Random thoughts. Options

[XS4lv1Truch0x]

well yea, im juss thinking about what to do. what do you guys think i should do?

I want to do something Unique, i wana try to avoid putting in a 3sgte cause everyone is doing it.

how does a 4agte sound and how hard would it be 2 build one up? i dont want the easy way out lol

its just thoughts, not like im really going to do it... "or am i lmao"

maybe i should get an mr2 and do a 4agte project on it instead of the celi.

b4 u guys start wanting 2 flame, i already know how an engine works and all of that so dont think i dont know what im talking about.

this is just comming from a bored dude lol

This post has been edited by XS4lv1Truch0x: Sep 26, 2006 - 12:46 AM

[playr158]

more air u compress the hotter the air gets.

therefore higher compression = more air = more heat which will ultimately lead 2 predetonation before the piston could complete its powerstroke.

lol thats how its bad, i read that somewhere.

so lower compression pistons are kind of ideal in a way.

high compression with a turbo would need higher octane gass to prevent detonation.

lowercompression with a turbo would still be efficient and could possibly still run on 87 octane with little risk of detonation.

higher compression doesn't mean more air...compression ratio has nothing to do with amounts of air....it determines how much the air gets compressed inside the cylinder...your CFM is what determines how much air goes in...CFM is comprised of MANY different variables...ie boost levels, engine VE (and what comprises VE) ect... and yes when you boost a car more heat is what comes hand in hand....higher compression does lead to slightly higher combustion chamber tempteratures but this can be controlled with timing advance/retard and proper octane levels...you need to research more about compression ratios cause your making generalized comments that arn't accurate...higher compression IS NOT BAD completely...if your setup is correct then your compression ratio will be built into your setup equation and you should have the tuning, fuel and other pieces to make it work correctly...
so stop making your general high compression is bad...low compression is good..

and most of all if you think you can run 87 octane on ANY form of boosted motor you REALLY REALLY REALLY need to rethink your information 87 octane isn't going to get you anywhere....my 1.8T STOCK requires 93 octane...you don't want to run 87 in anything...premium is a general requirement for any boosted motor....

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The more experience I get tuning many different types of turbocharged Toyota motors with good engine management systems and intercooling, the more convinced I am that the stock 8.5-8.7 compression of the gen2 and gen3 3SGTEs is probably a bit too conservative for those looking to get maximum safe power from pump gas setups. The caveat here is that proper tuning and engine management is critical from the time you start the newly-built higher compression engine and seat the rings in.

My opinions are based primarily on the performance results I am getting from the higher compression Caldina 3SGTE (9.0) as well as 2ZZ (11.5) and the 2AZ (9.6) motors when fitted with turbochargers. While the last two are not motors that you would praticularly want to run at higher boost levels, their ability to make substantially impressive power with modest sized turbos and very good torque off boost gives me the confidence to say that 9.5-9.8 compression ratios should be considered when rebuilding your 3SGTE if your primary purpose for it is going to be street use and an EMS is going to be involved from day one.

The characteristics improved by higher compression include 1) the ability to make more torque off boost and at lower RPMs 2) the ability to extract more peak power from a given turbo and 3) the ability to get better fuel economy while cruising (improved BSFC). In particular, the second point can be pivotal in terms of meeting stated power goals with a smaller turbo at the same boost level. This can result in substantial improvements in transient response and spool which coupled with the first point can result in a substantial torque curve improvement in the low and mid RPM ranges.

One factor which complicates research beyond the direct experience level is that the dyno registry rarely lists actual compression ratio and octane level of the fuel used. If these parameters could be factored, I'm sure that the results of using higher compression would be shown in a favorable light.

You simply run less timing advance in some areas of the map to compensate for the higher compression.

Boost is a measurement of how much air ISN'T getting into the engine. The goal is not to run XX PSI of boost on a given turbo. It's to run as little boost on that turbo as you can, and still achieve your power goal.

With more static compression, you won't have to run as much boost to reach the same RWHP number.

Ken

Just to compare to some current turbo'd performance cars... The all new BMW 335Ci Coupe which is the first TT BMW 3 series is running 10.2:1 compression ratio, 300hp @4800rpm and an AMAZING 300ft-lb of torque @ 1400rpm.

Quote:
Originally Posted by 510rob
Can you comment on how the combination of higher static compression and lower "boost" might modify the burn characteristics of the charge to allow it to burn more quickly so as to allow the tuner to use less ignition advance, or is my former theory all just a bunch of bunk old wive's tales?

It's exaclty what you said above. The higher static compression will modify the burn characteristics of the charge to allow it to burn more quickly so as to allow the tuner to use less ignition advance. There is less volume at ignition for the flame front to reach therefore the charge burns faster. There is more swirl in the cylinder.

Stroking just moves the torque curve to the left and decreases the rod to stroke ratio while CR adds torque and efficiency across the entire RPM range.

A local 2ZZ setup with a GT30R is making just over 450rwhp on 15psi with 100 octane. A similar 3SGTE with very well built head, same turbo and 9.0:1 static compression only pushes around 375rwhp at the same boost and octane ratings. Not an exact comparison, but the compression ratio has a lot to do with the extra 75rwhp

07 911 Turbo. 9.0:1 CR.. Nice!

just some small selections of information on CR taken from 1 mr2oc thread