After ill-health put my 13B REW project on hold (engine in, fuel system done, lots of work on the rest), a Greddy turbo RX8 came my way at a price that I couldn't really refuse. The conversion was done professionally 20,000 miles ago and the engine was rebuilt by a highly-respected rotary specialist and ECU changed 9000 miles ago.

She has been resprayed in white and has a carbon fibre bonnet and trunk. White is rare in the U.K., limited to less than 500 40th Anniversarys and R3s.

Alas, the compressions are rear 5.3 and front 6.2 normalised, so my general plan is to run her until the engine goes bang then convert her to 13B REW, in the hope that by then I'll be fit to do it. I'm getting the current project car stripped and all the bits stored.

Pics and full description to follow.

I look forward to discussing all things Greddy here.

 

Here is the description:
2004 model RX8 231 69800 miles M.O.T. 22/1/17 fitted with Greddy Turbo kit.
Engine fully re built by Haywood Rotary 7200 miles ago with custom rotors & porting.
At the same time the turbo was fully rebuilt and the Greddy ECU upgraded to an Adaptronic select custom built ECU.
This car has been extensively modified to a very high standard. Some of the parts fitted are;
Full body kit.
Carbon fibre bonnet.
Carbon fibre boot lid.
Carbon fibre roof wrap.
Carbon fibre splitters.
Mazda Speed forged monoblock ali wheels (very rare)
Eibach Federn wheel spacers.
Falken 225-14 SR18 tyres nearly new.
B.C. fully adjustable front & rear suspension professionally set up by Hayward.
Greddy front strut brace.
GT Spec rear strut brace..
Racing Aluminium Koyo radiator.
Personal plate T60RXB
Swoosh SM68 gauges fitted to top centre of dash (Oil Px. Water temp & Boost)
Steel sump guard plus steel air scoop deflector.
Cat 1 Sigma S Series alarm.

There are a few things that need sorting though: new battery & uprated starter motor, clean underside & underseal, replace missing front wheel well splash guards, build ducting for radiator and intercooler, repair or replace gauges, check and sort fault codes (P0410 (Air System problem) & P2097 (target air/fuel feedback system too lean) and trace an intermittent power steering failure.

 

Had to read that a few times to understand exactly what is going on here . Hope your health improves quickly and good luck with the new car !

 

Right, time has moved on. I've had other priorities and have an R3 with winter tyres to drive and a 13B REW project car to strip, so I've put this on the back burner until the last few days.

Anyway, I've made progress on stripping things to see what I've actually got. I've a little bit of oil in the intercooler piping; this isn't unusual but in my case is probably due to a blown oil seal. I've decided to play safe and will be removing the turbo for either a rebuild or complete replacement of the CHA. I'd like to upgrade the CHA with a water-cooled one, but there seems no easy way of doing this without spending $2,000+ and taking a long turn-around time on a Mazdamaniac upgrade. There are no turbo rebuild specialists near me, so that leaves either doing a rebuild myself or buying a replacement CHA; I can't find any rebuild instructions, but as I presume that I'll need to get the CHA rebalanced I may be better off buying a CHA (around $500 here in the UK).

I also had a look at the intercooler and air intake pipe sizes and posted on the Greddy FAQ thread.

 

A quick update.

I decided to replace the intercooler piping silicone joiners, replace all clamps and have a look at improving flow in the 90 degree casting out of the compressor. There was a little bit of oil in the pipes so I decided to take the turbo and exhaust manifold off to check them over. The good news is that the manifold is in lovely condition, I learnt a lot about taking nuts and bolts off a Greddy conversion that has been on for a year or 2 and I saved a fortune by being stuck under a car rather than going to the pub; on the other hand, I'm not confident in the turbo oil seals so will be overhauling the turbo (time & money) and spent far more hours than I care to think about getting well-rusted nuts & bolts off.

For the turbo, I'd like to introduce water cooling and upgrade the compressor and turbine wheels. Unfortunately, the upgraded T618Z turbos that were available a few years ago are now no longer available or the supplier won't send to the UK. I've also drawn a blank finding someone here in the UK who can build what I want. I've therefore reluctantly resigned myself to keeping the existing oil-only cooling and wheel sizes. I did see a billet compressor wheel for sale from Kinugawa, although I'm wary as I have so far found nothing on its comparative performance; if I can't find anything relevant then I'll just replace the CHRA with a new one (yes, I could rebuild the CHRA myself, perhaps fitting a billet compressor wheel, but I know a few people who've come a cropper doing their own rebuilds).

I've also decide to swap the existing gauge set-up for a combination of 52 mm boost and oil pressure gauges in a vent pod, oil and coolant temperature digital gauge in the dash and a tablet in the sat nav enclosure from the orange car connected to the Adaptronic ECU; I may put a fuel pressure gauge in the ash tray. The existing gauges will go to my 13B REW conversion kit.

 

I’ve been having a crisis of conscience over the last few days. I started out looking to do, at most, a little bit of work on the car, primarily because my life is a bit variable at the moment. However, the more I looked at the Greddy kit and its installation, the more I wanted to change and improve it; and I’ve not been able to stop myself: for example, I took off the charge air (intercooler) piping intending to just change the couplings and ended up removing the piping, intercooler and turbo (a long and frustrating task as it turned out) then spending hours looking at all the options for improving the turbo.

I’m going to sleep on what I want to do: either put it all back together with the minimum of changes and work or go to town. If I went to town, as well as the issues I mentioned earlier, I’d look at the following:
• Upgrading the turbo with water cooling, a bigger turbine wheel, a bigger compressor wheel and adding an oil supply restrictor. I’ve had some useful inputs on this on the Greddy FAQ thread and have emailed a few turbo specialists to see if they can build what I want.
• Plumbing the turbo actuator into the compressor outlet and adding a boost controller linked to the Adaptronic.
• Plumbing the BOV outlet into the air inlet.
• Wrapping the charge air (intercooler) piping with insulation.
• Adding water injection.
• Adding heat protection to limit heating of the LIM and transmission tunnel.

 

A turbo shop not too far away say they can machine turbine housings so, after much soul-searching, I've decided to go for a mild update of my standard Greddy. I’ll be fitting a water-cooled 20g (52.5/68 comp, 67.1/58.8 turbine) CHRA rather than go for more power with a 57 trim wheel, which is always an option for later on.

Buying a compressor housing with a wheel and a wastegate actuator, for which I’ll be specifying a 0.5 bar (7.2 psi) spring, seems better than machining the compressor housing.

For the turbine housing, machining for the bigger wheel seems the lesser of the evils available as 8 cm2 housings are too small and replacing the T3 flange on a 12 cm2 housing seems too risky and expensive.

I'll sleep on the housing issues then order over the weekend.

 

Std 20g cast wheel or 10 bade billet ?

 

Not decided yet. There is a range advertised and I want to make sure that there has been some science behind the ones I get. I'm also suspicious that some I've seen may not actually be available as advertised.

To be honest, I'm still not convinced over the way to go. I seem to have lots of solutions that are 90% available but none that are 100%. Sometimes I think of just getting a water-cooked TD06 CHRA then putting in the existing wheels, relying on careful refitting to get balance, then doing a completely new job if it goes bang.

 

Perhaps you need to think about what it is you are trying to achieve first ?

The stock Greddy turbo works just fine and lasts a decent amount of time (when set up right )for a power bump to around 250whp .

 

Thanks. Intuitively I know what I want in terms of power, which is nothing fancy as I want usability on my poor-quality and crowded roads, with a secondary factor of wanting to limit stress on the engine; the standard Greddy is ok for this. My confusion comes from my wanting to do better, particularly as alternatives may not be that much more expensive than repairing my T618Z.

My first intention was to just rebuild the existing turbo but (forgive me if I repeat or contradict myself, my brain is mis-firing a bit today) I then had second thoughts over longevity, the quality of rebuild kits and stories of problems after owner rebuilds. Then I saw that T618Z CHRAs were relatively expensive (I can get a 20g water-cooled CHRA for 3/4 of the price of T618Z oil-cooled ones) and could help my mate out with my turbine housing if buying a new T25 20g housing was better/cheaper than getting mine machined (I owe my mate a big favour, so I'm keen to do a housing swap even though I really want to simplify things by saying 'no').

I took my housings and wheels off my turbo last night. The turbine shaft is in good condition so I may now just get that 20g water-cooled CHRA and swap the wheels over once I've confirmed that the shafts are similar. Unfortunately, I now have to go away for a week and so won't be able to do any more hands-on for a while; what time I have will be spent in seeing if I can do some DIY on her housing to get her back on the road for a while.

 

I had an unexpected few hours spare so had a good look at porting the exhaust manifold and turbo housing.

I was surprised to find that my initial checks from measuring the manifold and housing flanges were misleading. The width and length of the T25-size openings may have been within 0.5 mm (0.02") of each other, but spraying paint with the flange gasket as a mask showed that the openings were offset lengthwise by 2 mm (0.08"). I therefore decided to port both flanges, effectively increasing the flow area there by 3-4%.

As well as smoothing out the insides of the manifold and housing to meet the new flange opening and take out the worst of casting roughness, I ground out more of the turbo housing than expected as there were relatively large undulations in the surface.

I limited myself to doing the minimum around the wastegate hole, effectively just removing crud, as I'm more concerned over pressure on the flapper opening the wastegate prematurely (and so reducing boost) at higher maf rates/RPM than I am over getting the hole free flowing (to reduce the risk of boost creep or spiking).

I'll post up some images and look at the downpipe flanges next week when I'm back home.

 

The fit of the turbo exhaust and downpipe flanges was better but still required some judicious porting.

I did a little porting of the cast pipe that attaches to the compressor outlet, in effect just taking out nasty casting marks. However, I find this casting more than a little disappointing: the 90 degree bend has a horrendously small radius then the height of the passage falls from 38 mm to 34 mm before widening out to 38 mm again. I'm therefore mulling over alternatives such as cutting off the housing flange, attaching a silicone 90 degree coupling and machining the compressor housing as a diffuser to work towards the 2" OD tube after the coupling. I'm a bit stuck for a few days as the compressor housing is at a turbo specialist having it machined to take the slightly larger 20g wheel.

After more innumerable hours trying to find the best turbo solution for me, I gave up on getting what I wanted and went for the best of what I could get in the space available: a new CHRA with water-cooling and larger wheels (20g 52.5/68 compressor and TD06H 67.2/58.8 11-blade turbine), machine out the 2 housings to fit the larger wheels, smooth out air flows by porting and smoothing and using substantial heat shielding for the cold sides (intercooler piping and LIM).

 

I wanted to do this but never got around to it . In hindsight I don't actually think it will improve efficiency much. Any gains you pick up get negated by the fact that the compressor starts working at a lower ,less efficient Pr range.

Sounds like a good compromise .

 

Alas, I've had a relapse of my medical condition and I'm having to give up working on cars for the foreseeable future. I've therefore sold the installation as a kit with engine. I'd already taken everything off the car as part of my overhaul and taking the engine out with my mate was easy (particularly with him doing all the work bits).

I still have my 13B REW conversion components and, although it's up for sale as a kit with or without the car, I still harbour hopes of recovering again and getting fit enough to work on it. I may therefore remain active on turbo matters, although more on the rotary swap sub-forum rather than this one.

Even if I sell the 13B REW conversion, I'll remain active here on the site as I intend to keep my R3 for a long time (even if I wasn't stuck on RX8s - I've had 8 so far - my wife wouldn't let me sell her).

So, thank you to everyone who has helped me with advice on this project. You're a great bunch of people.

Ian

 

Wishing you and your family the best for you going forward.