Shemyazaz Posted October 7, 2011 Share Posted October 7, 2011 Hey guys. I just got my first S30. I've been wanting one for a long time now, and one came up local cheap enough that I just couldn't pass it up. Its a 77' 280. The usual heap of rust, but its MY heap of rust. While I'm mitigating rust damage and replacing 30 year old suspension parts, I thought I'd make some decisions about the engine so I can start amassing all the necessary parts. I have been searching and absorbing as much info about the L series as I can, and a couple questions have arisen. I'm sure they have been asked before, but I certainly haven't found clear answers. I'm working with the current parts. L28E F54 block with P79 head. Flattop pistons. Haven't identified the intake manifold yet. R200 with CLSD. 5-speed trans....which I haven't pulled numbers off of yet. Planning on running a MS3 and relativly large turbo (something like .70ar cold and .86ar hot). 1. Ideally, what prep work would you do on a P79 head prior to application on a moderate turbo setup? 2. How does the stock cooling system hold up? 3. What fitment restrictions can I expect to deal with regarding the l28et exhaust manifold and aftermarket turbos? Any tips or suggestions? Quote Link to comment Share on other sites More sharing options...
luseboy Posted October 7, 2011 Share Posted October 7, 2011 Based off of what I have heard... the f54 block and p79 head are not ideal for a turbo application. For one, the flat-tops apparently have too much compression for use with a turbo (I'd think this would be fine). Also, the exhaust liners are known to break apart under pressure. This is no big deal if it runs through your exhaust, possibly damaging some tubing or a muffler. But it is a big deal when it takes out your turbo's exhaust turbine! You can remove the liners though, I've heard. I am not very knowledgable on turbos, but these are the things I have read. I have the same block and head and I decided to keep it NA. The choice is yours. Quote Link to comment Share on other sites More sharing options...
Shemyazaz Posted October 7, 2011 Author Share Posted October 7, 2011 As long as the SCR numbers I'm getting for this head/piston combination are correct (~8.5:1), then I'm not worried about that part. So the liners tend to jump out under pressure? Thats a good thing to know. Quote Link to comment Share on other sites More sharing options...
neotech84 Posted October 7, 2011 Share Posted October 7, 2011 It's really a matter of opinion, most people shy away form them due to the points noted by luseboy. While others have great success. The fact of the matter is that it's your money, spend how you like but my opinion is run what you got. Do more searching in the FAQ section there are some good reading on head selection and prep work. As far as the stock usdm manifold, it's square port so you will have to resolve that issue. But they flow quite well and the quench area is good. Just be careful on valve size they changed sizes during the p79 life. Quote Link to comment Share on other sites More sharing options...
Shemyazaz Posted October 7, 2011 Author Share Posted October 7, 2011 Thanks Neotech, I appreciate any information I can get. Do you happen to know of any of those old threads that have head prep info? I'm having some trouble finding them. Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted October 7, 2011 Share Posted October 7, 2011 I feel like you should read this, if you really want to make the most of a turbo that size you're gonna need some lower CR numbers. Anyway this thread is about exactly what you want to do. http://forums.hybridz.org/index.php/topic/82371-my-notes-on-the-na-l28-to-turbo-swap/ Quote Link to comment Share on other sites More sharing options...
ArchetypeDatsun Posted October 7, 2011 Share Posted October 7, 2011 There's a guy here that's running a P79 on his L28ET. I'm actually gonna be running a P79 on my L28ET because I got coolant in my engine and my P90A was bad the P79 is fine for boost. Try to see if you can source a L28ET block but If you really want run a turbo set up on that motor you got I wouldn't go more than stock boost. Quote Link to comment Share on other sites More sharing options...
Shemyazaz Posted October 7, 2011 Author Share Posted October 7, 2011 Why would I not want to go more than stock boost? Is the L28 really that prone to detonation? Or is this a warning aimed only at those trying to run hot turbo setups with a stock ECU? To clarify, I have no intentions of trying to run this without a fully programmable ECU. Thats a recipe for melted pistons. About those exhaust liners, are they a big deal to remove? Possibly just grind them out while cleaning up the ports? Quote Link to comment Share on other sites More sharing options...
ArchetypeDatsun Posted October 7, 2011 Share Posted October 7, 2011 (edited) Why would I not want to go more than stock boost? Is the L28 really that prone to detonation? Or is this a warning aimed only at those trying to run hot turbo setups with a stock ECU? To clarify, I have no intentions of trying to run this without a fully programmable ECU. Thats a recipe for melted pistons. About those exhaust liners, are they a big deal to remove? Possibly just grind them out while cleaning up the ports? I'm only telling you what I have read because I used to have a L28E in my 280zx, especially because the L28E can be prone to detonation if you don't have the proper set up. Installing some dome pistons or the dish pistons off an L28ET would solve your problem but I'm sure someone here is running a similar set as the one you want to run. The exhaust liners on the P79 most probably won't fall off, but if you try to grind them off be careful not to damage the head it is a risky move. BRAAP I believe is his screen name is running a P79 head in his turbo set up so far nothing wrong has happen. The exhaust liners actually help burn off any carbon it will probably help with the a turbo set up. I would run an Intercooler as I will in the future so you should be fine unless of course you wanna give it a try to get those liners off. Edited October 7, 2011 by 280zx@541 Quote Link to comment Share on other sites More sharing options...
duragg Posted October 7, 2011 Share Posted October 7, 2011 F54 comes in both flat and dished pistons, no? I think a big part of the detonation problem is the exhaust manifold proximity to the intake manifold. Its a giant heat-soak chamber. Awesome for changing plugs and oil. Crappy for a nice cool intake charge. Quote Link to comment Share on other sites More sharing options...
Shemyazaz Posted October 8, 2011 Author Share Posted October 8, 2011 F54 comes in both flat and dished pistons, no? I think a big part of the detonation problem is the exhaust manifold proximity to the intake manifold. Its a giant heat-soak chamber. Awesome for changing plugs and oil. Crappy for a nice cool intake charge. Yeah. Being a non cross flow head is probably one of the biggest drawbacks of the l28. Must be hell on the IAT. I imagine that aftercooling is a must for anything above the stock pressures. Of course, running a larger hot side will help keep some of that heat down. Meth injection is probably a godsend for this engine. I think I might get a hold of another head to prep while I'm gathering parts. That will help me keep my downtime low. Anyone know of a good used parts source for these? I looked at ebay, but the pickins seem a bit slim right now. Quote Link to comment Share on other sites More sharing options...
Leon Posted October 8, 2011 Share Posted October 8, 2011 I imagine that aftercooling is a must for anything above the stock pressures. Uh-oh. Quote Link to comment Share on other sites More sharing options...
Shemyazaz Posted October 8, 2011 Author Share Posted October 8, 2011 Uh oh? What did I do now? Quote Link to comment Share on other sites More sharing options...
Leon Posted October 8, 2011 Share Posted October 8, 2011 A little discussion we had recently: http://forums.hybridz.org/index.php/topic/101932-compound-and-twin-charging-discussion/ Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted October 8, 2011 Share Posted October 8, 2011 (edited) Too late....I heard it.....strange how it keeps coming up. Your P79 will run identical to the P90 on a F54 with flattops and I ran one 20,000 miles at 7psi boost without any liner issues. Higher boost............not so sure of liner longeivity. I did switch back to the p90 head because I was worried but they looked fine upon inspection. You won't be able to run as much boost as with the dished pistons but that is a bit debatable since I don't think I've seen anyone run high boost with forged flat tops in a L28 turbo car yet and the quench pad (p90 and p79) brings detonation resistence that is compromised by a dished piston. Of course, the dished piston is lower compression ratio. I've run 87 octane with 6psi and an intercooler without pinging and a good tune could possibly allow higher boost even with 87 since I am doing it on a non-tuned ecu that features pretty aggressive timing advance that was mapped for a non-turbo engine. I mentioned 87 but I don't recommend running anything but 92 or 93 octane with the f54 flat top and p79 combination. Edited October 8, 2011 by HowlerMonkey Quote Link to comment Share on other sites More sharing options...
Shemyazaz Posted October 8, 2011 Author Share Posted October 8, 2011 LOL. I see. Well, I have no attachments to the word so I'll discontinue using it to avoid any unnecessary arguments or conflicts. I will be running an intercooler. I'm pretty curious about this det thing though. This isn't really what you would call a "high compression" setup. Even with the non crossflow design I wouldn't figure it would be that prone to det without some serious design flaws in the combustion chamber. Is anyone here running flattops with a full management system who could chime in? I was running 15-19 psi (creep issues) on an NA VG30E block with a fairly large turbo, and once I got the tune worked out in the upper parts of the map det was hardly ever an issue unless I got some bad gas. That was at about the same CR as what this is supposed to be, so I figure there must be some issue with the head if people are having that much trouble. Quote Link to comment Share on other sites More sharing options...
FricFrac Posted October 9, 2011 Share Posted October 9, 2011 The P79 AND P90 have the best quench which will be important in preventing detonation. There is so much info on here about L28ET builds including high compression that it's difficult to dig up and/or post all the info. IIRC Flatblack was running a high compression setup but a simple search will reveal a lot.... The stock intake manifold is quite restrictive. Although the L series isn't a cross flow head by the time they got to the P90 the head had been tweeked and optimized a fair amount and breathes quite well. It's fairly simple to reduce radiated heat from the exhaust. Wrap the header, turbo and downpipe and increase the size of the stock heat shield and add a heat screen to the shield itself. Regardless of which way you go if you focus on efficiency (more efficient modern turbo, efficient intercooler and setup, etc) you will be able to squeeze more power from any engine. Tuning on a dyno will let you get the max from your spark map BEFORE detonation occurs but without a tune on a steady state dyno for each cell it's nearly impossible to optimize power AND keep a margin of safety. Quote Link to comment Share on other sites More sharing options...
Shemyazaz Posted October 9, 2011 Author Share Posted October 9, 2011 Sounds good FricFrac. Thanks for the reply. I've been digging around here, and sifted out enough good info that I'm pretty confident in this build. The wife and I are discussing target power output, and by the time we have the suspension installed in the next month or so we should be able to start scrounging up engine parts. Quote Link to comment Share on other sites More sharing options...
neotech84 Posted October 10, 2011 Share Posted October 10, 2011 I recall reading somewhere ( L6 FAQ?) that BRAAP prefers the P79 for the quench, the reference was NA so I can't voice his opinion on turbo. It sounds like you have a great plan and back-up for when things go wrong. Planning is key for anything, you sir have thought about this and are ready to move forward. I say, do it and don't look back. And Keep reading! It blows my mind some of the things people have done with whats considered "old technology". Quote Link to comment Share on other sites More sharing options...
NewZed Posted October 10, 2011 Share Posted October 10, 2011 (edited) Here's one thread that refers to the P79 and flat tops. I think that you might be misremembering some BRAAP comments. Post #18 is relevant. http://forums.hybridz.org/index.php/topic/96882-p90-vs-p79-cylinder-head-for-na-31l/ There is also another thread out there that discusses quench in detail (can't find it) Edit - found it - http://forums.hybridz.org/index.php/topic/63444-l6-squish-discussion-the-battle-against-detonation/page__pid__735389__st__40#entry735389 See #23, plus the link it refers to. Edit #2 - still not sure if the stock P-70/flat-top combo has the required low clearance to qualify as a bonafide "quench." Someone (maybe 1 fastZ? and BRAAP? and others) made some interesting comments about how there is no such thing as "some quench" or "partial quench". You either get a full quench or "squish", or you don't. I believe that means you're either pushing all of the unburned charge, that would otherwise detonate, out in to the burning charge, or there is a residual pocket of unburned charge that gets pressurized and explodes (as opposed to controlled burning). There were details in the thread about needing to get the top of the piston very close to the head at TDC in the squish area, otherwise your supposed "quench" area was ineffective. It seems about 50-50 on whether or not you can even use the N42 with flat tops using NA and avoid pinging, at the optimum timing advance. Most of what I've seen recommends a lower CR if you're going to use a turbo, unless you want to live on the edge. EDIT - Got my N42s mixed up with my P79s. Sorry, half of the above is irrelevant. The quench part I still wonder about. Edited October 11, 2011 by NewZed Quote Link to comment Share on other sites More sharing options...
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