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Question Turbo a 10.5:1 compression engine

Hey all,

I have seen a lot of talk about turbocharging (light boost) a 3.2L Carrera engine with 9.5:1 compression, but what are your thoughts on turbocharging 3.2L engine with 10.5:1 compression? Should you just change out the pistons for the US spec ones? Would the engine be that much closer to detonation at .5 bar? If another thread has already been started concerning this, please post the link. Thanks guys!
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Old 01-31-2008, 06:49 AM
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Could be done on E85, using twin plugs.
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Old 01-31-2008, 07:09 AM
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See it often on newer cars - aftermarket supercharging/turbocharging with higher compression.
5 lbs boost seems to be the limit on these factory cars (with no TP or other mods)
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Old 01-31-2008, 07:32 AM
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Well SAAB 9-5 Aero boosts 1.2 bar on 9.3:1 ex factory.

Also, factory C/R figures for Carrera mill are a bit ambigous. Lot's of people cc-ed the chambers and got different numbers.

I say a guy running whooping 1 bar of boost on 10:1 Alfa Romeo V6, using E85. I believe it was 2v/cylinder engine. I believe it's doable to have quite high boost on ROW Carrera mill, but not on what passes as fuel in US. E85 or shaving the pistons is the melody...
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Old 01-31-2008, 07:43 AM
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You have to remember all these newer generation cars which run higher C/R and higher boost are watercooled and have much more advanced engine management systems than the archaic Motronic DME's and also have knock sensors etc

If I were you, I'd slip in 9.5:1 pistons and whilst you've got the top end apart, put on some C2T head gaskets to drop the C/R even further to ~8.8:1 and you will be able to run 0.85bar (intercooled) all day every day for ~485 crank HP
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Old 01-31-2008, 02:10 PM
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I agree w/ WydRyd, any cars running that much compression with boost are much newer, advanced EFI systems, some are even using direct injection. You will surely have trouble with detonation i'm afraid. Even if you manage it well at first, with a fresh engine, as soon as you start to get carbon buildup, which you will when those valve guides get a taste of the extra heat that comes with boost, things will change. I'm currently experiencing detonation with a RUF RCT engine in a '94 RS America. A friend of mine bought one from an older gentleman in Illinois and it has terrible detonation at random times. Mostly at the torque peak, with some heat in the motor. It also consumes a fair amount of oil which is most likely taking up permanent residence in a new form in various parts of the combustion chamber. We've tried various fuel cleaners and it actually seems to amplify the problem. I guess they "soften" up the carbon and make more little "glow plugs"?? It has 70K miles on 94 valve guides and only runs .77bar with 8.5/1 and still makes at least 385hp-actually 365 to the wheels on a dynojet recently (it took 11 pulls to start detonating, AFR stayed perfect) BTW It has twin knock sensors w/ RUF EFI Just my $.02 good luck!!!
Old 01-31-2008, 05:07 PM
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I have to agree with the gang. For example, I recently dyno tuned a couple of 2.4 liter Pontiac Solstices with aftermarket turbo kits ($4500+install). They are 11:1 and as such can only run 6-7lbs boost AND you have to pull so much timing to eliminate most of the detonation to run that power output is only 185whp on a Dyno Dynamics(so about 215 on a Dynojet). Even then the ecu is still pulling timing in certain instances. Throttle response sucks too. Rebuilds on our engines are just too expensive to play with detonation, a good used solstice/HHR long block is under a grand. Lower compression is the way to go, you may be able to machine the piston tops, I know it's done on the 3.6 NA pistons for turbo/supercharging.
Old 02-01-2008, 08:30 PM
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The turbo and supercharger kits makers will tell you it won`t work,don`t do it. Yes it`s true that some modern turbo engines have high static compression ratios but the 3.2 Porsche at 10.5 is just not suited for it. You COULD run very low boost with the right chip and boost cooling but if you have the funds available by all means install the lower compression pistons,turbo gaskets and stronger rod bolts.As Wydryd says a reliable 500 HP is just around the corner with some simple mods and you`ll have no regrets doing it right...
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Old 02-02-2008, 12:04 PM
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Its not a 3.2L but a 993 with a stock 3.6L ( 11.5 comp) with 6psi of boost... its puting over 400hp at the wheels.
http://www.6speedonline.com/forums/s...ad.php?t=93992

So it can be done with a good EMG and tuning.
Old 02-02-2008, 02:31 PM
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Quote:
Originally Posted by herman maire View Post
Its not a 3.2L but a 993 with a stock 3.6L ( 11.5 comp) with 6psi of boost... its puting over 400hp at the wheels.
http://www.6speedonline.com/forums/s...ad.php?t=93992

So it can be done with a good EMG and tuning.
AHHHH, that's a different story! I thought you were referring to the 3.2 CARRERA motor!

Anyway, yes, it can be done on a 993 with the right changes to engine management. I believe the system running on that 993 is a Protomotive system. Protomotive have built their reputation on developing aftermarket kits for the naturally aspirated platforms and know their ***** when it comes to aftermarket turbocharging. Send Todd Knighton an e-mail... top guy
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Old 02-03-2008, 03:26 PM
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I'm doing all of this in stages as I don't have all funds right away. I've just started the valve job, so I don't have a clear idea yet of how much I am going to be spending on parts. The compression and leak down test numbers were very solid when I had the tests performed last summer, so I don't suspect any surprises.

I have the 9.5:1 compression pistons in right now, and I'd rather not lower the compression yet as I don't know how long it will be until I actually get the turbo in there. Where should I spend my extra cash (between $1500-2000) to prepare the engine for turbo charging? From what I've read and heard from you guys, I'm thinking about installing raceware head studs and rod bolts. Any suggestions?
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Old 02-05-2008, 08:22 AM
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Definately do the bolts at the very least for starters and either use the 9.5 pistons and some turbo gaskets or get the lower compression pistons. On these motors even 9.5 compression with turbo is pushing it,why restrict your available boost even more? you`ll see no reliable performance gains using the high comp pistons.
lf you`re not sure when you can swing the turbo conversion don`t sweat it, running low comp pistons for a while won`t be as bad as you think.l ran a turbo motor on straight fuel injection for a while and it didn`t kill me,it was still fast enough to have fun in. Good motivation to complete it also..
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Last edited by raceman; 02-05-2008 at 09:03 AM.. Reason: computer glitch
Old 02-05-2008, 08:54 AM
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I'm definitely following you on the "why restrict your available boost even more?" mentality. So simply by changing to turbo head gaskets I could lower my compression ratio? Could you send me a link to some gaskets that you'd recommend?
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Old 02-05-2008, 09:15 AM
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.......and are we certain that these gaskets are viable, ie deck height etc?
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Old 02-05-2008, 09:18 AM
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Quote:
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.......and are we certain that these gaskets are viable, ie deck height etc?
I have no idea. That's why I'm in here asking.
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Old 02-05-2008, 09:20 AM
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Quote:
Originally Posted by raceman View Post
Definately do the bolts at the very least for starters and either use the 9.5 pistons and some turbo gaskets or get the lower compression pistons. On these motors even 9.5 compression with turbo is pushing it,why restrict your available boost even more? you`ll see no reliable performance gains using the high comp pistons.
lf you`re not sure when you can swing the turbo conversion don`t sweat it, running low comp pistons for a while won`t be as bad as you think.l ran a turbo motor on straight fuel injection for a while and it didn`t kill me,it was still fast enough to have fun in. Good motivation to complete it also..
What exactly would turbo head gaskets do for me? Does it affect the compression or does it just make the engine more capable of handling a turbo?
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Old 02-06-2008, 07:35 AM
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Quote:
Originally Posted by WydRyd View Post
You have to remember all these newer generation cars which run higher C/R and higher boost are watercooled and have much more advanced engine management systems than the archaic Motronic DME's and also have knock sensors etc

If I were you, I'd slip in 9.5:1 pistons and whilst you've got the top end apart, put on some C2T head gaskets to drop the C/R even further to ~8.8:1 and you will be able to run 0.85bar (intercooled) all day every day for ~485 crank HP
Question: How do the C2T gaskets drop compression? I had these fitted and my heads were cut to accept them?

Les
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Old 02-06-2008, 03:24 PM
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rasises the head off the cylinder making for larger CC heads so to speak.

Persoanlly I would try to limit Your CR to 8.5:1 maybe 9:1 then boost the rest of the way..

Mine works wonderful off boost at 8.5:1 so don't worry. if you choose the correct turbo you will never no the difference. My friend has a t3/t4 and you can't even really tell when its boposting as it is boosting from right off idle all the way up..
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Old 02-07-2008, 01:00 PM
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Totally agree -

Builders generally recommend 7.5 for CIS and 8.0 for EFI as the ideal CR for a 911 aircooled turbocharged engine.
BTDT. Researched and received this answer from the builders I hold in high regard.
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Old 02-07-2008, 01:19 PM
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What would the C2T gaskets lower the compression to on stock Carrera?

It sounds like the preferred solution is install lower compression pistons. Have you guys found it more cost effective to get your existing, high-compression pistons machined or to purchase lower compression pistons? How much does it typically cost in either case?
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Old 02-07-2008, 01:25 PM
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