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Thread: Adding turbo to non-turbo ZX motor?

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    Registered User inline6's Avatar
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    Default Turbocharge a NA L28 ZX/P90 Combo in 240Z?

    Anyone have info with regard to turbocharging the 81-83 ZX normally aspirated motors vs. starting with the ZX turbo motor?

    From what I can see, the norm. aspirated motor for the 81-83 is an F54 block which is stronger (same as turbo), but it has flat tops. The turbo on the other hand has dished pistons. Is that the only difference in the block? Obviously the turbo has a P90 or P90a cylinder head and the non-turbo has a P79.

    Where am I going with all of this? With the modern capabilities of the electronic fuel injection systems we have today, can we bump up the compression ratio a bit by running the flat top ZX block and do "better" than the turbo ZX motor? How much of a bump in compression am a looking at with a P90 cylinder head on the flat top ZX block?

    I am thinking about that combination with a medium to small sized turbo and a cam like they are running in the project car in sport Z.

    Thanks.
    Last edited by inline6; 02-11-2004 at 07:25 PM.
    Garrett

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    I 'm not really sure what you are after by turning a non turbo into a turbo instead of using turbo pieces. the only improved technology you mention is EFI, If I was going to ad new technology to older pieces, and I am, I would want the best of the older pieces, and that would mean the pieces designed for use with a turbo. Bumping up the compression sounds good, but look at the history of turbocharged L series engines. I think you might find that more often than not the engines built with NA parts and subjected to turbo charging do not last nearly as long(Mileage-wise) as as those built with pieces engineered for turbo use.
    I am guessing you are going to mate a current model EFI system to the L series engine. I have just finished the "collecting stage", and after I move across town, will be beginning the "put it all together stage".
    I have the tools and the pieces, now to work on the time!
    Will
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    There has to be a pricey kit for this as it has been posted many times.
    If there was a kit for the early z maybe that could apply to the non-turbo ZX i am not sure.

    Try a search and maybe you'll find some info.

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    Registered User inline6's Avatar
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    Default What CR for L28 turbo?

    Looking at the How to Modify Your Nissan/Datsun OHC Engine, it does not appear to me that anything other than the pistons are different for 81-83 ZX turbo and non-turbo short blocks. The cranks and the rods share the same part number and so, must be identical.

    The block appears to be the same as well according to this taken from Honsowetz book, "On the L28 Turbo block 11010-P9080, introduced in the 280ZX Turbo in December, 1980, and non-turbo L28s in July, 1981, slits were put in the Siamesed cores to provide a coolant passage between the cylinders."

    On the question of strength of the pistons, hls30.com, you raise a good point. However, for what it is worth, both the turbo and the non-turbo motors use cast pistons from the factory, yes? Same crank, same rods means same pin height in the piston, right? Seems like a 10.9 cc dish is the only difference.

    What I have in mind is just a little different than that which is commonly done, I think... Instead of getting a ZX turbo motor and adding a bigger throttle body, and bigger turbo, and adding SDS or similar programmable electronic fuel injection/ingnition system, why not start with the NA-- higher compression short block and do those same mods?

    Fundamentally, what is the compression of a stock ZX NA short block with a P90 head in combination, and with the advances made in programmable fuel injection/ignition technology in the last 15 years, what CR can we safely run in a custom turbo motor setup these days?

    Anybody? I'll start looking. I wonder what the latest turbo cars are coming with (CR) from the factory. I bet that is a good place to start. WRX, EVO? Audi's?

    Garrett
    Garrett

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    You raise an interesting point. I'll have to do research too.

    Since the L28et will probably be cheaper for me anyway i'm sure that is the way i'll be going.

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    I Agree with you, there are only a few differences, the head assembly, the oil pump, the pistons-I have never seen anything that said the NA version was cast-though I have never seen anything saying that they weren't.
    The compression ratio was made to be lower to fight detonation, and true, modern engine management has more control than the rudimentary efi that came standard on 280z(x)s. Here in South Georgia the relative humidity and temperature during the summer mean that I need all of the help I can get to fight detonation. I also want to have some extra room to encroach on as I add modifications to the car.

    Everyhting I have found (CR) for turbo is 7.4 to 8.9 also with dished pistons-but I have not looked in a while. I would look at current 6cyl applications for comparison.

    I am doing something a little different to-though not with the non-turbo pieces.
    Will
    A Z is beautiful from any angle, I just happen to prefer to view from the drivers' seat!

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    Registered User inline6's Avatar
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    Ok. I should have titled this What compression ratio to run in a turbo?

    Here is a compression ratio calculator:
    http://www.turbofast.com.au/Tfcomp.html#readme

    I put in the following for the stock ZX turbo:
    Bore = 3.39 inches
    Stroke = 3.11 inches
    Deck Height = 0
    Gasket Thickness .050 inches
    Head Volume in cc's = 53.6 + 10.9 for the dished piston = 64.5

    CR result = 7.4 to 1

    Now take out the dish and you get 8.53 to 1. Interesting...

    WRX compression ratio is 8.0 to 1...
    Mitsubishi Evo is 8.8
    Even the 1996 300 ZX was 8.5 to 1

    I'm thinking there is no reason to go with the 81-83 ZX turbo block.

    Garrett
    Garrett

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    Back in the 80's the thinking was that you had to have low compression with turbos.

    Modern thinking is that the dont have to have such low compression that the 1980's engines had.
    www.nostalgictrio.com Skyline - Silvia - Fairlady Z
    www.ozdat.com The Australian Datsun site.
    www.cafepress.com/vintagedatsun

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    Interesting info-I will look into the piston particulars-somewhere there was a reason for using dished pistons-not just to change the CR-as I recall. There are enough suppliers that sell or can fab cast pistons that getting a set(assuming NA pistons are not cast) would not be too dificult. I will do some checking and get back with you.
    A Z is beautiful from any angle, I just happen to prefer to view from the drivers' seat!

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    Default You can run a 85 CR

    Thats not the problem, the problem lies in the pistons and rings on the NA block, thats why it is better to go with the turbo block.

    No other reason.

    Honestly though the time you would take to do and gather all that you need for the conversion you could easily have a complete turbo motor.

    I dont see the point.

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    I got 280zx Fever 280zx Fever's Avatar
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    F54 Turbo has differnt pistons dished.. and differnt oil pump.

    I have a F54 with the P90 head... compression isnt overaly huge.. i think its because the engine is tired but it would be around 8.5 or something.. same as N42 top and bottom..
    1979 280zx Fairlady Z
    HGS130-000713
    L28-306538

    1981 280zx
    HGS130-193087
    KHGS130MBC

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    Registered User inline6's Avatar
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    The point of all this is HP of course. A bump to compression from 7.4 to 8.5 should be worth some HP, increase in efficiency, and thus, gas mileage. I am also wondering if I would get and driveability improvement-- specifically with turbo lag or lack thereof. Is it reasonable to conclude that the bump in compression would give a little better performance when off the boost? Seems like the bigger the turbo (or the more lag), the more the bump in CR would help?

    Sounds like the durability of the pistons between the turbo and non turbo are in question. I'll look at them next if I can. Questions would be location on the piston (how far down from the piston tops, and size of rings? Any others? Seems like nissan would use the same blank and machine the dish in the turbo piston for cost, but higher temps may have required a change in those specs.

    Thanks for the info, all.
    Garrett

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    Wink Boost.

    I think a C/R around 8 or 8.5:1 would definately help with driveability off boost.
    A T3/T4 Hybrid would be good also to keep lag down. Also im sure you know things like BOV's help reduce lag.

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    I am not certian you didn't mean torque instead of HP.
    when HP changes-it is due to changes in torque-not the other way around.

    Adding HP does not necessarly add to gas mileage-the A/F ratio should be virtually the same in all properly tuned engines, thus a a bigger engine uses more fuel per stroke. A transmission made for a smaller hp motor(a Z transmission) moved between two motors capable of driving it properly (one moderate HP, and one High HP) will get better mileage form the lower HP motor because the # of revolutions the motor has to turn per mile is the same-regardless of the HP-but the amount of air and fuel used is different. The extra Hp will get you to speed faster, but will use more gas to do it, and to keep you there because the RMP between the engines at a given speed does not change.. All engines have one specific speed that uses the optimal resources for the amount of work actually being done. When the gearing allows a transmission to take advantage of or at least approach that speed you have the greatest gas mileage that engine is capable of.

    Raising the compression should add some torque and HPand therfor make driveability improvements-there are engine modeling programs (PCDyno) out there that will give some idea of what it should do with everything else constant.

    Don't forget the piston/ring land /ring design on the turbo version is not only set up for higher cyl pressures, but is thermally specked out too-get the heat out fast to lower the propensity for premature detonation!

    Turbo lag can be tuned out-a modern engine management system can be programmed for supplimental injection to dispose of lag(ad NOS and more gas to intake manifold, or CO2 to the turbo header, and you will spool the turbo up almost immediately at WOT.) or a turbo can be tailored to lower rpm driving.

    I think the true limiting factor of the 6cyl L series engine is the Head-that is where all of the current technology has been focussed-cyl wall treatments are virtually the same as they have been, Exhaust technology really hasn't changed, but we have multiple sets of valves per cyl, variable valve timing and more that has been added to the head, That is what is keeping power down in an NA engine, without forced induction, enough air will not move fast enough through the engine. If the head off a 6Cyl Olds Bravada would fit on a 6cyl L series, we would have a great new addition to performance-variable valve timing and programmable injection-I would consider transplanting the whole setup into a Z.
    Will
    A Z is beautiful from any angle, I just happen to prefer to view from the drivers' seat!

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    Registered User inline6's Avatar
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    Actually Gav,

    I am an old school NA guy that is just getting intrigued about adding the turbo. In the past, wrote off turbocharging as being too expensive and sufferering from driveability issues. I really like power to be controllable and thottle response to be quick. What are BOV's?

    My goal for the motor would be minimal lag with moderate power. I autocross from time to time for fun so the idea of a big turbo coming on with lots of boost after lots of lag would be totally unacceptible.

    I need to do more research in the archives here on turbo set ups. Obviously there is no shortage of info on the subject. Thanks for the T3/T4 hybrid tip. I'm committing that to memory as I continue researching.

    Garrett
    Garrett

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    mel
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    just now reading this post and i must say i'm astounded on how people respond to a very simple question. inline6, your questions from the beginning are absolutely right on. bottom line is that a turbo that is compatible for higher CR should produce more efficiency. and since the parts in questions are the same with the exception of dished pistons...then why the hell not. i have a 79 280 zx. my set up is good now. why buy a l28t version motor if i can upgrade to a turbo now. i don't get why people don't understand that. the point is simple and dont try to complicate things by writing a freaking novel to showcase your knowledge.

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    Quote Originally Posted by mel marabante View Post
    just now reading this post and i must say i'm astounded on how people respond to a very simple question. inline6, your questions from the beginning are absolutely right on. bottom line is that a turbo that is compatible for higher CR should produce more efficiency. and since the parts in questions are the same with the exception of dished pistons...then why the hell not. i have a 79 280 zx. my set up is good now. why buy a l28t version motor if i can upgrade to a turbo now. i don't get why people don't understand that. the point is simple and dont try to complicate things by writing a freaking novel to showcase your knowledge.
    Um I don't know if you noticed but this thread is ancient. I didn't notice until I'd spent 10 minutes answering some of the misinformation in previous posts
    Last edited by Mikez73; 05-14-2010 at 01:48 AM. Reason: not paying attention

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    All the same, we get notified by email of new posts to these old threads. And in this case, I'm still alive to see it!

    Thanks mel marabante. I think a lot of people just default to the ZX turbo motors because they were already turbo. I don't think that is necessarily the smart way to go. If you are going to run the stock efi, then maybe. Others have the experience here - not me.

    I have an F54 flat top now and decided to stay NA as I'm not ready to drop the cash or time on all the custom parts that I'd go with if I went turbo. I mean, I'd want to go aftermarket efi, custom intake, custom stainless exhaust, aftermarket injectors, etc. The works! Instead, I'm putting together a tripple 44 mikuni, big cam motor for now. I'd be willing to bet I won't be happy when all is said and done and I'll be pursuing the turbo route I was thinking about in 2004!
    Garrett

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    Quote Originally Posted by inline6 View Post
    All the same, we get notified by email of new posts to these old threads. And in this case, I'm still alive to see it!

    Thanks mel marabante. I think a lot of people just default to the ZX turbo motors because they were already turbo. I don't think that is necessarily the smart way to go. If you are going to run the stock efi, then maybe. Others have the experience here - not me.

    I have an F54 flat top now and decided to stay NA as I'm not ready to drop the cash or time on all the custom parts that I'd go with if I went turbo. I mean, I'd want to go aftermarket efi, custom intake, custom stainless exhaust, aftermarket injectors, etc. The works! Instead, I'm putting together a tripple 44 mikuni, big cam motor for now. I'd be willing to bet I won't be happy when all is said and done and I'll be pursuing the turbo route I was thinking about in 2004!
    Glad you're still alive to see it ...wish I'd left my answer now. Bang for the buck go turbo if you want big power. There was some misinformation in some posts. If you ever decide to go turbo repost...although after 6 years you probably know the errors I'm talking about. I got a chuckle out of the "t3/t4 helps with lag" statement

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    Quote Originally Posted by inline6 View Post
    ... I think a lot of people just default to the ZX turbo motors because they were already turbo. I don't think that is necessarily the smart way to go. If you are going to run the stock efi, then maybe....

    It is more a case of one stop shopping and economy. As pointed out earlier in the thread:
    Why search for parts and an answer and then have spend time fitting, fabricating, and tuning when with a single $300(what I bougt my last Running 280ZX Turbo for) purchase you can get everything that you need and have it all properly installed in another car and running well in two weekends or less-by yourself?

    As an addition, the 280ZX turbo was Nissans reaction to the Crown, BAE and other turbo kits that were built between 1973(the earliest reference to a turbo kit I can find), and the introduction of the 280ZXT for NA Z cars from. I have a COMPLETE BAE kit I pulled from a '80 ZX several years ago.
    http://www.classiczcars.com/forums/s...e+turbo&page=2 see post 29 for a picture. Getting one of these kits speeds up the process, but they are still certianly more complex than swapping parts-even the manual says that a mis tune coud kill your engine.

    I think most people would like to consolidate their efforts and get a working and proven system, rather than piece on together. I am sure a properly designed modern turbo system would be better than what was available in the 80s.
    There is a website that explains all about Nitrous, and how to build your own system, it proves that the system it explains is the best out there and why-but people still buy pre packaged kits that are clearly inferior. Why? could be several reason-risk, fear, even convenience...same reasons apply to this thread

    Anything is possible with enough time, talent and/or money to pay for them. Some people simply don't have the right combination of all three to get to the place you describe. The factory set up has proven relieable and effective, the aftermarket has been proven to have the ability to be just as reliable and more effective, but it has also proved to turn an L6 into a broken pike of junk very quickly.

    L28ET conversion: Low cost, short term project, great performance gain, Proven and long lived results-FSM applies directly to troubleshooting and maintenance.

    L28 Turbo Conversion: Much higher cost, long term project, potentially excellent performance gain/dead engine, mixed results. No step by step guide to troubleshooting-mixed equipment means the buck could get passed.

    "The smart way to go" depends on the talent/time/money of the one person making the decision.
    Last edited by hls30.com; 05-15-2010 at 09:50 AM.
    A Z is beautiful from any angle, I just happen to prefer to view from the drivers' seat!

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    If you can find a good l28et for $300 that is definitely the way to go. Offhand I can't think of many differences in the two cars but sourcing the parts might take some time. Offhand list of parts
    1. injectors (cheap, easy to find)
    2. exhaust manifold (I'd build one and relocate the turbo)
    3. oil pan (drill a hole for the return line)
    4. intake (I'd use an ic so that's a non issue)
    5. pistons (I'd keep the NA pistons)
    6. engine management (I'd want Nistune or MS anyway)
    7. oil pump (a new oil pump is a good idea anyway)
    8. gas tank (for my 240z anyway)
    9. fuel pump
    Bottom line is yes if a complete 280zxt parts car is available it makes things easier. Driving z31's for 10 years will give you a more relaxed view of modifying a car. Power adding aftermarket support for the z31 was pretty much nonexistent

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