im going turbo on my RS...i read on a thread here that said "if ur going ALL MOTOR, u'll need higher compression pistons"...now is this mean if im going turbo, then i DONT???

 

its not a yes or no question.

 

Do you want a better burn and faster spool, or big boost numbers and great lag? The first would be high compression; the second low compression. If you go high compression buy the N/A application JE
forged pistons. If you go low compression then it's up to you. I say use the N/A design because they retain the Quench zone on the piston to resist detonation if you ever wan to crank it up a bit more. On the low compression set-up it doesn't really matter, but the N/A design would still be a better choice to improve breathability and spool up. I would also buy the Endyn design for they match the head chamber better than the off-the-shelf variety.

 

try searching, there have been a few posts covering this in depth

 

High Compresion : YES

 

high comp = low psi boost

low comp = high psi boost

 

High Psi = Quick spool up and very much wanted low end torque. Imagine embarassing a Mustang off the line with-out holding the rpms up there too high and doing a clutch drop. I love the look on their faces when you burn them off the line.

 

its a matter of compromise...

power vs tuning/reliability vs turbo psi

a 10:1 CR motor at 10 psi will make for example 200 horse
a 9:1 CR motor at 10psi wil make for example, 190 horse.

jsut numbers- not realistic at all.

the 9:1 motor will be easier to tune, and will have a lesser chance at detonation than will the 10:1. BUT, the 10:1 will make more power for any given psi.

its a trade off.

its static vs effective compression.

Effective compression is the sum of the static compression, plus the additional compression added to the cylinder by a turbo or super charger, or any other forced induction tool for that matter. Effective compression is defined by the following formula:
E = C((B / 14.7) + 1)
Where E= Effective Compression, B= boost psi, and C= Static compression. Also remember that 14.7 is equal to 1 bar of boost.

 

ohh forgot to add-- read this:
http://store.yahoo.com/speedupgrade/turcommyt.html

Matt knows his ****.

 

wow i never knew i would get so much "real" answers here. thanx for ALL the info guys! but for now i think im gonna stay low compression "and call it a day". besides i cant find a cheap dyno place around here to properly "tune it"

but again thanx for the good info!!

 

do search under (creator) "Charlie Moua" in the arcihved files. I posted the same question like 3months ago & got a lot of good advice & replys.

 

I have seen a few high compression and boost posts in the past 3 months. I have done it and would recommend against anything higher than 9.8:1 for a street car. Even if you are fully built. Spool is really good and little to no lag. I will post some pics as to why not to do it tonight.

 

uh-oh.....

 

melikes compression

 

Sounds like someone used high compression dished piston in their set-up.
Dished pistons are a NO-NO when running high compression and boost haven't you ever listened to me preach that before? I'm sure you haven't though seeing as how I've only been a member for like three monthes. I could have told you **** happens when a crappily designed piston tries to handle boost like that. I'm telling all of you that the best is the forged N/A application pistons they promote a faster COOLER burn that's why they can use such high compression N/A because of the better burning characteristics. Wouldn't you want that to prevent detonation?

 

forged N/A meaning stock pistons? sorry for not knowing...

 

Stock pistons are not forged, they are cast.

So what you are saying is that for a turbo setup, the best pistons to use are aftermarket forged pistons which are designed for N/A use?

 

Nope used custom JE domed pistons. I would actually recommend a flat dished 9.8:1 for a better burn with FI. Will take pics when I get home tonight...

 

i am running 10:1 JE pistons on my Prelude..... i read soem things that say it should help elimniate lag, plus i figured if when i cost the headgasket with copper coating, i figured that it *should* casue the compression to drop a couple tenths of a point (i really coated it well), i also did not drastically over bore the iron sleeves (only factory specs), and i used ARP headstuds. once i get my Hondata installed and tuned, i should be able to run about 14psi daily. it's all about tuning, plus, with a H22, 10:1 isn't really high, it's actually the stock compression ratio, so i should be straight, especially since i'm only running an 18g turbo

 

Hmm so what are you saying? I have Arias 11.5:1 pistons. You're saying they handle the boost better? Like I know that it takes a much smaller turbo, but the piston design is better?

It would be nice if I didn't have to crack the block when I turbo in a year or so, but 11.5:1 is risky isn't it? Or is it a non-issue if I spend the money on a standlone system?

 

I've run 12.5:1 with 5 psi recently on pump gas.

The difference between domed and N/A is the simple fact N/A is designed to run higher compression and maintain combustion stabilty. Domed variety are designed to raise the compression, but do not take combustion stability into consideration.

Layman terms: Domed = We have higher compression pistons here, but
tuning is your worse nightmare.
N/A = We have higher compression pistons designed
specifically with higher compression and combustion
stabilty in mind. Easier for tuning with-out exotic
fuels.

With tuning it is very possible to run high compression N/A pistons with boost. It's all in the piston design. Let them keep running higher compression dished pistons all they want I'l have someone to watch blow their stuff up trying to keep up with me at the track. I'm not to sure about the Arias pistons though I've only dealt with Endyn's JE design and now I'm working on my own design. I hate being broke all the time. I'd say all you would need is a wideband, an egt monitor, and a standalone to take to a dyno and get some tuning in. Good luck with in just take it slow nothing drastic just to be careful thats' what I'm doing. If you most to feel safer run alcohol injection set very low or with a trigger in the cabin when you see the egt's rise squirt it. You'll at least know where your troubled spots are at so you can work them out. It's a slow process that's why most people forgo it and buy dished pistons.

 

could someone list the types of N/A designed pistons compared to the average domed high compression piston. this was mentioned but i want to be sure i understand it better and also which categories the different brands fall into, if any.

as was mentioned i'd think that SRP/JE pistons are the average "domed" piston and the Endyn rollerwave pistons are the "N/A designed" piston for a better combustion process.

edit: i'll be choosing turbo pistons eventually and was wondering what brand/style to go with. i'm more into the higher C/R even with a turbo setup, but i don't want to go crazy with over 11:1 C/R. i currently have a built B18C1 block with stock sleeves and 11:1 C/R SRP pistons which i was thinking of using for turbo before getting the block resleeved/overbored with new pistons in the 10-10.5:1 C/R range.

any input on this?




[Modified by sweet, 12:08 AM 12/10/2002]

 

N/A are just pistons designed and cleaned specifcally for your head and any work do to your head. They maximize the Quench zone to increase the stabilty and compression ratios. The normal domed variety are like the ones that I can order out of the catalog that haven't been matched up properly IE shaving or polished to maximize the quench area which is key to increasing stability (along with a few other things, but that's most important with Honda's). The Endyn rollerwaves are JE's just a better designed variety that do qualify as N/A (if they state it is). I do agree that JE's are the best regular market design I've seen though. An 11:1 would be a nice start on a turbo build if you ask me. Also I wouldn't lower the compression I'd keep it where it's at. You already own the pistons.


-N/A is just a way of saying not meant for any sort of forced induction or nitrous.-

 

So let's say I have a GSR motorthat I want to boost and want to keep the compression the same (10:1), would this be OK to just get the same compression as stock?
Or would I have to get like a 9.8:1 comp. flat top?

What piston brand does everyone recommend for boost?

 

I'd go JE same comp. as stock NO flat tops.