Engine mods - NA or TT?
 

Hey all - I'm in the process of building up my '81 ZX 2+2, and will be addressing the suspension, body, interior, etc., but I'm unsure of what I want to do with the engine. It's the stock L28E NA engine, and I was debating whether I should keep it NA or build a custom twin-turbo setup ... I plan on driving this car daily, as well as competing in drift and autocross events on weekends. I'm not aiming for driveline-shattering power numbers, but I would like to see as close to 280-300hp as possible with a smooth powerband - is this possible with NA tunes? I need to keep it emissions-legal, and the TT option might not sit well with the Utah State Emissions regulations. On either option, I was planning on using a P90 head from a turbo motor, as well as a crankshaft and possibly rods. I had considered the 3100cc stroke-up kit, but that might screw up my budget balance - I don't plan on spending more than $2500, $3000 at very most on the engine alone. She's quite a stout engine in stock form, so I'm optimistic about an NA buildup. TT setups on L28s, however, I hear are far and few between, so that's also a deciding factor :D . If I decide on the turbo option, I will custom-fabricate an intake manifold (2 throttle bodies ?) and a custom exhaust manifold and downpipes. Turbos would be two T25 units from a first-gen turbo Eclipse/Talon/Laser, and I would run twin intercoolers. I'll have sketches up on my site soon. Exhaust would be a 2.5" unit with high-flow cat and muffler for NA, or 3" with high-flow cat and muffler with turbo. Either setup would run an Electromotive TEC-III engine management system. Any comments, questions, or suggestions are welcomed and appreciated.
Also, if this question has been posted already, I apologize, I had little luck with the search function ...
Thanks in advance - Dave

I dont know if you are going to keep under 3 G's with all of the ideas you have. The cheapest way to go would be to get a turboed engine and then swap it with your n/a one. From there you can get a bigger turbo and up the boost. A custom TT setup is going to be very difficult to do because not alot of people do them (i have only seen one and that was on the internet), and its probably more time than you are willing to put into it if your goal is 300 horses. If your goal is 300 then just get a chevy 350 and a tranny from a junk yard, that will set you back about six hundered bux. Then you can build that up. Its a cheaper way and the after market for 350's is massive.

Dorifto, I say keep the N/A. Its alot easier to controll when autocrossing, you can get on and off the gas without a turbo kicking in and sending you side ways. I do agree that a turbo is alot of fun because i have a very fast one. But when I hit curvey Mtn. roads I have to be super carefull I don't take the fast way down(off the side of the hill). I have a better time and more controllable throttle response with my N/A on courses. Also Twin turbos are good with less lag, however a single turbo is more efficient. Yes it has more lag but when it comes in hold the hell on:)

I appreciate your comments, guys! I don't mean to offend or clash with anyone by saying this, but I'm sick of people telling me to drop a small-block in my car ... I know it's been done and it's cheap, but I'm a purist, of sorts - I will not stick an engine from a different company into my car - I respect those that can do it and make it work well, but I can't stand it myself. I have decided on running the TT setup for decreased lag, and because I probably won't autocross it as much as I previously thought, so lag isn't an issue. I will, however, drift this car on any occasion, so having the rear end step out under spool up is fine with me. I also like turbos on mountain roads because I feel I'm skilled enough to modulate the throttle to the degree that boost lag or kick is not a problem when cornering (I did not intend to say anyone was not a skilled driver by the previous comment). I'm not too worried about efficiency - though I should be - because I want the response of the smaller T25s, but I had thought about using a Garrett GT28RS "Disco Potato" turbo instead of the TT route. I do also realize that the cost will be signifigantly higher than I had planned, and that's fine. My day job is holding up fine, so as the paychecks keep coming, so will the FedEx guy with my parts. I also really enjoy NA engines, so the choice to go turbo was hard for me (I love the sound of a rowdy NA six-banger under the go-pedal :D), but I won't regret it. In the future, I'll build a 260Z or something like that, just for the NA engine ...

Good luck with that. Be sure to post pictures of your progress. I love seeing custom work.

Drifto, Thanks for your reply. I do encourage you to bulid your car with whatever setup you want, However a TT setup is cool, man thats going to be expensive. Just a thought for you: When drifting you want enough power to; on command get the rear out correct. I would say build the best of both worlds. Build yourself a rock solid bottom end with flat top pistons like what you find in a N/A. Have the block O-ringed and use a copper head gaskett Then use a single turbo like a Garrett T25. This small turbo will sustane 10psi at redline all day long, which is all the boost you would want on a 8.5 to 9to1 compression engine. What this will give you is an engine that has great off throttle response and very little lag. The added compression will spool the smaller turbo very fast so that a moments notice you can be stepin the rear out :D Now with this you are not going to be in danger of blowing a head gaskett. I know someone will probably say" you have to run dished pistons or it will detonaite" thats where your tuning comes in. Think about this, an turbo motor at 8 to1 compression can handle 15psi. So why can't you run a higher compression ratio with less boost? You can! My brother is running his VG30ET with an O-Ringed block and copper gasketts at over 20psi. Thats with 8 to 1 compression, same as a buick GN and they have known to run over 30 psi!! I personally think this would make a very strong engine with power all of the time, not just when the turbos comes in. And its hard to argue with that! By the way this is what I'm in the process doing with my 84 300 turbo. I'll be willing to bet I'll be able to blow my brothers doors off :) With a stock garrett t-3 turbo. From the out side you'll never know! Like I said this is just something to think about let me know what you think.

Thanks for the thoughts - I appreciate them. You are right about the compression ratio and boost deal - it's inversely related. More compression and less boost will yield the same results as more boost and less compression (at least the rods feel the same "boom" when ignition occurs :D) I have given much thought to my engine buildup, and have decided to run a non-turbo block and pistons with a turbo crank and rods, and run the turbo head with a custom turbo setup designed around a T25 or GT28. If I have the cash within the next year or so, I'll probably pick up a Garrett GT28RS "Disco Potato" turbo, and use that on the pressure side. I'll probably use a front-mount 3-row intercooler or equivalent. Thanks for the input, and keep it coming - my plans might change because of what y'all pitch in!

I have a question here... are you sure there's actually a difference between the turbo and non-turbo rods and crank? :D

Well, to be completely honest ... I'm not sure :D. I assumed that they would have to be stronger to withstand combustion pressure and turbo pressure. I could be wrong though ... :D

Fro what it's worth,(not much I'm sure), I don't know the dollar numbers but have you thought of supercharging the N/A? Procharger has a bolt on universal(ha) kit for tuners based on original HP. They claim a boost up to 22 or 24 psi. I'd have to check their site again to be sure. Check 'em out www.procharger.com. Just a thought.

I've thought of that and looked it up. Theoretically, it seems like an easy bolt on, but.......since we have older cars, a lot of the parts have to be modified or fabricated to get the job done right. Unless you're a wizzard with a torch, or know one, it looks like it could be a real hassle.

Just my opinion.

I asked because I think they are the same. Only the pistons themselves are different and the rings. But the pistons are the same casting. The difference is that they are dished and have thicker ring slots or whatever you call it. The NA L28 block is super strong and basically you just put in better rings to handle the extra pressure.

The F54 block is the same, N/A or Turbo. 79-83 blocks are all the same. They are also the strongest with internal webbing. Any high HP motor I would strongly suggest using this block.

Awesome - now I won't necessarily have to rebuild the bottom-end just yet :D So here's the plan - I'll run my stock F54 with the P90 turbo head, intake, exhaust, turbo, intercooler (assuming turbo ZX's have one), fuel injectors, and ECU. Am I missing anything? Also, is the turbo cam any different? What do you suppose this combo would make at, say, 8-10 pounds of boost (or is that too high to start with?) and 92-octane unleaded? If I were to take my pistons to an engine machine shop, do you think they'd cut my pistons so I could run turbo rings or doubled-up NA rings (or is this even a good idea?)? Running my stock NA hardware with turbo goodies sounds like a wallet-friendly plan, and since I live about 35-40 minutes away from an all-Z junkyard (that's where I plan to get my R200 LSD ;) ), I can get all the goodies fairly cheap. If I spy anything good, I'll let y'all know!
I'm loving your guys' opinions and comments - they're keeping me sane when it comes to decision making :D keep 'em coming!

That is true, the F54 is the same as far as the block, but it's years are 1981-83. Not all years of the 280ZX use the F54 block. The 280zx was made from 1979-83.

Thanks Bleach you are right. I dont know what I was thinking :confused: The 79-80 blocks were still N42 with dished pistons. There you go Drifto, you can get out cheap, use a 75-80 block with the dished pistons and your p90 head. I don't think I would go that route but at least I told you about it. However I would not have my N/A pistons cut. Just get you a set of dished pistons. Well Bleach I believe we have told everything we know!! HAHAHA :D

Ya, have fun! I would not waste my time doing what you are doing but maybe you have more time to waste than me. Just turbo the rebuilt NA engine and keep upping the boost till it blows up or catches fire. Then you can junk the car and go buy a 280zx turbo. :D

Catching fire? Scrapping the Z? :eek: These are things I'd rather not think about happening to my baby (she has sentimental value to me, cuz she's been in the family since new, aside from a brief ownership outside the fam). Unless I can find a cherry turbo 2+2 anywhere for cheap, I'm sticking with my Z. I appreciate the great amount of information that has been put into this thread - I've gained so much knowledge of Z engines and setups! I'll probably end up running 6-8psi through the engine (stock turbos run 7 dont they?) until I start blowing rings, or things start breaking ... hopefully that doesn't happen any time soon.

Anyone know anything about an L28ET in a 510 making 500-something hp? I'd like to know the specs of that engine :D ...

This is going out on a limb, but I'm a glutton for punishment, so here we go ... can I have the engine blueprinted to run to around 7000-7500rpm reliably under pressure? I'd like to install a hot cam and valvetrain goodies that will add to a very useful powerband, but add a little more in the upper-rpm range. I've drifted the Z several times bone stock, and I'm hitting the rev limiter way too soon in second gear - I'm thinking raising the max rpm capability of the engine will help with this problem. I could go get a taller gearset, but I don't feel like losing a 3.9:1 ratio - it's really great on the street. Speaking of which, how's the rev-limiter connected to the rest of the electrical system (or is it?), and can it be easily removed?

I didn't know there was a rev limiter. Maybe your valves are floating at redline... if so, your engine is wasted by now.

No limiter, huh? So basically, if the car were factory-stock, nothing wrong or out-of-spec, it should rev up till valve float takes over or it throws something? This is weird because it revs up to about 6500rpm then drops to about 5900-6000 and back up to 6500, in quick robotic fashion like a rev limiter ... :confused: If no 280ZXs had limiters, why does this occur? Could this be an add-on that the one out-of-family owner did?

I've only taken it up to 6500 a few times, and every time it did as mentioned above, with one exception being when I downshifted on the freeway to pass an old couple in a Z06, and I buried the tach needle, no problems ...

Anyone know what's happening? The engine was rebuilt by my brother about four years ago, and he used all Nissan-OEM parts where needed. He's built several early L28s and L24s, and they all run fine ...

Could this be another addition to the long list of Z finicky-ness? Is this car posessed?

Also, while on the rpm matter, can I take the engine above 7000 while on boost with the planned setup?

Isn't 6400rpm redline?!?

The OEM cam is fairly short duration. You won't be getting much air at that RPM. I would imagine you are experiencing some sort of valvetrain failure or lean burn/misfire at that rpm. Just a guess. The ECU for that fuel injection is pretty basic. It was designed back in 1974. I know for sure the distributor has no limiter.

yeah, the red's at 6400 ... so just the stock cam (and valve float) holding me back? Is the turbo cam any more aggressive, or would I be better off getting a hot performance cam than waste my time with the stocker? I'll be getting stiffer valvesprings and probably lighter valves in the future, maybe that'll help too.

By the way, now that you mention a lean burn / misfire condition, the supposed "limiter" I've been experiencing resembles a high-rpm misfire :p how silly of me to overlook that! Since the turbo head obviously flows better, would that (along with a hot cam) eliminate the high-end power fade as well? I might invest in either an Electromotive TEC-III or a MegaSquirt n'Spark management system in the future, and with upgraded fuel injectors, should be no problem controlling fuel and ignition. I guess right now the priority is to get the car running with the turbo setup...

Now, on a turbo intake manifold, there's an emergency pressure relief valve, right? If I remember correctly, it's set to open at around 7-8psi, and acts much like a blowoff valve ... any pros/cons of having this besides protection from overboosting? Also, is there a blowoff valve or an intake pressure vent anywhere on the manifold side of the turbo?

My apologies for being so annoying with handfuls of questions - I just like to know what I'm doing! :D

A head port on the intake and exhaust ports along with a really long duration cam is what you want for your high rpm adventures. Headers, 2.5" exhaust, port matched intake manifold, 60mm throttle (port matched as well) and any other intake work. Most people don't always run at those rpms but it sounds like you want all your power up there.
Go with about .460 lift and 290 duration for your cam. That'll give you power to 6500 rpm. Also, the turbo cam has different duration for intake and exhaust. It is made for a totally different engine. Do not build an NA engine thinking you'll just add a turbo later. The design of the two engines is totally different.
The turbo head only has mildly better exhaust flow; and its really only in theory. People race with the P79 head. No problem betting 200whp out of an NA L28 with that head. well, with lots of work done to the engine of course.

I like to think of myself as a boost-head, but in actuality, I don't know much about turbocharging non-turbo cars. I've had a good deal of experience with late-80s Dodge and GM turbo cars, as well as a few late-model Mitsubishi turbos. I do know a decent bit about NA engines, as I've built a good few myself. I also see the differences between NA and turbo engines. I'm simply trying to find a good balance between high-end NA power, and low-end turbo power. So I figure on running my stock non-turbo bottom-end and pistons, with turbo hardware up top. If I can get away with turbocharging the NA engine with the NA (P79) head, I'll do it - I've seen the capabilities of the P79 head in action on my brother's auto-x 260Z.

I don't plan on revving the engine too high for too long - I just want a long, usable powerband that's strong in the upper-rpm range yet still packs a punch down low in the revs. After all, she will be my daily as well as a dedicated drifter.

The next time this engine turns over it will be turbocharged. That's why the car is still on jackstands (and 'cuz the suspension's shot ... :D ) Is it possible or practical to run the P79 head with a stock Z turbo setup? That would mean I would only have to get the ECU and other fuel system bits, as well as the turbo intake manifold, correct?

Also, since I'm guessing the car is OBD-0, I could theoretically get away with running a stand-alone engine management system on an emissions-tested vehicle ... correct me if I'm wrong? I remember a friend telling me that the Honda world is something like that - if they're running an OBD-I equipped car, they can't legally run an OBD-II engine, and if they adapted the OBD-II engine to an OBD-I system, it would nullify the power gains originally sought after.

Yay! I love confusing everyone!! The help is much appreciated.

OBD-?
uhhh... I use the factory Bosch fuel injection. :p