The Turbo Conundrum
 

I've noticed alot of people feel that the 12.5:1 compression ratio in the new 2.0L engine the BRZ will own, makes a turbo setup impossible. This is something I don't really understand.

When it comes to the world of N/A performanced based engines now a days, the compression ratio is almost always too high to allow for any decent application of forced induction. But as far as the subaru engine goes, lowing the compression ratio is a piece of cake compared to most engines. And swapping in 9.0 or 9.5:1 compression pistons could easily allow for a 300-400whp turbo setup with little modification to the rest of the vehicle. This is assuming of course that Subaru continues to use forged rods along with their forged crank and the 6 speed trans is beefy enough to take it. Which based on the other applications of it, I would assume that the trans wouldn't be a huge issue at that level, minus maybe a clutch job.

I guess my question is why the 12.5:1 compression ratio has scared so many people off. As far as i'm concerned its not a huge job. Yes you'll have to tear the heads off, but if you plan on installing a system yourself, you probably have no problem doing that.

Note: Personally I plan to get a 2.5L in there somehow whether it be a complete swap or just a shortblock swap (to keep DI) because i'd rather have the extra torque. And have no intention of doing this, but I know alot of others are very interested in a high reving 2.0L turbo in this car, and feel like its impossible due to the CR, something I just don't understand.

i suspect most people dont want to go "all in" and replace the internals. also the engine will most likely use a modified version of stratified charge with dished pistons for cold start. so you would have to get rid of stratified charge with ecu tuning or get aftermarket dished pistons.

But if you're going with a turbo system, aftermarket tuning is a must anyways. And likely Cobb tuning will be the system of choice for ecu, which allows easy access to all perameters within the ECU. Cobb might even offer a standard map on their system that you can just load and go.

As for the pistons, with a boxer engine, you wouldn't even have to remove the shortblock to swap the pistons out. Its not much more involved than replacing the head gaskets. I guess to me it doesn't seem that involved, anyone going 300hp+ should be prepared for this type of work anyways.

To me the cost of all the parts and possibly labor for the install, likely needing complicated routing for the piping, would be the biggest issue for the average user.

Well it just depends on how my hp you want... with a compression ratio of 11.5:1 mahle pistons and better rod bearings us celica guys were seeing 300hp with no problems... daily beaten too with no problems for thousands of miles.....

Because we want to put the turbo on a stock motor, not have to build it for a turbo. And stock at 12:5.1 is to high for comfortability with a turbo for most people. Sure you can install lower compression pistons, but that would mean the initial cost for running a turbo, equates to having to build the motor (i.e. install lower compression pistons).

Aside from that, It probably will have the first turbo setup out, before it has a set of low compression available for it.

Goes back to people looking for cheap and easy again huh? Which just isn't smart. Just slapping a turbo on 90% of n/a only engines is a terrible idea.

yup most people who slap a turbo on dont look for more than 50 hp, those who do learn not to do it again unless they wanna beef up the motor...

at 300 rwhp this thing will be faster than a 5.0 mustang GT and in a car like this it more than necessary... lol

Has nothing to do with being cheap. You don't need to build every N/A engine just to run a turbo.

I.E. Scion tC...2az comes stock 9:6.1 compression. Runs 350-400whp before needing internals. At 10psi you make 300whp/300wtq.

Plenty of N/A motors out there can have a turbo on them and not fear of detonation with the proper tuning. But most of them are not running 12:5.1 compression either. Anything over 11 in compression is considered high compression to me. Great for N/A, but not for boost, creating the higher initial cost to run turbo because you have to drop the compression.

Dragonitti is right, and most N/A tuners look for more compression anyhow. The legacy and impreza N/A guys have a tough time finding a road for more compression. Which is why Frankenstein motors with EJ22 heads on EJ25blocks are had..or getting head-gaskets to raise compression.

You current turbo owners are a bit spoiled because of boost. high performance N/As are pretty fucking hardcore, and not many have experienced when and how to use that kind of power when boost junkies hype up turbos like its the best and only thing you need in motorsports.

There is no reason to automatically assume that the compression will be too high for boosting -- DI systems are VERY good at quenching knock.

You just assume that I'm a turbo only guy... When it comes to the small car game, I and many others, prefer a 4 cylinder turbo to keep weight down and even moreso the subaru motor for its low center of gravity. Honestly I'd prefer a H8 or an H6 with a screw type eaton supercharger on it for the torque factor while still keeping it a lightweight car, but both are a bit of a pipe dream.

At this point, that is what I'm counting on. 8 injectors should aid in that quite a bit.

A DI system is just a way of more fine tuning a engine for fuel quantity. Its not a miricle worker by any means tho. The amounts of pressure this high compression motor will produce combined with a turbo will likely lead to the motor dieseling.

If a certain motor under a certain amount of boost with standard injection started knocking at 9.5:1 CR, Direct Injection might allow the CR to be raised to 10.2 or 10.5:1 without knock occuring, but its not going to help much when you start trying to add any real sort of boost to a 12.5:1 motor.

You just proved my point. You prefer a turbo. And like many others, would want a turbo because it offers a certain level of power. AKA you are turbo spoiled, if you weren't, you wouldn't have made this thread, and complained about the compression ratio. You would have been more excited to get experience in N/A tuning. Are you saying you saying my assumptions are wrong? that you would love a low output high performance N/A to start with? tell me im wrong!

Keeping the weight down? you do know that turbos and superchargers add weight vs its NA counterparts.

H8? what car currently has flat8? None that i know of.


I am a turbo guy myself, its easy to get addicted to boost, but i know for a fact that id ditch any turbo setup for a properly tuned high performance N/A.

Id like to spend more time on throttle with an N/A and concentrate on rotation, rather get distracted by boost pressure, spend less time on WOT,and spend time feathering the throttle during rotation.

all you turbo guys, how much boost do you honestly think you can run on pump gas?

maybe relevant, maybe not:

http://heffnersperformance.com/heffner_ferrari.htm

fwiw the 458 has the same 12.5 CR and DI.

On a small sports car, yes i prefer a turbo. On a large car I do not.

N/A tuning is definately a fun thing to play with, but not on a car with so little N/A potential. The car will be realitively maxed out, we can't expect much more than 100hp/L.

Superchargers and turbos do add weight but not nearly as much as a V8 would with the same power output.

And no cars currently use an H8, tho i wish they did, thus why its a pipe dream.

4 psi. Maybe. But if the pistons aren't forged, which i'm guess they are not based on Subaru's track record, probably less.

I guess the only "good " thing about the expected compression is that you won't need to run a lot of boost to make the 300whp goal. Maybe 5psi will get you there on the right turbo (one that's responsive, dual BB and water cooled).

Why did you make a new thread? We already have one for this,Compression ratio 12.5:1. Bye-bye Super charger & Turbo build?. http://allch-chcar.com/saved/blankface.gif


I still say 12.5:1 is purrfect! >:3

Im sorry, when i read your posts i have a hard time understanding what your talking about. I feel like i have to translate, as if your English is bad or something.

Let me get this straight...

On a small lightweight sports car...you would prefer a turbo..i get that, many people do. whether you NEED boost depends on the application and use.

On a big heavy sports car..you would prefer a big engine. Right? turbo/supercharger are up in the air as long s the engine is big

and you believe that the FRS is maxed out, even with that airbox, the 3 metal cats that are restricting exhaust flow, economical fuel maps, less aggressive timing maps, with its already 100hp/l just short of s2000 territory and still the 2nd best N/A power output under $100k USD....and your saying its less N/A potential?

I have a feeling you only are interested in sports cars that are close to supercar status. Not entry level sports cars. with a price range of 15k-25k which will have performance standards different than territories such as 370z/GTR/Corvette/911/Mustang/etc..

:word:

EJ internals are NOT compatible with the FB/FA motor, they can't be used.

So in order to even do what you are saying, someone is going to have to design and manufacture rods/pistons for the motor.

So what you're saying is, you have no idea, and you haven't done any math, let alone simple experiential postulating whatsoever to back it up.

Here's how it's going to happen in reality:
1.) People buy the car
2.) Power Whores will fabricate turbo setups
3.) The smart ones will calculate that with 93 octane and the stock 12.5:1 static CR, they can minimize risk with 6 PSIg, or push the envelope with 9 PSIg. Of course, if the stock powertrain can't physically handle the added power, something will break. If it stays together, and the power level is acceptable, Job Well Done.
3b.) The adventurous ones will keep cranking up the boost until they find the transient fuse...which is hopefully the same as the long-duration fuse.
4.) Stronger components will go in. Perhaps at this point, lower static CR pistons, assuming the CFD was appropriately transferred from the stock pistons so to not ruin the DI fueling swirl.
5.) With stronger powertrain, boost will be cranked up until further breakage or desired power level is achieved. Job Well Done.

1. 12:5.1 is nothing for a DI car. Add a turbo, the HPFP can handle it. The rods and pistons are the concern, especially on this type of rod design.

2. COBB will not have an AccessPort for the N/A ECU. Nope not going to happen, for the STI BRZ car yes, since this setup should be the same as the new gen WRX/STI it would be a simple as adding ECU serial. I can't even get them to make an AP for the R53 MINI which is supercharged, that's with 15+ owners at least wanting it too.

3. Properly sized DI Turbo > N/A.

1. 12.5:1 isn't "nothing", it's 12.5:1. Your in-depth knowledge of the engine weak-points are appreciated.

2. Who cares? Cobb isn't the only player. STI BRZ.."yes", then "should"? Your hopes-n-dreams don't count for reality.

3. Your opinion is noted.

I can care less about a COBB AP. I don't want one button control. Give me something that's integrated.

http://3.bp.blogspot.com/_vRfuHN52y5...n_keyboard.jpg

Agreed. And I'm saying this as my brothers Turbo'd car (10:1 CR no less) Sits not 10 feet from where I am.

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A million times this. :Ban:

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Make no mistake, I'm still going to boost it. Just at a minimal PSI :)

ill boost when it replaces my current track car

http://www.ft86club.com/forums/attac...1&d=1321399594

Read up on DI -- it's much more than that, and it is really fantastic for tuning boosted engines!

The major problem with high CR pistons is that they tend to hold hot spots along the piston crown, and those hot spots make detonation more likely.

However, the incredibly atomized and precise targeting of fuel capable with DI means you can much more easily quench hot spots, and thus prevent knock.

Remember, running rich is all about cooling the piston with unburnt fuel. With DI you can do that far more precisely and effectively and use a leaner mixture.

Now it is certainly true that if you raise cylinder pressure high enough, something will break, even without detonation -- but that is not really going to much matter for a point or two of compression if the crank or piston rings simply can't handle, say, 30 psi.

I bet it will be possible to push 6-8 psi if not a bit more without undue risk -- and that should net you a nice bump in torque and power.

the big x factor was really tuning, and it sounds like the ECU will be reflashable, which is great!

http://i.imgur.com/TT4CJ.jpg

Anyone else casually glancing at join dates before reading threads?

Anyone else casually glancing at join dates before reading threads?[/QUOTE]

So your saying if I joined at a later date I have no knowledge of cars?
That's really ignorant.

And I agree with what's been said you turbo happy guys are spoiled.
I have two cars currently sitting in my garage a 700whp 1967 hemi dart and a 400whp 1990 300zx tt. you can make more then a 100hp per liter and this is from a 1967 motor with no where near the technology we have today to squeeze even more power and it's carb which has a lot less potential then di the first car proves this and I promise you it is no where near maxed out and it is all motor! No boost no nitrous. And I promise there is nothing like driving an all motor car even a 200hp one. Now I love turbos I think they are a great thing that can provide a lot of hp potential(and trust me I have one tattooed on my arm I am a huge fan of turbo cars) but they are in no way the only hp solution or even the best for this car there are a lot of things I will do to this car before I boost it, if I boost it.

So your saying if I joined at a later date I have no knowledge of cars?
That's really ignorant.

And I agree with what's been said you turbo happy guys are spoiled.
I have two cars currently sitting in my garage a 700whp 1967 hemi dart and a 400whp 1990 300zx tt. you can make more then a 100hp per liter and this is from a 1967 motor with no where near the technology we have today to squeeze even more power and it's carb which has a lot less potential then di the first car proves this and I promise you it is no where near maxed out and it is all motor! No boost no nitrous. And I promise there is nothing like driving an all motor car even a 200hp one. Now I love turbos I think they are a great thing that can provide a lot of hp potential(and trust me I have one tattooed on my arm I am a huge fan of turbo cars) but they are in no way the only hp solution or even the best for this car there are a lot of things I will do to this car before I boost it, if I boost it.[/QUOTE]

I think the benefit of turbos being power adders, without being too hard on the mileage, far outweighs the benefits of all-motor / N/A power on this car because it IS a sport semi-eco-car, in my opinion. But I'm not a turbo expert... I just feel like the engine is new, it has high compression, and there is not enough miles put on a STOCK motor, let alone a blown one to just slap a turbo on there (for any worthwhile power at least).

If I could get 330 hp out of this car some how and not be scared of blowing it up, I'd be totally happy.... but I don't think it's gonna happen...

This motor definitely has potential, I would love to see the NA Potential, if it can reach 230whp I'm going that route. I'm sure the motor will be able to handle a 57mm turbo yielding 300whp with support fuel mods. As someone on here mentioned... it'll all be in the tuning. If anything, we can lower the compression a little bit with a thicker head gasket, I know this works for a 2jzge, I'm not sure if it'll work the same for a boxer motor though.

Boosting the car without causing it to explode in a masterpiece of disaster will be the easy part. As others have said, DI changes the game on the detonation factor.

Be harder to figure out how to (efficiently) place that shit into the engine bay and keep the factory peripherals. That bay is crammed!


In any case, as with most newer cars, I expect within short time and order there will be a plethora of FI kits and whatnot available from reputable tuners to sate any power mongers thirst. Me? I'm waiting to see if Toda does their N/A magic with this engine.

FWIW, if I had to choose between being whined (turbo) at all day, or screamed (N/A), I'll take screamed. :D

Stopped there...we're talking from the factory, meeting current (absurdly strict) emissions standards, maintaining everyday drivability for the not hardcore types, and reliability to backup a factory warranty......not aftermarket tuning.

oh, and
http://i40.tinypic.com/rutb2x.jpg

I drive my z everyday. But besides that point I think a lot of people are underestimating what this car will get out of just an intake exhaust and a tune, I think this car has a lot more power straight from the factory then they are saying which is why they made the ecu tunable. I think they have this engine so tuned down for mpgs and emissions that we will get a noticeable amount of power just from tuning the car.

Ever seen the engine bay of a 300zx?

a 57mm turbo for 300whp? :lol:

Oh YEAH! Well I'm going to bolt a 4531mm Turbo on mine with 982763cc injectors with a 9817905862103GPH fuel pump and run 789 octane fuel and make 1.876 Trillion HP! So shut it! :attention_whore:

-Joe:thumbsup: