z-ya Posted September 2, 2005 Share Posted September 2, 2005 Anyone Running Boost on F54 Flat tops and P90 Head? I figure the CR to be around 8.5:1. A 2mm gasket will lower it to around 8:1. Are the F54 OEM flat top pistons up to lets say 7psi of boost? Thanks Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 2, 2005 Share Posted September 2, 2005 Isn't Drax running flattops w/P90? Seem to remember that... and pinging issues... Quote Link to comment Share on other sites More sharing options...
mario_82_ZXT Posted September 2, 2005 Share Posted September 2, 2005 8.5:1 isn't too high to turbocharge, you get the off boost response of an NA car with the added bonus of boost. I have also been told that flat top pistons and the P90 head make an excellent quench design, again, really good for turbo charging. This is going to be the setup I build when I have time/money/no school. Mario PS I believe Pallnet is running this with SDS with great results. Quote Link to comment Share on other sites More sharing options...
Guest Jason84NA-T Posted September 2, 2005 Share Posted September 2, 2005 Yup, any C/R up to the low 9's will work well turbocharged. While 7.8:1-8.3:1 will work best for an all-out power machine, the added response and fuel economy of a higher compression engine is well worth it IMO. I've had turbo VG's with all available factory compression ratios (9:1, 7.8:1 and 8.3:1). I liked the higher compression mostly for the lowend pull and gas milage. My brother had a P90A head on L28T in his 240 with both the dished (first) and flat (second) pistons. At 16PSI on a T3, the car had run its best times on the higher compression. Again, obviously, more power with the same boost pressure. Quote Link to comment Share on other sites More sharing options...
z-ya Posted September 2, 2005 Author Share Posted September 2, 2005 So would you guys say that the Nissan OEM flat tops are as strong at the Nissan OEM turbo pistons? I believe that their design is similar. Thanks, Quote Link to comment Share on other sites More sharing options...
mario_82_ZXT Posted September 2, 2005 Share Posted September 2, 2005 So would you guys say that the Nissan OEM flat tops are as strong at the Nissan OEM turbo pistons? I believe that their design is similar. Thanks' date='[/quote'] The turbo pistons have a dish, which lowers compression, and is not good for quench. The other difference is I think the ring lands are stronger on the turbo pistons (I think), but the NA's can take a beating. For a sweet setup, go forged! Mario Quote Link to comment Share on other sites More sharing options...
turbobluestreak Posted September 2, 2005 Share Posted September 2, 2005 One word "SEARCH". yes non turbo flat tops can be used but any repeat any detonation will break the ring lands. But then again I've just broke my turbo dished pistons with detonating under 20 lbs of boost. You can do it but don't except it to last too long. tbs Quote Link to comment Share on other sites More sharing options...
frank280zx Posted September 5, 2005 Share Posted September 5, 2005 That is what xander did, it is a very nice aproach,a n modern aproach to turbocahraging, that i will do aswel when my engine fails Quote Link to comment Share on other sites More sharing options...
Sean73 Posted September 5, 2005 Share Posted September 5, 2005 Yes. I am running flattops. Pallnet also runs this setup. A search will yield lots of info and debate. Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted September 5, 2005 Share Posted September 5, 2005 I used to run 12psi with a P79 and flat tops. The throttle response was great. It's in the engine managment. Quote Link to comment Share on other sites More sharing options...
spork Posted September 6, 2005 Share Posted September 6, 2005 Slightly different answer, but I had custom pistons made and went with flat tops for the better quench and am using a 2mm HKS Gasket and I'm at 7.8:1 I know this isn't exactly what you were asking, but the stock flat tops will work great...but detonation will kill them. If you can afford it, and plan on making a lot of power or pushing your car hard, Forged pistons may be a good investment for your project. Quote Link to comment Share on other sites More sharing options...
AK-Z Posted September 6, 2005 Share Posted September 6, 2005 It was my impression that the stock pistons could handle up to 225hp. BTW has anyone seen a TT exhaust manifold for the L engines before. I know that they used to sell them in japan but didn't sell them state side because the steering collum got in the way. Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted September 6, 2005 Share Posted September 6, 2005 Again, not exactly a straight away answer, but my old 3.1 liter forged stroker was a about an 8.7:1 compression motor (I did not cc the head, so the exact # is unknown). I could run no more than ~10 psi without getting detonation on 93 octane. I did run 21 psi on 110 octane without any problems and could have run more I am sure. I know many of you hear the newer cars running 8.5:1 or 9:1 compression ratios on turbo cars, but that is newer technology (4 valve heads, cross flow , etc). My point is that the L series motor as we know isn't the best design. Having both the intake and exhaust on the same side and all the heat that is generated under the manifold, hampers performance to say the least. My next forged motor (currently in it's preliminary stage, as I am about to order pistons) will be more along the lines of 7.5:1 or maybe even a little less. The lower your compression (within reason), the more boost you can run without detonating on lower octane fuel. The additional boost more than makes up for a slight loss in compression and off boost throttle response with a significant increase in horsepower, in my opinion anyway. If your plan is quick throttle response, are not planning to run a lot of boost on pump gas, or are going for better fuel consumption, then by all means a 8.5 - 9.0 compression L28 turbo motor is great. If you would like to safely run higher boost on pump gas, don't mind sacrificing throttle response for more daily driven horsepower, then go low compression All I know is that I can make significantly more power with my stock 7.5:1 compression 2.8 liter long block by running more boost on pump gas than I could make with my 8.7:1 compression 3.1 liter forged stroker motor on pump gas where I was limited to that 10 psi. just my .02 Quote Link to comment Share on other sites More sharing options...
stagefumer11 Posted September 6, 2005 Share Posted September 6, 2005 Intresting read. Im really keen on doing this myself. But not really sure what the early l28'e had in the block design. Im swaping all the turbo gear off my l20et and putting in GTR 440cc injectors to make up for the fuel side. Im sure in term this would stop the large pinging isues knowen to doing this ? Quote Link to comment Share on other sites More sharing options...
Drax240z Posted September 6, 2005 Share Posted September 6, 2005 Isn't Drax running flattops w/P90? Seem to remember that... and pinging issues... Nope, I'm running turbo pistons with an N42 head. 8.3:1 CR. Pinging issues were a combination of tuning, and oil burning caused by a bad turbo seal. Quote Link to comment Share on other sites More sharing options...
Gollum Posted September 6, 2005 Share Posted September 6, 2005 z-gad, was your head stock on the 3.1 liter? Was it ported and polished? I'd assume this would make a bit of a difference. But I see your point. And once again, most of the problems with the L series come down to the head.... Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted September 6, 2005 Share Posted September 6, 2005 The P90 head had a mild port and polish. The valve guides were cut, bowl area was opened up, and valves were unshrouded out to the 91mm gasket. The valves were also stainless, undercut and swirl polished. There weren't any high sharp edges or high spots in the combustion chamber, and the chamber area was polished as well. I did suffer from a poor cam choice though... It was a pretty decent head. On a side note, the new project head has been professionally ported and sonic tested repeatedly (was ported, tested for thickness, ported again, for 9 weeks, until maximum flow was achieved). The head is an E88, has 1.65" intake ports, uses oversize 5/16 (very narrow stem) Chevy valves, and worked chamber area. It was used on a race motor back in the 80's and has been sitting since. An old racer buddy of mine reluctantly parted with it, but knows it is going to a good home. I will compensate for the high compression head with a significant dish in the piston. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 6, 2005 Share Posted September 6, 2005 Nope, I'm running turbo pistons with an N42 head. 8.3:1 CR. Pinging issues were a combination of tuning, and oil burning caused by a bad turbo seal. Well I guess I had THAT wrong... oops. On the quench and 2mm gasket thing mentioned by spork. I thought those were mutually exclusive. Quote Link to comment Share on other sites More sharing options...
Clifton Posted September 6, 2005 Share Posted September 6, 2005 I had an L26 (flat tops) with turbo a long time ago. It was fine up to 10 psi. Detonation ended up killing it when I got greedy with the boost. Knock is the limiting factoy not HP of boost. Quote Link to comment Share on other sites More sharing options...
violacleff Posted September 6, 2005 Share Posted September 6, 2005 but my old 3.1 liter forged stroker was a about an 8.7:1 compression motor (I did not cc the head, so the exact # is unknown). I could run no more than ~10 psi without getting detonation on 93 octane. Wow that sucks. I was hoping for at least 15 psi on pump gas with a proper tune at 8.5:1. 10 psi is pathetic. Quote Link to comment Share on other sites More sharing options...
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