what compression ratio for more boost
 

curently running 17psi what would be a good compression ration if i wanted to up the boost to around 25psi and what make rod/pistons would be good i know weisco ones are top not but ideally want some a little more pleasing on the pocket

thanks

1:1

What's your setup? What turbo? What's the car used for? How much power are you looking to make? Is English your first language? Are you 17 and from California by chance?

sorry for my punctuation spend alot of time on msn messenger

no i'm not 17 nor am i from california i am a 22 year old mechanic from england

im using a gt2876r ball bearing garret item it gets used as a daily driver and as a track toy my friends have skylines and evo's and i am on a quest for more power from what they call my hairdresses car

it currently produces 277bhp from a 1600 and i dont want to up cc

What the fuck mate? Why dont you learn how to use bloody periods and capitals you fucking wanker. Does this look like msn messenger to you?

miataturbo.net :ne: msn messenger

why don't you cock suckers go bitch somewhere else

madmalc it is really kind of a trade-off. The higher compression your pistons are the more power you will make off boost, but the less air you can cram in. Pistons with lower compression have less power off boost, but help you cram more air into the motor.

Sorry i appoligised! Dont particually like being called a fucking wanker

I asked quite a sensible question, which i had hoped i would get a sensible answer! Oh how wrong could i be! Quite right, how the question was written wasn't very well worded but it was easy enough to understand.

Certainly looks welcoming to a newbie if this was the 1st post they read.

WTF? This isn't m.net. He types like a 17 year old kid, doesn't search, and expects serious responses?

I understand the lower/high compression ratio pros/cons, just really wondered what other people were using for similar boost levels and which makes were good and recomended

To be totaly honest money isn't the issue here more the fact of what is good and well recomended

not every thread needs to become a flame... simple typing errors aren't enough cause to deface a thread that could yield useful info even if the topic has been covered before imo.

this is the engine bay

Attachment 208139

at miata.net they are more concerned with spelling and grammar than they are about compression ratios. so no, this is not miata.net

I'm sorry but seriously, if you dont put thought and care to neatly organize your thoughts into coherent posts then why should others? You know what im saying?

Agreed. He can just type like a normal person and the discussion go forth. There's a difference between a typo and I-don't-give-a-shit-how-I-type. Anyways, he says he's from England, so I'll back off if he tries to type decent. But his first post was not even trying. That wasn't "simple typing errors" as the kid from Cali says... Like the OP said, imagine what all the newbs will think if they come here and see a bunch of kids that can't even type. Looks like the OP is typing fine now.

madmalc- most here don't build setups to run 25 PSI, so real world info is tough to come by. Around 9:1 comp is usually what most run for big boost/big power turbo setups. Personally, I would recommend 8.5:1 or so unless you plan on swapping in a huge set of cams where you'll need the extra comp to get your effective compression ratio back up. hustler on the forum recently had very good results running 8.5:1 compression with a similarly sized turbo. Do a search for threads started by him and you'll find plenty of info on his setup and dyno graphs.

possibly a little jelousy from patsmx5 and saml01 because i want to run 25psi of boost :(

any sensible answers would be great i know a bit lazy but i dont have time to trawl through all threads with 25psi in

FWIW; I just bought these: BELFAB RACING PRODUCTS

And I think another forum member did too. I bought mine with 9.0:1 compression. They have other options.

You knew what I meant y8s.

8.5:1 Supertech pistons.

Belfab rods.

I did, but at the same time, I know you guys hate to see this place fill up with dum noobs the same way I hate to see this place fill up with eleventy billion Catman style "fix yer grammar" posts.

If money is not really the main issue here and want to do it right the first time around, then you really need to find a donor 94-97 engine for about $300-$400. You could look for a 99-00 with the better head for $800-$1000, but that may be more than you want to spend. You are already going to be spending a good $1700-$2000 to get everything and build the engine. That $300-$400 will be make a huge difference and it is very easy to do.

Trust me you will kick youself later for not finding a decent donor motor and swapping that in with it.

I am going to go the belfab kit route here in the next few weeks too. Looks to be a decent kit, especially for the price. FWIW, I am going with the 9.0, but you may want to go with the 8.5 with that much boost.

I think he's on the other side of the pond ;)

It's not like it's overly difficult to type decent. :jerkit: Pretty sure I'm not the only one that hates reading blocks of words with no punctuation or capitalization. And the fact that it's usually a newb who also failed to search doesn't help either.

This forum is getting full of more BULLSHIT every day.

Oh yeah, might not be as cheap as I thought then. But come on it cuoldn't be that much to ship 250lbs internationally can it. I'm sure you know it's real cheap right?

I know I keep stepping in it...

like rharris said, a 1.8 block with the 99 head is the way to go. If you are going to try to push 25psi then you might as well get a good flowing head and some good cams so that you can make the most power for you pressure, since it seems you are going to go big power.

ahahahhahahahahahahahahaahhaa.

Throwing money at a shitty engine and an even shittier car is something to be jealous over?

I'm jealous that an idiot like you can get through life typing the way you do.

Yeah; right! :giggle::giggle::giggle:

Weird. The language has their name on it. People from over there with class are typically very particular about how it's used. And the rest are where West Virginia came from. My apologies to any tarheels who may be offended by that.

If the OP doesn't run some kind of air filter on that turbo, he should be banned from all forums for life.

the lack of searching is a different issue entirely.

seriously though, i understood his question. and what confuses me a little (and I'm not picking on you, pat) is that everyone continues to help this guy even in spite of his total disregard for spelling and punctuation.

just call him an idiot and be done with it.

madmalc: here's a tip before my suggestion takes effect: try to communicate more clearly and you'll get where you want to be MUCH faster. save the cheeky chav talk for the Max Power boards or whatever.

US and UK - Two countries separated by a common language.

Do you have any data logs or dyno graphs? I would like to see what your boost versus RPM is like with that turbo. You should be making a buttload of power already at 17 psi with a GT2876.

Compare it to Paul's setup; stock '99 long block and a GT2560R making 300 hp at the wheels on 14 psi. I'd say 25 psi isn't what he really needs.

Well, if you recall, the last discussion on compression ratios turned into a rather lengthy thread. Of course, the proper answer was mentioned by me towards the beginning, so he could have just missed it in the other useless posts.

I would think you would be used to it by now.

To the OP:

You want to run the highest CR you can without crossing the knock thresh-hold. Seeing as the premium gas on the other side of the pond is a higher octane, you could do well with a 9:1CR and still not have any issues with a good size turbo, a good FMIC, and some good tuning. You could even go with something higher (9.5+:1) and run some water/meth to keep it from knocking. My advice, goto a tuner and engine builder with experience with Miatas. What part of the UK are you in? I have know a few shops in N. Ireland that would be able to help you.

lets see your bag of shit then

my spec

gt2876r turbo (ball bearing garret)
t3 actuator 17psi sping
inconel tubular manifold
3" turbo back

3 angled oversized valves
titainium valve springs
solid lifters
obx stage 2 cams
vernier pulleys
ported and polished head
port matched inlet and exhaust manifolds
RC750cc low imp injector
tunertoyz dual feed rail
walbo 225 fuel pump
sard afpr

4lb flywheel
6 puk padle clutch
quaife straight cut gearbox
concentric release bearing
balanced prop and uprated uj's
1800 diff casing cusco lsd

gaz coilovers
fm antiroll bars
rose jointed drop links
rose jointed adjustable rear top arms
rose jointed front track control arms with drop spaces
lock stop spacers
fully poly bushed

hispec 4pot billet calipers
2 piece split front discs alloy bell and steel brake surface
mintex race pads
mk2.5 279mm grooved rear discs
mintec race pads
willwood brake bias valve
hydraulic handbrake (slave cylinder mounted to standard handle)
braided flexi's

rota 16x7 front wheels
rota 16x8 rear wheels
yokohama tyres

hydra nemis engine managment (self tuned)
etb instruments digi dash
momo carbon fibre seats
trs 5point harnesses


........................some how i very much doubt a shitty car, oh and its got nitrous

Suuper tempted to go find a pile of dog poo and throw it in a Ziploc.

madmalc, the only thing less impressive than whipping out a page-long parts list to try to prove that you're somehow better than someone else is whipping that parts list out after asking such a basic question. There have been multiple discussions about what compression ratios various people have gone with and for what reasons, and all of those threads can be turned up with a little use of the search function.

If you intend to stick around, I would suggest you not only learn to use the search function, but your shift keys as well - you invented the damn language, so you should use it properly. If that sounds elitist, it's because it is. This isn't Hondatech, and we don't talk like we're on MySpace. Asking intelligent questions with proper grammar will trigger informed, intelligent, and coherent responses like you've never seen on any other forum; asking stupid questions without capitalization will get you a thread full of bullshit. Take your pick.

Jealous?

Die.

I just read through two pages of posts and realized there is no useful information here except a lesson in English. Maybe there should be some educated responses and useful information provided. Stop the child talk and get to business or don't answer his post. It is not required from forum members to answer to every post. If you don't have anything to add DON'T ANSWER. If the bull shit about English did not come across there might be some useful information here.

You missed a post:

for shizzle.

Wouldn't want to race him. He might beat even me if he is sprayin'.

Better check the welds on your intake man.

Isnt the answer to this question sort of simple? What ratio? A lower one. 9:1 is pretty common for the higher power guys, so common sense would tell you shoot for the same or lower.

FWIW 9:1 (also Supertech pistons and Belfab rods, nizzle) is what I am using on my built motor. Results and dyno plots to follow.

Hustler is showing good results with 8.5:1 so that can work too. His timing map in boost is sick.

I have the same strut bar but for the life of me I can't remember who makes it? do you know?
Sorry about off topic post**

figured it out 10-AE right. sorry OP

This in an 8.5:1 motor:
http://i44.tinypic.com/29z1kqt.jpg (RPM is not accurate...spooled-up at 4k rpm)
everyone is afraid to run compression that low, but they're also afraid to post dyno's with that much torque. However the beauty is in the spark map:
http://i43.tinypic.com/14vtvrk.jpg
Good luck find someone else making 250wtq at 15psi, its going to be even tougher to find someone who's done it on a dynodynamics box...so add the standard 10% differential and look for someone making 275wtq on a dynojet. If you can find someone making that much torque and whp, its not going to be on the higher compression ratios everyone is using here.
Dig through this thread and you'll probably learn something.

Everyone I've spoken to or discussed this with wasted no time in talking shit about how I fucked up on my motor with the compression ratio, the turbine housing is too big, or whatever else...but they're also dropping their jaws when the drive the car or get steam rolled by it.

you want i should add 6 psi and see how much torques I got?

incidentally, squirrel performance requires me to crank the VE% way up to 130 at peak power to get 250 hp at 9.6 psi. I dont know why they leave the VE so low. FI engines are not running 89% VE.

I'd like to see it with the same turbo on a 9.5 motor for a comparison between comp ratios.

This forum is obsessed with spool like a IRTB fanboi with his ass-ripping throttle response.

10:1 close enough?

with the same turbo, yes.

I've got the same turbine...