time for new pistons

facko · Post by **facko** » February 25th, 2006, 1:09 pm

since two of my stock pistons cracked its time to buy four new ones. I was looking at just getting some new oem stock ones but then i figured insteada waiting for those to break to get better ones. So this is what im plannin on, tell me if im correct in my thinking, i can just buy oem b6t pistons right? im hoping this will work because those are only 40 bucks a piece plus shipping on http://www.importperformance.net. Will the b6t pistons bolt up to the nonturbo rods? thx for the help

osargeant · Post by **osargeant** » February 25th, 2006, 3:04 pm

My only worry would be that you are going from pistons with 9.4:1 to 7.8:1 compression which means that your offboost performance will be noticeable, even the spool up time will be affected.

The key advantage is that you will be able to run more boost. I would more be tempted to use new stock MX3 pistons or go forged one time.

facko · Post by **facko** » February 25th, 2006, 3:23 pm

yea thats the other thing i was concerned about. Ill probably just get the new oem mx3 pistons. I figure if im gonna go for the stronger pistons ill just wait till i can afford to buy the stronger rods w/ them. thx alot for the input

BuGS · Post by **BuGS** » February 25th, 2006, 4:04 pm

Why don'y you just go find a BP and swap that in. I bet you could find a low milage one. Then you would have 9:1 compression and pistons/rods that can hold 300whp easy.

MazdaManiacMx3 · Post by **MazdaManiacMx3** » February 25th, 2006, 4:10 pm

I agree with bugs

WingleBeast · Post by **WingleBeast** » March 16th, 2006, 12:05 pm

correct me if im wrong here... but dosent forced induction run better off from less compression pistons?

i would figure it would be a good move, since then you could get more PSI of boost out of your kit, low end you will suffer but high end rpms should be better.

like i said i could be wrong

facko · Post by **facko** » March 16th, 2006, 3:53 pm

well the compression does let you run more boost, but (atleast to my knowledge) low compression + low boost is gonna end up with less hp than a higher compression on the lower boost. And i dont really have the money thats entailed w/ adding more boost (bigger injectors, better fuel management ect.) So the stock pistons Does seem like a better deal for me just condsidering my financial situation. Also just leaving the car apart till i could afford that doesnt work well either cuz im struggling to pay for the gas in my impala (what ive been driving since the mx3 went down) cuz that big v8 gets like 8 mph

And as for the bp, whenever schools out over summer i am planning on finding a bp somewhere and then getting the goodies for that to be turbod then swap it in

JWMotorsports · Post by **JWMotorsports** » March 17th, 2006, 2:28 pm

The higher the compression, the higher the octane rating needed. Some Pro cars run 10+:1 compression but thats why they are running straight Methanol (type of Alcohol). A good ratio for a street car is around 9:1 for most people. As long as you feed it enough fuel and keep your EGT's under 1500-1600*F MAX you should be fine. We are running 22-25psi on a stock B6t bottom end and my EGT's never pass 1200*F under WOT due to our VERY conservative tuning. Keep your timing turned down around 0-5* under boost and your AFR's around 11.5-12.0 for starting. You always want to start rich and work your boost up to where you want it. Then adding timing and pulling fuel gradually. The key is taking your time and not rushing!

Juans_93_MX3 · Post by **Juans_93_MX3** » March 17th, 2006, 11:57 pm

WingleBeast wrote:correct me if im wrong here... but dosent forced induction run better off from less compression pistons?

i would figure it would be a good move, since then you could get more PSI of boost out of your kit, low end you will suffer but high end rpms should be better.

like i said i could be wrong

BIG TIME MYTH
http://www.mx-3.com/phpbb2/viewtopic.php?t=41406

So, why do you turbo guys think that a lower compression turbo motor makes more power? Does that make any sense when you really think about it? A turbocharger is a power adder? So why deplete power that was there to begin with? The answer I usually get to that is "So I can run more boost!" Well, sorry to rain on your parade, but more boost does not always equal more power. Check out this mathematical example of effective compression:

A motor with a 10.0:1 static CR boosting 10psi
10psi/14.7psi = .68
.68 + 1 = 1.68
1.68 x 10 = 16.8 effective CR

A motor with an 8.5:1 static CR boosting 10psi
10psi/14.7psi = .68
.68 + 1 = 1.68
1.68 x 8.5 = 14.28 effective CR

Now tell me who is going to make more power? The higher CR motor, or the lower CR motor?
So, maybe add more boost to the lower CR motor, right? Wrong...

A motor with an 8.5:1 static CR boosting 13psi
13psi/14.7psi = .88
.88 + 1 = 1.88
1.88 x 8.5 = 15.98 effective CR

Now you see, even adding 3psi of boost, still does not equal the effective CR of the higher compression, lower boost motor.

fieromx3 · Post by **fieromx3** » March 18th, 2006, 12:10 am

high compression is only good with low boost u would not want to boost high with high compression otherwise u can blow up engine. its not like u can have a 10-1 compression with 20psi.....well maybe u can for about 10 seconds. maybe im even wrong here??

JWMotorsports · Post by **JWMotorsports** » March 18th, 2006, 7:06 pm

OCTANE....OCTANE....OCTANE son

.........go to a NOPI or NDRA event and ask one of the Pro Teams that question and they will tell you the same thing I just told you in my previous post. Please don't take this as me bashing you...I'm not...just trying to help you understand...I started in your shoes 9 years ago.

WRC guys are running compression ratios and boost pressures that most people though only achievable in wet dreams!

Franko · Post by **Franko** » March 21st, 2006, 9:51 am

JWMotorsports wrote:WRC guys are running compression ratios and boost pressures that most people though only achievable in wet dreams!

Haha!

ccreech · Post by **ccreech** » March 21st, 2006, 1:41 pm

JWMotorsports wrote: WRC guys are running compression ratios and boost pressures that most people thought only achievable in wet dreams!

I Nominate this for post of the month.