Steven280ZX

well guys i'm really confused now and lets see if we can get a bit of a debate going here. i'm told that dished pistons decrease c/r and therefore allow us to run more boost from the turbo. this is older thinging. nowadays there are not dished pistons in turbo charged cars. so why would someone whos doin a turbo conversion get dished if they could get flat tops that would survive the heat at a c/r of 9.5. i was talkin to brian from wiseco pistons and he said most ppl are running flat tops at a 9.5 c/r. so here's the question. to dish or not to dish?

SHADY280

i would dish here steve, dont forget that was the old way of thinking, these are older cars with 1970's head designs

Steven280ZX

well the wiseco guy said that other Z's have been flat topin it and thats what he had in his zx a while ago. i told him to keep the c/r at down to about 8.3 but these things would be able to hold the turbos boost and a wet shot of nos so i dont see y else i'd need to dish. dished just lowers the c/r and the stock c/r is at 8.3 for na and 7.4 for turbo. so y lower compression given these circumstances?

SHADY280

c/r for the stock n/a is 8.8:1 with dished pistons, and 8.3:1 with dished with larger chambered heads for the turbo cars. so basicly, whatever comes stock is good enough on the turbo engine, and is basiclly the head that makes the difference. the p79/p90 heads are for turbo only in there unmolested state. deck .080" off them and they make wicked n/a heads

Steven280ZX

well wut i was plannin was a 1mm overbore and flat top pistons w/ 8.3 c/r. i can still run loads of boost and 300hp would be a walk in the park. so still im sorry if i didnt understand correctly but i still dont see y bother dish?
EDIT: my head is a P79 and i no these can still tackle the job

NismoPick

You have 2 options...

Correct dished pistons = option to run more boost

Flat top pistons = less boost

Remember, as you increase boost, you increase CR. If you start w/ a high CR, then when you boost, your CR gets really high (running 8:1+ CR, at 10psi boost you'd be at about 16:1 CR)... higher CR requires higher octane to prevent detonation. It's your choice... but Nissan wasn't stupid when they built the L28ET w/ dished pistons.

NismoPick

Really? I'd like an explanation on that one....

Steven280ZX

well remember man i'm regurgitating wut the guy told me. he says bout 18 psi can be ran in this setup... realistic? if the c/r is at 8.3 how much boost can be ran? how low must it be so that i can run bout 20 and can a pray for 20 miles to hte gallan?

NismoPick

You need to read some books





I'm serious... do research before jumping into this project. You need to learn some stuff.

There's also lots of old threads here on ZDriver talking about L28ET setups.

Bleach

First of all, if you run stock flat tops in a P79 head you have.. umm, exactly what came from the factory in 1981-83. So you will have 8.8:1 not 8.3:1
1mm overbore will increase the air intake so you'll end up most likely with 8.9:1
Like was said, the reason newer turbo cars can have higher static compression is because of engine technology... that is something you don't have. When was the L-series designed? about 1967 dude!!!! 1968 510 had the L16 and you're still using that engine design.
Even the fuel injection is based around a 1975 Bosch system.
If you wanted to run 8.9:1 compression, at the very least get MegaSquirt and spark that way you have fully programable engine management.

The 350Z has awesome head design and 10:1 compression or so. With modern fuel injection most companies would not want to run more than 5psi on one without dropping the compression. Keep in mind they got almost 100hp gain with that 5psi due to other factors... but still...

18psi is a lot and your advisor is not all that smart. That would be actually close to what the max pressure these engine can handle at stock comression ratio of 7.4:1 If your engine is running good you should have way more than 300hp at that point.

If you go withflat tops, get a 2mm head gasket and other fuel management. If you don't have money for that then just run the engine stock. Up the boost later. You can still get 300hp if that's what you want. It will cost you either way you go. There are no shortcuts unless you want to just blow your engine real fast. Dump a 100hp shot in there along with 18psi and go cry to your buddy about how he gave you bad advice when your pistons shoot out through your oil pan.

Is this guy trying to sell you flat top forged pistons or something?

Steven280ZX

he's tryin to sell me flat top forged pistons ur rite but at first i told him i wanted dished(there they same price) so he went thru pros and cons.
what i had in mind for a setup was a upgraded fuel, spark, air intake, and cam, to go along w/ the pistons and turbo. so ok final questoin. flat top means not much boost can be ran but dished means more can go in. how much of a dish and how much boost to reach 350 - 400hp?

NismoPick

Stock dished should be much cheaper than forged.... I'd get away from that guy!!! Dished should be about $350-$400... forged $750+

If we need to spell it out for ya... BUY NISSAN L28ET PISTONS.

EDIT
To get to 400hp... you're going to need:

T3/T4 hybrid
External Wastegate
MegaSquirt
450cc injectors
Big *** intercooler
MLS headgasket
etc etc etc

EDIT AGAIN.... bro, like I said before, there's tons of threads about this on here... search it. We can re-type this stuff all day, but it's already been said.

And we can feed you info all day, but if you don't research it for yourself, you won't learn.

Steven280ZX

ok got it dished pistons she will be. umm whats the c/r u turbo guys r runnin? did u keep it around the same at 7.4? i want an idea of what others are doing?

Steven280ZX

sorry for any mix up they wer $800 cuz they wer 87mm forged dished pistons

NismoPick

YES... 7.4:1 CR

NismoPick

Read my edits above.

Steven280ZX

hmmm how much boost does tht support?
damn nismo after all this u must think im sum kinda stupid kid like blackcrow but yeah man do i appreciate it.
EDIT: oops just read ur edit disregard this post

Steven280ZX

ok so before we go crazy lemme just tell u what im doin
fuel system:
450cc injectors
pallnet fuel rail
255lph fuel pump
air intake:
60mm throttle body
intake manifold ported and polished to match head
Block:
87mm forged DISHED pistons
turbo oil pan
Head:
msa cam kit
Turbo and components:
garrette t3/t4 hybrid ball bearing (GT 28 i think it was)
spearco intercooler
sandwhich addapter to tap into oil feed lines
uhh well i think thats it?
remember i got some years to work on this

NismoPick

NO NO!!! Don't say that!!!

You're fine... I always push for people to do their own research. If you go fully studded you can prolly run 20psi boost.... you're not going to want to run 20psi all the time.

Steven280ZX

ding ding u hit the nail on the head
im gunna do 2 setting oops forgot megasquirt
race track and fuel effiecnet(see how much mpg i can pump out w/out messin her up)

NismoPick

ARP head studs, crank studs, rod bolts.

MLS headgasket

Steven280ZX

u really think i need those? or just for raceing?

NismoPick

fuel efficiency depends on how well the driver can stay off the throttle.

NismoPick

ya kiddin right?

Steven280ZX

... course im kiddin stock wouldnt hold up i new id need a headgasket cuz mine was blown hey forgot to update engines in pieces outa bay took her apart fully cept crank rods and pistons r still in block