fyi, wiseco does not make a 9.0:1 piston - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-16-2007, 01:16 PM   #21
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Hurm, my stock 1.6 spooled that size turbo to 10psi just a little past 4k. With no tuning done... and a damaged turbine wheel.
well, I'm hoping for 12 psi by that mark, so this supports my thoughts.
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Old 11-16-2007, 01:19 PM   #22
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hopefully I don't have to mill too much off the head, so I then have to sell the pistons I have currently and buy another set of 8.6 pistons, and still be fucked in the long run with a car that is either going to pop the motor because of too high compression, or be sluggish off boost because of low compression.
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Old 11-16-2007, 01:20 PM   #23
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Welcome to the world of compromise.
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Old 11-16-2007, 01:21 PM   #24
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Hustler,

Do you have a Megasquirt?
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Old 11-16-2007, 01:22 PM   #25
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Hustler,

Do you have a Megasquirt?
yes
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Old 11-16-2007, 01:25 PM   #26
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Man, this is kind of exciting for me. Maybe i'll be able to run some serious timing when i get Jerry to tune the car.
Edit:
Just checked the paperwork on my pistons part #k553m835
Kind of weird that every website except wiseco's catalog says these pistons are 8.6-9.0:1 while wiseco's catalog is saying 8.5-8.8:1.
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Old 11-16-2007, 01:26 PM   #27
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well, I'm hoping for 12 psi by that mark, so this supports my thoughts.
You obviously haven't seen my turbine wheel
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Old 11-16-2007, 01:29 PM   #28
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now I kinda wish I wasn't selling these. I tried to not think about stuff so much, so I put the pistons up, and they sold. Now I'm feeling like I may have fucked up. lol, I'm a walking catastrophe of indecision.
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Old 11-16-2007, 01:32 PM   #29
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I would say keep what you have and either

A. Increase off boost timing (you have low comp pistons, you can afford to). You could even have the water/alky injection that you have come on while in vacuum and add an enormous amount as in the example I gave above. We were running C16 and added between 18-25* of timing off of boost, this gave us an extra ~40whp while in vac, much more useful than 1-3rpm earlier spool as far as I'm concerned.

B. Retard your timing while off boost to spool the turbo earlier. I only did this a few times at the request of customers so I don't know about the long term effects on the turbine but short term it decreased lag about 500-1000rpm (talking 70+mm turbos). You could even make a separate map for this...
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Old 11-16-2007, 01:33 PM   #30
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Just don't sell them, if they haven't shipped you can still give a refund?
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Old 11-16-2007, 01:34 PM   #31
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B. Retard your timing while off boost to spool the turbo earlier. I only did this a few times at the request of customers so I don't know about the long term effects on the turbine but short term it decreased lag about 500-1000rpm (talking 70+mm turbos). You could even make a separate map for this...
MS table switching anyone?? Only one toggle away.
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Old 11-16-2007, 02:10 PM   #32
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I did something similar on another MR2, I connected the two-step switch on a TECII to the upper clutch safety switch and gave the clutch enough free-play that you could press the pedal enough to activate it with out engaging the clutch. At any point you could lightly touch the clutch pedal and get a near instant 20-30psi (depending on rpm).
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Old 11-16-2007, 02:11 PM   #33
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so i guess I should go ahead and pull the trigger on these 9.0:1 JE's. I hope they fit with the probe rods.

Its either the 2618 JE's, or the 4032 supertechs. I don't know if I want more strength, or less thermal expansion. I'm leaning toward the 2618 JE's since the 9.0 considering the higher compression.
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Old 11-16-2007, 02:29 PM   #34
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If you want your turbo to spool sooner, do headwork. You could drop spool RPM by 5% by cleaning up the ports of casting marks and port matching the intake to the head. That's probably more difference than you'll see going from 8.6 to 9.0 compression pistons. If you were to unshroud the valves enough, reduce the shortside radius, blend the bowls into the throat and combustion chambers correctly, etc, etc, you could drop spool time closer to 20%. Not only would it drop spool time, but your getting 20% increase EVERYWHERE. The motor would make more power everywhere, which seems to be what your after. You want 250whp total, but you want a strong motot that's peppy not slugish. You would be MUCH better off improving the head to gain a 10% increase in power vs. upping compression to compensate for flow. The motor will have more potential for boost and you'll be less prone to detonation. Your way overthinking how important compression is. You should read some books about this stuff. There is a certain degree of science to it.

From Corky Bell's book 'Supercharged' "...Raising the compression ratio only increases the efficiency of burning the same amount of air/fuel ratio. The best to be hoped for in changing the compression ratio is about 4% more power per compression ratio point." (26 Bell)

Your already second guessing yourself about selling the 8.6's, so I wouldn't "go ahead and pull the trigger on these 9.0 JE's" Instead you need to read some **** and learn what your doing so you can make an informed decision, instead of this random spur-of-the-moment ****.

Edit: using Bell's numbers, you could see possible gains up to 1.6% in power going from 8.6:1 to 9:1 comression ratio pistons. Wow.
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Old 11-16-2007, 02:34 PM   #35
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Keep your current 8.6:1 pistons and spend $35 and deck your head .020 and you will be at 9:1.
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Old 11-16-2007, 02:34 PM   #36
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Originally Posted by cjernigan View Post
Just don't sell them, if they haven't shipped you can still give a refund?
noooooooooooooooooooooooooooooooo

hey i run 10:1 compression on a turbo car. it feels like my old celica off-boost. celica was 8.5:1.
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Old 11-16-2007, 02:36 PM   #37
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Originally Posted by patsmx5 View Post
If you want your turbo to spool sooner, do headwork. You could drop spool RPM by 5% by cleaning up the ports of casting marks and port matching the intake to the head. That's probably more difference than you'll see going from 8.6 to 9.0 compression pistons. If you were to unshroud the valves enough, reduce the shortside radius, blend the bowls into the throat and combustion chambers correctly, etc, etc, you could drop spool time closer to 20%. Not only would it drop spool time, but your getting 20% increase EVERYWHERE. The motor would make more power everywhere, which seems to be what your after. You want 250whp total, but you want a strong motot that's peppy not slugish. You would be MUCH better off improving the head to gain a 10% increase in power vs. upping compression to compensate for flow. The motor will have more potential for boost and you'll be less prone to detonation. Your way overthinking how important compression is. You should read some books about this stuff. There is a certain degree of science to it.

From Corky Bell's book 'Supercharged' "...Raising the compression ratio only increases the efficiency of burning the same amount of air/fuel ratio. The best to be hoped for in changing the compression ratio is about 4% more power per compression ratio point." (26 Bell)

Your already second guessing yourself about selling the 8.6's, so I wouldn't "go ahead and pull the trigger on these 9.0 JE's" Instead you need to read some **** and learn what your doing so you can make an informed decision, instead of this random spur-of-the-moment ****.
I'm familiar with the concept. However, that's 4% peak hp. There is no way to tell power levels at low rpm levels without doing more math than I know how. I do not want this car to drive how my old turbo corrado or jetta did. The corrado went from 130lb/ft to 460 in 700rpm. It was impossible to drive.

The car was impossible to drive.
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Old 11-16-2007, 02:38 PM   #38
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noooooooooooooooooooooooooooooooo

hey i run 10:1 compression on a turbo car. it feels like my old celica off-boost. celica was 8.5:1.
if you hadn't sent the ching-dow last night, I would have held on to these.
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Old 11-16-2007, 02:44 PM   #39
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yeah, spend $2000, and enjoy living with your fucked up mistake, shitty slow car which never spools.
This statement confirms to me that you don't know **** about motors....
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Old 11-16-2007, 02:47 PM   #40
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This statement confirms to me that you don't know **** about motors....
That's what I was thinking. He should read up about engines as he's too critical. He would be better informed and happier in the end when his motor opperates as he wants it to.
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