well the main reason the wrx or the sti would be slow without the turbo is the fact that they run a low compression. another reason is the low displacement.

The other companies need to use a higher displacement to gain the torque of the turbo and they need the higher compression to gain the horsepower.

 

I'm just trying to figure out if there's more bang for the buck in a car that doesn't rely on the turbo to perform well. My nightmare with this car is the turbo dies, then I'm stuck with a crappy 4 cylinder car that does 60 in ten seconds until I can buy a new turbo.

 

if your turbo dies your stuck with a 3000 lbs paper weight til you replace the turbo.

Do not drive your car with a blown turbo.

 

This is why I love forums. I'm a computer guy, not a car guy. My limit with cars mechanically is changing the oil, filters, headlights, things like that. Not engine stuff. lol. So why can't it drive without the turbo? Mine's fine, I'm just curious.

 

most of the time when the turbo goes it has small metal particles that could possibly get forced thru the motor.

 

Echoing what's been said in here, the reason why N/A (Naturally Aspirated, or non forced induction) cars are either as fast or faster than the WRX is:
1) Higher Compression Ratios, more compression = more bang from gas and air = more power.
2) Higher displacement and more cylinders. More cylinders = more explosions per revolution = more power.
3) Tuning. Typically they run more lean than a turbo charged engine, more air in the fuel mix = more powerful explosion = more power.
4) Valves, head design, exhaust/intake manifold design etc... The leftover stuff can all be fine tuned to get more power out of the motor. Where as with a turbo charged car, to get anything out of it you have to tune for it, N/A engines simply perform better with just better airflow. Tuning still helps of course, but it's not as necessary.

With turbocharged or supercharged applications, everything is calculated, fine tuned, recalculated and executed to the "T". You HAVE to be able to tune it correctly, otherwise you'll either get crappy power, or you'll get too much power and blow the motor. When you're forcing more air into the engine it changes things. Heat is created by both methods which requires more fuel and an intercooler to keep the charge temperatures down. Too much heat = detonation = blown motor. Less heat = more air per cycle = more power IF tuned for. Turbocharging is an exact science, more so than you're average N/A engine. Though these days, N/A engines are getting pretty elaborate and are pushing the edges of the possible more and more, so they are getting more and more fidgety. Honda has done some godly work with their K-series engines. Pushing greater than 100hp per liter out of an N/A 4 banger is quite the feat.

Anyways, I'm going to stop typing now or I'll keep going on, and on, and on.

 

There are many sides to this coin..it all comes down to personal preference. Bo and Anub1s covered it pretty well; another thing to consider is the AWD system on our cars. We lose a good bit of power due to having to push 4 wheels around; power that would be available for quicker acceleration from a roll if we were using 2WD. This is one of the reasons why an average V6 sedan like an Altima or Accord is nearly as fast (in some cases faster) than a WRX when accelerating from 30mph to 70mph.

I owned a G35c for a while...great car, and a great engine, but I had gotten used to a forced-induction powerband, and the V6 bored me pretty quickly.

 

I owned a G35c for a while...great car, and a great engine, but I had gotten used to a forced-induction powerband, and the V6 bored me pretty quickly.

Some of those cars, like the G37x are awd and still just as fast. I'm just trying to understand the car, that's all. So if turbos are so finicky, does that mean if I get the Cobb AP mapping it myself is a bad idea?

 

Turbo?!?!?!

hey man,

dont worry about blowing your turbo. its not gonna happen unless you bought a lemon or someting is seriously wrong with your car. im having a blast with my stock turbo. it all depends on how you drive.. if you beat on your car, i would worry more about the transmission. theres modifications you can do that will give you nice performance without worrying too much about blowing **** up like an exhaust or an intake. i got my car bone stock and 1 year ago with 45,xxx miles on it. since then ive done a full exhaust (headers, sti uppipe, perrin downpipe, custom catback, greddy tic muffler.) , cold air intake, ive dropped it almost 3 inches, running cobb stage 2, custom ground kit.. other then that, just little things. my car pulls hard, probably not compared to some of these guys on here but its fast enough for me. the only problem ive had so far is that my clutch is starting to go. understand i beat on my car everyday.... EVERY DAY! to the floor countless times a day. stock clutch starts to go after a while but my turbo is running strong. anyway, im just trying to ease your worrys, dont be too freaked about something happening to your whip dude. its all good, and if you were to ever blow your turbo, send me a pm because i can def help you out for cheap. if i wasnt so nervous about blowing my trans, the fp green and fmic and new injectors and fuel pump and gift card for a free tune would all be in my 05 right now. haha good luck. symmetrical awd ftw.

 

The WRX is a 2.5 liter 4 cylinder and you're comparing it to 3.7 liter V6 engines and 4.0, 4.6, and 6.2 liter V8 engines? It was not long ago that 6 cylinders could not push 265hp without turbos.

The 2.5 boxer is a phenominal engine making great power. Even stock with no turbos the engine produces 170hp. That's pretty good. Take 2.5 and double it to equal 5.0, now double the hp too - 340hp. So if the WRX had a 5.0 flat 8 it would be producing 340 hp, still not bad. If the WRX had a 6.2 liter flat 8 which is the same displacement as the Camaro it would produce 425hp. So IMO the WRX is right up there with V8's in power to displacement.

If the WRX had a 3.7 liter flat 6 which is the same displacement as the G37 it would produce 260hp/260tq that's not bad at all and right up there with most V6 engines.

Turbos even the playing field IMO and with 265hp/250tq for a 2.5 flat 4 that's amazing power, and with the STI its 305hp! Wow! I remember when the 3.0 V6 twin turbo 300Z was producing that same power back in the early 90s and that was for a $40k car - 15 years ago!

I would like to see Subaru put the flat 6 with a turbo in the Impreza - would probably be good for 375hp!

 

I would like to see Subaru put the flat 6 with a turbo in the Impreza - would probably be good for 375hp!

Why would you want to make the Impreza even more front-heavy? Getting that kind of power out of the current engine isn't that difficult anyway, but a lighter car with ~325hp would be much more fun. Personally, I'd rather have them keep the flat-4 w/ STi sized turbos and a slightly more aggressive factory tune and you're well into the 300s as far as power while keeping the lighter engine. I'll take less weight over added power any day of the week.

 

Each person has the thing that tickles their fancy - for some people it's turbos, for some people it's displacement, etc. BUT as far as competing cars that have AWD, subaru has certainly taken advances on providing some of the best AWD support. For reference, please watch the video provided below. Symmetrical AWD > other AWD.
http://www.youtube.com/watch?v=2OzK-oRPCbs

 

Great video! :thumbup:

 

OP: I would seriously recommend reading up on forced induction. Here's a place to start:
http://en.wikipedia.org/wiki/Forced_induction

There is essentially only one way to increase the torque out of an internal combustion engine tremendously -- very broad, but somewhat applicable -- and that is to increase the amount of oxygen in the cylinders so more fuel can be combusted. There are two methods to accomplish this feat: 1. increase the displacement of the engine i.e. the GM LS-2 engine displaces 6 liters of volume to produce approx. 400 hp or 2. Forced induction whereas a turbo/supercharger physically forces air into the cylinders to create a similar situation. A WRX 2.0L with 14.7 PSI of boost (1 ATM) will be a stoichiometric equivalent to a naturally aspirated 4.0 L engine running at optimum efficiency IF the turbocharger doesn't create excess heat.

There are two problems with the last statement I made: First, a turbocharger is not at peak efficiency over the full RPM range. That is the turbo has an efficiency range that may be limited to approx. 4000 RPM over which the boost will be maximized. For a stock WRX, the efficiency range is about 2000 - 5500 RPM (I believe) therefore the power is robbed at redline. This can be remedied with a larger turbo, but at the expense of greater boost threshold and greater lag (worse driveability IMO). A supercharger will have a greater efficiency range, but is overall less efficient than a turbocharger due to the parasitic loss from the supercharger pulley. The second issue with the statement above is that I mentioned a 4.0 L engine running at optimum efficiency. This assumes that the naturally aspirated engine is operating as a perfect vacuum and equalizing to exactly atmospheric pressure in the cylinders. This does not occur without the aid of a passive forced induction system such as Ram Air. Furthermore, the absolute pressure in the cylinders decreases as the RPM increases because breathing is not as efficient at this rotational speed. Variable camshaft and valve lift timing aims to increase the volumetric efficiency at these RPM ranges, as does forced induction.

Clearly Subaru chose to take the small displacement/forced induction approach, mostly due to the fact that symmetrical AWD requires the engine to be stuffed in the very front of the car. A big GM LS engine would cause the car to be veryyy front heavy.

 

Once again, another thread that has taught me some things I did not know.

 

Fantastic post Zax

 

Is it possible to make the WRX twin turbo?

 

Absolutely. But if you're sticking with a stock turbo it's pretty worthless to go with a twin scroll kit, from what I've read. You're spool time is already quick with the smaller turbos, so slapping two smaller turbos under the hood isn't going to be very beneficial.

If you're looking for faster spool times there are other mods you can do that are chaper than a twin scroll kit and more beneficial. An external wastegate setup, hi-flow cross pipe, port and polishing of your exhaust manifold, or ceramic coating are all great options to help your spool time and get more power from your stock setup.

 

If you mean twin turbo as in having two identical turbos then you could possibly do it, but it won't be cheap. I am not sure what you would have to do with the ECU though. It would be a big project indeed. My friend has a twin turbo BMW 335i and it is quick as hell.

 

The 335i comes stock with twins. :screwy:

You wouldn't have to do anything to the ECU but retune it for your twin scroll setup. They make twin scroll kits with VF 37s? (I think) that are direct swaps for the WRX. But you aren't really going to get any real benefit out of it.

 

ugh i know ive seen a tt'ed wrx/sti before but i cant find it now

 

I agree about naturally aspirated engines getting boring after a while. Straight power all the way through gets old. I had an '04 GTO and it was fast but I got sick of it quick. Forced Induction is the way to go for the fun power band.

 

I would be fine with a car with a larger motor with a turbo placed further back.

I saw last night where a gorgeous 260z rotisserie restoration with a full 300zx swap sold for only $12K. While the purist in cringes slightly and the NA straight six was a joy in my 280, the claimed 400hp FI v6 sounds like it might do the trick.