9.-1 Compression?

[sleepinGSX]

Anyone have it or know much about it. I have read a little about it but nothing with alot of facts. I heard its pretty streetable and good for alot off boost, so does anyone on this borad have it or give me some info on it.

 

[Thalomos]

I plan on doing it when my car needs a rebuild.

 

[Antilles]

got it, street it, boost it. 20k miles no problems.

 

[ProStreetOnline]

9.0:1 is fine, but keep in mind... you can make more power on the street with more reliability with lower compression, and higher boost than you can with higher compression and lower boost.

 

[talonted_one]

Originally posted by prostreetonline
9.0:1 is fine, but keep in mind... you can make more power on the street with more reliability with lower compression, and higher boost than you can with higher compression and lower boost.

word!

honestly if I ever hit the lottery I would rather go 7.8:1 forged on a built motor an pump in stupid amounts of boost.

 

[niterydr]

well it depends what you call 'alot of boost', to me 22psi on pump gas is approaching 'alot of boost' for that particular setup. I personally am going 8.5:1, but thats cause im 'mild' and like to be in the middle .

 

[sleepinGSX]

Hey antilles, did u notice a big difference after the switch, when do u hit boost ? Im sure if u had a 1g it would b a big difference but u got any numbers with that motor ?

 

[greathuskie]

i want to go to 9:1 compression one of these days

 

[Antilles]

I spool dead on at 3k with the small 16G. not much difference there. There was a ton of power with the motor though. I went with a 2G ported exhaust manifold, the 9:1 pistons, no BS shafts, a ported and polished head and some other little things. It made a very large difference on what was a mostly stock car.

as for results, i trapped 109 mph in the 1/4 with race gas. 20 psi on the small 16g. i had some creep, but that same creep also caused spark blowout and misfire, so i figure it evens out.

you can make more power with less boost on high comp. pistons. but you can probably run more boost with lower comp. pistons. i guess the high compression pistons are more for smaller turbos that cant run tons of boost, or guys that want to go all out and can really tune.

 

[taylorspl]

Originally posted by Antilles
i guess the high compression pistons are more for smaller turbos that cant run tons of boost, or guys that want to go all out and can really tune.

Or want to run race gas all the time. also you get more power from increasing boost than CR the only thing that will do is aid spool up.

 

[Slowboy]

9.0:1 is fine, but keep in mind... you can make more power on the street with more reliability with lower compression, and higher boost than you can with higher compression and lower boost.

9.0:1 is great for the street. You have a very efficient head, you might as well use it. I can run 23-24 psi on the street with a 9:1 motor with no issue's at all on 92-93 octane. I have two different motors, two different cars, different turbos, both 9:1 that can run all day at 22-23 psi with no issues.

If you are a beginner, you may want to stick to 8:1 or 8.5:1... 9:1 is a little more tricky to tune.

Regards,

Mike Huml

 

[jw]

Mike, what setup do you have? I am curious to know how to tune with higher compression pistons with a simple setup.

 

[Slowboy]

I have never had anything more than an AFC, and use a stock ECU. I also switched from a 1st gen mas to a 2nd gen mas earlier this year with good success. The 1g mas only got me to 123.5 MPH, and just switching to the 2g mas, no other mods made 126.58.

I find that 99% of the people I work with, and from my own car that a lot of the tuning is in the timing.... Not just the base timing, but the way the cams are degreed, etc....

I have my FWD up and about now, and am running 22 psi on pump gas with very little knock. ( less than 4 counts top of fourth, GT12 turbo ) and the ecu is giving me about 23 degrees advance.

This engine has about 300 miles on it, so I will be taking it easy for a bit, but would love to get it on a dyno soon.

It took a while to get the cams dialed in ( stockers for now ) but the car seems to run very well, other than all the used sensors I had to use.... PITA.... but you know how it goes when the car is close to being together and you just have to drive it.....

Regards,

Mike Huml

 

[Pennywise]

Mike what all do you do to te motors? I really don't want to spend 3k on a built block from buschur. I was wanting to have a 9:1 cp with one of your gt12's. because I will have the high cp and quick spooling turbo wouldn't want n2o. could I just get rods and pistons for the block? I wouldn't push more then 24psi on 93 oct. please help me out...o yeah this will be used with an aem ems, also give me advise on cams and head work also. once I get the talon I will sell my car and i'll have 7-8k to play around with

 

[Oreopride18]

I have to grab something off of probetalk.com.

9:2.1 CR + 12psi = 16.7 DynamicCR
8:1.1 CR + 15.7psi = 16.7 DynamicCR

http://www.probetalk.com/forums/showthread.php?s=&threadid=52029

To be safe on the tuning side I think i'll get 8.5:1. 9.1:1 will see less lag and be jsut as reliable. The only catch is how much detonation will it take until you can properly "balance" the engine out? I can't afford much

 

[Slowboy]

I just sent you a PM...

Regards,

Mike Huml

 

[JoeG]

9:1 makes for a quicker spool, right? (please correct me if i'm wrong)


when i do the jdm swap, i wanna have the motor rebuilt with 9:1, and 262/272 cams...

 

[Tevenor]

Originally posted by Oreopride18
I have to grab something off of probetalk.com.

9:2.1 CR + 12psi = 16.7 DynamicCR
8:1.1 CR + 15.7psi = 16.7 DynamicCR

http://www.probetalk.com/forums/showthread.php?s=&threadid=52029

To be safe on the tuning side I think i'll get 8.5:1. 9.1:1 will see less lag and be jsut as reliable. The only catch is how much detonation will it take until you can properly "balance" the engine out? I can't afford much

This is utter crap. That is a completely false formula and no where near realistic. It's a lot more complicated than that.

The simplest formula I have found is this:

Effective Compression Ratio = Static Compression Ratio x ( 1 + boost/14.7 )^1/2

Originally posted by Oreopride18
The only catch is how much detonation will it take until you can properly "balance" the engine out? I can't afford much

What are you talking about? Detonation? Properly balance the engine out? Please explain as I am lost.

 

[Polk]

It is safer to make power on boost than power on compression in a turbo car for the newbie.

Mike is right, timing is very important. You have to watch your knock counts as well you egt's when playing with timing. They pretty much go hand and hand when tuning on a turbo car.



Guys just remember take baby steps when trying to run a lot of boost on pump gas.


Polk

 

[Oreopride18]

This is utter crap. That is a completely false formula and no where near realistic. It's a lot more complicated than that.

That is how it works for a SPECIFIC evenly setup. You have to assume that it is the same turbo for both:

9:2.1 CR + 12psi = 16.7 DynamicCR
8:1.1 CR + 15.7psi = 16.7 DynamicCR

12psi out of a 16g is a lot different than 12 psi out of a 14b. Different flows would equal a different psi for a different turbo. I really shouldn't have to explain that. Basically, assume the above setup is on the same turbo.

What are you talking about? Detonation? Properly balance the engine out? Please explain as I am lost.

A lower compression engine (say, the stock 7.9:1 on my car) leaves a lot of room for tuning over an upgraded 9.1:1 engine. Higher compression = less room to work with on the psi-end of things. If you have a 8.5:1 you can work around running 19psi on a 20g and on pump gas; and y9o ucan do this tuning without having to worry about detonation.

Now try the above again on 9.1:1 compression. The psi won't be as high but your compression from the engien WILL be higher and it will be constant. You mess up tuning by 2 or 3 psi on the 8.5:1 you can still walk away with an ok engine. You mess up by 2 or 3 psi on som,ething like 9.1:1 or 10.1:1 then you are in a whole different mess.

Simple enough?

 

[jw]

Originally posted by Oreopride18

12psi out of a 16g is a lot different than 12 psi out of a 14b. Different flows would equal a different psi for a different turbo. I really shouldn't have to explain that.

What crap is that? I can understand if you are comparing a 16g and 14b at 20+psi because of lower outlet air temperature and higher PR at the exhaust due to smaller housing. At low boost, you dont see much different.

You should just say tuning instead of "balance" the engine as it has totally different meaning.

 

[Tevenor]

Originally posted by Oreopride18


That is how it works for a SPECIFIC evenly setup. You have to assume that it is the same turbo for both:

Huh? Are you saying the laws that govern force induction an engine change based on if its a Probe versus the rest of the world? I don't care what setup, the formula is wrong and it just simple doesn't work like that.

Originally posted by Oreopride18

9:2.1 CR + 12psi = 16.7 DynamicCR
8:1.1 CR + 15.7psi = 16.7 DynamicCR

12psi out of a 16g is a lot different than 12 psi out of a 14b. Different flows would equal a different psi for a different turbo. I really shouldn't have to explain that. Basically, assume the above setup is on the same turbo.

Leave air flow out of this. It has nothing to do with this discussion. You are trying do introduce a per time unit of measure in a dynamic system to a point-in-time discussion.

What does your compression mean? I am assuming you mean 9.2:1 and 8.2:1 as I don't have the foggiest idea what 9:2.1 and 8:2.1 means since that equates to 4.29:1 and 3.81:1 ratios.

Originally posted by Oreopride18

A lower compression engine (say, the stock 7.9:1 on my car) leaves a lot of room for tuning over an upgraded 9.1:1 engine. Higher compression = less room to work with on the psi-end of things. If you have a 8.5:1 you can work around running 19psi on a 20g and on pump gas; and y9o ucan do this tuning without having to worry about detonation.

Now try the above again on 9.1:1 compression. The psi won't be as high but your compression from the engien WILL be higher and it will be constant. You mess up tuning by 2 or 3 psi on the 8.5:1 you can still walk away with an ok engine. You mess up by 2 or 3 psi on som,ething like 9.1:1 or 10.1:1 then you are in a whole different mess.

Tuning means taking what you have and making it run the best possible. WTFF does 'You mess up tuning by 2 or 3 psi on the 8.5:1 you can still walk away win an ok engine' mean?

I will make this very simple for you. You can't just add boost to static compression ratio and say Voila! It doesn't work that way. It's not a linear system.

Compression is just another factor in tuning an engine. Just like fuel pressure, injector sizing, cooling efficiency, etc. Yes Higher compression will help spool and decrease the detonation limit on 2 identical setups. The problem is there is no such thing as identical setups. Every engine reacts differently, even with the same builder and parts. Each one has its quirks and characteristics.

 

[candela]

ouch

 

[insane147]

i dont understand why people get so insulted by simple questions from people with alot less experience. its like they are taking revenge or something. but he is right.

 

[Tevenor]

Originally posted by insane147
i dont understand why people get so insulted by simple questions from people with alot less experience. its like they are taking revenge or something. but he is right.

Are you referring to me? If so, then you misread this thread entirely. I get insulted when misinformation gets passed off as fact. Now, what does 'but he is right' mean? Who is right?