dump pipe advertised from a UK based seller. It seemed such a good idea, given the quantity of cast off WRX TD04L turbos, and their approximate sizing matching what we need, that in an uncharacteristically impetuous move I hit 'buy it now'. So apparently I have a summer project! Like everyone I am pretty busy these days, but I am hoping that with a regular hour here and there I can get this up and running on my NA8 by the end of February when local track days, hill climbs etc begin. I figure I need to have a goal or it will just take forever and I will lose interest. With the first shot fired I have gone to eBay again and bought a little generic intercooler and a kit of alloy intercooler bends with silicone sleeves and stainless clamps. Then I went down to a local speed shop here in Hobart which specializes in Subarus and rescued a GC8 TD04L and a GT Pumps GTPS01 from the scrap metal bin so I have something to join the manifold to the dump pipe to start trying to set things up. I have worded up same shop that I am in the market for a good condition cast off and apparently something is in the works. The throw away turbos had some useful looking pipe fittings and things and I even wondered if the GTPS01 might even be worth rebuilding - it was not leaking or burning oil and both wheels are good, but has shaft play. So, other than the turbo to come, that should hopefully be all the big bits I need. Everything else I will deal with as it comes up.

I thought there may be some interest in this newly available item so decided to post up here. If it is in the wrong place please let me know. I hope the pictures come out as I have never posted one here before.

Thanks for reading this far, Omar

[smy0003]

Looks like it'll need to be externally gated?
The more options there are, the better, so thanks for posting.

[omx500]

Looks like it'll need to be externally gated?

Thanks for your reply. There is no provision on the manifold for an external wastegate. I think the extra cost and complexity is not what this manifold solution is about. The internal wastegate on my TD04L opens just under 80 degrees when bolted onto the dump pipe which is heaps enough.

[smy0003]

That's good news, from the pictures it looked like an internal gate would not be able to swing far enough outwards due to the dump.

Sent from my LG-H815

[NitroDann]

Looks great it probably works really well.

Dann

[datfreak]

subed - nice find! Is that manifold secondhand or new, looks to be in very good condition.
Does td04 have the same flanges as td05?
Obviously built engine but

[omx500]

subed - nice find! Is that manifold secondhand or new, looks to be in very good condition.
Does td04 have the same flanges as td05?
Obviously built engine but

Yep new. In WRX turbos there are TD04 and TD05 with same inlet and outlet patterns. I'm pretty sure a TD04L done right would be OK on a standard motor. Cheers

[omx500]

First session of actual work on the project went OK. I had a bunch of now superfluous stuff on the inlet side to remove - then had to find the standard parts I 'put away somewhere safe' about 5 years ago.

[omx500]

Manifold fitted on beautifully. Had to turn the CHRA to get the drain to face down. The compressor cover seems to have best clearance with the outlet facing slightly upwards of horizontal as this is the smallest radius. First picture of turbo mounted is GC8 TD04. Second is GT Pumps GTPS01 which looks like it is based on a TD05-16G. Clearance is similar. Haven't worked out how the rotation will affect mounting the wastegate yet....oops picture order seems to be reversed. Picture annotations are correct.

[omx500]

Had to rotate the power steering pump inlet pipe to clear the compressor cover inlet. There seems to be a second position it can be moved to if I drill and tap a cast start hole. This will make the power steering pump inlet pipe sit vertically which is better for packaging anyway. Will move the power steering reservoir as it is in the way of my proposed path to the intercooler. Of a bit more concern is the dump pipe which at the moment cannot be fitted to the turbo as it is fouling on the horizontal rib on the firewall. I have drawn in blue pen the amount of material I think will need to be removed to make it fit acceptably. Seems the same with both turbos (photo is with TDO4L fitted). I'm not going to cut anything until the turbo I have ordered (Mamba GTX2860RS) arrives so I can check exact fitment. Also, just remembered that the heater pipe mount usually bolted to a lower exhaust manifold flange bolt will require minor reprofiling to fit on the new manifold. No biggie, but mentioned for completeness (no picture yet sorry).

[omx500]

Just a couple of quick photos of the heater water return pipe mount tab which required modifying to fit the new manifold. I have been in contact with the manifold manufacturer who advises that the interference of the dump pipe with the firewall has been previously noted. Depending on tolerances small modifications to the firewall have been required on NA8C and NB8A. He has also sent me CAD of a new dump pipe he is working on. I have ordered one of these for when they are available and will document changes including dyno differences. He also sent me photos of other installs which have given me ideas for mine. I have been waiting for my local speed shop to open to order new braided line fittings to move my oil cooler and filter remote mount. Should make a bit more progress this week (hopefully).

[omx500]

Looks great it probably works really well.

Dann

BTW thanks for the vote of confidence in the manifold. I have plenty of respect for your technical opinion and appreciate the time you take to share and assist.

[omx500]

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Final picture of the power steering pump inlet. With it rotated anti-clockwise as shown it is well away from the compressor inlet. The locating pin and bolt hole were already there. Had to tap the bolt hole with M6x1.0 bottom tap, but no drilling required. Thank you Mr Mazda.

[omx500]

I used to have my remote mount for the oil filter on the passenger side right where the compressor outlet needs to run. The oil cooler core was in front of the radiator, and the oil was always too cold so I had to go around with a piece of cardboard in front of the cooler (I do live in Tasmania after all). So pulled the whole lot out, moving the core to behind the radiator on the driver's side, and the remote mount over the driver's side front strut tower. A few things to get around but got there in the end; only had to make one hose twice, so better than average really.

[omx500]

I know this is supposed to be about the manifold but just in case anyone is interested, here are some photos of my intercooler installation. The core of this unit is 550mm wide x 230mm tall. It is of bar and plate construction and looks to be a perfectly adequate unit purchased from a reputable Australian seller (business) on eBay. I fitted the intercooler without removing the front bar cover, which I was relieved about as I hate bodywork. Removed the 'grille' from inside the bar cover, the undertray and pushed everything up from underneath. There are some very thoughtfully provided brackets in front of the radiator (thank you again Mr Mazda)

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to which I bolted this simple frame

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and put some rivnuts in the top of the intercooler (no mounting bosses provided despite them appearing in the photo of the item on eBay)

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then just bolted down through the frame into the top of the intercooler. It all seem to fit in pretty well and the outlets are in a pretty good place to send upwards into the engine bay.

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