fyi, wiseco does not make a 9.0:1 piston
11-16-2007, 12:19 PM
#22
Tour de Franzia
Thread Starter
iTrader: (6)
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,085
Total Cats: 375
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.
Reply
0
0
Welcome to the world of compromise.
11-16-2007, 12:25 PM
#26
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.
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.
Reply
0
0
11-16-2007, 12:29 PM
#28
Tour de Franzia
Thread Starter
iTrader: (6)
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,085
Total Cats: 375
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.
Reply
0
0
11-16-2007, 12:32 PM
#29
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...
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...
Reply
0
0
11-16-2007, 12:34 PM
#31
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...
Reply
0
0
11-16-2007, 01:10 PM
#32
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).
Reply
0
0
11-16-2007, 01:11 PM
#33
Tour de Franzia
Thread Starter
iTrader: (6)
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,085
Total Cats: 375
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.
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.
Reply
0
0
11-16-2007, 01:29 PM
#34
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.
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.
Reply
0
0
11-16-2007, 01:36 PM
#37
Tour de Franzia
Thread Starter
iTrader: (6)
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,085
Total Cats: 375
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 ****.
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 ****.
The car was impossible to drive.
Reply
0
0
