Getting Tuned Soon. What psi to tune for SAFELY.
 

Im running 7.5:1 compression.
Bone Stock D series.
z1 block y7 head, hf mani, 42/48, 2g DSM IC Front Mounted,
DSM 450's, 2.5 inch crushed dp and 3 inch piping after that.
Im running 11-12 psi now untuned.
Ive made plenty of 4th and 5th gear pulls on the dx trans and it hasnt blown.
Wondering if I should risk tuning it for 14 psi. I figure since it hasnt blown untuned on around 12, it should be able to take a bit more TUNED well.

Not many people have had any experience with this setup, so im basically in the dark on the limits of it.
BTW Ill be using a 2.5 bar map when I get tuned.

Any input would be appreciated.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

14 psi on a stock d???? nope. you'll melt your pistons or throw a rod quick status, or definetely blow a headgasket. tops keep it 10-12psi on stock. forge internals. then up the boost later. but tune now for 10-12. (id say closer to 10 personally).

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

Why run 10 psi on 7.5:1 compression lol.
I might just stick with 12 psi.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

---- with 7:1 and a 42/48 turbo I'd do 15psi. that wont make much power, but make sure you have a good intercooler to cool those charge temps down.

EDIT: I tuned or 12 psi on a 10.2:1 compression and a bigger turbo stock motor and its fine. Just get a good tune and FMIC.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

Thanks for the input.
I guess ill leave it up to what my tuner thinks I should do.
I dont plan on getting a fmic.
Im broke as it is, and had to scrape up the money for the tune.
What motor were you running 10:1 with 12 psi.
The z1 rods arent as thin as b7 rods, but not as thick as z6 rods.
Thats what scares me the most.

As the car strands now untuned it is faster than my last setup that ran 13.7 that was also untuned.
My goal is low 13's on this motor stock.
With 14 psi I think I can do that or better on street tires.

Anymore feedback would be great.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

its in a B16A (my current setup). You should worry more baout your pistons than your rods. get a good tune for 10-12 psi and I think you'd be fine, but on that small turbo and low compression I would run 15. You said you arent going to run an FMIC? are you going to be intercooled at all? If not, my advice is to wait until you get a good intercooler.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

Ive been running the car the way it is for months now.
11-12 psi. Dsm ic front mounted.
If im running now not melting a piston, with God knows how shitty a AFR, I think it can do 14 tuned well.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

If I was in your shoes...

ASSuming you havn't been detonating due to a shitty timing situation, and your internals aren't fatigued, I would go read a compressor map for your turbo, find the most PSI you can run efficiently, then work your way up to there.

Make sure you're not detonating, that's the key. I would also look for other people making shittons of power off low compression D-series' because that's pretty much your setup.

Good luck, you better hit 12's soon...;)

Brett

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

Not many people go under 8.5:1 on D's so I have no resources.

But your advice sounded good.
Ive got to learn how to read a compressor map, and work from there.
BTW the only think holding me from 12's IMO is my Dx trans.
I feel I can go at LEAST low 13's when im tuned, I just might need that trans to break 12's.
But it could happen.

Thanks for the good advice.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

15psi all the way! Go for the gold Joe 8) I think with that low of a compression your pretty safe at 15 if not alil higher.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

T'is true, I would take a look at people running Vitara pistons, I'm fairly sure the compression is really low (maybe not 7.5), so that should at least give you a good baseline to aim for.

DX trans/Lack of power ;) Whichever you'd like to blame it on...

As for learning compressor maps, I direct you here: http://community.asiaosc.org/~zaliman/TurboSelector.htm

Just from plugging in some numbers, disregarding temperature and air density changes(which you SHOULD be calculating as well, don't worry it's all there) You look to be about at the limit of peak efficiency right around 15 psi, if you're flowing approx. 200cfm or 15 lbs/min of air.

That's also reading this map http://www.turbocalculator.com/compr...maps/t3-50.jpg T3, 50 trim which I think is what you're running, but I could be wrong, so make sure you've got the right map.

Brett

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

Lack of power maybe.
Some people said my last setup should of made 140-150 whp,
but it went 13.7 in a 4 door.
So ---- power lol.

Thanks for all the info.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

also, check this out for compressor map how to read info: http://www.honda-tech.com/zerothread?id=142398

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

why the ---- such low comp. ??? higher comp. with less boost is better than lower comp. with more boost. i'd rather run 9.5:1 comp. with 12 psi., then i would 7.5:1 with 15 psi :P

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

I wouldn't. I like being able to run tons of boost without knock. Do you?

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

no, psi is a ricer's unit of measurement. what good does it do to say "i'm running 15 psi", if a guy with higher comp. is running 10-12 psi. and making more power and spooling up much faster? lowering comp. takes away power, which in turn causes more lag, and we all know how much of a beast low comp. honduh's are before the turbo actually spools ::) but if you just want to be able to say, "i'm running 15 or 20 psi", then yeah, low comp. is the way to go.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

I'm well aware PSI is an irrelevant measurement, but I also feel strongly towards the fact that compression has a much lesser effect than a lot of people think.

I won't lie, I've never compared the two, so I am talking out of my ass here, but from what I've read the window for knock becomes a lot smaller as you up the compression. Considering that most factory turbo cars run under 9:1 compression, and the fact that the majority of the people on this site are not supar tunarz, I'd say the bigger window you can get the better.

And ---- low spool. Design your manifold properly, run some water injection, and don't worry about power before the spool. It's not like FWD cars have traction from a dig anyways :P

Anyways, at the end of the day it's not about saying I can run more PSI than you, it's the fact that I can make more power than you because I can run more boost without knocking. So you know what? Props to D16Y8-Z6 for doing something different, and maybe opening some people's eyes.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

trust me, i'm well aware of tuning principles ;) i personally see no need what so ever to go with 7.5:1 comp. ever, especially when there are 400+whp on PUMP GAS (which i shouldn't have to explain the difference of only using pump gas) with as high as 9.5:1 comp. without having to raise the octane level. and no, being able to run more boost with that low of comp. isn't necessarily going to net you more power, because like i already said, lowering comp. takes power away from teh motor, so that extra boost you're running is making up for lost power anyways. i do have personal experience tuning higher and lower comp. cars, and personally have run both. i have 9:1 comp. right now in my b16 and i wish i had went with 10:1 and lower boost.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

Thast why I stuck with stock internals on mine for now. If I blow this setup anytime soon, I plan to buy some stock forged replacements.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

All other things being equal, a lower CR is going to allow you to make more power. Much more.

Look at the point you reach detonation as having reached a certain density with the compressed air/fuel. With a lower CR, you have significantly MORE combustion chamber volume and can fit significantly MORE compressed charge before you hit a dangerous/knock prone density...

... it's not that simple, because when you start making more power you also start making more heat, but there is still a significant general trend of lower compression being capable of more power and being more detonation resistant for a given power output.

Melted pistons are a problem with cylinder temps - broken ringlands a problem with combustion pressure spikes - broken rods due to being jackhammered on by detonation - etc.

YAAAARR!!

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

Just to clear some things up.
I didnt NOT go out, and build a 7.5 c/r motor on purpose.
I bought a low mileage jdm d15 vx for 100 bucks. Longblock.
AS A SPARE.

So when I blew my 10.1:1 c/r y7/b7 block setup, this is what I had laying around, and I used it.

So i threw the y7 head and z1 block together and made 7.5 c/r.
It doesnt bother me 1 bit.
And the off boost power isnt as bad as people expect.
Plus with a turbo this small I have boost a bit after 2k so how can I complain ?

Anyway, I like it.
Its quick.
Its currently enough for me.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

obviously or no one would run lower comp. piston's at all, but come on, we're talking about 7.5:1 comp. here for 15psi with a .48/.42 t3 snail, that things going to be lacking some serious power. cut the pirate bull ---- joey, you don't even live near the ocean you land lover, ARRRRRRRRRRGH!!!!!!!!! :-*

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

Yes and no. Mostly yes, but sometimes no. Dick's 8:1 LS with the high lift 250 duration cams that idled pissy was quite a bit more powerful than a stock LS even without the turbo on. Dynamic cylinder filling and camshaft plays more of a part than CR.

Guy in this case might have lucked into a good combination of engine dynamics... but unless you've got something up your sleeve not being mentioned here, I agree that intentionally building 7.5:1 CR for a streetcar is like shooting yourself in the foot. Guy says he threw together what was laying around to save $0.44, and everything turned out pretty well, I believe him.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

Track times soon.
If traction is there, Ill be golden.
I just swapped in an s20 B000.
On the street it smokes 2nd gear bouncing off the rev limiter, but i doubt it will at the track.
Its got the infamous 3rd gear grind though that kills my life.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

got that grind to man. :'(

I have to let my RPM get below 2500prm before I can put it into 3rd and sometimes that takes quite a while. I found a trick though. if you put it into fourth real quick then put it in 3rd as if you are downshifting, it doesnt grind, but you gotta be fast/precise to pull that off at crunch time.

Re: Getting Tuned Soon. What psi to tune for SAFELY.
 

I just double clutch the upshift and its fine.

But of course ill be beating it at the track full throttle shifting.