Project RBZ - RB26 Swapped 240Z | Page 4 | The Z Club of Great Britain
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Project RBZ - RB26 Swapped 240Z

Discussion in 'Hybrid Z cars' started by Garaculas, Aug 24, 2020.

  1. Garaculas

    Garaculas
    Z Club Member

    The choice of turbo in a build like this is quite important so I've spent some time on Excel today calculating everything out and plotting some points on the compressor maps on the Garrett website. Super helpful that they offer this level of detailed information, the only one that does i believe! So i went about doing all of the required calculations and got an Airflow value for peak torque and maximum RPM, then plotted them on the graphs for the three turbo's i was looking at. The G30-660, G30-770 and G30-990.

    Garrett.JPG

    Excusing the appalling colour of the points (can't seem to change them so thank Microsoft for Grey and Orange) you can see that the 660 would be inefficient at peak RPM whereas the other two would be at peak efficiency at peak RPM and working well at peak torque. In the areas of the chart that the RB26 will be operating the two turbo's compare very closely and ultimately comes down to running either the G30-770 with a larger rear housing (1.01AR) or the G30-900 with a smaller rear housing (0.83AR). I think the 770 with the larger rear housing is going to be the way to go as it's going to utilise the efficiency of the compressor well and spool up a bit later which will help with keeping traction.

    Obviously the calculations assume a few things and they're only an indicative finger in the air but it's really good of Garrett to offer these tools with the explanations of how to get there. If anyone's interested in doing this themselves then there's loads of tools on the Garrett website and you can even use their Boost Advisor which will do most of the calculations for you.

    Engine build and mapping is all being done by Mark Gillam over at Abbey Motorsport.
     
  2. Robbie J

    Robbie J
    Z Club Member

    Been a while since I've been to Abbey. In my view, they are pretty good but can be expensive and if they make a mistake they don't really want to fix it. They killed a double plate clutch in my R33 GTR once as they fitted the wrong part. RK Tuning fixed it, I wonder if Ron has moved on from handwritten receipts today. That was a long time ago.

    I was thinking of those turbos as well but they were in short supply and a rebuild of what I had is a good start. Approx 380BHP is going to make it quick enough to start with for me. I can always get more later if I need it
     
  3. Robbie J

    Robbie J
    Z Club Member

    I had 2 small N1 type turbos on my R33GTR and only about 450BHP but she pulled really well from low revs. I drove a few big horsepower Skyline GTRs, great fun but not really usable on the road
     
  4. Garaculas

    Garaculas
    Z Club Member

    Interesting feedback! To be honest I’m not 100% set on where I’m going just yet but have heard good things about Abbey and don’t mind them not being the cheapest as long as the work is high quality. Marks seems good from the talks we’ve had so far but always open to other places at this early stage. Already changed once!

    Yeah I’ve been in a couple of big power GTRs over the years and they’re kind of a one trick pony, keen to make sure the Z is usable hence all the research and planning up front now. I think a good 3/400 low boost will be ample for most driving but the option of 550 at the flick of a switch would be fun :)
     
  5. Robbie J

    Robbie J
    Z Club Member

    yes, there is not much weight to these cars + those turbos will spin up really fast.... I might see one in my future
     
  6. Garaculas

    Garaculas
    Z Club Member

    A big piece of the puzzle arrived from the US today, the RWD sump! I did quite a bit of shopping around for an appropriate sump to fit the S30 chassis and kept coming to people recommending to talk to Patrick Bowser, a bloke on Facebook...

    I reached out and less than a month later here we are, made to order and made to measure an RB in a Z chassis. Large volume, baffled and with a windage tray built in this thing is really smart and also comes with a new oil pickup.

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    Did a quick test fit so see how it all looked.

    6E997D09-7D03-4880-ABED-4F82CABD56EB.jpeg
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    Super happy with the fit and a really nice piece of kit. I think I’ll change the hardware to some different bolts with washers but really chuffed with this, one of the big pieces of the puzzle ticked off the list!
     
    tyroguru and jonbills like this.
  7. Pondo

    Pondo
    Z Club Member

    :drool: That looks the business
     
  8. Jay.

    Jay.
    Z Club Member

    Have a Pat pan on mine too, they're great!
     
  9. Garaculas

    Garaculas
    Z Club Member

    More exciting post today, this time in the form of some future wheels! I’ve been on the lookout for some Watanabe RS Eight’s since I first bought the car but they often tend to be hard to find, expensive and the wrong sizes. I couldn’t justify spending well over £1000 on some wheels (plus a load more on shipping) that I would just strip down and bin most of except for the centres.

    Thankfully a set of reconditioned centres came up for sale that I just had to have and here they are!

    01BBF65F-69B1-4985-896B-71EDF9B3F401.jpeg 104B86F4-CDA5-47BE-B590-C108DA2C186D.jpeg 188BDCD7-A3C4-41C1-9BC7-C1DDE465921B.jpeg 448EFECE-48C1-4E1D-B3FD-506141DBC27A.jpeg E2A0FC24-1CEC-4859-8B4D-8773642C8595.jpeg 46B8792B-22EC-4E08-B5D2-C8C2745AD0AA.jpeg

    The plan is to use the JR19s for the time being whilst the car is being built and then when the bodywork gets done, and the arches fitted, these will get rebuilt. Hoping to get them tailor made to fit the car perfectly, with new lips and barrels, to allow as much rubber as possible. Still not decided on 16 or 17 inch but that’s a problem for future me!

    Over the moon with the condition of them and looking forward to getting them rebuilt and on the car as one of the final pieces of the project :)
     
  10. Ian

    Ian
    Z Club Member

    Nice. If I was doing my build again I'd also remove the spare wheel well and build a custom tank in its place.


    Are you sure you want to go single turbo, in almost all cases the single turbo S30s seem to be less driveable, not as good on the road and often slower (due to being harder to put the power down despite there being the same or more of it) than a decent twin turbo setup. I'm certain staying with twins was the right choice. Its so great on the road, many I have talked to with single turbo S30s do not share the same experience. I run 490lbft on mine yet due to the boost curve I can easily utilise this.

    I have often thought about going single for power closer to 600hp but then realise I'd almost certainly get less enjoyment from it and that I barely use high boost on my current setup so whats the point of going for more. Most of the time I run low boost which I guess is around 400hp, high boost is 482hp, plus one of the things I love about my car is how low I get good boost, so much fun sitting at 70mph @3000rpm and having what feels like instant spool, passing on a motorway is super fun. Wow, I'm getting nostalgic thinking about it, I cant wait until its back on the road.



    I am running one of pats sumps, or rather I was, I'm going to build a new one, that sump was great on the road but I have had a few issues on track, I will either modify it with extra trap doors and add some wings or start afresh. I have a thick steel flange so I'm tempted to start again as this will provide extra stiffness and a better mating surface. Because of the enormous cost of the engine I want to make sure I go overboard with oil supply, can't afford to have a failure.
     
    Garaculas likes this.
  11. Garaculas

    Garaculas
    Z Club Member

    Thanks a lot for the write up and feedback Ian, really do appreciate it! The single vs twin argument is one I've gone back and forth on in my mind multiple times but have decided to go single due to it being easier to work on, simpler and easier to manage the heat. I hear what you're saying about the character and usability of the twins but surely a properly selected and tuned turbo from 2020 can compete with a couple of older tech turbos from 30 years ago?

    I could understand if the factory setup was compound, so had the benefit of one larger and one smaller turbo, but the fact that it has two identical turbos says to me that the right setup should be able to at the very least compete? I know there are some aspects which the twins will always win out on, like the fact the standard manifolds are shorter, but I'm confident i can do a good job with a properly selected and setup G-Series turbo. I think part of the problem is people get too greedy and feel the need to slap a big turbo on to impress people in carparks and on the dyno. Like you i don't expect to see myself using high boost very much at all and I'm very mindful of wanting to make a car that is fun and usable, not just a dyno queen.

    I had already had these thoughts about the Pat sump and am planning to run an Accusump to try and mitigate any issues i might run into. I can control and monitor how the accusump is working with the ECU so the aim is to see how much work it's having to do once i get the car on track and if i need to bolster this with some more sump volume and extra baffles then that's what we'll do. Like you i can't afford to be pulling the engine out for rebuilds every couple of years so am trying to do everything belt and braces to protect against an oopsie at this stage rather than afterwards!
     
  12. Robbie J

    Robbie J
    Z Club Member

    The Turbo you are thinking of has a very fast spin-up hence you should be OK. The turbo's on my R33GTR where N1's and took a few maps and diverter pipe to stop "shuffle" but today that would be easy to map out. Less is more hence aiming for 380BHP which should be plenty to start with for me....
     
  13. Ian

    Ian
    Z Club Member

    Granted there are not any really new turbos that mount like stock, but modern turbos are not too different from something like an HKS GT-SS turbo. It would be nice if Garret would make a new turbos for repalement of the stock setup using as many modern design features as possible.




    Yes, this is always a big problem, people just want bragging rights and don't even consider driveablilty or how much power their chassis can put down nicely even with a well setup suspension. I almost made this mistake but I am now very glad I didn't follow through.



    You can definitely do a great job with a modern single. But they will always ramp up more aggressively than twins, the good thing is you can control this with electronics quite well these days. If I was building an engine for an R32 or R34 GT-R then I'd beo going single turbo without a doubt as with the AWD you don't have the same traction concerns and with a RWD car with limited tyre width options.

    One of the tuners I talked to before my build actually suggested going for a bigger single than I had thought of because he thought it would be easier to control the boost ramp than a small single but it didn't sit well with me because you are going to have less response and higher boost threshold because of this.
     
  14. Mark N

    Mark N
    Z Club Member

    They already do make drop in turbos in the GTX and Gen 2 GTX series.
    I've been toying with the idea swapping out the pair of HKS GT-RS in my R34 for these:

    https://www.atpturbo.com/mm5/mercha...p&Product_Code=GRT-TBO-G27&Category_Code=RB26

    To make them work, I would also need bigger injectors and another ECU.



    ..........and better brakes!
     
  15. Ian

    Ian
    Z Club Member

    I didn't make that clear enough, modern turbos in the 500-550hp range is what I meant. ^^They are way to powerful for use in an S30^^

    And of course there are turbos that can make this, like my GT-SS, but I want the most modern tech not for more power but for similar power with better response, lower boost threshold and better efficiency.
     
  16. Garaculas

    Garaculas
    Z Club Member

    Funny you should say that.. I had a chat with Andrew Hawkins last night, of Motive Garage fame in Australia, and he said exactly this. He strongly advises going for a 35 frame Garrett as the smaller 30 frame turbos will spool too quickly in my application and make it much worse to drive. He recommended going with the smallest 35 frame i can find which is currently the GTX3576r Gen II with a 0.82AR rear housing on petrol or 1.01AR if i was running E85. Andrew has extensive experience with tuning RB26s, both in and out of GTRs, so i'm very tempted to follow his advice! It slightly messes up my manifold plans but we can work around that hopefully.
     
    Pondo likes this.
  17. Ian

    Ian
    Z Club Member

    Considering Andrews experience with RB engines I'd think his advice would be pretty solid.
     
    Garaculas likes this.
  18. Garaculas

    Garaculas
    Z Club Member

    Couple of vital bits arrived today for the RHD conversion, inner tie rods and steering rack bushes for the Subaru rack. Read quite a few threads on different forums about using these Volvo inner rods to adapt from the Subaru rack to the Datsun outer rods, let’s hope it all works out when the rack arrives later this week!

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    Also ordered a tubular front subframe, RB engine mounts and RB25 gearbox mount from Apex Engineered. Also using Ron at STS imports to help me get the parts over from the US and using this smaller order as a test run before the big Techno Toy Tuning order at the end of the year so fingers crossed!

    Also had a really good chat with Dave at DY Engine Services today and think I’m going to be trusting them to rebuild the RB and get it tuned. Exciting times!
     
    Ian, Rushingphil and jonbills like this.
  19. Garaculas

    Garaculas
    Z Club Member

    Decided to delve a bit further into Andrew's advice on the GTX3576r Gen II turbo and plotted the same data as before (this time in red to make things easier).

    upload_2021-3-11_10-28-45.png

    As you can see it seems Andrew does indeed know what he's talking about! :) The G30-770, although in the good efficiency area of the graph, was at the bottom of it. The G30/900 and the G35-900 have the same graph and as previously stated wouldn't be working near peak efficiency with the RB. This turbo however is right in the meat of the efficiency for most of its time so definitely looks like the right choice!

    Going from G to GTX does mean i need to rethink my manifold options and Andrew also recomended split pulse so going to try and source everything to make that happen. Fingers crossed!
     
  20. Ian

    Ian
    Z Club Member

    If I were going single I'd be keen to go with a GTX and definitely twin scroll. I'm sure manifold shouldn't be an issue, loads of choice out there.
     
    Garaculas likes this.

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