Brettus

iTrader: (2)

Are you talking about the turbo intake pipe being 2.4" or the exit ? Normally there is a cast elbow at the exit to fit a 2" coupler.

Ian_D

Thanks. I had a quick look this afternoon. The compressor outlet does indeed have a cast elbow with an outer diameter of 2". I may replace all the hose clamps so may take all the pipes out and measure them all.

As an aside, when I bought this car with the turbo conversion already fitted I told myself I wouldn't look too closely at the build itself, but it seems that I can't help myself. I had a play with the spreadsheet I built for my 13B REW turbo conversion to see what the optimal sizes of pipe are; however, it all seems a lot of effort without full details of the turbo I've got and when any gain from optimal pipe diameters is lost amongst the effects of having so much 3" diameter pipe to the throttle body.

Brettus

iTrader: (2)

In my experience there is next to nothing to gain by increasing the pipe diameters on a stock Greddy setup.

Ian_D

Thanks. I think you're right, although:

• That depends on what the kit sizes were in the first place (aftermarket kits may have different sizes to the original), which takes me back to my original question of what the pipe sizes should be.
• I'd prefer to phrase that 'nothing to gain overall' as changing the pipe sizes improves some parameters and degrades others.

BTW I think experience is much more valid than design calculations here as there is so much uncertainty and a wide range of operating conditions to balance out. I don't want to write much as I'd get carried away quickly and I've had great trouble finding good information on the internet (to post on other threads, not here, as this one isn't the right place for discussion). That said:

• My calculations indicate an 'ideal' pipe size of either 2" or 2.25" depending on the boost/power level chosen and car use. Broadly, these calculations suggest 2" pipe suits a street car and 2.25" pipe suits a max power track car. Note that these diameters are substantially lower than the 3" used on my car in the long section before the throttle body, which has roughly twice the cross-sectional area of the smaller pipes (2.25 and 1.78 to be exact).
• Most discussions are for piston engines where air flow rates for a given power are different to those for rotary engines (which have lower volumetric and combustion efficiencies). As a rule-of-thumb I multiply piston engine CFMs for a given [generally maximum] power level by 1.2 to get the equivalent rotary engine CFMs.
• Just about everything with numbers has fundamental errors, for example (1) using CFM (essentially the volume of the charge air mass flow under atmospheric pressure at the air inlet) instead of the actual volume at the pressure and temperature at that point (which will vary with a whole host of factors such as boost pressure and compressor efficiency) and (2) ignoring changes in the speed of sound with temperature. As an example of the scale of the errors, at 14.7 psi nominal boost, 700 cfm and a 2.25" bore, their simple calculations give a Mach Number of 0.39, close to their 'optimum' of M0.4, yet I calculate the actual Mach number just after the compressor exit as, ignoring boundary layers and other niceties, 0.22, quite a difference, and this falls by some 6% in a similar pipe after the intercooler (mainly because increased density from reduced temperature outweighs other effects, including those of pressure drops and the lower speed of sound at lower temperatures).

9krpmrx8

iTrader: (46)

Don't waste your time overthinking it, there are no serious gains to be made.

Ian_D

Thanks. I'd certainly advise others to leave the pipe sizes alone.

That said, I'm happy with the time I spent in the calcs as I did them out of professional pride (I was an aircraft systems engineer for 20 years) and interest rather than in any expectation of changing the pipe sizes. In any case, they took less than 5 minutes (I already had the spreadsheet I'd produced for my 13B REW).

I took the pipes off and measured them properly. The section from the compressor to the intercooler is all 2" then steps up at the intercooler entry; this is fine for my power, which is just as well because there isn't space for anything larger on my RHD car over the first 2/3. The cast elbow out of the intercooler has a 2.4" OD followed by a section of 2.4" OD tube into a long sweeping 3" tube to the TB; ideally I'd like to see a smaller diameter for the first part, but widening out to 3" without disrupting flow into the TB is a pain to do properly and, as the experienced guys say, changing isn't worth the effort.

In conclusion, thanks for the advice, I'll stick with what I have. I also have something more important to chew over as the pipes had a lot of oil in them, a thimble full, so if there isn't an issue with the crankcase ventilation and/or catch can then I'll be pulling and rebuilding the turbo (8000m since rebuild); I've found a thread on oil in the intercooler pipes and will post on that when I've investigated further.

Update 1: the exit hose from the catch can dumps behind the RHS headlight near the rad fans, which could explain the oil film on everything in the engine bay,and suggests the turbo oil seal(s) have gone. Ah well, an overhaul kit is only $100 and removing the turbo wil be another thing I'll have experienced.

Update2: In cleaning the MAF sensor housing on the air intake I saw that the reduction down to the 2.4" OD main pipe is an abomination on my kit. I'll therefore be changing that to give a much smoother transition.

Brettus

iTrader: (2)

When you take the turbo out you should take a look at the turbo exit elbow . I always felt that was a really bad design . I did port mine as best I could but I think some small gains could be had by eliminating that part for something that flows better.

9krpmrx8

iTrader: (46)

I port matched mine as well. I can't speak to any gains from doing that though.

Ian_D

Right, I set to work removing my Greddy turbo for rebuild using the instructions on how to do this from MazdaManiac's upgrade kit here as I could find nothing here to help or suggest problems. I made notes as I went so I could post a 'how-to' if there was more to the job than in those instructions.

I'm now part way through the removal, getting as far as removing the engine mount before deciding to check ahead to spot any problems as my kit has been on for a few years and will almost certainly have rusted nuts and bolts (I have penetrating fluid, breaker bars, blowtorch, candle wax and nut-splitters ready). I test-ran getting at the nuts and bolts for the downpipe, oil drain fitting, turbo-to-manifold and engine manifold, spending a very unhappy half hour getting increasingly frustrated at not being able to get proper access to many of them; for example, getting at one of the 2 oil drain bolts seems almost impossible. I then ran out of time.

I'll start the process again tomorrow and hope to find solutions as I go. I suppose I could remove the engine or drop the engine and front sub-frame a little, but that's a lot of work and potential complication that I'd prefer to avoid.

In the mean time, is there a knack to getting at the nuts and bolts and getting enough leverage if they're rusted on? Do I need any special tools?

9krpmrx8

iTrader: (46)

Unbolt the engine mounts and push the engine to the drivers side. Or are you RHD?

For the turbo to manifold, I have a tiny 10mm box end wrench that I grinded down to fit just perfect to get enough movement to remove and install the turbo to manifold bolts.

As for rust, you just need a good pentrant oil.

Ian_D

Thanks. I'm RHD. I can cope with reversing driver and passenger for the car sides, but can't do much about the steering column.

I've got spare spanners and a grinding wheel to modify them easily, plus a tool shop 5 mins away if I need replacements or anything special.

Getting a penetrant oil into the turbo to downpipe bolt threads is difficult as they are a long way down from the bolt heads. I've already sheared the lowest of the 5 bolts despite a couple of hours soaking; I should be able to get the shaft out when I've got the turbo off, but in the meantime I'll have to spend a few minutes getting the cat/decat off.

Update 1: Getting the 5 downpipe-to-turbo bolts off took me over 3 hrs, including unexpected work to get access and the odd coffee break. To get more room I had to take off the cat/decat, LHS engine mount and bracket then move the engine towards the LHS (to give more room and move the wastegate actuator away from the sub-frame bolt it was fouling on; I used the car's scissor jack between the engine and sub-frame with the engine supported by a trolley jack angle in the right direction) and lower the engine as far as practical. I had to grind off part of a 12 mm spanner and a 3/8" drive 12 mm socket to get a proper grip on the bolt heads; my 1/2" drive sockets were too wide for the available space. I had to juggle various wobbly extender bars, UJs, short breaker bars and ratchets.

Update 2: Now the 1 bolt on the oil drain pipe and 3 nuts on the turbo-to-manifold flange are proving quite a challenge:

• One of the 2 oil drain pipe bolts was accessible with a 10 mm 1/4" drive socket and came off quite easily. However, the other bolt is hiding in a cave made by the turbo and the manifold and resisted all my attempts to get at it with all the sockets and spanners that I had. I've therefore ordered a crow's foot set and a 10 mm hinged spanner. Fortunately, what I thought was a shadow on the oil drain flange turns out to be a cutout, which means that I can just loosen the bolt and slide the drain off, thus solving my concerns over getting the bolt back in on refit.
• One of the 4 turbo-to-manifold flange nuts took a 12 mm spanner and came off OK with lots of heating and candle wax. I can't get at one of the other 3 nuts until I've got the oil drain flange off. No matter how hard I tried, I couldn't get a 12 mm ring or open-end spanner on the other 2 nuts and a 13 mm spanner was a bit loose. I tried heat, candle wax and a 13 mm spanner but the nut ridges rounded. I've therefore ordered a 1/2" (12.7 mm) spanner in the hope that fits, otherwise I'll have to grind out the nuts. I won't know about the other nut until I've got the oil drain pipe off.

Update 3: Phew, finally got that bolt and 3 nuts off:

• The 10 mm bolt for the oil drain flange and its cave proved more than a match for the crow's foot and flexible spanner as there just wasn't room to get them on the nut. However, I succeeded by cutting a 1/4" drive socket as short as I could at both ends, cutting out one side of the drive socket, taping a drive extension into the drive socket so that it could articulate whilst being held in, putting the socket on the nut and turning the extender with a T-bar.
• For the 3 remaining turbo-to-manifold nuts, 2 came off after long heating (heat as long as I thought was right then heat for that time again) but the other resisted all my attempts with various spanners and sockets until I gave up and ground the nut off.

Ian_D

All the threads I can find over upgrading the standard Greddy T618Z are somewhat out of date or are no longer available (at least for where I am, in the UK; some like the BNR upgrade may still be available in the US). I have 3 choices for my turbo that needs a rebuild:

• Fit a repair kit and get the CHRA rebalanced (the cheapest option), say £200 ($250) with balancing.
• Buy a new CHRA direct replacement like the one here. £299 is, say, $375 + import duties (another $70?)).
• Buy a new CHRA with a billet compressor, which will help flow more air, like the one here. £399 is, say, $500 + import duties (another $100?)).

Now, I can make a decision between the cheaper rebuild and a direct replacement CHRA. Does anyone have any information or views on the billet compressor, which I assume will run a lot better at higher engine RPM where the standard compressor runs out of steam?

9krpmrx8

iTrader: (46)

I have an upgraded (54trim water cooled CHRA and Comp turbo billet compressor wheel) T618Z and all I can say is to get it done professionally. I had one bad rebuild and it didn't last a year, my current rebuild has about 30,000 miles on it. But I also have a turbo oil pressure regulator setup and I attribute some of the reliability of this turbo to that.

BNR also makes a great setup in the 60-1 and if I had to do it all over I would go with that.

Ian_D

Thanks. I'm beginning to think that I'm better off paying the extra for a new CHRA than attempting a rebuild. That leaves the question of whether the billet compressor is worth the extra; I've just had an email saying that I can get, with delivery, that direct replacement CHRA for £330 (say $415) if I order in the next day or so; this compares to £500 (say $625) for the billet assuming that I have to pay import taxes, a difference of some $210. Unless the billet is significantly better then I'm probably better off going for a direct replacement.

I like the BNR 60-1, although I did hear of early issues with holding boost. However, I can only find one for sale (on RX7.com) and they won't quote for shipping to the UK; even if they shipped to the UK, the cost of taxes and delivery (including sending my turbo to them) puts the price up to over $1,500, which is worse than it sounds as the pound-dollar exchange rate has bombed over the last few months. I also have to bear in mind that my engine's compressions are poor and that I have a 13B REW conversion to fit, so spending the extra $1,000+ on a BNR might quickly turn out to be a waste of money if the engine goes bang.

Brettus

iTrader: (2)

I have had a To4E 57 trim and the 60-1 . The 57 trim wins my vote as the better match for the configuration . The 60-1 wheel turns the turbo into a slow spooling turbo that can't utilise the capacty of the compressor . The 57 (or 60) trim is way more fun and is a nice bump in power over stock.

JimmyBlack

I agree with Brettus, I've had both, and the 57 trim is way more driveable than the 60-1. It does lose a bit of top end, but you spend most of your time with the foot on the floor in the rpm range where the 57 trim is similar (mid range) or better (3-4krpm). The only thing I'd add to Brettus' comment is that there is an 11 blade turbine wheel available for the Greddy/Mitsubishi turbo, and I'd get this wheel also if you're rebuilding as it should improve top end performance without impacting spool - win/win.

So to recap, the 57 trim billet compressor wheel, 11 blade turbine wheel, professionally clearanced and balanced.

A few points to be aware of - The comp wheel swap will require the turbo shop to clearance the compressor housing. In some cases this may require a larger compressor housing (which is actually better for low pressure turbos like ours). Best to check with them on this before proceeding as a new housing adds a bit of money to the build. When swapping the turbine wheel you don't need to clearance the turbine housing, but you do need to have the assembly balanced so you should get all the work done at the same time so it only needs to be balanced once.

Ian_D

Guys, thanks. I don't have a turbo shop in reasonable travelling distance so I had a look on the internet for an hour or 2 without finding anything definitive on upgrading (eg will the available T04E compressor wheels fit my Greddy shaft; eBay T04E compressors have a 6mm bore and the T618Z has a 6.5 mm bore). I'm busy over the next few days and will have another look nearer the weekend.

Incidentally, the turbo was fitted with a new CHRA less than 8,000 miles ago. I had a look at it closely; it seems to be a bog-standard T618Z. When I turned the turbo on its end, I had a deluge (over a thimble-full) of oil come out the compressor exit, which took me by surprise as I expected little oil to be left in the CHRA and even less to pass the compressor seal. I couldn't find anything wrong with the turbo drain fitting and hose.

JimmyBlack

Pretty sure the turbo shop had to get my new compressor wheel bored to 6.5mm to fit the Mitsubishi/TD06 (T618) shaft. If you choose to, you can get parts from the Kinugawa website, or from their local UK dealer if one exists. Here's a link to the turbine wheel I have (and highly recommend):
Turbo Turbine wheel Mitsubishi TD06H 20G turbocharger 11 blades Spool fast

Check my first turbo build thread for some more details and pics from when I had my turbo rebuilt.

For what it's worth, I think welding an external wastgate onto the back end of the Greddy manifold would address the real performance bottleneck of the Greddy turbo setup more effectively than a turbo wheel change. Having said that, I'd still get the wheel upgrades if you're rebuilding the turbo.

Ian_D

Thanks.

Looking only at the original Greddy turbo, and therefore ignoring the options of a different turbo and/or a complete redesign, I can see 4 main options:
1. Leave the turbo as standard i.e. 18g trim. 240-260 RWHP?
2. Upgrade to 20g trim (52.5/68 comp, 67.1/58.8 turbine). 260-280 RWHP?
3. Upgrade to 25 g trim (60.2/78 comp). 240-260 RWHP? 320-340 RWHP?
4. Upgrade to Garrett 57 trim comp and larger turbine wheel, which is effectively a half-way house between the 20g and 25g trims. 290-310 RWHP?
As I expected, the compressor maps I can find move the compressor sweet spots to higher boost pressures and higher air mass flows as the compressors get larger.

Which option is best therefore probably depends primarily on what power level you want, with options and cost also considerations (for example, for £433-£520 ($570-$670 say) I can get a water-cooled 20g CHRA and compressor housing that may fit with a machined turbo housing compared to £315 ($400 say) for a replacement standard CHRA). Cost involves more things than just the turbo itself as upgrades may be needed elsewhere at the higher power levels; for a 20g I'd look to modify or upgrade the wastegate actuator and for a 25G/60.1 also upgrade the injectors, fuel pump, ignition, intercooler and intercooler piping.

Additionally, I want to look at wastegate, intercooler and intercooler piping sizes and performance to check that they won't be overloaded.

My current feeling is to fit a 20g (see here or here) as that would give me water-cooling and a little performance gain without large changes to the rest of the system. The Garrett 57 trim remains a candidate though; some good news is that I'll be passing near a turbo shop tomorrow and can pop in for a chat over what I want to do; the bad news is that I've had something unexpected come up and will be short of time to mull things over until Monday.

I'll also want to check if the, presumably larger, compressor housings will fit in the space we have available and have machining of the existing housing as a back-up.

Strangely, I can get a 60-1 TD06H water-cooled CHRA and compressor housing for £310 ($400 say) substantially cheaper than the same manufacturer's 20g TD06H at £520/$670.

BTW my car has no Aux port blanking, presumably because the Adaptronic ECU can handle that well, and I have no plan to blank it.

As an aside, I modified my 13B REW spreadsheet to play around with various turbo configurations and settings. It broadly supported what other people have been saying and allowed me to plot on compressor maps; however, I'm wary of putting much store on the results as I struggled to benchmark a lot of my assumptions (there is far less information out there on the Renesis than on the 13B REW, and some of it just seems plain wrong).

Ian_D

The original Greddy kit fits both LHD and RHD cars, albeit the compressor [air inlet and intercooler] pipes are a close fit around the steering column and installation is a bit more fiddly.

However, when modifying the T618Z turbo with a larger compressor wheel, either by machining the existing housing or using an of-the-shelf housing without a flange on the outlet*, what restrictions does the steering column place on the compressor pipes?

With diversions into other interesting questions such as finding an aftermarket wastegate actuator that would fit the available space, I spent a few hours looking for answers on build threads here without really getting anywhere.

I'm therefore looking at putting my turbo and engine mounts back on so I can play around with various pipe sizes and locations. If anyone can add some info from their own experience that would be a big help.

*The image shows an example. I need to measure carefully for this one as the outlet pipe might be too long (for it and the attached piping to clear the various obstructions), getting either the existing or supplied wastegate actuator to fit might be difficult, and modifying the housing might be difficult (welding such high-silicon castings is not always easy).

Ian_D

My turbine housing has a small crack emanating from the wastegate hole. I know that such stress-relieving cracks are pretty common and I'm not too bothered over the one that I've got, which is just as well as I can't find a remotely-suitable replacement for the T618Z's snail.

However, I've been asked for my opinion on the much larger crack shown in the image, where I'm unable to give a reassuring answer. A search here throws up the odd mention of such cracks, without images, where the general response was 'don't worry about it', but I suspect these cracks were smaller.

Can anyone shed some light on when we should be getting worried over these cracks?

Brettus

iTrader: (2)

Mine had a crack there worse than that . I put it back in and didn't have an issue with it .

JimmyBlack

Mine had a crack between WG port and turbine wheel outlet. I have run it at 12psi and up to 30+psi of exhaust backpressure for over a year without an issue for me.

Ian_D

Brettus & Jimmy, thanks.

I looked at the image more closely and noticed what looked like carbon build-up on the lip (above the crack, between 1 o'clock and 3 o'clock in the image). He tells me that the lower side of the crack is slightly higher at the lip, so there is a small gap between the flap and the lip, hence the build up. Does this change your view? Of course, he can get that machined so the lip is level (at least for now).

Ian_D

My mate is thinking of copying me in upgrading the turbo and has come up with the idea of killing 2 birds with one stone by fitting a modified TD06 20g with a 12 cm2 (A/R 0.89) turbo housing rather than machine the existing one. See the image and here.

At first glance this snail has the right wastegate and exit flanges. I had a quick look but couldn't find any suitably-thin flange adapters here in the UK, so I think he'll have to get the T3 flange replaced with a T25 one and do some porting.

I explained to him the general consequences of increasing turbo A/R (less power/ slower spool at low/med RPMs and more power at higher RPMs). I think the larger A/R might suit the larger wheel better, but have no experience of this Greddy. On the other hand, Greddy might have looked at a 12 cm2 housing and rejected it in favour of the smaller10 cm2 one.

What do people think of increasing the turbine A/R like this?